C3.1 Periodic Table Revision Higher

Transcription

1 C3. Periodic Table Revision Higher Q. The periodic table on the Data Sheet may help you to answer this question. (a) Newlands and Mendeleev both designed periodic tables in which the elements were put in the order of their relative atomic masses. When the elements are put in this order a few of them are placed incorrectly when compared with a modern periodic table. (i) Give one example of a pair of elements that would be placed incorrectly if they were in the order of their relative atomic masses.... and... () Explain why placing these two elements in the order of their relative atomic masses would not be correct. () In the modern periodic table the elements are put in order of their atomic (proton) numbers. Explain how the positions of the elements in the periodic table are linked to the electronic structure of their atoms. (Total 4 marks) Q2. The periodic table was developed over about 200 years. In 869, a Russian scientist, Dimitri Mendeleev, arranged the 60 known elements into his periodic table. Mendeleev put the elements in order of their increasing atomic weights. Then he put elements with similar chemical properties in the same columns. He left gaps in his periodic table. The modern periodic table on the Data Sheet may help you to answer these questions. (a) Mendeleev s periodic table was produced without any knowledge of the atomic structure of elements. State why Mendeleev left gaps in his periodic table Page ()

2 The modern periodic table was produced with knowledge of the atomic structure of elements. The modern periodic table is an arrangement of the elements in terms of their atomic structures. Explain how (3) (Total 4 marks) Q3. Read the information about the development of the periodic table and answer the questions that follow: The modern periodic table on the Data Sheet may help you to answer these questions. (a) Döbereiner suggested that calcium (Ca), strontium (Sr) and barium (Ba) were also a triad. Use relative atomic masses to explain why. () Page 2

3 Suggest why Döbereiner s ideas were replaced by those of Mendeleev. () (c) Lithium, sodium and potassium are in Group. All these elements react with water. Describe what you see when potassium is added to water. (d) In terms of electronic structure, explain why: (i) elements in the same group of the periodic table have similar chemical properties () transition elements have similar properties even though they are not in the same group (iii) in Group, lithium is less reactive than potassium. (Total 9 marks) Q4. Lithium is a very reactive metal. (a) Lithium reacts with cold water. Page 3

4 (i) Which physical property of lithium is seen during this reaction?... () Which chemical property of lithium will be shown by the universal indicator?... () Complete the sentence by writing in the missing numbers. Lithium has an atomic number of 3 and a mass number of 7. This means that an atom of lithium has... protons... electrons and... neutrons. (3) (Total 5 marks) Q5. The following article appeared recently in the Manchester Gazette. Sodium Drum Blaze Scare A 20 litre drum containing sodium burst into flames when it reacted violently with rainwater at a Manchester factory. It is believed that the sodium, which is normally stored under oil, had been accidentally left outside with the lid off. A factory worker put out the blaze before the fire services arrived, and a leading fire fighter said, It was fortunate that potassium wasn t involved as it would have reacted more violently and exploded. These Group alkali metals can be very dangerous. (a) Group metals are stored under oil. Suggest why.... () Balance the equation which represents the reaction between sodium and water. Na + H 2O NaOH + H 2 () (c) Explain why the Group metals are called the alkali metals () Page 4

5 (d) Explain, in terms of electrons, why potassium reacts more violently than sodium (3) (Total 6 marks) Q6. Three elements in Group 2 of the periodic table are beryllium (Be), magnesium (Mg) and calcium (Ca). Their mass numbers and proton numbers are shown below. The electronic structure is shown for beryllium and calcium. (a) In a similar way, draw the electronic structure for magnesium. (3) The three elements have similar chemical properties The reactivity of these elements with non-metals, increases from beryllium to magnesium to calcium. Explain these two statements in terms of atomic structure. (6) (Total 9 marks) Page 5

6 Q7. (a) What is the name given to the block of elements in the middle of the Periodic Table which includes vanadium? () Some of the properties of vanadium are shown in this list. It has a high melting point. It is a solid at room temperature. It is a conductor of electricity. It is a good conductor of heat. It forms coloured compounds. If forms crystalline compounds. It forms compounds that are catalysts. Select two properties, from the list above, which are not typical of a Group metal (Total 3 marks) Q8. Complete the table which shows some of the physical properties of bromine, chlorine and iodine. Melting point in C Boiling point in C Physical state at 23 C Colour of vapour Bromine Chlorine greenish Iodine (Total 2 marks) Page 6

7 Q9. A teacher demonstrated the reactivity of the halogens to some students. Halogen vapour was passed over heated iron wool in a fume cupboard. The teacher s observations are shown in the table below. Observations During the reaction Bromine The iron wool glowed Chlorine The iron wool glowed After the reaction A red brown solid had been produced A dark brown solid had been produced Iodine The iron wool did not glow A black solid had been produced (a) From these observations what conclusion can be made about the order of reactivity of the three halogens? Explain your conclusion In terms of electronic structures, explain why iodine is less reactive than bromine Page 7 (3) (Total 5 marks)

8 Q0. In sea water the bromine is present as bromide ions (Br ). The equation below shows how chlorine can be used to displace bromine from sea water. Cl 2(g) + 2Br (aq) Br 2(g) + 2Cl (aq) Explain, as fully as you can, why chlorine can displace bromine from sea water. To obtain full marks your answer should refer to electronic structure (Total 3 marks) Page 8

