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ICSE Class 10 Chemistry Question 6 of 62

Study of Compounds — Sulphuric Acid — Question 14

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14
Question

Question 14

State how addition of –

(i) copper

(ii) NaCl

to hot conc. H2SO4 serves as a test for the latter.

Answer

(i) When Cu is added to hot conc. H2SO4, colourless suffocating (SO2) gas is evolved. The gas turns orange coloured acidified potassium dichromate solution to green colour.

Cu + 2H2SO4 (conc.) →Δ\xrightarrow{\Delta} CuSO4 + SO2 + 2H2O

(ii) When NaCl is heated with conc. H2SO4, colourless pungent smelling HCl gas is evolved.

NaCl+H2SO4[conc.]→<200°CNaHSO4+HCl\text{NaCl} + \text{H}_2\text{SO}_4 [\text{conc.}] \xrightarrow{\lt 200 \degree\text{C}} \text{NaHSO}_\text{4} + \text{HCl}

Dense white fumes are produced when a rod dipped in NH3 soln. is brought near the test tube containing HCl gas.