Acids,Bases and Salts

Transcription

1 Acids,Bases and Salts BASIC CONCEPTS: We are familiar with the utility and important of acids, bases and salts in our daily life. For example The sour taste of vinegar is due to acetic acid (CH 3 COOH). Sodium hydroxide (NaOH) is a base, which is used in the preparation of soaps. Sodium Chloride (NaCl) is common salt, which is useful as food ingredient. It may not be possible to identify all the salts by their taste as in case of acids and bases. They have their own characteristics which help in their identification. Apart from common salt (NaCl0, washing soda, baking soda, copper sulphate etc. are some of the well known salts we came across quite often. In general, salts, are formed by the chemical combination of acids and bases. In this chapter, we will discuss all the three types of compounds : acids, bases and salts. In order to know whether a substance is an acid or a base we should first know the meaning of the term acid-base indicator or just indicator. 1. Indicators: It is dye that changes color when it is put into acid or a base. It gives different colors in acid and base. The three

2 2. common indicators to test for acids and bases are : Litmus, Methyl orange and phenophthalein. The most common indicator used testing acids and bases in the laboratory is litmus, which can be used in the form of litmus solution or in the form of litmus paper. It is of two types : blue litmus and red litmus. Litmus is a natural indicator, whose neutral colour is purple. IMPORTANT FACTS: 1. An acid turns blue litmus to red. 2. A base (or alkali) turns red litmus to blue. The methyl orange is a synthetic indicator whose neutral colour is orange. (i) Methyl orange indicator gives pink colour in acid solution. (ii) Methyl orange indicator gives yellow in basic solution. The phenolphthalein is a synthetic whose neutral colour is colourless. IMPORTANT FACTS: (i) Phenolphthalein indicator is colourless in acid solution. (ii) Phenolphthalein indicator gives pink colour in basic solution.

3 Olfactory indicators: The olfactory means relating to the sense of smell. Those substances whose smell changes in acetic or basic solutions are called olfactory indicators. IMPORTANT FACTS: Onion has characteristics smell. When a basic solution like sodium hydroxide solution is added to a cloth stripe treated with onions, then onion smell cannot be detected. An acetic solution like hydrochloric acid, however, does not destroy smell of onions. Thus can be used as a test for acids and bases. 2. General Characteristics Properties of Acids: Sour Taste: Almost all acidic substances have a sour taste. Action on Litmus Paper: Acids turns blue litmus to red. Action on Methyl Orange: Methyl orange turns pink when its solutions are added the solution of an acidic substances. Corrosive Nature: Most of the acids are corrosive in nature. They produce a burning sensation on the skin and holes in the clothes on which they fall. Reaction with Metals: Acids react with active metals like zinc, magnesium etc. generally with the evolution of hydrogen gas. The reactions may be represented as follows: Zn(s) + dil. H 2 SO 4 (aq) ZnSO 4 (aq) + H 2 (g) Zn(s) + 2HCl(aq) ZnCl 2 (aq) + 2HCl(aq) It is a displacement reaction. In this reaction hydrogen of H 2 SO 4 is

4 displayed by zinc. This proves that sulphuric acid contains replacable hydrogen. Tips for students: The metal in the above reactions displaces hydrogen from the acids. This is seen as hydrogen gas. The metal combines with remaining part of the acids and forms a compound called a salt. The reaction of a metal with an acid can be summarized as: Acid + Metal Salt + Hydrogen gas Reaction with Metal Carbonates: Acids decomposes metal carbonates to liberate carbon dioxide and to form corresponding salts and water. Metal carbonate + Acid Salt + Water + Carbon dioxide (i) When sodium carbonate is treated with dilute hydrochloric acid the carbon dioxide is liberated and sodium chloride and water are formed. Na 2 CO 3 (s) + 2HCl(aq) 2NaCl(aq) + H 2 O + CO 2 (g) (ii) When calcium carbonate is treated with dilute hydrochloric acid then carbon dioxide is liberated and calcium chlorine and water are formed. CaCO 3 (s) + 2HCl(aq) CaCl 2 (aq) + H 2 O(l) + CO 2 (g) Reaction with Metal Hydrogen Carbonates: Acids react with metal bicarbonates to give out carbon dioxide with effervescence and forming the corresponding salt and water. NaHCO 3 (aq) + HCl(aq) NaCl(aq) + H 2 O(l) + CO 2 (g) Reaction with Bases: When an acid reacts with a base, it forms salt and water. As a result the acidic properties of the acid disappear. The process is called neutralization. The reaction between an acid and a base to give a salt and water is known as a neutralization reaction. Example : NaOH(aq) + HCl(aq) NaCl(aq) + H 2 O(l) Or Reaction with Metallic Oxides: Metallic oxides like quick time i.e.,

5 calcium oxide (CaO), Copper (II) oxide (CuO), magnesium oxide (MgO) etc. react with acids to form salt and water. CaO(s) + 2HCl(aq) CaCl 2 (aq) + H 2 O (salt) (water) CuO(s) + 2HCl(aq) CuCl 2 (aq) + H 2 O (salt) (water) 3. General Characteristics Properties of Bases: Bases have Bitter Taste: Bases possess a bitter taste. Slipper or Soapy Touch: They possess a slippery touch like soaps. Action on Litmus Paper: They turn red litmus blue. Action on Phenolphthalein: They turn phenolphthalein solution pink. Corrosive Nature : Some bases like caustic soda (sodium hydroxide), caustic potash (potassium hydroxise) etc. produce a burning sensation on the skin. Reaction with Bases: The reaction between an acid and a base is called neutralization reaction. This reaction gives a salt and water. NaOH(aq) + HCl(aq) NaCl(aq) + H 2 O(l) Reaction with Metals: Some bases like sodium hydroxide and potassium hydroxide react with active metals like zinc and aluminium to liberate hydrogen gas with formation of salt. 2 NaOH + Zn Na 2 ZnO 2 + H 2 (sodium hydroxide) (zinc) (sodium zincate) (hydrogen) 2 NaOH + 2 Al + H 2 O 2NaAlO 2 + 3H 2 (sodium hydroxide) (aluminium) (water) (sodium aluminate) Reaction with Non Metallic Oxides: When carbon dioxide (CO 2 ) which is a non metallic oxide passed through lime water that is Ca(OH) 2 which is a base, they react to produce salt (CaCO 3 ) and water. Ca(OH) 2 (aq) + CO 2 (g) CaCO 3 (s) + H 2 O(l) (lime water) (white precipitate) KNOWLEDGE BOOSTER All bases react with acids to form salt and water, this shows that non-metallic oxides are acidic in nature. 4. What Happens to a Base in a Water Solution? When bases are dissolved in water, they produce hydroxide ions in the solution. For example, NaOH + Water Na + + OH - NH 4 OH + Water NH OH -

