. In which reaction is nitric acid acting as an oxidising agent? A. CuO + 2HNO3 → Cu(NO3)2 + H2O B. Cu + 4HNO3 → Cu(NO3)2 + 2H2O + 2NO2 C. Na2CO3 + 2HNO3 → 2NaNO3 + H2O + CO2 D. NaOH + HNO3 → NaNO3 + H2O

B. Cu + 4HNO3 → Cu(NO3)2 + 2H2O

Explanation:

A redox reaction is one in which oxidation and reduction reactions are occuring simultaneously.

In a redox reaction, an oxidizing agent is reduced ( its oxidation state decreases) whereas a reducing agent is oxidized (it's oxidation state increases).

The nitrogen in the nitrate (v) ion, NO3-, exists in the +5 oxidation state. Therefore it would be acting as an oxidizing agent in any reaction in which it's oxidation state becomes less than +5 after the reaction.

Let us then consider each of the reactions:

A. Reaction 1: in this reaction, the oxidation state of nitrogen remains +5 as what is simply an exchange of radicals in a neutralization reaction.

B. Reaction 2: in this reaction, trioxocarbonate (v) acid oxidizes Copper atom to Copper (ii) ion, while itself it is reduced to Nitrogen (IV) oxide. The oxidation state of nitrogen changes from +5 to +4

C. Reaction 3: in this reaction, what occurs is an exchange of radicals by a displacement reaction. The oxidation state of nitrogen remains the same

D. Reaction 4: in the reaction, what occurs is a neutralization reaction, and the oxidation state of nitrogen remains the same.

Therefore, the correct option is B.

the answer is 1260

you spend 7 hours in school for 1 school day with 5 school days in 1 school week with 36 school weeks in a school year.

7*5*36= 1260 it's all about multiplying