Question

Which of the following is a chemical change AND WHY?

A)when copper sulphate crystals are heated,they become white.

B)When Lead Nitrate is heated,we get reddish brown fumes.

C)When ferrous sulphate crystals are heated,the colour of the crystal changes
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Answer 1

B)is the chemical change because

NO2 and O2

When lead nitrate is heated strongly, NO2 and O2 are given out.

2Pb(NO3)2 (s) ------> 2PbO (s) + 4NO2 (g) + O2 (g)

In this decomposition reaction, the colourless compound lead nitrate forms a yellow compound, lead monoxide, and brown fumes of nitrogen dioxide gas are evolved.

Since the decomposition of lead nitrate is brought about by heat, it is actually an example of thermal decomposition.

Answer 2

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