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Strength of Acids and Bases

Give reason f...

Question

Give reason for the following:
(d) Colourless concentrated sulphuric acid in a test tube changes to blue on adding a small piece of copper to it.

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Solution

Colourless concentrated sulphuric acid in a test tube changes to blue on adding a small piece of copper to it because copper displaces hydrogen from sulphuric acid and forms blue coloured copper sulphate.

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Q. When concentrated sulphuric acid was added to an unknown salt present in a test tube a brown gas(A) was evolved. This gas intensified when copper turnings were added to this test tube. On cooling, the gas(A) changes into a colourless solid(B).
Why does gas(A) change to solid on cooling?

Q. When concentrated sulphuric acid was added to an unknown salt present in a test tube a brown gas(A) was evolved. This gas intensified when copper turning were added to this test tube. On cooling, the gas(A) changed into a colourless solid(B).
Identify (A) and (B).

Give reasons for the following :

(a) Sulphuric acid forms two types of salts with NaOH,

(b) Red brown vapours are produced when concentrated sulphuric acid is added to hydrogen bromide,

(c) A piece of wood becomes black when concentrated sulphuric acid is poured on it,

(d) Brisk effervescence is seen when oil of vitriol is added to sodium carbonate.

Q. (a) When concentrated sulphuric acid was added to an unknown salt present in a test tube a brown gas (A) was evolved. This gas intensified when copper turnings were added to this test tube. On cooling, the gas (A) changed into a colourless solid (B).

(i) Identify (A) and (B).

(ii) Write the structures of (A) and (B).

(iii) Why does gas (A) change to solid on cooling?

(b) Arrange the following in the decreasing order of their reducing character :
HF, HCI, HBr, HI

(c) Complete the following reaction :

X e F_{4} + S b F_{5} \to

Q. When concentrated sulphuric acid is added to copper sulphate it gives :

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Strength of Acids and Bases

Standard X Chemistry

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