Question

when the following equation is balanced with the smallest possible integer coefficients, what is the coefficient of h+?
_cr +_h+ --->_cr3+ +_h2
a 5
b 2
c 4
d 6

Explanation:

Step1: Write half - reactions

Oxidation: \(Cr
ightarrow Cr^{3+}\), electrons lost \(= 3e^{-}\)
Reduction: \(H^{+}
ightarrow H_{2}\), electrons gained \(= 2e^{-}\)

Step2: Balance electrons

Multiply oxidation half - reaction by \(2\): \(2Cr
ightarrow 2Cr^{3+}+6e^{-}\)
Multiply reduction half - reaction by \(3\): \(6H^{+}+6e^{-}
ightarrow 3H_{2}\)

Step3: Combine half - reactions

\(2Cr + 6H^{+}
ightarrow 2Cr^{3+}+3H_{2}\)

Answer:

D. 6