Chem2 hw9s - Yoon Seong Meen – Homework 9 – Due 11:00...

Info iconThis preview shows pages 1–3. Sign up to view the full content.

View Full Document Right Arrow Icon
Yoon, Seong Meen – Homework 9 – Due: Nov 14 2007, 11:00 pm – Inst: James Holcombe 1 This print-out should have 27 questions. Multiple-choice questions may continue on the next column or page – fnd all choices beFore answering. The due time is Central time. 001 (part 1 oF 1) 10 points Balance the redox reaction C + K 2 Cr 2 O 7 + H 2 SO 4 CO 2 + K 2 SO 4 + Cr 2 (SO 4 ) 3 + H 2 O . What is the coe±cient oF K 2 SO 4 in the balanced equation? Correct answer: 2 . Explanation: Balance the halF reactions: 0 C -→ +4 C O 2 + 4 e - 6 e - + +6 Cr 2 - 2 O 7 2 - -→ +3 2Cr Equate the e - : 3 h 0 C -→ +4 C O 2 + 4 e - i 2 h 6 e - + +6 Cr 2 - 2 O 7 2 - -→ +3 2Cr i Add the balanced halF reactions: 3 0 C +2 +6 Cr 2 - 2 O 7 2 - -→ +4 3CO 2 + +3 4Cr Neutralize the remaining charges with ex- isting counterions in acid 3C + 2K 2 Cr 2 O 7 + 8H 2 SO 4 3CO 2 + 2K 2 SO 4 + 2Cr 2 (SO 4 ) 3 + 8H 2 O . 002 (part 1 oF 1) 10 points Balance the redox reaction HNO 3 + H 3 PO 3 NO + H 3 PO 4 + H 2 O . What is the coe±cient oF H 3 PO 4 in the bal- anced equation? Correct answer: 3 . Explanation: Balance the halF reactions: +3 P -→ +5 P +2 e - +5 N +3 e - -→ +2 N Equate the e - : 3 h +3 P -→ +5 P + 2 e - i 2 h +5 N + 3 e - -→ +2 N i Add the balanced halF reactions: 3 +3 P +2 +5 N -→ 3 +5 P +2 +2 N Neutralize the remaining charges with ex- isting counterions in acid 2HNO 3 + 3H 3 PO 3 2NO + 3H 3 PO 4 + H 2 O . 003 (part 1 oF 1) 10 points Zinc Silver 1 . 56 V V Voltmeter e - e - 1 M Zn 2+ (aq) 1 M Ag + (aq) Salt bridge to carry ions In this electrochemical cell, what is the cathode? 1. the solid silver electrode correct 2. the solid zinc electrode 3. the Zn 2+ (aq) ions in the 1 M solution 4. the Ag + (aq) ions in the 1 M solution Explanation: Zn(s) + 2Ag + (aq) Zn 2+ (aq) + 2Ag(s) Reduction occurs at the cathode. In this cell the reduction halF reaction is Ag + (aq) + e - Ag(s) .
Background image of page 1

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

View Full Document Right Arrow Icon
Yoon, Seong Meen – Homework 9 – Due: Nov 14 2007, 11:00 pm – Inst: James Holcombe 2 Ag + cations are attracted to the solid Ag electrode where they are reduced to Ag(s). 004 (part 1 of 3) 10 points Consider the mercury cell below. Zinc anode Steel cathode HgO, KOH and ZnO combined in an aqueous paste What is the electrolyte? 1. KOH correct 2. HgO 3. ZnO 4. steel Explanation: 005 (part 2 of 3) 10 points What is the oxidizing agent? 1. ZnO(s) 2. Zn(s) 3. HgO(s) correct 4. Hg( ) Explanation: 006 (part 3 of 3) 10 points What are the reactants for the reaction? 1. Zn, Hg 2. HgO, KOH 3. HgO, Zn correct 4. Zn, ZnO 5. HgO, ZnO 6. Zn, KOH Explanation: The balanced reaction is HgO(s) + Zn(s) Hg( ) + ZnO(s) 007 (part 1 of 1) 10 points For the reaction Cu(s) + Ag + (aq) Cu + (aq) + Ag(s) 1. Cu is oxidized at the cathode and Ag is reduced at the anode. 2.
Background image of page 2
Image of page 3
This is the end of the preview. Sign up to access the rest of the document.

{[ snackBarMessage ]}

Page1 / 7

Chem2 hw9s - Yoon Seong Meen – Homework 9 – Due 11:00...

This preview shows document pages 1 - 3. Sign up to view the full document.

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