The Arts Academy at Benjamin Rush Chemistry Mr. Wagenhoffer Everyday Chemicals Reaction Project. Name: Date:

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1 The Arts Academy at Benjamin Rush Chemistry Mr. Wagenhoffer Everyday Chemicals Reaction Project Name: Date: Apparatus & Chemicals: household ammonia NaI 3.0 M HNO 3 chemical fertilizer Dry NH 4 Cl 0.10 M AgNO 3 bleach 1.0 M NH 4 Cl 0.20 M BaCl 2 table salt 8.0 M NaOH disposable pipettes (3) baking soda 3-in test tubes (6) Ba(OH) 2 dry pellets Epsom salts 18 M H 2 SO 4 red & blue litmus paper vinegar 2.0 M HCl 100-ml or 150-ml beaker solid unknown containing chalk Ba(OH) 2 (sat. solution) CO -2 3, Cl -1, SO -2 4, &/or I -1 ions Discussion: One important aspect of chemistry is the identification of substances. The identification of minerals - for example, fool s gold as opposed to genuine gold -was and still is of great importance to prospectors. The rapid identification of a toxic substance ingested by an infant may expedite the child s rapid recovery, or in fact it may be the determining factor in saving a life. Substances are identified either by the use of instruments or by reactions characteristic of the substance, or both. Reactions that are characteristic of a substance are frequently referred to as a test. For example, one may test for oxygen with a glowing splint; if the splint bursts into flame, oxygen is probably present. One tests for chloride ions by adding silver nitrate to an acidified solution. The formation of a white precipitate suggests the presence of chloride ions. Since other substances may yield a white precipitate under these conditions, one confirms the presence of chloride ions by observing that this precipitate dissolves in ammonium hydroxide. The area of chemistry concerned with identification of substances is termed qualitative analysis. In this experiment you will perform tests on or with substances that you are apt to encounter in everyday life, substances such as table salt, bleach, smelling salts, and baking soda. You probably don t think of these as chemicals and yet they are, even though we don t refer to them around the home by their chemical names (which are sodium chloride, chlorine, ammonium carbonate, and sodium bicarbonate, respectively), but rather by a trade name. After observing some reactions of these household chemicals, you will partially identify an unknown. Your task will be to determine whether the substance contains the carbonate (CO 3-2 ), chloride (Cl -1 ), sulfate (SO 4-2 ), or iodide (I -1 ) ion. [Caution: Even though household chemicals may appear innocuous, NEVER mix them unless you are absolutely certain you know what you are doing. Innocuous chemicals, when combined, can sometimes produce severe explosions or other hazardous reactions.] Note: for all of the procedures, make sure to follow all directions. There are many pieces of extra information that are necessary for completing the conclusion questions to this project. The procedures will be marked via roman numerals. Items to fill in on your results sheet are shown by a highlighted number in parenthesis (). Procedure: A. Household Ammonia i. Obtain 5 ml of household ammonia in a beaker and hold a dry piece of red litmus paper over the beaker, being careful not to touch the sides of the beaker or the solution with the paper. Record your observations (1). ii. Repeat the operation using a piece of red litmus paper that has been moistened with distilled water. Do you notice any difference in the time required for the litmus to change colors or the intensity of the color change? Record your observations (2). Ammonium salts are converted to ammonia, NH 3, by the action of strong bases; hence, one can test for the ammonium ion, NH 4 +1, by adding sodium hydroxide, NaOH, and noting the familiar odor of NH 3 or by the use of red litmus. The net reaction is as follows: NH 4(aq) +1 + OH (aq) -1 NH 3(aq) + H 2 O (liq)