9 C3.2 Water Chemistry Revision Higher Q. Rainwater falling on limestone rocks can form caves. (a) Complete the sentences by choosing the correct words from the box. acidic alkaline dissolves hard reacts soft tastes You may use each word once or not at all. Rainwater is an... solution which... with limestone. The solution formed in the lake is known as... water. One advantage of drinking the water from the lake is that it... better than rainwater. (4) Samples of water were tested by shaking with soap solution. The results are shown in the table. Water sample (50 cm 3 ) Volume of soap solution to form a lather in cm 3 lake 5 boiled lake 3 rain (i) What is seen when only 0 cm 3 of soap solution is shaken with 50 cm 3 of water from the lake? () Why did the rainwater need only cm 3 of soap solution to form a lather? () Page 9

10 (iii) Why did the water from the lake need 5 cm 3 of soap solution to form a lather? () (iv) Explain why boiled water from the lake needed only 3 cm 3 of soap solution to form a lather. (Total 9 marks) Q2. Good quality water is needed for a healthy life. In the United Kingdom, obtaining safe water for drinking is as simple as turning on a tap. The water is made safe to drink by water companies. However, in many parts of Africa and Asia, water used for drinking is contaminated and untreated. It is estimated that 2.2 million people die each year as a result of drinking contaminated water. DADA DANESHANANDA, Man with filtered water from the Mafi-Zongo water project. (a) Sea water is not used as drinking water. Suggest why () Explain why water for drinking is filtered and then treated with chlorine (Total 3 marks) Page 0

11 Q3. Two problems of hard water are scale and scum, as shown in the pictures of a heating element and a wash basin. (a) Explain the difference between scale and scum Explain how hard water can be made soft using an ion-exchange column. (Total 4 marks) Q4. Water is a natural resource. Drinking water in some parts of the UK is soft, but in other parts drinking water is hard. Calcium ions in water cause water to be hard. There are two types of hard water, permanent hard water and temporary hard water. Permanent hard water can be caused by calcium sulfate (CaSO 4) dissolved in the water Temporary hard water can be caused by calcium hydrogencarbonate (Ca(HCO 3) 2) dissolved in the water (a) Temporary hard water causes the formation of scale on heating elements. Page

12 (i) Explain how scale forms on heating elements Suggest why scale on heating elements causes problems () Permanent hard water can be softened. (i) Explain how adding sodium carbonate (Na 2CO 3) softens permanent hard water Explain how a water filter containing carbon, silver and ion exchange resin softens permanent hard water (Total 7 marks) Q5. This information has been taken from two bottles of Australian spring water. Page 2

13 (a) The labels show the names of the ions present in Ridgway and Homeland spring waters. Describe how these ions got into the water. Both Ridgway and Homeland spring waters are hard. (i) There are two ions shown on the labels which make these spring waters hard. Name one of these ions. () Ridgway spring water is about twice as hard as Homeland spring water. Use the information on the labels to explain why. (iii) Describe how you could use soap solution to show that Ridgway spring water is about twice as hard as Homeland spring water. You should state how the experiment is made fair. (3) Q6. The label shows the ions present in the bottle of spring water. This water is temporarily hard. (a) Name the compound that would be present in the greatest amount if this water were evaporated to dryness. (i) What is hard water? State one advantage of hard water. () Page 3

14 (c) Describe an experiment that would show that this water is temporarily hard. (4) (d) This hard water may be softened as shown. What name is given to this process? () Q7. The chemical compositions of two samples of hard water, A and B, are shown in the table. Sample A Sample B ph 9 8 Ions present: Concentration in mg/litre Ca 2+ Mg 2+ Na HCO 3 CI 2 SO 4 NO Page 4

15 (a) What does the ph value tell you about these samples? Use the information in the table to explain what is meant by hard water. () (c) What would be the effect of using temporarily hard water in a kettle? (d) (i) Explain which sample of water is permanently hard. (3) How could this hardness be removed? () (e) State one advantage of drinking hard water. () Page 5

16 C3.3 Calculating and explaining energy changes Revision Higher Q. Methanol can be made when methane reacts with oxygen. (a) The energy level diagram for this reaction is shown below. (i) What is the energy change represented by A?... () Use the energy level diagram to explain how it shows that this reaction is exothermic A student did an experiment to find the energy released when methanol burns in air. The student: weighed a spirit burner containing methanol set up the equipment as shown in the diagram recorded the initial temperature Page 6

17 lit the spirit burner put out the flame when the temperature of the water had risen by about 20 C stirred the water and recorded the highest temperature of the water reweighed the spirit burner containing the methanol. The student repeated the experiment and recorded his results. Experiment Experiment 2 Experiment 3 Initial mass of spirit burner and methanol in g Final mass of spirit burner and methanol in g Initial temperature in C Highest temperature in C Temperature change in C Use the diagram and the information in the table to answer the questions. (i) The main error in this experiment is energy loss. Suggest one way that the equipment could be changed to reduce energy loss.... () The temperature change in Experiment 2 is greater than the temperature change in Experiment and Experiment 3. Explain why (iii) Suggest one reason why the student repeated the experiment.... () (iv) Use the temperature change in Experiments and 3 to calculate how much energy is released when g of methanol burns. The equation that you need to use is: Energy released in joules = 00 x 4.2 x mean temperature change Burning g of methanol releases... J Page 7 (Total 9 marks)

18 Q2. Read the information about energy changes and then answer the questions. A student did an experiment to find the energy change when hydrochloric acid reacts with sodium hydroxide. The equation which represents the reaction is: HCl + NaOH NaCl + H 2O The student used the apparatus shown in the diagram. The student placed 50 cm 3 of hydrochloric acid in a glass beaker and measured the temperature. The student then quickly added 50 cm3 of sodium hydroxide solution and stirred the mixture with the thermometer. The highest temperature was recorded. The student repeated the experiment, and calculated the temperature change each time. (a) The biggest error in this experiment is heat loss. Suggest how the apparatus could be modified to reduce heat loss. () Suggest why it is important to stir the chemicals thoroughly. () (c) Which one of these experiments was probably carried out on a different day to the others? Explain your answer. () Page 8

