Question

(a) Give an example for a combination reaction which is exothermic.
(b) Identify the oxidising agent, reducing agent in the following reaction :
H2S+Cl2 >2HCl+S

(c) Name the phenomenon due to which the taste and smell of oily food changes when kept for a long time in open. Suggest one method to prevent it.
CBSE Class X Science SA 2 (3 Marks)

Answer 1

C+O2-Co2+heat
I think Rancidity It should be fully packed

Answer 2

(i) CaO+H20------>Ca(OH)2+HEAT

It is a combination reaction because two compounds on reaction give one product.As heat is also evolved it is an exothermic reaction.

(ii) oxidising agent-Cl2

Reducing agent-H2S

(iii)this is called rancidity.to prevent it oily foods must be kept in airtight containers.