6 KOH + Water K + + OH - Mg(OH) 2 + Water Mg OH - Thus, a base is defined as follows: A base is a substance which when dissolved in water gives (OH - ) ions in the solution. KNOWLEDGE BOOSTER (i) The compound C 2 H 5 OH contains OH group but it does not ionize in the aqueous solution to gives OH - ions. Hence,it is not a base. (ii) All bases do not dissolve in water. An alkali is a base that dissolves in water. They are soapy to touch,bitter and corrosive as they may cause harm. (iii) Never taste or touch them as they may cause harm. 5. What Happens to an Acid or a Base in a Water Solution? When acids are dissolved in water.they give free hydronium ions (H 3 O + or H + ) Examples: HCl(g)+H 2 O(l) H 3 O + (aq)+cl - (aq) H 2so - (aq)+ H 2 O(l) 2 H 3 O + (aq)+so 4 2- (aq) CH 3 COOH(aq) +H 2 O(l) H 3 O + (aq)+ CH 3 COO - (aq) Thus, an acid is defined as follows: An acid is a substance which when dissolved in water, gives hydronium ions (H 3 O + or H + ) in the solution. 6. Mixing of Bases or Acids with Water An Exothermic Process: The process of mixing bases or acids in water is a highly exothermic reaction. If we dissolve bases like sodium hydroxide or potassium hydroxide in water, the solution is found to be hotter. This shows that dissolution of bases in water is an exothermic process. KNOWLEDGE BOOSTER The acid must always be added slowly to water with constant stirring. If water is added to a concentrated acid, the heat generated may cause the mixture to splash out and cause burns.

7 7. Effect of Dilution on Hydroxide (OH - )Ions and Hydronium(H + ) ions and Concentration of Acids and Bases: Mixing an acid or base with water results in decrease in the concentration of ions( H 3 O + / OH - )per volume such a process is called dilution and the acid or the base is said to be diluted. 8. Strong and Weak Acids:The acids which are almost completely ionized when dissolved in water are called strong acids. Hydrochloric acids(hcl),nitric acids(hno 3) and sulphuric acids (H 2 SO 4 )are strong acids because they give large around of H + ions in the solution. Such acids are called strong acids. Their dissociation is represented by putting a single arrow ( ) towards the ions produced showing their complete dissociation or ionization. HCl + water H + (aq) + Cl - (aq) HNO 3 + Water H + (aq) + NO 3 - (aq) H 2 SO 4 + Water 2H + (aq) + SO 4 2- (aq) On the other hand, acids like acetic acid (CH 3 COOH), formic acid (HCOOH). Carbonic acid (H 2 CO 3 ).Phosphoric acid (H 3 PO 4 ) etc. when dissolved in water dissociate only partially in the solution. As a result the amount of H + ions produced in small. Such acids are called weak acids. Thus, the acids which are partially ionized when dissolved in water are called weak acids. CH 3 COOH + Water CH 3 COO - (aq) + H + (aq) acetic ion H 2 CO 3 + Water 2H + (aq) + CO 2-3 (aq) Hydrogen ion HCOOH + Water HCOO - (aq) + H + (aq) Formate ion 9. Strong and weak bases: Bases which are almost completely dissociated ionized in their solution are called strong bases. Bases like sodium hydroxide (NaOH) and potassium hydroxide (KOH) when dissolved in water dissociate completely into ions. As a result, they give large amount of OH - ions. Their dissociation is represented by putting a single arrow ( ) towards the ions produced. Thus NaOH + Water Na + (aq) + OH - (aq) KOH + Water K + (aq) + OH - (aq) On the other hand, bases like ammonium hydroxide (NH 4 OH). Calcium hydroxide, Ca(OH) 2 etc. when dissolved in water dissociate only partially to give hydroxide ions. As a result the amount of OH - ions produced in the

8 solution is small. Thus, the bases which are partially dissociated/ionized in their aqueous solution are called weak bases. 10. How Strong Are Acid or Base Solution: The strength of any solution of an acid or base can be determined from the concentration of H + (aq) or OH - (aq) in the solution. We can do this by making use of universal indicator, which is a mixture of several indicators. The universal indicators show different colours of mixtures at different concentrations of hydrogen ions in a solution. A Danish Biochemist S.P.Sorensen (1909) proposed that strength of acidity of a solution be expressed in terms of parameter called ph. The p in ph stands for poting in Germans meaning power. On the ph scale we can measure ph from O (very acidic) to 14 (very alkaline). Higher the hydronium ion concentration, lower is ph value. The ph of a neutral solution is 7 to 14, it represents an increase in OH - ion concentration in the solution, that increase in the strength of alkali. KNOWLEDGE BOOSTER: [H + ] = [OH - ], then the solution to be neutral. [H + ] > [OH - ], then the solution is said to be acidic. [H + ] < [OH - ], then the solution is said to be alkaline or basic. Relationship between ph values and the acidic or basic nature of any aqueous solution at 298K is shown below: Fig.2.1. The ph values and the acidic or basic nature of any aqueous solution at 298K (-25 0 C). The ph values of some common solutions are given below: ph values of some common solution: Blood Saliva Urine Gastric juice Coffee Beer Tomato juice Wine Lemon juice Vinegar HCl (1M) Solution ph

