Question

Which one of the following processes involve chemical reactions?
(a) Storing of oxygen gas under pressure in a gas cylinder
(b) Liquefaction of air
(c) Keeping petrol in a china dish in the open
(d) Heating copper wire in presence of air at high temperature

NCERT Class X
Science - Exemplar Problems

Chapter_Chemical Reactions And Equations

Answer 1

the answer to this question is option c because when petrol is kept in a china dish and in open it will evaporate and this process cannot be reversed thus has a property of chemical reaction

Answer 2

Heating copper wire in presence of air at high temperature involves chemical reaction. (Option d)

• When copper is heated in the presence of air in a very high temperature,a chemical reaction takes place.

• In this situation,the highly heated copper reacts with the oxygen of the air to form a thin layer of copper oxide on the surface of metallic copper.

• This formation of  thin layer of copper oxide is certainly a chemical reaction.

• Chemical equation :

2Cu + O2 -----> 2CuO