CBSE Class 10 Science 2021 Term 1 Solved Paper

Question : 27

Total: 60

Study the experimental set up shown in given figure and choose the correct option from the following:

P	Q	Change observed in calcium hydroxide solution
(a) K2CO3	Cl2 gas	No change
(b) KHCO3	CO2 gas	No change
(c) KHCO3	H2 gas	Turns milky
(d) K2CO3	CO2 gas	Turns milky

Solution:

In the given experimental setup, P is potassium carbonate (K2CO3) which when treated with dil HCl, reacts vigorously producing carbon dioxide gas (Q) leaving the aqueous state of potassium chloride. The released carbon dioxide gas turns lime water milky due to the formation of calcium carbonate. The reaction can be represented as:

K2CO3( s)

Potassium carbonate

+2‌HCl(l)→H2O(l)+

CO2(g)↑

Carbon dioxide

2‌KCl(aq)

Potassium chloride

Ca(OH)2(aq)

Calcium hydroxide

(Lime water)

CO2(g)

Carbon dioxide

→

CaCO3( s)

Calcium carbonate

(White ppt)(Makes limewater milky)

H2O(l)

water

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