19 (d) Suggest why experiment 4 should not be used to calculate the average temperature change. () (e) Calculate the average temperature change from the first three experiments. Answer =... C () (f) Use the following equation to calculate the energy change for this reaction. energy change in joules = average temperature change Answer =... J () (g) Which one of these energy level diagrams, A or B, represents the energy change for this reaction? Explain why. () (Total 7 marks) Q3. A student burned four fuels and compared the amounts of energy they produced. The student set up the apparatus as shown in the diagram. The heat produced when each fuel was burned was used to raise the temperature of 00 g of water. The student noted the mass of fuel burned, the increase in temperature and whether the flame was smoky. Page 9

20 The results are shown in the table. Fuel Mass of fuel burned (g) Temperature increase ( C) Type of flame Ethanol 4 24 Not smoky Methanol 3 9 Not smoky Peanut oil 2 20 Smoky Vegetable oil 5 Smoky (a) The student suggested that the vegetable oil was the best fuel for producing heat. Explain why. Suggest an environmental problem that could be caused when large amounts of vegetable oil are burned. Suggest how the problem could be overcome. (c) An energy level diagram for the burning of vegetable oil is shown below. Which of the energy changes A, B or C: (i) represents the activation energy... shows the amount of energy given out during the reaction? () Page ()

21 Q4. HYDROGEN FUEL OF THE FUTURE It has been suggested that hydrogen could be used as a fuel instead of the fossil fuels that are used at present. The equation below shows how hydrogen burns in air. 2H 2 + O 2 2H 2O + heat The hydrogen would be made from water using energy obtained from renewable sources such as wind or solar power. The water splitting reaction requires a lot of energy. (a) Hydrogen was successfully used as a fuel for a Soviet airliner in 988. Why would hydrogen be a good fuel for use in an aeroplane? The water splitting reaction is shown in the equation below. 2H 2O 2H 2 + O 2 Calculate the energy needed to split the water molecules in the equation into H and O atoms. 2H 2O 4H + 2O (c) On the Periodic Table, hydrogen is placed on its own at the top and in the middle. It is difficult to position it because it has the properties of metals and non-metals. (i) Where would you expect hydrogen to be placed on the periodic table on the basis of the arrangement of electrons in hydrogen atoms? () Explain your answer. () Give one way in which hydrogen behaves like a metal. Page 2 ()

22 (iii) Give one way in which hydrogen behaves like a non-metal. () (Total 8 marks) Q5. Hydrogen could be the fuel used in all cars. One advantage is that when hydrogen reacts with oxygen only water is produced. The chemical equation for this reaction is: 2 H 2 + O 2 2H 2O This equation can be written showing the structural formulae. 2 H H + O O 2 H O H (a) Use the bond energies in the table to calculate the energy change for this reaction. Bond Bond energy in kj H H 436 O = O 498 O H Energy change =... kj (3) Suggest why the bond energy of O = O is higher than the bond energies of both H H and O H () (c) In terms of bond energies, explain why hydrogen can be used as a fuel (Total 6 marks) Page 22

23 Q6. Methanol (CH 3OH) can be made by reacting methane (CH 4) and oxygen (O 2) in the presence of a platinum catalyst. The reaction is exothermic. An equation that represents the reaction is: 2CH 4 + O 2 2CH 3 OH (a) The energy level diagram for this reaction is given below. (i) Use the diagram to explain how you know that this reaction is exothermic () Explain, in terms of the energy level diagram, how the platinum catalyst increases the rate of this reaction () The equation can also be written showing the structural formulae of the reactants and the product. Page 23

24 (i) Use the bond energies given in the table to help you to calculate the energy change for this reaction. Bond Bond energy in kj C H 435 O = O 498 C O 805 O H Energy change =... kj (3) In terms of the bond energies, explain why this reaction is exothermic () (Total 6 marks) Q7. You will find the information on the Data Sheet helpful when answering this question. This equation shows the reaction between ethene and oxygen. C 2H 4 + 3O 2 2CO 2 + 2H 2O The structural formulae in the equation below show the bonds in each molecule involved. Page 24

25 Use the three stages shown at (a), and (c) below to calculate the nett energy transfer when the formula mass ( mole) of ethene reacts with oxygen. (a) Write down the bonds broken and the bonds formed during the reaction. (Some have already been done for you.) Calculate the total energy changes involved in breaking and in forming all of these bonds. (Some have already been done for you.) (4) (c) Describe, as fully as you can, what the figures in tell you about the overall reaction. Page 25

26 C3.4 Further analysis and quantitative chemistry Revision Higher Q. The label is from a packet of Low Sodium Salt. (a) A student tested some Low Sodium Salt to show that it contains carbonate ions and chloride ions. (i) Describe and give the result of a test for carbonate ions. A student identified chloride ions using acidified silver nitrate solution. State what you would see when acidified silver nitrate solution is added to a solution of Low Sodium Salt. () (iii) Flame tests can be used to identify potassium ions and sodium ions. Suggest why it is difficult to identify both of these ions in Low Sodium Salt using a flame test. () ( Q2. Tennis players sometimes use smelling salts to help revive them. The active chemical in smelling salts is ammonium carbonate, (NH 4) 2CO 3. Describe how smelling salts can be tested to show that they contain ammonium ions and carbonate ions. Give the results of the tests. (a) Test and result for ammonium ions Test and result for carbonate ions (Total 4 marks) Page 26

