Question

Balance the following chemical equation by the half-reaction method in acidic conditions. Show your work. P4 + NO3–→ H2PO4– + NO(A) What is the oxidized element?_________ What is the reduced element?_________
(B) Write balanced half reactions for the oxidation reaction:
(C) Write balanced half reactions for the reduction reaction:

Answer 1

A. Nitrate is the reduced element.

B. Phosphorus is the oxidized element.

C. oxidation half reaction:  $\frac{1}{4}$ P4 + 4H2O ⇒ H2PO4- + 6H+ + 5e

D. Reduction half reaction: NO3- +4H+ 3e- ⇒ NO + 2H2O

Explanation:

P4 + NO3–→ H2PO4– + NO(A)

nitrate is the reduced element as it has lower its oxidation state.

phosphorus is the oxidised element as it has increase in oxidation number.

B) OXIDATION REACTION:

Phosphorus has undergone oxidation from P0 to P5

$\frac{1}{4}$ P4 + 4H2O ⇒ H2PO4- + 6H+ + 5e-

C) REDUCTION REACTION:

Nitrate ion had undergone reduction from nitrate anion to nitrous oxide.

N+5 to N+2

NO3- +4H+ 3e- ⇒ NO + 2H2O

REDOX REACTION:

now multiplying oxidation reaction with 3 and the reduction reaction with 5

$\frac{3}{4}$P4 + 5NO3- +2H+ + 2H2O⇒ 5NO+3H3PO4-