When few drops of dilute sulphuric acid is added to Salt ' R ' and heated, a colourless gas is released which turnsmoist lead acetate paper silvery black.

ICSE Class 10 Chemistry 2023 Solved Paper

Study the following observations and name the anions present in each of the reactions.

Question : 59

Total: 88

Solution:

' R ' is sodium sulphide. When it heated with. dil. H2SO4 a colourless gas H2S is released which turns moist lead acetate paper to silvery black, due to the formation of lead sulphide.
‌

Na2S

′R′

+‌H2

SO4

‌ dil. ‌

→‌Na2SO4+H2S↑
(CH3‌COO)2‌Pb+H2S→‌

PbS

‌ Black ‌

+CH3‌COOH
Anion is S2− (Sulphide)

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