27 Q4. (a) Four bottles of chemicals made in the 880s were found recently in a cupboard during a Health and Safety inspection at Lovell Laboratories. The chemicals are correctly named. You are provided with the following reagents: aluminium powder barium chloride solution acidified with dilute hydrochloric acid dilute hydrochloric acid silver nitrate solution acidified with dilute nitric acid sodium hydroxide solution. (i) Describe tests to show that these chemicals are correctly named. In each case give the reagent(s) you would use and state what you would see. Test and result for carbonate ions: Test and result for chloride ions: Test and result for nitrate ions: Page 27

28 Test and result for sulfate ions: (5) Suggest why a flame test would not distinguish between these four chemicals. () Instrumental methods of analysis linked to computers can be used to identify chemicals. Describe two advantages of using instrumental methods of analysis. Q5. A student carried out a titration to find the concentration of a solution of hydrochloric acid. The following paragraph was taken from the student s notebook. I filled a burette with hydrochloric acid cm 3 of 0.40 mol/dm 3 potassium hydroxide was added to a flask. 5 drops of indicator were added. I added the acid to the flask until the indicator changed colour. The volume of acid used was 35.0 cm 3. (a) What piece of apparatus would be used to measure 25.0 cm 3 of the potassium hydroxide solution? () Name a suitable indicator that could be used. () (c) Calculate the number of moles of potassium hydroxide used. Moles of potassium hydroxide =... mol (d) Calculate the concentration of the hydrochloric acid. The equation for the reaction is: KOH + HCl KCl + H 2O Concentration of hydrochloric acid =... mol/dm 3 (Total 6 marks) Page 28

29 Q6. An oven cleaner solution contained sodium hydroxide. A 25.0 cm 3 sample of the oven cleaner solution was placed in a flask. The sample was titrated with hydrochloric acid containing 73 g/dm 3 of hydrogen chloride, HCI. (a) Describe how this titration is carried out. (3) Calculate the concentration of the hydrochloric acid in mol/dm 3. Relative atomic masses: H ; Cl 35.5 Answer =... mol/dm 3 (c) 0.0 cm 3 of hydrochloric acid were required to neutralise the 25.0 cm 3 of oven cleaner solution. (i) Calculate the number of moles of hydrochloric acid reacting. Answer =... mol Calculate the concentration of sodium hydroxide in the oven cleaner solution in mol/dm 3. Answer =... mol/dm 3 Q7. (a) This label has been taken from a bottle of vinegar. Vinegar is used for seasoning foods. It is a solution of ethanoic acid in water. In an experiment, it was found that the ethanoic acid present in a cm 3 sample of vinegar was neutralised by cm 3 of sodium hydroxide solution, of concentration 0.20 moles per cubic decimetre (moles per litre). Page 29

30 The equation which represents this reaction is CH 3COOH + NaOH CH 3COONa + H 2O Calculate the concentration of the ethanoic acid in this vinegar: (i) in moles per cubic decimetre (moles per litre); Concentration =... moles per cubic decimetre in grams per cubic decimetre (grams per litre). Relative atomic masses: H = ; C = 2; O = 6. Concentration =... grams per cubic decimetre The flow diagram shows some reactions of ethanoic acid. Page 30

31 Give the name of: (i) gas A,. () alkali B,. () (iii) ester C,. () (iv) catalyst D,. () (v) carboxylic acid salt E.. () (Total 9 marks) Q8. (a) Vinegar is used for seasoning foods. It is a solution of ethanoic acid in water. In an experiment, it was found that the ethanoic acid present in a cm 3 sample of vinegar was neutralised by cm 3 of sodium hydroxide solution, of concentration 0.20 moles per cubic decimetre (moles per litre). The equation which represents this reaction is CH 3COOH + NaOH CH 3COONa + H 2O Calculate the concentration of the ethanoic acid in this vinegar: (i) in moles per cubic decimetre (moles per litre); Concentration =... moles per cubic decimetre in grams per cubic decimetre (grams per litre). Relative atomic masses: H = ; C = 2; O = 6. Concentration =... grams per cubic decimetre Page 3

32 C3.5 The production of ammonia Revision Higher Q. Early atmospheres on Earth contained ammonia (NH 3). (a) (i) Complete the sentence. Our atmosphere today is made up of about... % nitrogen. () Today we convert nitrogen back to ammonia mainly for the production of fertilisers. What do plants convert the nitrogen in these fertilisers into? () The conversion of nitrogen to ammonia is shown. (i) When making ammonia, what is one source of hydrogen? () Apart from ammonia, name one other product formed during this conversion. () (c) The main reaction is the formation of ammonia from nitrogen and hydrogen. (i) Complete and balance the equation for this reaction....(g) +...(g)...nh 3(g) Name the metal catalyst used in this reaction. () (iii) This reaction does not work successfully at room temperature (20 C) and needs a much higher temperature of 400 C. Explain why. Page 32

33 (d) Draw a diagram to show the arrangement of the electrons in a molecule of ammonia. The electron arrangement of each atom is hydrogen and nitrogen 2.5. Q2. Ammonia is used in the production of fertilisers. The flow diagram shows the main stages in the manufacture of ammonia. Study the flow diagram and then answer the questions. (a) What is the purpose of the iron in the reactor?... () In the reactor the equation to produce ammonia is: N 2(g) + 3H 2(g) 2NH 3(g) (i) The equation shows that the reaction is reversible. Explain how the reaction reaches an equilibrium.... () The best yield of ammonia at equilibrium is produced at a low temperature. Explain why Page 33

34 (iii) The best yield of ammonia at equilibrium is produced at a high pressure. Explain why () (Total 5 marks) Q3. Ammonia is made from nitrogen and hydrogen in the Haber process. N 2(g) + 3H 2 (g) 2NH 3 (g) (+ heat) Flow Chart for the Haber Process Effect of temperature and pressure on the amount of ammonia at equilibrium Page 34

