2. What is the reduction half-reaction for the following unbalanced redox equation?

Cr2O7^2– + NH4^+ Cr2O3 + N2

A.) Cr2O3 -> Cr2O7^2–
B.) Cr2O7^2– -> Cr2O3
C.) NH4^+ -> N2
D.) N2 -> NH4^+
I think it is B...?

3. Which oxidation-reduction reactions are best balanced by the half-reaction method?

A.) covalent reactions
B.) acid-base reactions
C.) ionic reactions
D.) intermolecular reactions
I think it is C....?

With practice you will learn what oxidizes and what reduces. To help let me give you the oxidation states and you figures these out for yourself.

Cr is +6 on the left and +3 on the right.
N is -3 on the left and zero on the right.

For the second question, AFTER you have balanced the reactions as far as change of electrons is concerned, don't you usually add H^+ (if acid) or OH^-(if base) and water? So what's the answer.

For question 2, the correct answer is B) Cr2O7^2– -> Cr2O3. In the given redox equation, Cr2O7^2– is being reduced to Cr2O3.

For question 3, the correct answer is B) acid-base reactions. The half-reaction method is most commonly used to balance oxidation-reduction reactions in acidic or basic solutions, which are often encountered in acid-base reactions.

To find the reduction half-reaction for the given unbalanced redox equation, you need to identify the species that is being reduced.

In the equation: Cr2O7^2– + NH4^+ -> Cr2O3 + N2, the species NH4^+ is being reduced because it is gaining electrons and being converted into N2.

Therefore, the correct reduction half-reaction is: NH4^+ -> N2 (Option C).

For the second question, the half-reaction method is most commonly used to balance ionic redox reactions. Therefore, the correct answer is C.) ionic reactions.