Question

In the equation, $\text{BiO}_{3}^{-}+6\text{H}^{+}+xe^{-}\rightarrow \text{Bi}^{3+}+3\text{H}_{2}\text{O}$ What is the value of x?

• A. 2
• B. 3
• C. 4
• D. 6

Hint:

Using oxidation states is the fastest way to find the number of electrons in a half-reaction. Bismuth goes from +5 to +3; since $5 - 3 = 2$, it requires 2 electrons!

Answer 1

The Correct Option is A

Step 1: Understanding the Concept:
In a balanced half-reaction, the total charge on the reactant side must equal the total charge on the product side.

Step 2: Formula Application:
Total reactant charge = Total product charge.

Step 3: Explanation:
Reactant side: $(-1) + (+6) + x(-1) = 5 - x$. Product side: $(+3) + 0 = +3$. Equating them: $5 - x = 3 \implies x = 2$. (Alternatively, check oxidation states: $Bi$ goes from +5 in $BiO_3^-$ to +3 in $Bi^{3+}$, which is a gain of 2 electrons).

Step 4: Final Answer:
The value of x is 2.