35 (a) Use the information given above and your knowledge of the Haber process and reversible reactions to help you to answer this question. State which conditions of temperature and pressure would give the highest percentage of ammonia at equilibrium. Explain why. (4) The Haber process uses a temperature of 450 C and a pressure of 200 atmospheres. Explain why these conditions are chosen. (3) Q4. In the Haber process, nitrogen and hydrogen react to make ammonia. N 2(g) + 3H 2(g) nitrogen + hydrogen 2NH 3 (g) ammonia % ammonia present at equilibrium Pressure in atmospheres Temperature in ºC Page 35

36 The actual conditions used in the Haber process are usually 450 C and 200 atmospheres. (a) What effect does increasing the pressure have on the percentage of ammonia made? Use the balanced symbol equation to explain why. A lower temperature of 00 C gives high percentages of ammonia at most pressures. Why is this temperature not used in the Haber process? () (c) Describe and explain the effect of an increase in the temperature on the reaction between nitrogen and hydrogen in the Haber process. (3) (Total 6 marks) Page 36

37 C3.6 Alcohols, Carboxylic Acids and Esters Revision Higher Q. The structures shown are of the first two members of a homologous series of organic compounds. Methanol Ethanol (a) (i) Complete the diagram for propanol, the next member of the homologous series. C C C Propanol () Which one of the statements about ethanol is correct? Tick ( ) one box. Statement Tick ( ) Ethanol dissolves in water to form a neutral solution. Ethanol reacts with sodium to produce chlorine. Ethanol does not burn in air. () Ethanoic acid (CH 3COOH) can be produced from ethanol (CH 3CH 2OH). (i) What type of reaction happens when ethanoic acid is produced from ethanol?... () State one use of ethanoic acid.... Page 37 () (Total 4 marks)

38 Q2. The structures shown are of the first three members of a homologous series of alcohols. (a) (i) Draw a ring around the correct general formula for alcohols. C n H 2n+ OH C 2n H 2n+ OH C n H 2n+2 OH () What is the formula of the functional group for alcohols?... () Ethanol is the alcohol used in alcoholic drinks. (i) When ethanol dissolves in water the solution formed is not alkaline. Tick ( ) the reason why the solution formed is not alkaline. Reason Tick ( ) Ethanol can be used as a solvent. Ethanol dissolves in water to form hydroxide ions. Ethanol has only covalent bonds in its molecule. () Ethanol is used as a fuel because ethanol burns in oxygen. Complete and balance the chemical equation for this reaction. C 2H 5OH +...O 2 2 CO (c) Ethanol can be oxidised to produce the compound shown. Page 38

39 (i) Draw a ring around the correct answer to complete the sentence. acidic. When this compound dissolves in water, the solution formed is alkaline. neutral. () Ethanol reacts with this compound to produce the organic compound shown. C 2H 5OH + CH 3COOH CH 3COOC 2H 5 + H 2O Complete the sentence. The type of organic compound produced is.... () (Total 7 marks) Q3. (a) This label has been taken from a bottle of vinegar. Vinegar is used for seasoning foods. It is a solution of ethanoic acid in water. In an experiment, it was found that the ethanoic acid present in a cm 3 sample of vinegar was neutralised by cm 3 of sodium hydroxide solution, of concentration 0.20 moles per cubic decimetre (moles per litre). The equation which represents this reaction is CH 3COOH + NaOH CH 3COONa + H 2O Calculate the concentration of the ethanoic acid in this vinegar: Page 39

40 (i) in moles per cubic decimetre (moles per litre); Concentration =... moles per cubic decimetre in grams per cubic decimetre (grams per litre). Relative atomic masses: H = ; C = 2; O = 6. Concentration =... grams per cubic decimetre The flow diagram shows some reactions of ethanoic acid. Page 40

41 Give the name of: (i) gas A,. () alkali B,. () (iii) ester C,. () (iv) catalyst D,. () (v) carboxylic acid salt E.. () (Total 9 marks) Page 4

42 C3. Periodic Table Revision Higher Markscheme M. (a) (i) argon and potassium or tellurium and iodine or cobalt and nickel accept correct symbols allow argon and calcium it would place them in incorrect groups (owtte) idea of not being placed with elements which have similar properties or converse argument accept would not have same number of electrons in outer shell allow it would put them in wrong period if linked to argon and potassium / calcium do not accept reasons based just on protons do not accept metals and non-metals mixed up any two from: each successive atom has one more electron atoms in the same group have the same number of electrons in their outer shells / energy levels number of electrons in outer shell = group number across a period an energy level / shell is being filled in the next period the next energy level / shell is being filled accept period number = shell number M2. (a) for undiscovered elements 2 [4] because the elements are in order of number of electrons or proton number because the number of energy levels / shells is the number of the period because the number of electrons in the outer energy level / shell is the number of the group, except in the case of the noble gases [4] Page 42

43 M3. (a) 40 (Ca) + 37 (Ba) 2 = 88.5 accept a recognition that the average is near 88 or it is the average of the other two accept Sr is midway between Ca and Ba (c) eg newly discovered elements / atoms didn t fit (into triads) or didn t apply to all elements / atoms or lot of exceptions he = Döbereiner ignore Mendeleev left spaces or not enough evidence any two from: fizzes / bubbles / gas hydrogen alone is insufficient ignore incorrect name if gas stated violent / vigorous / explodes / very fast reaction accept container explodes ignore strong reaction floats / on surface ignore sinks moves (very quickly) melts (into a ball) bursts into flame accept (bright) light ignore colour / glow gets smaller / (reacts to) form a solution / dissolves / disappears etc steam / gets hot (owtte) ignore alkaline solutions or change in colour etc 2 (d) (i) same number of electrons in outer shell accept energy level for shell accept a correct reference to a specific group eg (all) have one electron in outershell / (all) lose one electron (when they react) electrons fill an inner / 3 rd shell accept energy level for shell accept d-level being filled accept specific reference to 3rd shell accept descriptions in terms of 3d & 4s etc Page 43

44 (iii) it = lithium accept energy level for shell or converse reasoning for potassium outer shell electron closer to nucleus accept fewer shells / smaller atom more (electrostatic) attraction (to nucleus) / electrons less likely to be lost accept less shielding / isn t much shielding ignore nucleus has more influence but accept nucleus has more influence over the outer electron(s) do not accept magnetic / gravitational attraction [9 M4. (a) (i) low density accept floats (on water) forms an alkaline solution with water accept alkali (metal) or basic do not accept group metal 3 or three (protons) 3 or three (electrons) 4 or four (neutrons) [5] M5. (a) acts as barrier between sodium and air / oxygen / water (vapour) accept because they are reactive ignore oil will not react 2Na + 2H 2O 2NaOH + H 2 allow multiples / fractions (c) these metals react with water producing an alkaline solution or Page 44

45 produce solution with ph greater than 7 / high ph owtte allow produce OH. ions not these metals are / form alkalis ignore strong ph (d) it = potassium outer electron must be mentioned once for all 3 marks bigger atom or outer shell electron further from nucleus or more shells or converse argument for sodium less reactive provided sodium is specified less attraction to nucleus or more shielding not less magnetic attraction outer electron more easily lost ignore potassium reacts more easily [6] M6. (a) each shell completed correctly [for written award mark] for mark each 3 idea that chemical reactions of metals, involves losing electrons for mark Page 45

46 these three elements have the same number of electrons in the outer shell/highest energy level gains mark but these three elements all have two electrons in the outer shell/highest energy level gains 2 marks All form ions with a 2+ charge gains all 3 of these marks reactivity depends on how easily the electrons are lost for mark the further the electrons are from the nucleus/the higher the energy level they are in, the more shells the atom has* then the more easily they are lost for mark in calcium the electrons are further from the nucleus than in magnesium than in beryllium for mark or as you go down the group... (*not just the more electrons...) 6 [9] M7. (a) transition / transitional metals / elements / d-block for one mark coloured catalyst (accept high melting point) for mark each 2 [3] M8. one mark for all the three physical states and one mark for both colours, i.e. marks are for fully correct columns liquid red or brown accept orange gas solid purple accept violet [2] M9. (a) the conclusion is that chlorine and bromine are more reactive than iodine any suitable comparisons about the Page 46 extent to which the iron

47 wool glowed eg because iron glowed with chlorine and bromine but did not glow with iodine iodine is less reactive than bromine because the iodine (atom) is bigger or outer electrons (level / shell) further from the nucleus accept converse for bromine therefore the forces attracting an incoming electron are weaker or there is more shielding of the forces attracting an incoming electron therefore the outer electron gained less easily Max 2 if no mention of outer energy level / shell or of outer electron(s) [5] M0. chlorine atom smaller than bromine atom / has fewer shells / chlorine is higher in the group than bromine so it is more reactive the outer electron / extra electron is more strongly attracted with chlorine than bromine / bromide (owtte) / more shielding with bromine / less shielding with chlorine an extra electron is more easily gained by chlorine or chlorine can take an electron from bromide ion (not bromine) for mark each [3] Page 47

48 C3.2 Water Chemistry Markscheme M. (a) acidic reacts hard tastes (i) scum / no lather / precipitate rain water is soft / pure / nothing dissolved / no limestone not distilled (iii) lake water is hard / not soft / contains calcium compounds / dissolved limestone not impurities (iv) softened by boiling / loses hardness temporary hardness removed / decomposition of calcium salts [9] M2. (a) contains (large amounts of) dissolved solids / difficult to remove dissolved solids allow salty / too much salt allow sea water makes you thirsty / vomit allow polluted / untreated / contaminated filtered: removes solids / removes insoluble material / dirt ignore large objects chlorine: kills/destroy bacteria/microbes/ germs etc allow disinfect / sterilise or gets rid of bacteria ignore purify / clean [3] Page 48

49 M3. (a) scale (solid) formed when heat decomposes dissolved calcium / magnesium compounds owtte allow: scale is formed when hard water is heated / boiled (to leave magnesium / calcium compounds) scale is calcium carbonate / CaCO 3 or magnesium carbonate / MgCO 3 ignore evaporate scum (ppt) formed when soap reacts with calcium / magnesium (ions) owtte allow scum is formed when hard water reacts with soap scum is calcium stearate / magnesium stearate calcium (ions) / Ca 2+ / magnesium (ions) / Mg 2+ replaced by hydrogen ions / H + / sodium ions / Na + [4] M4. (a) (i) on heating, the calcium hydrogencarbonate decomposes forming a scale of insoluble calcium carbonate the scale reduces the efficiency of the heating element or the scale increases energy costs / uses more energy (i) the sodium carbonate / carbonate ions react with calcium / magnesium ions, forming a precipitate of calcium carbonate / magnesium carbonate therefore the water is softened because this removes the calcium / magnesium ions, which cause hardness, from the water sodium / hydrogen ions are present in the ion exchange resin Page 49

