xtra_probs_wk6

xtra_probs_wk6 - Extra Problems for Chapter 20 1. Balance...

Info iconThis preview shows pages 1–7. Sign up to view the full content.

View Full Document Right Arrow Icon
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Background image of page 2
Background image of page 3

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Background image of page 4
Background image of page 5

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Background image of page 6
Background image of page 7
This is the end of the preview. Sign up to access the rest of the document.

Unformatted text preview: Extra Problems for Chapter 20 1. Balance the following equations by the half-reaction method. a) acidic: HgZI-IPO4(s) ,+ Au(s) + Cl'(aq) ——> Hg(l) ’+ H2P02(aq) + AuCl;(aq) [3,2,8,3H+=6,3,2] b) basic: Agzs<s> + Cr(OH)3(s) —+ Ago) + Hs—(am +_Cr,02'(aq) [3,2,7OH—=6,3,2,5H20] c) HNOZ ——> NO; + NO [3:1,2,IrF,H20] -2- 2. What reaction occurs when the standard hydrogen electrode functions as I a) an anode? [H2(g) a 2W(aq)+26’l b) acathode? c) What does standard mean here? 3. A zinc electrode immersed in 1 M zinc chloride is connected to a standard hydrogen elec- trode employing a salt bridge. The zinc electrode is observed to dissolve and a cell voltage of 0.763 V is recorded. a) Give the balanced cell reaction. b) What is 8°(Zn2+|Zn)? [—0.763 V] 4. A half cell constructed from a silver electrode surrounded by 1 M AgNO3 is connected to a standard hydrogen electrode using a salt bridge. The cell voltage is observed to be 0.800 V while metallic silver plates out. a) Give the balanced cell reaction. b) What is 8°(Ag+|Ag)? [0.800 V] -3- 5. A voltaic cell is constructed from the following half v cells: (1) H+(aq, O. 10 M )[H2(g, 0.90 atm) and H+(aq, 2.00 M )|H2(g, 0.50 atm). a) Which half cell, (1) or (2), contains the cathode? b) What is the voltage of the cell? - [0.085 V] 6. Given K2Cr04(aq) + Ag(s) + FeCl3(aq) —> AgZCrO4(s) + FeC12(aq) + KC1(aq) a) Balance the reaction by the half-reaction method. [1,2,2=1,2,2] b) If AG" = -62.5 kJ what is A8° for the reaction? [0.324 V] c) What is 8°(Ag2CrO4(s)|Ag(s)) if 8°(Fe3+lF62+) = 0.770 V? [0.446 V] 7. For the following reaction CIO§(aq) ——> CIOZ(aq) + ClO§(aq) a) Balance the reaction in basic solution by the half—reaction method. b) Write the anode half reaction. c) What is the reducting agent? d) What is the oxidizing agent? 6) Write the reaction’s product quotient. f) If the standard reduction potential for the anode is 0.17 V and that for the cathode is 0.35 V what is Ae° for the reaction? g) What is the equilibrium constant for the reaction? [1. 21 x 106] -5- 8. An electrochemical cell is based upon the following half-reactions A13+(aq) + 3e‘ —> Al(s) 80 = —1.66 V Ag+(aq) + e” —-> Ag(s) 8° = 0.799 V where the A1 electrode is immersed in a solution of aluminum nitrate and the silver electrode 'is immersed in silver nitrate. ' a) What is the spontaneous chemical reaction? b) If [A1(NO3)3] = 0.100 M and [AgNO3] = 0.150 M what is the cell potential? [2.43 V] c) Does the cell potential increase, decrease, or remain the same when the following changes occur to the standard cell? (Show your reasoning) I) AgNO3 (s) is added to the Ag+/Ag half-cell compartment and dissolves. 2) The size of the aluminum electrode is doubled. 3) NaCl(s) is added to the Ag+/Ag half—cell compartment precipitating some of the Ag” as AgC1(s). 4) Water is added to both half-cell compartments until the solution volume is doubled. 5) The silver electrode is replaced with a platinum electrode. 80 = 1.19 V for Pt2+lPt 9. How many hours will it take to deposit 0.45 g of metallic tin from Sn2+ if 0.125 A passes through the cell? [1.6 hr] 10. For the battery reaction Pb(s) + Pb02(s) + 2HSOZ(aq) + 2H+(aq) —> 2PbSO4(s) + 2H20(l) AH° = -3159 kJ and AS° = 263.5 J K"1 a) What is the equilibrium constant at 25°C? b) What is Ae" at 25°? c) What is A80 at -20°C? (1) What is the equilibrium constant at -20°C? e) What is A8 at -20°C if [H2304] = [HSOZ] = [H+] = 4.5 M? [1.28 x 1069] [2.04 V] [1.98 V] [8.79 x1078] [2.05 V] -7- Potentially Useful Information PV = nRT ‘qV 2 AE (with only PV work) q 2 CAT ‘ qp _= AH (with only PV work) AE = q + w r w = —PextAV (PV work) H = E + PV 2‘ AS = qreV/T (at constant T) I G = H — TS At constant T, P AG = AH — TAS AG = AG0 + RT an where AGO = —- RT an welec(max) = AG = — nFAe where Q = It = nF A8 = A80 — (0. 0257/11) In Q (at 25°C) where A9" = (RT/nF)1n K K = °c + 273.15 R = 8.314472 J mol‘1 K‘1 = 0.082057 L atm mol‘l K'1 F = 96, 485. 338 0 mol'1 P :1 atm = 760 mm Hg = 1.01325 bar ...
View Full Document

Page1 / 7

xtra_probs_wk6 - Extra Problems for Chapter 20 1. Balance...

This preview shows document pages 1 - 7. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online