2 iii. Place about 1 milliliter (20 drops) of 1 M NH 4 Cl, ammonium chloride, in a test tube and hold a moist piece of red litmus paper in the mouth of the tube. Record your observations (3). iv. Now add about 1 ml of 8M NaOH and repeat the test. The NaOH will be found in the fume hood in the back. [Do not allow the litmus paper to touch the sides of the tube because it may come in contact with the NaOH, which will turn it blue.] If the litmus paper does not change color, gently warm the tube, but do not boil the solution (get permission from instructor). Record your observations (4). v. You may suspect that ordinary garden fertilizer contains ammonium compounds. Confirm your suspicions by placing some solid fertilizer, an amount about the size of a pea, in a test tube; add 1 ml of 8M NaOH and test as above with moist red litmus paper. Does the fertilizer contain ammonium salts (5)? What is the active ingredients in smelling salts? vi. Carefully waft the gases from a smelling salt packet to see if you detect a familiar odor. Record your observations (6). Most ammonium salts are stable; for example, the ammonium chloride solution that you tested above should not have had any effect on litmus before you added the sodium hydroxide. However, (NH 4 ) 2 CO 3 is quite unstable and decomposes to ammonia and carbon dioxide: (NH 4 ) 2 CO 3(s) 2 NH 3(aq) + CO 2(g) + H 2 O (g) Smelling salts contain ammonium carbonate that has been moistened with ammonium hydroxide. (see above reaction) What about an instant cold pack? Instant cold packs are useful in many situations where ice is unavailable. These cold packs also contain ammonium salts that act in a new way. Upon mixing an ammonium chloride salt with barium hydroxide, a solution will form with a familiar scent. vii. Take a small scoop of ammonium chloride and place it at the bottom of a small 50.0 ml beaker. On top of this, place a small scoop of barium hydroxide. Stir the resulting mixture with a stir rod. Feel the bottom of the beaker and carefully waft the substance. Record your observations (7) The reaction with ammonium chloride and barium hydroxide follows the following formula: 2(NH 4 )Cl (s) + Ba(OH) 2 (s) BaCl 2 (aq) + 2NH 3 (g) + 2H 2 O (l) B. Baking Soda, NaHCO 3 Substances that contain the carbonate ion, CO 3-2, react with acids to liberate carbon dioxide, CO 2, which is a colorless and odorless gas. Carbon dioxide, when released from baking soda, NaHCO 3, by acids (for example, those present in lemon juice or sour milk) helps to raise the cake: note baking soda is also called sodium bicarbonate. NaHCO 3(s) + H +1 (aq) Na +1 (aq) + CO 2(g) + H 2 O (liq) viii. In a small, dry test tube, place a small amount of baking soda (about the size of a pea). Then carefully add 2 or 3 drops of concentrated (18 M) sulfuric acid, H 2 SO 4 (located in the fume hood) and notice what happens. Record your observations (8). [CAUTION: Concentrated sulfuric acid causes severe burns. Do not get it on your skin. If you come in contact with it, immediately wash the area with copious amounts of water.] ix. Repeat this procedure, but use vinegar in place of the sulfuric acid. Record your observations (9). A confirmatory test for carbon dioxide (CO 2 ) is to allow it to react with an aqueous solution of barium hydroxide, Ba(OH) 2. A white precipitate of barium carbonate, BaCO 3, is produced: CO 2(g) + Ba(OH) 2(aq) BaCO 3(s) + H 2 O (liq) Many substances, such as eggshells, oyster shells, and limestone, contain the carbonate ion. Decide whether common blackboard chalk contains the carbonate ion by running the following test: x. Place a piece of chalk in a dry test tube; add a few drops of 2.0 M HCl (located in the fume hood). Test the escaping gas for CO 2 by carefully holding a drop of Ba(OH) 2, suspended from the tip of a pipette or eye dropper, a short distance down the mouth of the test tube. Be sure that the loop does not touch the sides of the test tube. Clouding of the drop is due to the formation of BaCO 3 and proves the presence of the carbonate ion. [NOTE: Breathing on the drop will cause it to cloud, since your breath contains CO 2!] Record your observations (10).

