Balance the redox reaction H+ (aq) + Cr (s) --> H2 (g) + Cr2+ ?

I do not know why they multiplied the reaction by two at the very end.
I keep getting 2H+ + Cr ---> H2 + Cr2+ (Might be wrong)

Thank you.

1 Answer
anor277
Apr 17, 2018

Well, you have it. Use the method of half-equations....Cr(s)+ 2H^+ rarr Cr^(2+) + H_2(g)

Explanation:

Hydrogen ion is REDUCED to dihydrogen gas..

H^+ +e^(-) rarr 1/2H_2(g) (i)

"Chromium metal" is oxidized to "chromous ion":

Cr(s) rarr Cr^(2+) +2e^(-) (ii)

And so we add TWO of the former to one of the latter: 2xx(i)+(ii)

We do the multiplication to eliminate the electrons, which are particles of CONVENIENCE...

Cr(s)+ 2H^+ rarr Cr^(2+) + H_2(g)

It would be hard to find an acid that would perform the oxidation selectively.... Chromous acetate is obtained by reduction of Cr^(3+) with zinc metal....

Claro?

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