Question

question 33 (1 point)
how many electrons are transferred in the following balanced redox reaction?
5no₂⁻(aq) + 6h⁺ + 2mno₄⁻(aq) → 5no₃⁻(aq) + 2mn²⁺(aq) + 3h₂o(el)
○2
○4
○6
○8
○10
question 34 (1 point)
how many hydroxide ions must be added to this reaction to balance in basic conditions? 5no₂⁻(aq) + 6h⁺ + 2mno₄⁻(aq) → 5no₃⁻(aq) + 2mn²⁺(aq) + 3h₂o(el)
○6 to the reactant side
○6 to the product side
○6 to both sides
○3 to the right side
○this reaction cannot be balanced in basic conditions

Explanation:

Question 33

Step1: Determine oxidation states

For \( \text{NO}_2^- \) to \( \text{NO}_3^- \): N in \( \text{NO}_2^- \): let oxidation state be \( x \), \( x + 2(-2) = -1 \Rightarrow x = +3 \). N in \( \text{NO}_3^- \): \( x + 3(-2) = -1 \Rightarrow x = +5 \). Each N loses \( 5 - 3 = 2 \) electrons. There are 5 N atoms, so total loss: \( 5 \times 2 = 10 \) electrons.

For \( \text{MnO}_4^- \) to \( \text{Mn}^{2+} \): Mn in \( \text{MnO}_4^- \): \( x + 4(-2) = -1 \Rightarrow x = +7 \). Mn in \( \text{Mn}^{2+} \) is +2. Each Mn gains \( 7 - 2 = 5 \) electrons. There are 2 Mn atoms, so total gain: \( 2 \times 5 = 10 \) electrons.

Step2: Confirm electron transfer

Electrons lost = electrons gained = 10.

The reaction in acidic conditions has \( 6\text{H}^+ \) on the reactant side. To balance in basic conditions, add \( 6\text{OH}^- \) to both sides (to neutralize \( \text{H}^+ \) and form \( \text{H}_2\text{O} \)). \( 6\text{H}^+ + 6\text{OH}^-
ightarrow 6\text{H}_2\text{O} \). On the reactant side, we had \( 6\text{H}^+ \), so adding \( 6\text{OH}^- \) to reactant side (and product side, but the \( \text{H}^+ \) and \( \text{OH}^- \) form \( \text{H}_2\text{O} \) on reactant side, and adjust \( \text{H}_2\text{O} \) on product side). Wait, the original acidic reaction has \( 6\text{H}^+ \) (reactant). To go to basic, add \( 6\text{OH}^- \) to reactant side (to react with \( \text{H}^+ \) to make \( \text{H}_2\text{O} \)). So the number of \( \text{OH}^- \) added to reactant side is 6.

Answer:

10

Question 34