50 therefore the water is softened because these ions take the place of calcium / magnesium ions that cause hardness in the water M5. (a) water came into contact with rocks / ground / soil ignore mountains erode gets first mark [7] ions or compounds or chemicals or they dissolved / soluble / leached / reacts / forms a solution do not accept gets picked up accept water dissolves them from the rocks for 2 marks (i) calcium or magnesium accept Ca 2+ or Mg 2+ or Ca or Mg do not accept Ca + alone answers must involve both calcium and magnesium totals required for 2 marks Ridgway: Ca + Mg = 53 Homeland: Ca + Mg = 27 accept there is (almost) twice as much Magnesium and Calcium in Ridgway water for mark (iii) equal volumes / quantities / amounts of water add soap with / shaking / mixing / agitation same amounts of soap = max 2 do not accept just add do not accept solid soap the harder sample (Ridgway) needs 2 more soap to give lather or the less hard sample (Homeland) needs half as much soap to give lather can get twice as much scum with harder (Ridgway) sample [8] Page 50

51 M6. (a) calcium allow formulae carbonate (i) soap allow 2 marks for contains CaSO 4 / Ca(HCO 3) 2 / Ca 2+ / Mg 2+ forms scum / no bubbles / no lather allow mark for contains Ca / Mg do not allow contains CaCO 3 taste / strengthen bones, teeth etc / health reason e.g. less heart disease / makes better beer (c) (shake with) soap; makes scum / no lather boil (a fresh sample) retest with soap result/comparison alternative answers: boil (not to dryness) cloudiness in water/some deposit formed if a comparison is made with a sample of a soft water, a further 2 marks would be possible (d) ion-exchange Page 5 [0]

52 M7. (a) weak not slightly 2 alkaline / base mark independently contains Ca 2+ / Mg 2+ / named calcium compound / correct formula do not accept reference to soap not calcium / magnesium (c) build up of fur / scale / forms CaCO 3/ precipitate formed not scum wastes energy / less efficient / takes longer to boil (d) (i) sample B contains (calcium) sulphate / SO 4 2 not softened by boiling / does not contain many HCO 3 ions / cannot precipitate CaCO 3 by use of ion-exchange / washing soda / distillation not detergent / soap (e) strengthen bones, teeth / taste not good for you / healthier [0] Page 52

53 C3.3 Calculating and explaining energy changes Markscheme M. (a) (i) activation energy or energy needed to start the reaction the reaction is exothermic because the energy level / value of products is less than the energy level / value of reactants allow the reaction is exothermic because arrow B goes down or methanol is below methane and oxygen or arrow C is bigger than arrow A for mark allow energy level of products is lower unqualified or the energy level of reactants is higher unqualified for mark 2 (i) use a lid / cover over the calorimeter or any mention of how the calorimeter could be safely enclosed / insulated a greater mass of methanol was burned in Experiment 2 therefore the temperature change was greater because more energy was transferred / released (iii) any one from: to improve or check repeatability / quality of results to make it easier to spot an anomalous measurement to be able to calculate an average mean value (iv) 8820 (J) for correct answer if answer is incorrect allow one mark for 2 used as the mean temperature change 2 [9] Page 53

54 M2. (a) eg plastic (beaker) / insulation / lid / cover or any mention of enclosed any sensible modification to reduce heat loss ignore prevent draughts ignore references to gas loss all the substances react or all (the substances) react fully / completely or heat evolved quickly or distribute heat accept to mix them so they react is insufficient for the mark accept increase chances of (successful) collisions / collision rate increase do not accept rate of reaction increase / make reaction faster (c) experiment 2 and different / higher / initial / starting temperature accept experiment 2 and the room is hotter / at higher temperature do not accept temperature change / results higher (d) temperature change does not fit pattern accept anomalous / odd or it is the lowest or it is lower than the others or it is different to the others results are different is insufficient (e) 7 / 7.0 (f) ( ) = 2940 ecf from (e) (g) diagram A and reaction exothermic / heat evolved / Δ H is negative / temperature rises accept energy is lost (to the surroundings) [7] Page 54

55 M3. (a) either: calculations: all correct (ethanol = 6, methanol = 3, peanut oil = 0, vegetable oil = 5) ignore repetition of data from table unqualified or implication of correct calculation (vegetable oil) gives largest temperature / heat increase per gram (owtte) allow produced most heat in proportion to the fuel used owtte for mark 2 any one from: owtte smoke ignore references to crops/food soot carbon carbon monoxide carbon dioxide global warming / climate change / greenhouse gases (air) pollution harmful/poisonous scrub / wash the gases owtte filter / remove (gases / fumes / appropriate named substance) owtte (add extra oxygen) can burn more efficiently owtte use a cleaner fuel owtte plant more trees or similar linked to CO 2 any sensible answer don t burn so much fuel insufficient alone ignore extractor fans / air conditioning (c) (i) A B [6] Page 55

56 M4. (a) low density; gives out light energy when burnt; combustion product is not harmful; any two for mark each 2 attempt to add bond energies; e.g. adding O-H bond energies answer = = 856 for mark each 2 (c) (i) Group : elements in a group have the same number of electrons in outer shell first because only one electron or Group 7: because needs one electron to complete outer shell for mark each 2 forms H + ion for mark (iii) forms molecules; low melting point (gases); or form covalent bonds forms H ion for mark [8] M5. (a) reactants 2 H-H + O = O = 370 (kj) products 4 O-H = 856 (kj) energy change = 486(kJ) O=O has a double (covalent) bond or O-H and H-H only have single (covalent) bonds Page 56