9 NaOH (1M) NH 4 OH (1M) Mg(OH) 2 (saturated) Battery acid (40% H 2 SO 4 ) Importance of ph in Everyday Life: In biological Systems (i.e., Plants and Animals): Our body works within the range of 7.0 to 7.8. The ph plays an important role in the survival of animals, including human beings. Living organisms can survive only in narrow range of ph change. When ph of rain water is less than 5.6, it is called acid rain. When acid rain flows into the rivers, it lowers the ph of the river water. The survival of aquatic life in such rivers becomes difficult. Most of the plants grow best ph of the soil is close to 7. If the soil is too acidic or too basic, the plants grow badly or do not grow at all. The soil may be acidic or basic naturally. The soil ph is also affected by the use of chemical fertilizers in the field. The ph of acidic soil can reach as low as 4 and that of the basic soil can go upto 8.3. Chemicals can be added to soil to adjust its ph and make if suitable for growing plants. In Digestive System: ph a vital role in the digestion of food and other biochemical reaction inside the human/animal body. Our stomach produces hydrochloric acid which helps in the digestion of food without harming the stomach. During indigestion the stomach produces two much acid and this cause pain and irritation. The problem is called acidity. It is cured by medicines called Antacid. The most common used antacid contains magnesium hydroxide which is a weak base and neutralizes the excess acid. Tooth Decay Caused by Acids: Tooth decay starts when the ph of the mouth is lower than 5.5. Tooth enamel made up of calcium phosphate is the hardest substance in the body. It does not dissolve in water but is corroded when the ph in the mouth is below 5.5. Bacteria present in the mouth produce acids by degradation of sugar and food particles remaining in the mouth after eating. The amount of acid produced is high when we eat sweets or sugary food. The saliva produced in the mouth by the salivary glands is alkaline and partially neutralizes the acids produced in the mouth. However, the excess acid has to be removed by cleaning the teeth with a good quality tooth paste. These tooth pastes are alkaline in nature and neutralize the excess acid present in the mouth and prevent tooth decay.

10 Self Defence Animals and Plants through Chemicals Warfare: When we are stung by an honey bee or yellow ant we feel pain or irritation. This is due to the acid (formic acid i.e.methanoic acid), injected into our skin by the bee or the ant. To get the relief, we apply the solution of mild base like baking soda. Similarly, nettle plants have leaves with stinging hairs. If these are touched accidently they cause a lot of pain again due to formic acid injected by these leaves into the skin. Nettle is a herbaceous plant which grows in the wild. Its leaves have stinging hair, which cause painful stings when touched accidently. This is due to the methanoic acid secreted by them. A traditional remedy is rubbing the area with the leaf of the duck plant, which often grows beside the nettle in the wild. Given below is the table of some naturally occurring acids: Natural Source Acid Natural Source Acid Vinegar Orange Tamarind Tomato Acetic acid Citric acid Tartaric acid Oxalic acid Sour milk (curd) Lemon Anti sting Nettle sting Lactic acid Citric acid Methanoic acid Methanoic acid 12. Salts: Salts are the ionic compounds consisting of two parts, one part carrying a positive charge and the other carrying a negative charge. Salt as a whole is electrically neutral because the number of positive and negative ions present in the salt are equal. Or Salt is a product of neutralization reaction between an acid and a base. Example: NaOH + HCl NaCl + H 2 O (base) (acid) (salt) (water) NH 4 OH + HCl NH 4 Cl + H 2 O (base) (acid) (salt) (water) KOH + HNO 3 KNO 3 + H 2 O (base) (acid) (salt) (water) MgO + H 2 SO 4 MgSO 4 + H 2 O (base) (acid) (salt) (water)

11 Some common salts and their formulae: Table 2.1: Some Common Salts and Their Formulae Salt Formulae Positive ion Negative ion Sodium chloride Sodium sulphate Sodium nitrate Potassium nitrate Copper sulphate Zinc sulphate Calcium carbonate Sodium carbonate Calcium chloride Aliminium sulphate Ammonium chloride NaCl Na 2 SO 4 NaNO 3 KNO 3 CuSO 4 ZnSO 4 CuCO 3 Na 2 CO 3 CaCl 2 Al 2 (SO 4 ) 3 NH 4 Cl Na + 2Na + Na + K + Cu 2+ Zn 2+ Ca 2+ 2Na + Ca 2+ 2Al 3+ + NH 4 Cl 2- SO 4 - NO 3 - NO 3 2- So 4 2- So 4 2- CO 3 2- CO 3 2Cl - 2-3SO 4 Cl - Family of Salts: The salts are classified into different families either on the basis of the acid or on the basis of the base from which they have been obtained. The parent acids and bases of some salts are identifies as follows: Table 2.2: Writing the Names of Some Salts: Formula of the Salt Parent Name of the Salt 1. Na 2 CO 3 2. CaCO 3 3. CaSO 4 4. Ca 3 (PO) 4 ) 2 5. CuSO 4 6. CH 3 COONa Acid H 2 CO 3 Carbonic acid H 2 CO 3 Carbonic acid H 2 SO 4 Sulphuric acid H 3 PO 4 Phosphoric acid H 2 SO 4 Sulphuric acid CH 3 COOH Acetic acid Base NaOH Sodium hydroxide Ca(OH) 2 Calcium hydroxide Ca(OH) 2 Calcium hydroxide Ca(OH) 2 Calcium hydroxide Cu(OH) 2 Copper hydroxide NaOH Sodium hydroxide Sodium carbonate Calcium carbonate Calcium sulphate Calcium phosphate Copper sulphate Sodium acetate ph of Salts : A salt is formed by the reaction between an acid and a base, so we

12 should expect that the solution of a salt in water will be neutral towards litmus. Though the aqueous solutions of many salts are neutral (having ph of 7). Some salts produce acidic or basic solution when dissolved in water. The ph values of some of the salt solutions are given below: Salt Solution ph Nature Sodium chloride solution Ammonium chloride solution Sodium carbonate solution Neutral Acidic Basic Depending upon the nature of the acid and base reacting to form the salt,the salts can be classified in to the following four types: 1. Salts of strong acid an strong base : A few examples are given below:nacl,nano 3, KCl,K 2 SO 4,KNO 3. These salts on dissolving in water produce strong acid and strong base. Example: NaCl + H2O NaOH + HCl Strong base Strong acid Hence, the acid and the base produce neutralize each other completely. As a result the solution is neutral with ph=7. 2. Salts of weak acid and strong base: A few examples are given below: Na 2 CO 3, NaHCO 3, CH 3 COONa These salts on dissolving in water produce a strong base and weak acid, Example: Na 2 CO 3 + 2H 2 O 2NaOH + H 2 CO 3 Strong base Weak Acid The strong base produced dominates over the weak acid. Hence,the solution is basic with ph>7. 3. Salts of strong acid and weak base: A few examples are given below: NH 4 Cl,CuSO 4,AlCl 3,ZnSO 4 etc. These salts on dissolving in water produce a strong acid and weak base. example: CuSO 4 + 2H 2 O Cu(OH) 2 + H 2 SO 4 Copper(II)Sulphate Copper(II)hydroxide Sulphuric acid (weak base) (Strong acid) The strong base produces dominates over the weak base. Hence, the solution is acidic with ph<7. 4. Salts of weak acid and weak base.