3 C. Common Table Salt, NaCl Chloride salts react with sulfuric acid to liberate hydrogen chloride, which is a pungent and colorless gas that turns moist blue litmus paper red: 2 Cl -1 (s) + H 2 SO 4(aq) 2 HCl (g) + 2 SO 4-2 (aq) This reaction will occur independently of whether the substance is BaCl 2, KCl, or ZnCl 2 ; the only requirement is that the salt be a chloride. For KCl, the complete equation is 2 KCl (s) + H 2 SO 4(aq) 2 HCl (g) + K 2 SO 4(aq) Another reaction characteristic of the chloride ion is the reaction with silver nitrate to form the white insoluble substance - silver chloride, AgCl: Cl -1 (aq) + AgNO 3(aq) AgCl (g) + NO 3-1 (aq) xi. Place in a small, dry test tube an amount of sodium chloride about the size of a small pea and add about 2-4 drops of 18 M H 2 SO 4. Very carefully note the color and odor of the escaping gas by fanning the gas with your hand toward your nose (using the wafting technique.) DO NOT PLACE YOUR NOSE DIRECTLY OVER THE MOUTH OF THE TEST TUBE. Record your observations (11). xii. Complete the equation NaCl (s) + H 2 SO 4(aq) >? (12). xiii. Place a small amount (about the size of a pea) of NaCl in a small test tube and add 15 drops of distilled water, then add 1 drop of 3 M HNO 3. Next add 4-5 drops of 0.10 M AgNO 3 and mix the contents. Record your observations (13). xiv. Why should you use distilled water for this test (14)? xv. Confirm your answer by testing with tap water for chloride ions. Add 1 drop of 3 M HNO 3 to about 2 ml of tap water and then add 5-6 drops of 0.10 M AgNO 3. Does this test indicate the presence of chloride ions in tap water (15)? Sodium ions impart a bright yellow color to a flame. When potatoes boil over on a gas stove or the campfire, a burst of yellow flame appears due to the presence of sodium ions. Simply handling a utensil will contaminate it sufficiently with sodium ions from the skin so that when the utensil is placed in a hot flame, a yellow color will appear. D. Epsom Salts, MgSO 4. 7H 2 O Epsom salts are used as a purgative, and solutions of this salt are used to soak tired, aching feet. The following tests are characteristic of the sulfate ion, SO xvi. Place a small quantity of Epsom salts in a small, dry test tube and add 2-3 drops of 18 M H 2 SO 4. Record your observations (16). Note the difference in the behavior of this substance toward sulfuric acid compared with the behavior of baking soda toward sulfuric acid. xvii. Place some Epsom salts (an amount the size of a small pea) in a small test tube and dissolve in 1 ml of distilled water. Add 2 drops of 3.0 M HNO 3 and then 2-3 drops of 0.20 M BaCl 2. Record your observations (17). Barium sulfate is a white, insoluble substance that forms when barium chloride is added to a solution of any soluble sulfate salt, such as Epsom salts, as follows: SO 4-2 (aq) + BaCl 2(aq) BaSO 4(s) + 2Cl -1 (aq) E. Bleach, Cl 2 Water Commercial bleach is usually a 5 percent solution of sodium hypochlorite, NaClO, or NaOCl. This solution behaves as though only chlorine, Cl 2, were dissolved in it. Since this solution is fairly concentrated, direct contact with the skin or eyes must be avoided! The element, Cl 2, behaves very differently from the chloride ion. Chlorine is a pale, yellow-green gas, has an irritating odor, is slightly soluble in water, and is toxic. It is capable of liberating the element iodine, I 2, from iodide salts: Cl 2(aq) + I -1 (aq) I 2(aq) + 2 Cl -1 (aq)

