Question

(a) What is done to prevent rancidity in foods containing fats?
(b) $CuO+H_2\to Cu+H_{2}O$
In the above reaction which substance is being oxidised and which is reduced?

Answer 1

A. Antioxidants are often added to fat-containing foods in order to prevent the development of rancidity due to oxidation.

B. In this reaction, copper (II) oxide reacts with hydrogen to generate copper metal and water. This is an oxidation- reduction reaction, in which some species are oxidized and some reduced.

The oxidation number of copper goes from +2 (in CuO) to 0 (in Cu), while hydrogen's oxidation number goes from 0 (in H2) to +1 (in water). The oxidation number of oxygen stays the same and is equal to -2.

In oxidation, the oxidation number increases as the species lose electron(s). Since the species gain one or more electrons in reduction, the oxidation number decreases.

Thus, hydrogen is oxidised while copper is reduced. We can also say hydrogen is the reducing agent, while the copper (II) oxide is the oxidising agent.