13 Example: CH 3 COONH 4 (Ammonium Aceatate) When this salt is dissolved in water, it produces weak acid and weak base. Hence, the solution is almost neutral. 13. Chemical from Common Salt: Chemically common salt is sodium chloride.its simples formula is NaCl. This is the Salt that you use in food. The main source of common salt is the sea water. Sea water contains about 3.5% of soluble salts, the most common of which is sodium chloride (2.7 to 2.9%) Common salt is also found in the form of solid deposits in several ports of the world. Due to the presence of impurities, it is often brown in color and is called rock salt. Beds of rock salt were formed, when seas/lakes dried up the past. Common Salt A Raw Material for Chemicals: We can obtain many useful substances/chemicals from common salt. Thus, the common salt is the raw material for many chemicals. These chemicals are: Sodium hydroxide(naoh) Bleaching powder (CaOCl 2 ) Sodium hydrogen carbonate (NaHCO 3 ) Sodium Carbonate(Na 2 CO 3 ) 14. Sodium Hydroxide: NaOH commercially, sodium hydroxide is also called caustic soda. It is a strong base. Manufacture of Sodium Hydroxide by Common Salt : Sodium hydroxide is manufactured by electrolysis of an aqueous solution of sodium chloride(called brine).this process is called chloralkali process because of the products formed chlor for chlorine and alkali for sodium hydroxide.when electricity is passed through brine(aqueous solution of sodium chloride),the following reactions take place. 2NaCl(aq)+2H 2 O(l) 2NaOH(aq)+Cl 2 (g)+h 2 (g) During the electrolysis, chlorine gas is produced at the anode (positive electrode)and hydrogen gas is produced at the cathode(negative electrode) sodium hydroxide solution is formed near the cathode. i.e. At cathode: H + + e - H H + H H 2 At anode: Cl - Cl + e - Cl + Cl Cl 2 Uses: The three useful products obtained by the electrolysis of an aqueous solution of sodium chloride are: (1) Hydrogen,(2) Chlorine and (3) Sodium hydroxide. 1. Uses sodium hydroxide: For degreasing sheets/rods etc. For manufacturing soaps and detergents. For manufacturing paper.

14 For making artificial textile fibres. 2. Uses of Chlorine : It is used : As germicide and disinfectant for sterilization of water in the swimming pool. In the manufacture of bleaching powder,chloroform,hydrochloric acid, explosives like DDT etc. In the manufacturing of hydrochloric acid. In the manufacturing of poly vinyl chloride (PVC), pesticides, chlorofluoro carbons (CFC s), chloroform. Carbon tetrachloride, paints dye-stuffs. 3. Uses of Hydrogen : It is used : In the hydrogenation of oils to obtain solid fats. In the production of hydrochloric acid. To make ammonia for fertilizers. To make methanol 15. Bleaching Powder: Chemically it is a calcium oxychloride, CaOCl 2 or Ca(OCl)Cl. It is also called chloride of lime. Preparation: Bleaching powder is produced by the action of chlorine on dry slaked lime [Ca(OH) 2 ]. Ca(OH) 2 (s) + Cl 2 (g) CaOCl 2 (s) + H 2 O(l) (slaked lime) (bleaching powder) Properties: Some of the important properties of bleaching powder are given below : Colour and Odour: It is a yellowish-white powder which strongly smells of chlorine. Solubility in water: It is soluble in cold water. The unreacted lime present in it however remains undissolved Exposure to air: When bleaching powder is exposed to air, it reacts with atmospheric CO 2 to give chlorine gas. CaOCl 2 (s) + CO 2 (g) CaCO 3 (s) + Cl 2 (g) Reaction with acids: Bleaching powder reacts with HCl and H 2 SO 4 to give off Cl 2 gas. CaOCl 2 + 2HCl(dil.) CaCl 2 (aq) + H 2 O(l) + Cl 2 (g) CaOCl 2 + H 2 SO 4 (dil.) CaSO 4 (s) + H 2 O(l) + Cl 2 (g) Uses : Bleaching powder is used : For bleaching cotton and linen in the textile industry. For bleaching wood pulp in paper factories and for bleaching washed clothes in laundry. As an oxidizing agent in many chemical industries.

15 For disinfecting drinking water to make it free of germs. 16. Baking Soda: The chemical name of baking soda is sodium hydrogen carbonate. The formula of baking soda is NaHCO 3. Sometimes it is added for faster cooking. Manufacturing : It is manufactured by reacting a cold solution of sodium chloride with carbon dioxide and ammonia. NaCl + NH 3 + H 2 O + CO 2 NaHCO 3 + NH 4 Cl (sodium hydrogen (ammonium Carbonate) chloride) Properties: Some of the \important properties of baking soda are given below : State and Solubility: It is white crystalline substance, which is sparingly soluble in water. Action of heat: On heating, it decomposes to give sodium carbonate, and CO 2 is liberated. 2NaHCO 3 Na 2 CO 3 + CO 2 + H 2 o (baking soda) Uses : Some important uses of baking soda are given below : For making baking powder : Baking powder is a mixture of baking soda (sodium hydrogen carbonate) and a mild edible acid such as tartaric acid. When baking powder is heated or mixed in water, the following reaction takes place : NaHCO 3 (aq) + H + (aq) CO 2 (g) + H 2 O(l) + Sodium salt of acid (baking soda) (from tartaric acid) Carbon dioxide produced during the reaction causes bread or cake to rise making them soft and spongy. Baking sodium is also an ingredient in antacids. Being alkaline, it neutralizes excess acid in the stomach and provides relief. It is also used in soda-acid fire extinguishers. IMPORTANT FACTS: Soda-acid fire extinguishers contain a solution of sodium hydrogen carbonate (baking soda) and sulphuric acid. When the extinguisher is inverted, sulphuric acid spill and reacts, with sodium hydrogen carbonate. The reaction produces a large quantity of carbon dioxide and water. H 2 SO 4 + 2NaHCO 3 Na 2 CO 3 + CO 2 + H 2 O The high pressure of the gas produces a stream of effervescent liquid through the nozzle. The effervescencing liquid is a mixture of carbon dioxide and water. When the mixture is direct towards fire, carbon dioxide surrounds the burning. The burning objects which cuts off the supply of air and put off the fire.