4 Another reaction characteristic of iodides is that they form a pale yellow precipitate when treated with silver nitrate solution: AgNO 3(aq) + I -1 (aq) AgI (s) + NO 3-1 (aq) xviii. Dissolve a small amount (about the size of a pea) of sodium iodide, NaI, in 1 ml of distilled water in a small test tube; add 2 drops of 3 M HNO 3, then add 4-6 drops of 0.1 M AgNO 3 solution. Record your observations (19). xix. Solid iodide salts react with concentrated sulfuric acid by instantly turning dark brown, with the slight evolution of a gas that fumes in moist air and with the appearance of violet fumes of iodine vapor. This must take place outside or in the hood. Mr. Wagenhoffer will complete this procedure. Record your observations (20). For Testing an Unknown Compound The table below summarizes the behavior of these ions towards sulfuric acid, H 2 SO 4. Reaction of Solid Salt with H 2 SO 4 Ion Reaction CO 3-2 Cl -1 SO 4-2 Colorless, odorless gas, CO 2, evolved Colorless, pungent gas, HCl, evolved, which turns blue litmus red No observable reaction Violet vapors of I 2 formed I -1 Keep this information in mind when answering the final questions for the project. There will be some theoretical questions based on this reactivity with sulfuric acid. Understanding this will help you to predict what may or may not occur.

5 Lab Report Data Sheet A. Household Ammonia, NH 3 1. Effect of ammonia on dry red litmus 2..Effect of ammonia on moist red litmus 3. Effect of NH 4 Cl on litmus 4. Effect of NH 4 Cl + NaOH on litmus 5. Fertilizers contain ammonium salts? Yes No 6. Smelling salt 7. Ammonium Chloride + Barium Hydroxide: B. Baking Soda, NaHCO 3 8. Effect of H 2 SO 4 on NaHCO 3 9. Effect of vinegar on NaHCO Chalk contains the carbonate ion? Yes No C. Common Table Salt, NaCl 11. Effect of H 2 SO 4 on NaCl 12. H 2 SO 4(liq) + NaCl (s) 13. Effect of AgNO 3 on NaCl 14. Why use distilled water? 15. Tap water contains the chloride ion? Yes No D. Epsom Salts, MgSO 4. 7H 2 O 16.. Effect of H 2 SO 4 on Epsom salts 17. BaCl 2 + Epsom salts E. Bleach, Cl 2 Water 18. Bleach + NaI 19. AgNO 3 + NaI 20. From Mr. Wags Demo Effect of H 2 SO 4 on NaI

6 Concluding Questions: 1. Based on the project tests, how could you differentiate between sodium chloride (common table salt) and sodium iodide (a poison)? Show the specific reactions. 2. Do you think that washing soda, Na 2 CO 3, could be used for the same purpose as baking soda, NaHCO 3? Would Na 2 CO 3 react with HCl? Write the chemical equation. Write the chemical equation for the reaction of NaHCO 3 with HCl. 3. Sodium benzoate is a food preservative. What are its formula and its solubility in water (research online). 4. Ethyl acetate is the main ingredient in fingernail-polish remover and is very flammable. What is its boiling point and formula (research online)? 5. Rubbing alcohol is an aqueous solution of 2-propanol. What is another name for 2-propanol? What is its boiling point (research online)? 6. Household vinegar is a 5 percent aqueous solution of acetic acid. Give the chemical formula for acetic acid. Hint: it is a polyatomic acid 7. What are the main active ingredients in drain cleaning products (such as draino)? See the example in the classroom.

7 8. Explain why it is not advisable to try to clean an enclosed shower stall with a solid cleanser such a Comet or Ajax along with some bleach. Hint what is in bleach that could be dangerous to come into contact with? 9. Why should you use distilled water rather than tap water when making chemical tests? Hint think of steps Assume that you had a mixture of solid sodium carbonate and sodium chloride. How could you show the presence of both the carbonate and the chloride ions in this mixture? 11. Assume that you had a mixture of solid sodium sulfate and sodium iodide. How could you show the presence of both ions in this mixture? 12. Consider the reaction for the instant cold pack (from step 7): 2(NH 4 )Cl (s) + Ba(OH) 2 (s) > BaCl 2 (aq) + 2NH 3 (g) + 2H 2 O (l) From your observations, what part of the reaction do you think provided the pungent odor? Explain your reasoning.

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