We’re being asked to determine the substance that can oxidize I-(aq) to I2(s).
Recall the mnemonics LEO GER.
Loss Electrons → Oxidation → Reducing Agent
Gain Electrons → Reduction → Oxidizing Agent
This means the element that gains electrons/reduced is the oxidizing agent while the element that loses electrons/oxidized is the reducing agent.
The ease to remove an electron from an element is also related to cell potential.
Using Table 20.1, which substance can oxidize I- (aq) to I2 (s)?
A) Br2 (l)
B) Cu2+ (aq)
C) Ag (s)
D) Br- (aq)
E) Ni2+ (aq)