16 17. Washing Soda: Washing soda is sodium carbonate containing 10 molecules of water of crystallization i.e., it is sodium carbonate decahydrate. Thus, its molecular formula is Na 2 CO 3.10H 2 O. Anhydrous sodium carbonate (Na 2 CO 3 ) is generally called soda ash. Manufacturing: Washing soda is produced from sodium chloride in the following steps : (i) A cold and concentrated solution of sodium chloride (brine) is reacted with ammonia and carbon dioxide to obtain sodium hydrogen carbonate. NaCl + NH 3 + H 2 O + CO 2 NaHCO 3 + NH 4 Cl Sodium hydrogen carbonate formed is slightly soluble in water, so it precipitates out as solid. (ii) Sodium hydrogen carbonate is separated by filteration, dried and heated. On heating sodium hydrogen carbonate decomposes to form sodium carbonate. 2NaHCO 3 Na 2 CO 3 + CO 2 + H 2 O (iii) Anhydrous sodium carbonate is dissolved in water and recrystallised to get washing soda crystals containing 10 molecules of water of crystallysation Na 2 CO H 2 O Na 2 CO 3.10H 2 O (soda ash) (washing soda) Uses : Some important uses of washing soda are given below : It is used in glass, soap and paper industries. It is used in the manufacture of sodium compounds such as borax. Sodium carbonate can be used as a cleaning agent for domestic purposes. It is used for removing permanent hardness of water. KNOWLEDGE BOOSTER: When washing soda is kept open in the air, the crystals of washing soda lose nine molecules of water of crystallization to form a monohydrate which is a white powder. This process is called efflorescence. Na 2 CO 3.10H 2 O(s) Na 2 CO 3.H 2 O(l) + 9H 2 O(g) (white powder) 18. Plaster of Paris : It is calcium sulphate hemihydrates. Its molecular formula CaSO 4. ½ H 2 O. Preperation : It is prepared by heating gypsum (CaSO 4.2H 2 O) at 373K. CaSO 4.2H 2 O(s) CaSO 4. ½ H 2 O(s) + 1 ½ H 2 O During the preparation of plaster of paris, temperature should be controlled

17 carefully. Otherwise, anhydrous calcium sulphate (CaSO 4 ) will be formed. Properties : Some important properties of plaster of paris are given below. Colour : It is white odourless powder. Reaction with water : When plaster of paris is mixed with water it forms a hard mass, and changes to GYPSUM. CaSO 4. ½ H 2 O + 1 ½ H 2 O CaSO 4.2H 2 O Uses : It is used for setting fractured bones in the right position and in making casts in dentistry. It is used in making the surface smooth e.g that of walls, ceiling etc. In making decorative designs on the ceiling, pillars etc. In making chalks for writing on the black board. KNOWLEDGE BOOSTER: I. Plaster of Paris should be stored in a moisture proof container because the presence of moisture can cause slow setting of Plaster of Paris by bringing about its hydration. II. Plaster of Paris is used in hospitals for setting fractured bones in the right position to ensure correct heating. It keeps the fractures bone straight. This use is based on the fact that when Plaster of Paris is mixed with water and applied around the fractured bones and limbs, it sets into hard mass, which keeps the bone joins in a fixed position 19. Are the Crystalline Salts Really Dry? The water molecules which form part of the structure of a crystal are called water of crystallization.the salts which contains water of crystallisation are called hydrated salts. Water of crystallization is the fixed number of water molecules present in one formula unit of salt. (i) Copper Sulphate crystals contain 5 molecules of water of crystallisation in one formula unit and it is written as CuSO 4.5H 2 O. (ii) Sodium Carbonate crystals contain 10 molecules of water of crystallisation in one formula unit and it is written as Na 2 CO 3.10H 2 O. (iii) Calcium Sulphate crystals contains 2 molecules of water of crystallisation in one formula unit and is written as Na 2 CO 3.10H 2 O. STRUCTURAL QUESTIONS AND ANSWERS Q.1.You have been provided with three test tubes.one of them contains distilled water and the other two contain an acidic solution and basic solution, respectively. If you are given only red litmus paper how will you identify the contents of each test tube?

18 Answer: (a) Put the given red litmus paper in all the test tubes, turn by turn. The solution which turns red litmus to blue, will be a basic solution. (b) Now put the blue litmus paper obtained above in the remaining two test tubes one by one. The solution which turns blue litmus paper to red, will be the acidic solution. (c) The solution which now effect on any litmus paper will be neutral and hence it will be distilled water. Q.2. Why should curd and sour substances not be kept in brass and copper vessles? Answer : When acidic substances like curd or other sour substances are kept in copper or brass vessels, they react to form toxic compounds and make the food stuff not fit for consumption. So, these substances should not be kept in brass and copper vessels. Q.3. Which gas is usually liberated when an acid react with a meta? illustrate with an example. How will you test for the presence of this gas? Answer: Usually hydrogen gas is liberated when a metal reacts with an acid. E.g. Zn + H 2 SO 4 ZnSO 4 + H 2 (zinc) (sulphuric (zinc (hydrogen) Acid) sulphate) Presence of hydrogen gas can be tested by passing the gas through soap solution and then bringing a burning candle near the soap bubble filled with the gas. The soap bubbles bursts and the hydrogen gas burns with a pop sound. Q.4.) A metal compound reacts with dilute hydrochloric acid to produce effervescence. The gas evolved extinguish a burning candle. Write a balanced equation for the reaction if one of the compounds formed is calcium chloride. Answer. The gas evolved carbon dioxide. Metal compound is calcium carbonate CaCO 3 (s) + 2HCl(aq) CaCl 2 (aq) + CO 2 (g) + H 2 O(l) (Compoud A) (hydrochloric (calcium (carbon Acid) chloride) dioxide) Q.5. Why do HCl, HNO 3 etc. show acidic characteristics in aqueous solution while solutions of compounds like alcohol and glucose do not show acidic character? Answer.The acidic character of a substance is due to the presence of hydrogen ions [H + (aq) ions] in its aqueous solution. HCl, HNO 3 etc. show acidic properties because they produce hydrogen ions when dissolved in water. The solutions of compounds like glucose and alcohol do not show acidic character because they do not ionize in water to produce hydrogen ions.

