Question

write the chemical equation of the following changes have taken place with an example of each change in colour change in temperature formation of precipitate

Answer 1

Fe + CuSO4 -----> FeSO4 + Cu
in this reaction when iron reacts with copper sulphate, copper sulphate is blue in colour change into green in colour called iron sulphate as a result of displacement reaction.

CaO + H2O-------> Ca(OH)2 + heat
in this reaction when calcium oxide reacts with water to increase the temperature and forms a Calcium Hydroxide. it is due to exothermic reaction.

BaCl2 + Na2SO4 ----> 2NaCl + BaSO4
when Barium Chloride reacts with sodium sulphate it forms Barium sulphate as a precipitate. it is due to precipitation reaction.

Answer 2

Answer:

In Chemistry, some chemical reactions are confirmed with physical changes, since the products can't be identified with the naked eye.

Some of these changes are - changes in colour, temperature, precipitate formation, turbidity, etc.

Explanation:

In Chemistry, some chemical reactions are confirmed with physical changes, since the products can't be identified with the naked eye.

Some of these changes are - changes in colour, temperature, precipitate formation, turbidity, etc.

We are asked for specific physical changes, and we shall stick to them today -

1. Change in colour

$Fe + CuSO_4 \rightarrow FeSO_4 + Cu$

This is a displacement reaction, wherein iron displaces the sulphate ion from copper sulphate. Initially, the solution is blue in colour, owing to copper sulphate, but after the reaction takes place, the solution turns green, owing to ferrous sulphate.

2. Change in temperature

$CaO + H_2O \rightarrow Ca(OH)_2 + \Delta$

This is a combination reaction, wherein Calcium Oxide combines with water to form Calcium Hydroxide, with the release of heat. This makes it an exothermic reaction, and there's an increase in temperature.

We also note that, for a decrease in temperature with the progress of the reaction, the reaction is endothermic.

3. Formation of a precipitate

$BaCl_2 + Na_2SO_4 \rightarrow 2NaCl + BaSO_4 (\downarrow)$

This is a double displacement reaction, where Barium Chloride reacts with Sodium Sulphate to form Barium Sulphate (which is insoluble, and thus, precipitates) and Sodium Chloride. This can also be called a precipitation reaction.

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