AP Chapter 4: Reactions in Aqueous Solution Name

AP Chapter 4: Reactions in Aqueous Solution Name WarmUps (Show your work for credit) Date 1. Date 2. Date 3. Date 4. Date 5. Date 6. Date 7. Date 8.

AP Chapter 4: Reactions in Aqueous Solution 2 WarmUps (Show your work for credit) Date 1. Date 2. Date 3. Date 4. Date 5. Date 6. Date 7. Date 8.

AP Chapter 4: Reactions in Aqueous Solution 3 Warmups and problems will be collected before you take the test. Read Chapter 4: Reactions in Aqueous Solution and Chapter 19.1 Know selected solubility rules Know metal activity series Answer the following problems in the space provided. For problems involving an equation, carry out the following steps: 1. Write the equation. 2. Substitute numbers and units. 3. Show the final answer with units. There is no credit without showing work. Electrolytes 1. Identify each of these substances as a strong electrolyte (S), weak electrolyte (W), or nonelectrolyte (N): (a) Ba(NO 3) 2, (b) Ne, (c) NH 3, (d) NaOH (e) CH 3COOH 2. Identify the species that carry the electric current when electricity is passed through an aqueous electrolyte solution. Solubility & Precipitation Reactions 3. Characterize the following compounds as soluble (S) or insoluble (I) in water: (a) Ca 3(PO 4) 2, (b) Mn(OH) 2, (c) AgC1O 3, (d) Al(NO 3) 3 (e) K 2S. 4. Write balanced molecular and net ionic equations for the following reactions. Show states. (a) AgNO 3(aq) + Na 2SO 4(aq) (b) BaCl 2(aq) + ZnSO 4(aq) (c) (NH 4) 2CO 3(aq) + CaCl 2(aq) 5. A student found that a sulfuric acid solution conducts, however, after the addition of a certain amount of a barium hydroxide solution to the sulfuric acid solution, the light began to dim, even though Ba(OH) 2 is also a strong electrolyte. Write a balanced equation for this reaction and explain why the light dims as the reaction proceeds.

AP Chapter 4: Reactions in Aqueous Solution 4 Acids & Bases 6. Identify each of the following species as a Bronsted acid (A), base (B), or both(ab): (a) PO 4 3 (b) ClO 2 (c) NH 4 + (d) HCO 3 (e) HBr Redox 7. Give oxidation number for the underlined atoms in the following molecules and ions: (a) Cr 2O 7 2 (b) CaI 2 (c) A1 20 3 (d) H 3As0 3 (e) TiO 2, 8. Identify which reactions are redox: (a) 2AgNO 3(aq) + Na 2SO 4(aq) Ag 2SO 4(s) + 2NaNO 3(aq) (b) 2NO 2(g) N 2O 4(g) Balancing Complex Redox Equations 9. Balance the following redox equations: (a) H 2O 2 + Fe 2+ Fe 3+ + H 2O (in acidic solution) (b) CN + MnO 4 CNO + MnO 2 (in basic solution) (c) Br 2 BrO 3 + Br (in basic solution)

AP Chapter 4: Reactions in Aqueous Solution 5 10. Predict the outcome of the reactions represented by the following equations by using the activity series, and balance the equations. Also for each equation, write the balanced oxidation halfreaction. (a) Cu(s) + HCl(aq) (b) Br 2(s) + NaI(aq) (c) Mg(s) + CuSO 4(aq) (d) Cl 2(g) + KBr(aq) Concentration 11. Calculate the molarity of each of the following solutions: (a) 6.57 g of methanol (CH 3OH) in 1.50 X 10 2 ml of solution (b) 7.82 g of naphthalene (C 10H 8) in 85.2 ml of benzene solution. 12. Calculate the volume in ml of a solution required to provide the following: (a) 2.14 g of sodium chloride from a 0.270 M solution (b) 4.30 g of ethanol from a 1.50 M solution 13. Water is added to 25.0 ml of a 0.866 M KNO 3 solution until the volume of the solution is exactly 500 ml. What is the concentration of the final solution? 14. A 46.2 ml, 0.568 M calcium nitrate solution is mixed with 80.5 ml of 1.396 M calcium nitrate solution. Calculate the concentration of the final solution.