19 Q.6. Why does an aqueous solution of an acid conduct electricity? Answer. The aqueous solution of an acid conducts electricity due to the presence of charged particles called ions in it. For example when hydrochloric acid (HCl) is dissolved in water, then its aqueous solution contains hydrogen ions [H + (aq)] and chloride ions [Cl - (aq)]. These ions carry electric current. Therefore, due to the presence of H + (aq) ions and Cl - (aq) ions, a water solution of hydrochloric acid conducts electricity. Q.7. Why does dry HCl gas not change the colour of the dry litmus paper? Answer. Dry HCl does not contain H + ions. That is why it does not change the colour of dry litmus paper. Q.8. While diluting an acid why is it recommended that the acid should be added to water and not water to the acid? Answer. The process of mixing water to concentrated acid is highly exothermic in which a large amount of heat is evolved. (i) When the concentrated acid is added to the water, then the heat is evolved gradually and easily absorbed by the large amount of water. (ii) If water is added to concentrated acid then a large amount of heat is evolved at once. This heat changes some of the water to steam explosively which can splash the acid on our face or clothes and cause acid burns. Q.9. How is the concentration of hydronium ions (H 3 O + ) affected when a solution of an acid is diluted? Answer. On dilution of an acid solution, the concentration of hydronium ions (H 3 O + ) per unit volume decreases. Q.10. How is the concentration of hydroxide ions (OH - ) affected when excess base is dissolved in a solution of sodium hydroxide? Answer. Concentration of OH - ions per unit volume in the solution increases. Q.11. You have two solutions, A and B. The ph of the solution A is 6 and ph of the solution B is 8. Which solution has more hydrogen ion concentration? Which of these is acidic and which one is base? Answer. (a) Solution A of lower ph value of 6 has more hydrogen ion concentration. (b) Solution A oh ph value 6 is acidic and the solution B of ph value 8 is basic. Q.12. What effect does the concentration of H + (aq) ions have on the nature of the solution? Answer. Higher the concentration of H + ions in a solution, more acidic is the solution. Q.13. Do basic solution have H + (aq) ions? If yes, then why are these basic? Answer. Even the basic solutions have hydrogen ions [H + (aq) ions] in them which

20 come from the ionization of water in which the base is dissolved. They are basic because the concentration hydroxide ions [OH - ions] in them is much more than the concentration of hydrogen ions. Q.14. Under what soil condition do you think a farmer would spread or treat the soil of his fields with quick lime (calcium oxide) or slaked lime (calcium hydroxide) or chalk (calcium carbonate)? Answer. A farmer would treat the soil of his fields with quick (calcium oxide) or slaked lime (calcium hydroxide) or slaked lime (calcium hydroxide) or chalk (calcium carbonate) if the soil is too acidic, having a low ph value. All these materials are bases and hence react with the excess present in the soil and reduce its acidity. Q.15. What is the common name of the compound CaOCl 2. Answer. Bleaching powder. Q.16. Name the substance which on treatment with chlorine yields bleaching powder? Answer. Calcium Hydroxide [Ca(OH) 2 ]. Q.17. Name the sodium compound which is used for softening hard water. Answer. Sodium carbonate (washing soda). Q.18. What will happen if a solution of sodium hydrogen carbonate is heated? Answer. Sodium carbonate is formed. Q.19. Write an equation to show the reaction between plaster of paris and water? Answer. CaSO 4. ½ H 2 O(s) + 1½ H 2 O(l) CaSO 4.2H 2 O(s) Q.20. A solution turns red litmus blue, its ph is likely to be (a) 1 (b) 4 (c) 5 (d) 10 Answer. The solution which turns red litmus blue is basic. Hence its ph should be greater than 7. Therefore (d) is the correct option. Q.21. A solution reacts with crushed eggshells to give a gas that turns lime water milky. The solution contains (a) NaCl (b) HCl

21 (c) LiCl (d) KCl Answer. The eggshells are made of calcium carbonate and the gas which turns lime water milky is carbon dioxide. Carbon dioxide gas can be formed by action of an acid solution on calcium carbonate (or eggshells). So, the solution contains HCl. Q ml of solution of NaOH is found to be completely neutralized by 8 ml of a given solution of HCl. If we take 20 ml of the same solution of NaOH, the amount of HCl solution (the same solution as before) required to neutralize it will be (a) 4 ml (b) 8 ml (c) 12 ml (d) 16 ml Answer: In this case the amount of the same HCl solution required to neutralize,it is also double. So, the correct option is (d). Q.23. Which one of the following types of medicines is used for treating indigestion? (a) Antibiotic (b) Analgesic (c) Antacid (d) Antiseptic Answer. ( c) Antacid Q.24. Write word equations and then balanced equations for the reactions taking place when (a) dilute sulphuric acid reacts with zinc granules. (b) dilute hydrochloric acid reacts with magnesium ribbon. (c) dilute sulphuric reacts with aluminium powder. (d) dilute hydrochloric acid reacts with cross fillings. Answer. (a) The word equation is: Zinc + Sulphuric acid Zinc sulphate + Hydrogen The balanced equation will be : Zn + H 2 SO 4 ZnSO 4 + H 2 (b) the word equation is : Magnesium + Hydrochloric acid Magnesium Chloride + Hygrogen The balanced equation will be:

22 Mg + 2HCl MgCl 2 + H 2 (c) The word equation is : Aluminium + Sulphuric acid Aluminium Sulphate + Hydrogen The balanced equation will be : 2Al + 3H 2 SO 4 Al 2 (SO 4 ) 3 + 3H 2 (d) the word equation is : Iron + Hydrochloric acid Iron(II) + Chloride + Hydrogen The balanced equation will be : Fe + 2HCl FeCl 2 + H 2 Q. 25.Compunds such as alcohols and glucose also contain hydrogen but are not categorised asacids. Describe an activity to prove it. Answer. Only those substances containing hydrogen are considered to be acids which dissolve in water to produce hydrogen ion [H + (aq) ions]. The hydrogen containing compounds such as glucose and alcohol are not categorised as acids because they do not produce hydrogen ions [ H + (aq) ions] when dissolved in water. Activity: Take 100 ml beaker and place cork in which two nails are fixed, in the beaker. Now connect the nails to the two terminals of 6 volt battery. Then pour some glucose in the beaker and switch on. The bulb does not glow and ammeter does not show any deflection. This shows that glucose solution do not conduct electricity. So, they are categorised as acids. Q.26.Why does distilled water not conduct electricity,whereas rainwater does Answer: Distilled water does not conduct electricity because it does not contain any ion compounds(like acids,bases or salts) dissolve in it. When rain water falls to the earth through the atmosphere,is dissolves an acidic gas CO from the air and forms some carbone acid(h 2 CO 3 ). Carbonic acid provides some H + (aq)ions and CO 3 2- (aq) ions to rain water. Due to the presence of these ions,rain water conducts electricity. Q.27.Why do acids not show acidic behavior in the absence of water? Answer. In case of acid water helps in the disssociation to give hydronium ions (H 3 O + ). In absence of water hydronium ions are not produced. That s why the acid show acidic behaviour only in the presence of water.

