Question

Carbon reacts with an acid to form carbon dioxide, water and nitrogen dioxide.
(a) Name the acid used in the reaction.
(b) Write a balanced chemical equation for the reaction that occurs.

Hint:

Concentrated nitric acid usually acts as an oxidizing agent because it decomposes to give nascent oxygen: 2HNO_3 2NO_2 + H_2O + [O].

Answer 1

This reaction shows that carbon is reacting with an acid and the products formed are carbon dioxide, water and nitrogen dioxide.

From these products, we can identify that the acid used must be nitric acid.

This is because nitric acid is a strong oxidizing acid.
It not only reacts as an acid, but it also oxidizes carbon to carbon dioxide.
At the same time, nitric acid itself gets reduced to nitrogen dioxide.

(a) Name the acid used in the reaction:
The acid used is concentrated nitric acid (HNO₃).

(b) Balanced chemical equation for the reaction:

C + 4HNO₃ → CO₂ + 2H₂O + 4NO₂

Explanation of balancing:
- Carbon atoms: 1 on both sides
- Hydrogen atoms: 4 on left and 4 in 2H₂O on right
- Nitrogen atoms: 4 in 4HNO₃ and 4 in 4NO₂
- Oxygen atoms: 12 on left and 12 on right

So the equation is correctly balanced.

Final Answer:
(a) Concentrated nitric acid
(b) C + 4HNO₃ → CO₂ + 2H₂O + 4NO₂