Multiple Choice
What is the balanced half-reaction for the oxidation occurring at the anode in the galvanic cell: Co(s) | Co2+(aq) || Cu2+(aq) | Cu(s) in an acidic solution?
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6. Chemical Quantities & Aqueous Reactions
Balancing Redox Reactions: Acidic Solutions
Multiple Choice
Which of the following is the correctly balanced equation for the oxidation-reduction reaction of SiO_2 + Y → Si + Y^{3+} in acidic solution?
A
SiO_2 + 4Y + 8H^+ → Si + 4Y^{3+} + 4H_2O
B
SiO_2 + 6Y + 12H^+ → Si + 6Y^{3+} + 6H_2O
C
SiO_2 + Y + 2H^+ → Si + Y^{3+} + H_2O
D
SiO_2 + 2Y + 4H^+ → Si + 2Y^{3+} + 2H_2O
Verified step by step guidance1
Identify the oxidation and reduction half-reactions. Silicon in SiO_2 is reduced from +4 oxidation state to 0 in Si, and Y is oxidized from 0 to +3 in Y^{3+}.
Write the half-reactions separately: the reduction half-reaction for SiO_2 to Si, and the oxidation half-reaction for Y to Y^{3+}.
Balance atoms other than H and O in each half-reaction. For the reduction half-reaction, balance Si atoms; for the oxidation half-reaction, balance Y atoms.
Balance oxygen atoms in the reduction half-reaction by adding H_2O molecules, and balance hydrogen atoms by adding H^+ ions since the solution is acidic.
Balance the charges in each half-reaction by adding electrons (e^-), then multiply the half-reactions by appropriate coefficients so that the electrons cancel out when the half-reactions are added together, resulting in the balanced overall equation.
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