57 (c) hydrogen can be used as a fuel because when it reacts with oxygen more energy is released in bond making than used in bond breaking therefore the reaction releases energy or the reaction is exothermic M6. (a) (i) energy / heat of products less than energy of reactants owtte allow products are lower than reactants allow more energy / heat given out than taken in allow methanol is lower allow converse allow energy / heat is given out / lost allow ΔH is negative [6] lowers / less activation energy owtte allow lowers energy needed for reaction or it lowers the peak/ maximum do not allow just lowers the energy (i) bonds broken: (2 435) = 368 allow: (8 435) = 3978 bonds made: (2 805) + (2 464) = 2538 allow: (6 435) + (2 805) + (2 464) = 548 energy change: = ( )70 allow: = ( )70 ignore sign allow ecf correct answer (70) = 3 marks energy released forming new bonds is greater than energy needed to break existing bonds owtte allow converse do not accept energy needed to form new bonds greater than energy needed to break existing bonds Page 57

58 [6] Q7 (a) Bonds broken Bonds formed number type number type 3 [O=O] 4 [O H] each for mark 2 Total energy change Total energy change in breaking bonds in forming bonds = = 856 each for mark Total = 3758 Total = 5076 each for mark 4 (c) net energy transfer = 38 this energy is released in the reaction/it is an exothermic reaction each for mark [N.B. credit e.c.f. (a) and (c)] 2 [8] Page 58

59 C3.4 Further analysis and quantitative chemistry Revision Higher Markscheme M. (a) (i) hydrochloric acid / HCl accept any (named) acid carbon dioxide / CO 2 accept bubbles / fizz / gas or limewater gets milky ignore add limewater do not accept other named gases 2 nd mark dependant on first mark accept for this answer only heat gives CO 2 / limewater milky = mark (white) precipitate / solid ignore names of substances even if incorrect accept white deposit / substance do not accept any coloured precipitate (iii) eg flame colour of (Na) and flame colour of (K) interfere / mask / mix with each other accept can t see the colours or difficult to determine the colour or both produce different colours or a correct statement of colours or hard to distinguish (i) eg essential (mineral) or everyone needs it / some (salt) or problems with health if have no salt accept preservative / flavouring / taste it = salt (all) foods contain / use it / sodium chloride / salt mark positively ie no list principle advantages any two from: ignore economic arguments throughout or people eat less salt more people will be healthier (should have) less heart disease (should have) less cancer Page 59

60 (more people with) lower blood pressure 2 disadvantages any one from: ignore references to too much / too little (salt) not everyone affected not enough evidence does not provide choice undemocratic less taste / flavour ignore no flavour / taste shorter shelf life / not preserved (as long) ignore references to sell by dates too much potassium chloride might be bad M2. (a) test: add NaOH allow any group / 2 hydroxide or hydroxide (ions) or OH incorrect or no reagent = 0, except add NaOH and aluminium or heat / warm could get result mark result: gas turns (red) litmus blue / ammonia is given off accept alkaline gas / ammonia produced do not accept blue litmus turns blue allow any acid-base indicator with correct result [8] test: add (dilute) acid named acid incorrect or no reagent = 0 result: gas gives (white) solid / precipitate with limewater or goes white with limewater accept CO 2 produced gas turns limewater milky / cloudy / white (ignore misty) allow calcium hydroxide for limewater [4] Page 60

61 M3. (a) sodium carbonate / sodium hydrogencarbonate / sodium bicarbonate Na 2CO 3 / NaHCO 3 ie sodium / sodium ions ( mark) carbonate / carbonate ions ( mark) incorrect formula including Na and CO 3 = mark 2 calcium chloride CaCl 2 ie calcium / calcium ions ( mark) chloride / chloride ions ( mark) incorrect formula including Ca and Cl = mark 2 (c) iron or iron(ii) ions Fe 2+ ferrous ions ignore anions ignore nickel / chromium do not accept iron(iii) or ferric ions5 [5] Q4 (a) (i) each correct test and one result = mark one other result for any test = mark this mark can only be awarded once Na 2CO 3: HCl (odourless) gas () CO 2 / carbon dioxide () NaCl: AgNO 3 white ppt () silver chloride () NaNO 3: Al + NaOH pungent /sharp smell / choking gas () NH 3 / ammonia () Na 2SO 4: BaCl 2 white ppt () barium sulphate () Page 6

62 all would give a yellow / yellow-orange (flame) / same coloured (flame) / same results allow orange (flame) or they all contain sodium owtte any two from: ignore cost fast / quick or comment about speed ignore human error small amounts accept any valid answer sensitive / accurate accept operators do not need chemical skills ease of automation sample not used up reliable / efficient can be left to run / continuous analysis ignore results can be saved 2 [8] M5. (a) pipette / burette named indicator eg methyl orange / phenolphthalein not universal accept litmus but not litmus paper (c) 2 for correct answer = 0.0 Page 62

63 (d) KOH HCl 0.0 moles HCl in 35 cm 3 = for correct answer 0.3 = () (with correct working = ) [6] M6. (a) hydrochloric acid in burette indicator note volume at end / neutralisation point titre must be HC mole HCl = 36.5g /36.5 = 2 moles / dm 3 2 for correct answer (c) (i) allow e.c.f. ie their 2 for correct answer = 0.02 moles 0.02 = 0.8 mol / dm 3 Page 63

64 allow e.c.f. ie their (c)(i) M7. (a) (i) e.g. moles NaOH = moles of acid or formula: [9] 0.2 = M = rounding to 0.0 loses mark = = 0.6(M) M = 0.6(M) ecf for arithmetical error correct answer 2 marks 36 ecf (a)(i) 60 correct answer 2 marks gets mark relative formula mass of ethanoic acid = 60 for mark 0.6 incorrect molar mass gains second mark only 2 (i) A = hydrogen / H 2 B = sodium hydroxide / NaOH or sodium oxide / Na 2O (iii) C = ethyl ethanoate (acetate) / CH 3COOC 2H 5 / CH 3CO 2C 2H 5 (iv) D = (concentrated) sulphuric acid / H 2SO 4 do not accept dilute sulphuric acid Page 64