Which of the following substances is capable of reducing bromine, Br2?

Cl- H2 Ni or Au

I think its H2

I think you are right; however, I also think Ni will do it.

Br2 + 2e ==> 2Br^-
H2 ==> 2H^+ + 2e
----------------------

Br2 + 2e ==> 2Br^-
Ni ==> Ni^2+ + 2e
------------------------

To determine which of the substances is capable of reducing bromine (Br2), we need to understand the concept of reduction and the relative reactivity of the substances.

Reduction is a chemical process that involves the gain of electrons or the decrease in oxidation state of a substance. In this case, we are looking for a substance that can donate electrons to bromine (Br2) and, therefore, reduce it.

Comparing the substances mentioned:

1. Cl-: Chloride ion (Cl-) is not a strong reducing agent. It has a full octet and is stable with its oxidation state of -1. Therefore, it cannot easily donate electrons to reduce bromine.

2. H2: Hydrogen gas (H2) is a common reducing agent. It can donate two electrons to reduce bromine from its diatomic form (Br2) to bromide ion (Br-).

3. Ni: Nickel (Ni) is not known to possess strong reducing properties. Therefore, it is less likely to reduce bromine.

4. Au: Gold (Au) is a noble metal and generally does not readily undergo reduction reactions. It is unlikely to reduce bromine.

Based on this analysis, you're correct. Hydrogen gas (H2) is capable of reducing bromine (Br2).