19. The oxidation number of carbon changes from in this redox reactionc 2Mnoi (a

Question

19. The oxidation number of carbon changes from in this redox reactionc 2Mnoi (aq) 3C,0,2 (aq) +40H (aq) (A) +6 to +4 (B) +4 to +3 (C) +3 to +4 (D) +3 to +6 20. Which species is the most powerful reducing agent at standard conditions? Na (aq)+ e Na(s) Fe' (aq) 2e Fe(s) E 0.40 V E' m 0.54 V 21. For this galvanic cell reaction 3HNO, (aq) Bro, (aq) 3H (aq) 3NO, (aq) Br (aq) the Nernst equation implies that the galvanic cell will have a more negative voltage if you: (A) increase the pH. B) decrease the Br concentration. (C) increase the Bro, concentration, (D) increase the NO, concentration. 22. The reaction Zn(s) Ni" (aq) Zn" (aq) Ni(s) occurs in the galvanic cell shown. Which statement is (A) Electrons flow to the Zn electrode. Na ions flow toward the Ni electrode. Electrons flow to the Zn electrode. Na ions flow toward the Zn electrode. (C Electrons flow to the Ni electrode. Na ions flow toward the Ni electrode. (D) Electrons flow to the Ni electrode. Na ions flow toward the Zn electrode.

Explanation / Answer

Q19

Carbon goes from:

C2O4 = -2

O2 = -2 so

2*C + 4(-2) = -2

2C = -2 + 8

2C = +6

C = +6/2 = +3

to

CO3 = -2

C + 3(-2) = -2

C = -2+ 6 = +4

it goes from +3 to `4

choose C

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