AP Chapter 4: Reactions in Aqueous Solution 6 15. Given a stock solution of 1.26 M HCl, how many milliliters of the stock solution are needed to make: (a) 32.0 ml of 0.41 M HCl (b) 410 ml of 0.075 M HCl Gravimetric Analysis 16. A sample of 0.6760 g of an unknown compound containing barium ions is dissolved in water and treated with an excess of Na 2SO 4. If the mass of the BaSO 4 precipitate formed is 0.4105 g, what is the percent by mass of Ba in the original unknown compound? 17. Commercial marble contains a high percentage of calcium carbonate. A 5.37 Kg sample of marble is dissolved in excess HCl, and the resulting solution is reacted with sodium phosphate. The resulting precipitate is collected by filtration and found to weigh 4730 g. (a) Write a balanced equation for the reaction of calcium carbonate and HCl. (b) Write a balanced equation for the precipitation reaction. (c) What is the percentage of calcium in the marble sample? AcidBase Titration 18. What volume of a 0.50 M HC1 solution is needed to neutralize completely each of the following: (a) 10.0 ml of a 0.30 M NaOH solution (b) 10.0 ml of a 0.20 M Ba(OH) 2 solution

AP Chapter 4: Reactions in Aqueous Solution 7 Redox Titration 19. The SO 2 present in air is mainly responsible for the acid rain phenomenon. Its concentration can be determined by titrating against a standard potassium permanganate solution. The unbalanced half reactions for this titration are: 2 SO 2 SO 4 and MnO 4 Mn 2+ (a) Write the balanced redox equation (b) Calculate the number of grams of SO 2 in a sample of air if 7.37 ml of 0.00800 M KMnO 4 solution are required for the titration. 20. Oxalic acid (H 2C 2O 4) is present in many plants and vegetables. If 24.0 ml of 0.0100 M KMnO 4 solution is needed to titrate 1.00 g of impure H 2C 2O 4 sample to the equivalence point, what is the percent by mass of H 2C 2O 4 in the sample? The net ionic equation is 2MnO 4 + 16H + + 5C 2O 4 2 2Mn 2+ + 10CO 2 + 8H 2O Visible Spectroscopy 21. A commonly used dye in the food industry is called brilliant blue. This dye has a molar absorptivity of 130,000 cm 1 M 1 at 630nm. (a) What color does this dye absorb? (b) Describe the physical process within the dye that is responsible for the absorption of light? (c) If the pathlength of a spectrophotometer is 1.0 cm, what concentration of a brilliant blue solution would have a transmittance of 0.32 (32%)?

AP Chapter 4: Reactions in Aqueous Solution 8 How to Balance Complicated Redox Reactions Many redox reactions cannot be balanced by inspection. When inspection does not work, the following process will give a properly balanced equation. Although the process is not difficult, all the steps must be done correctly and in the proper order. 1. Write the unbalanced reaction and, if aqueous, note whether it is acidic or basic. Example: S + HNO 3 SO 2 + NO + H 2O (obviously acidic) 2. If the reaction is in aqueous solution, break ionic substances into their ions. Do not breakup molecular substances, weak acids, weak bases, polyatomic ions or oxides. Example: S + H + + NO 3 SO 2 + NO + H 2O 3. Determine which atoms are oxidized or reduced by assigning oxidation numbers. 0 +5 +4 +2 Example: S + H + + NO 3 SO 2 + NO + H 2O Therefore S is oxidized and N is reduced. 4. Write separate half reactions for the oxidation and reduction steps. Oxidation: S SO 2 Reduction: NO 3 NO 5. Balance each half reaction using X,O,H,e in order. X: balance atoms other than O & H O: balance O using water H: balance H using H + E: balance charge using electrons Oxidation: S SO 2 X: S already balanced O: 2H 2O + S SO 2 H: 2H 2O + S SO 2 + 4H + e: 2H 2O + S SO 2 + 4H + + 4e Reduction: NO 3 NO X: N already balanced O: NO 3 NO + 2H 2O H: 4H + + NO 3 NO + 2H 2O e: 3e + 4H + + NO 3 NO + 2H 2O

AP Chapter 4: Reactions in Aqueous Solution 9 6. Multiply each half reaction by a number to make the number of electrons equal. In this example, the lowest common denominator is 12. Oxidation: 3x (2H 2O + S SO 2 + 4H + + 4e ) 6H 2O + 3S 3SO 2 + 12H + + 12e Reduction: 4x (3e + 4H + + NO 3 NO + 2H 2O) 12e + 16H + + 4NO 3 4NO + 8H 2O 7. Add the two half reactions and cancel anything that is exactly the same on both sides. 6H 2O + 3S 3SO 2 + 12H + + 12e 12e + 16H + + 4NO 3 4NO + 8H 2O 3S + 4H + + 4NO 3 3SO 2 + 4NO + 2H 2O 8. If the reaction is in basic solution, add the same number of OH ions to both sides of the equation as there are H + ions. Combine OH and H + ions to form water and cancel water molecules if appropriate. This example is NOT in basic solution, but if it were, this is what would happen. Add OH : 4OH + 3S + 4H + + 4NO 3 3SO 2 + 4NO + 2H 2O + 4OH Combine H + & OH to form H 2O: 4H 2O + 3S + 4NO 3 3SO 2 + 4NO + 2H 2O + 4OH Cancel H 2O: 2H 2O + 3S + 4NO 3 3SO 2 + 4NO + 4OH 9. Double check.