23 Q.28. Five solutions A, B, C, D and E when tested with universal indicator showed ph of 4, 1, 11, 7 and 9 respectively. Which solution is (i) Neutral (ii) Strongly alkaline (iii) Strongly acidic (iv) Weakly acidic (v) Weakly alkaline? Arrange the ph in the increasing order of hydrogen ion concentration. Answer. (i) Neutral : D(pH = 7) (iii) Strongly alkaline : C(pH = 11) (iv) Strongly acidic : B(pH = 1) (v) Weakly acidic : A(pH = 4) (vi) Weakly alkaline : E(pH = 9) Increasing order of hydrogen ion concentration C(11) < E(9) < D(7) < A(4) < B(1) Q.29. Equal length of magnesium ribbons are taken in test tubes A and B. Hydrochloric acid (HCl) is added to test tube A while acetic acid (CH 3 COOH) is added to test tube B. In which test tube will the fizzing occur more vigorously and why? Answer: Fizzing occurs due to the evolution of hydrogen gas produced by the action of acid on magnesium ribbon. Fizzing will occur more vigorously in test tube A because hydrochloric acid is a strong acid containing more hydrogen ions [H + (aq) ions]. Acetic is a weak acid containing less amount of hydrogen ions and hence produces slow fizzing. Q.30. Fresh milk has ph of 6. How do you think the ph will change as it turns into curd? Explain your answer. Answer. When the milk turns into curd, its ph will fall below 6 i.e., will become more acidic. This is because an acid (lactic acid) is produced when milk turns into curd. Q.31. A milk man adds a very small amount of baking soda to a fresh milk. (a) why does shift the ph of the fresh milk from 6 to slightly alkaline (b) why does milk take a long time to set as curd Answer. (a) Fresh milk is made slightly alkaline by adding a little of baking soda so that it may not get sour easily due to the formation of lactic acid in it.

24 (b) the slightly alkaline milk takes a longer time to set into curd because the lactic acid being formed during curdling has to first neutralize the alkali present in it. Q.32. Plaster of paris should be stored in a moisture proof container. Explain why? Answer. Plaster f paris absorbs water and set into a hard mass, which makes the plaster of paris unusable. Q.33. What is neutralization reaction? Give two examples Answer. When an acid reacts with a base to form salt and water it is called neutralization reaction. For example (i) NaOH + HCl NaCl + H 2 O Sodium Hydrochloric sodium water Hydroxide acid chloride (base) (acid) (ii) KOH + HNO 3 KNO 3 + H 2 O Potassium nitric potassium water Hydroxide acid nitrate (base) (acid) Q.34. Write two important uses of washing soda and baking soda? Answer. Washing soda: (i) It is used for washing clothes (laundry purposes) (ii) It is used for softening water. Baking soda: (i) It used for preparing baking powder. (ii) It is used as an antacid. IMPORTANT NCERT ACTIVITIES Activity 2.1 AIM : To tst the given samples with the help of red litmus solution, blue litmus solution, phenolphathalein and methyl orange indicators. MATERIAL REQUIRED : Samples of hydrochloric acid (HCl), sulphuric acid (H 2 SO 4 ), nitric acid (HNO 3 ), acetic acid (CH 3 COOH), sodium hydroxide (NaOH), calcium hydroxide [Ca(OH) 2 ], potassium hydroxide (KOH), magnesium hydroxide [Mg(OH) 2 ] and ammonium hydroxide (NH 4 OH) PROCEDURE:

25 1. Take each of the above solutions in separate test tubes. 2. Test the nature of these solutions by adding a drop of red litmus solution, blue litmus solution, phenolphathalein and methyl orange indicators. Observe the change in Colour and Record your Observations: Sample solution Red litmus solution Blue litmus solution Phenalphathalein solution indicators Methyl orange indicator HCl H 2 SO 4 HNO 3 CH 3 COOH NaOH Ca(OH) 2 KOH Mg(OH) 2 NH 4 OH No Change No Change No Change No Change Blue Blue Blue Blue Blue Red. Red Red Red No Change No Change No Change No Change No change (Colourless after sometime) Colourless Colourless Colourles Colourless Pink Pink Pink Pink Pink Pink Pink Pink Pink Yellow Yellow Yellow Yellow Yellow (Colourless after sometime) OBSERVATION : Acidic substances turn blue litmus red. Basic substances turn red litmus blue. Phenolphthalein remains colourless in acidic substances whereas it becomes pink in basic substances. Methyl orange becomes pink in acidic substances and yellow in basic substances. CONCLUSIONS : HCl, H 2 SO 4, HNO 3 and CH 3 COOH are acidic in nature while NaOH, Ca(OH) 2, KOH, Mg(OH) 2 and NH 4 OH are basic in nature. ACTIVITY 2.2

26 AIM : To test the given samples with help of olfactory indicators, (onion extract). MATERIAL REQUIRED : Take finely chopped onions in a plastic bag aloing with some strips of clean cloth, dilute HCl solution, dilute NaOH solution. PROCEDURE : 1. Tie up the bag tightly and leave overnight in the fridge. 2. Take two of the cloth strips (which are used for acids and bases) and check their odour. 3. Keep the cloth stirps on a clean surface and put a few drops of dilute HCl solution on one strip and a few drops of dilute NaOH solution on the other. 4. Rinse both cloths strips with water and again ckeck their odour. 5. Note your observations. OBSERVATIONS : Onion has a characteristics smell. When basix solution, like sodium hydroxide solution is added to cloth strip treated with onions, then the onion smell cannot be detected. An acidic solution like hydrochloric acid, however does not destroy the smell of onions. CONCLUSIONS : HCl is acedic in nature and NaOH is basic in nature. ACTIVITY 2.3 AIM: To test the given samples with the help of olfactory indicators (vanilla extract). MATERIAL REQUIRED: Dilute vanilla essence, dilute HCl, dilute NaOH, two test tubes. PROCEDURE: 1. Take some dilute HCl solution in one test tube and dilute NaOH solution in another. 2. Add a few drops of dilute vanilla essence to both test tubes and shake well. 3. Shake the test tubes. 4. Note your observations. OBSERVATION: Vanilla extract has a characteristic pleasant smell. If a basic is added to vanilla extract, then we cannot detect the characteristic smell of vanilla extract. An acid substance however, does not destroy the smell of vanilla extract.

