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Chapter 17 and 18 Review. You may use Appendix C, Periodic Table, Formula Sheet, and Calculator. Question 1. Use the half- rxn method to balance the following equations for redox rxns in basic solution. Answer:. Question 2.
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Chapter 17 and 18 Review You may use Appendix C, Periodic Table, Formula Sheet, and Calculator
Question 1 • Use the half-rxn method to balance the following equations for redox rxns in basic solution Answer:
Question 2 • Write equations for the half rxns and the overall cell rxn and calculate the standard cell potential for the voltaic cell diagram, shown below Answer: E°cell= 0.56 V
Question 3 • Can we use sodium metal to displace Mg2+ (aq) from solution? If the rxn does occur, write the half-equations and the net equation. If the displacement rxn does not occur, write the equation for the rxn that does occur. Answer: E°cell= 0.357 V, therefore YES it is spontaneous
Question 4 • Write the equilibrium constant expression for the following reaction, and determine the numerical value of Keq at 25°C. Is the reaction favored? Answer: E°cell= -0.13 V therefore, not favored
Question 5 • A voltaic cell represented by the following cell diagram has a cell potential of -0.015 V. Calculate [Ag+] in the cell. Answer: 0.098 M
Question 6 • What is the electric current, in Amperes, if 212 mg of Ag(s) is deposited at the cathode in 1435 seconds in the electrolysis of AgNO3(aq)? Answer: 0.132 A
Question 7 • Calcium carbide reacts with water to form acetylene (C2H2), a gas used as a fuel in welding. The other product is calcium hydroxide. The heat of reaction is -128.0 kJ/molrxn. How many kJ of heat are transferred in the reaction of 3.50 kg calcium carbide with 1.25 L of water? Answer: -4.44 x 103 kJ
Question 8 Considering all temperatures, when will a reaction always be thermodynamically favored? Answer: exothermic and increase in entropy
Question 9 • The following are data for the vaporization of toluene (C6H5CH3) at 298 K: • ΔS°=99.7 J mol-1 K-1 • ΔH°=38.0 kJ mol-1 • Calculate the equilibrium vapor pressure, in mmHg, of toluene at 298 K. Answer: 27 mmHg
Question 10 • The normal boiling point of diethyl ether, CH3CH2OCH2CH3(l), is 34.66°C. Calculate the vapor pressure, in mmHg, of diethyl ether at 32.50°C Answer: 706 mmHg
Question 11 • The following two spontaneous reactions are used in commercially available cold packs. Explain how the second law of thermodynamics is obeyed, considering all the information given below: