Bright Tutorials Bright Tutorials
ICSE Class 7 Chemistry Question 6 of 9

Air and Atmosphere — Question 3

Back to all questions
3
Question

Question 3

(a) What happens when (i) mercuric oxide and (ii) potassium nitrate are heated?

(b) Why is potassium chlorate not used for laboratory preparation of oxygen?

Answer

(a)

i. When mercuric oxide is heated, it decomposes to give mercury and oxygen.

2HgO →heat\xrightarrow{\text{heat}} 2Hg + O2

ii. When potassium nitrate is heated, it decomposes to give potassium nitrite and oxygen.

2KNO3 →heat\xrightarrow{\text{heat}} 2KNO2 + O2

(b) Potassium chlorate is heated to a high temperature to obtain oxygen gas which may cause

  1. cracking of glass apparatus being used.
  2. accidents and burn injuries. Thus potassium chlorate is not used for laboratory preparation of oxygen gas.