27 CONCLUSION: Dilute HCl solution is acidic in nature and dilute NaOH is basic in nature. ACTIVITY 2.4 AIM: To show that acid reacts with metals to liberate hydrogen gas. MATERIAL REQUIRED: Dil.H 2 SO 4 test tube, zinc granules, match stick, candle, delivery tube, stand etc. PROCEDURE (Case A): 1. Take about 5ml of dilute sulphuric acid in a test tube and add a few tube and ad a few pieces of zinc granules to it. 2. Note your observation. OBSERVATION: It is observed that a brisk reaction takes place at the surface of zinc granules. CONCLUSION: This shows that reaction is taking place with the evolution of gas. PROCEDURE (Case B): 1. Pass the gas being evolved through the soap solution. OBSERVATION: The soap bubbles filled with the gas rise up. CONCLUSION: This shows that the gas is lighter than soap solution. PROCEDURE (Case C): 1. Take burning candle near a gas filled bubble. OBSERVATION: The bubble bursts and the gas present in it catches fire with pop sound. CONCLUSION: This shows that gas is hydrogen.

28 ACTICVITY 2.5 AIM: To show the reaction of metal with alkali. MATERIAL REQUIRED: Granulated zinc metal, test tube, sodium hydroxide. PROCEDURE: 1. Place few pieces of granulated zinc in the test tube. 2. Add 2ml of sodium hydroxide solution and warm the contents of the test tube. 3. Record the observation. OBSERVATION: Zinc metal dissolves in sodium hydroxide and form sodium zincate (Na 2 ZnO 2 ) and hydrogen gas (H 2 ). ACTIVITY 2.6 AIM: To show acid reacts with metal carbonate to liberate carbon dioxide. MATERIAL REQUIRED: Two test tubes, label them as A and B, 0.5gm sodium carbonate, 0.5gm sodium hydrogen carbonate, dilute HCl, lime water [Ca(OH) 2 ].

29 PROCEDURE: 1. Take two test tubes. 2. Label test tube as A and B. 3. Take about 0.5gm of sodium carbonate (Na 2 CO 3 ) in test tube A and about 0.5gm of sodium hydrogen carbonate (NaHCO 3 ) in test tube B. 4. Add about 2mL of dilute HCl to both the test tube. 5. Note your observation. OBSERVATION: Acid reacts with metal carbonate and metal hydrogen carbonate to give salt, carbon dioxide and water. CHEMICAL REACTION: Test tube A: Na 2 CO 3 (s) + 2HCl(aq) 2NaCl(aq) + H 2 O(l) + CO 2 (g) Test tube B: NaHCO 3 (s) + HCl(aq) NaCl(aq) + H 2 O(l) + CO 2 (l) PROCEDURE: 1. Pass the gas produced in each case through lime water [Ca(OH) 2 ]. 2. Note your observation. OBSERVATION: We observe that the lime water turns milky. CONCLUSION: Lime water turns milky, showing that the gas evolved is carbon dioxide, and it is due to the formation of white precipitate of calcium carbonate. Ca(OH) 2 (aq) + Co 2 (g) CaCO 3 (s) + H 2 O(l) (Lime water ) (White ppt)

30 If excess of carbon dioxide gas is passed through lime water, then the white precipitate formed first dissolves due to the formation of a soluble salt called hydrogen carbonate, and the solution becomes clear again. CaCO 3 (s) + Co 2 (g) + H 2 O(l) (white ppt) ACTIVITY 2.7 Ca(HCO 3 ) 2 (aq) (Soluble in water) AIM: To demonstrate neutralization reaction between acid and base. MATERIAL REQUIRED: 2mL of dilute NaOH, one test tube, two drops of phenolphthalein solution. PROCEDURE (A) : 1. Take about 2mL of dilute NaOH solution in a test tube 2. Add 2 or 3 drops of phenolphthalein solution and observe the colour of the solution. OBSERVATION: The colour of the solution will turn pink. CONCLUSION: The solution will turn pink, which shows that it is basic in nature. PROCEDURE (B) : 1. Add dilute HCl to the above solution drop by drop. 2. Observe the colour change for the reaction mixture. OBSERVATION: The pink colour of the solution in the test tubes just disappears. The solution becomes colourless. CHEMICAL REACTION: NaOH + HCl NaCl + H 2 O CONCLUSION: All the sodium hydroxide base taken in the test tube has been completely neutralized by hydrochloric acid. The colour of the phenolphthalein indicator changes from pink to colourless because no more sodium hydroxide base is left unreacted in the test tube. The reaction mixture has become neutral. It is an example of neutralization reaction. ACTIVITY 2.8 AIM: To study the reaction of metallic oxide with acids.

31 MATERIAL REQUIRED: Small amount of copper oxide, a beaker and dilute hydrochloric acid. PROCEDURE: 1. Take a small amount of copper oxide in a beaker. 2. Observe its colour. 3. Add dilute hydrochloric acid. 4. Observe the change in colour. OBSERVATION: The black copper oxide changes to blue-green coloured copper sulphate solution. CHEMICAL REACTION: CuO(s) + 2HCl(dil.) CuCl 2 (aq) + H 2 O(l) Black copper blue-green oxide CONCLUSION: Bases react with acids to form salt. ACTIVITY 2.9 AIM: To show that solution of an acid can conduct electricity. MATERIAL REQUIRED: Hydrochloric acid, two nails, cork, 100mL beaker, 6 volt battery, bulb and switch. PROCEDURE: 1. Fix two nails on the cork. 2. Connect the nails to the two terminals of a 6 volt battery through a bulb and a

32 switch 3. Place the cork in a 100mL beaker. 4. Now pour some dilute HCl in the beaker. 5. Switch in the current. 6. Note your observation. OBSERVATION: The bulb will start glowing. CONCLUSION: Solution of acid can conduct electricity. ACTIVITY 2.10 AIM: To show that glucose and alcohol solutions do not conduct electricity. MATERIAL REQUIRED: Solutions of glucose or alcohols, two nails on a cork, 100mL beaker, 6V volt battery, a bulb and a switch. PROCEDURE: 1. Fix two nails on a cork and place the cork in a 100mL beaker. 2. Connect the nails to the terminals of a 6V battery through a bulb and a switch as shown in figure. 3. Now pour some glucose or alcohol solutions, in a beaker. 4. Switch on the current. 5. Not your observation. OBSERVATION: Bulb does not glow. CONCLUSIONS: