What do you observe when
(a) CO2 is passed through lime water first and then a little in excess?
(b) HCl is passed through silver nitrate solution?
(c) H2S is passed through lead nitrate solution?
(d) Cl2 is passed through potassium iodide (KI) solution?
(e) Cobalt chloride paper is introduced in water vapour?
Write the balanced equations for each of the above.
(a) When CO2 is passed through lime water first in small amounts it turns lime water milky. This is due to the formation of insoluble calcium carbonate.
Ca(OH)2 + CO2 ⟶ CaCO3 ↓ + H2O
When excess of the gas is passed through the solution, milkiness disappears. This is due to the formation of a soluble bicarbonate.
CaCO3 + CO2 + H2O ⟶ Ca(HCO3)2 [soluble]
(b) When HCl is passed through silver nitrate solution, a white ppt. of silver chloride is formed.
HCl + AgNO3 ⟶ AgCl ↓ + HNO3
(c) When H2S is passed through lead nitrate solution, black ppt. of PbS is formed.
Pb(NO3)2 [colourless] + H2S ⟶ PbS ↓ [black] + 2HNO3
(d) Cl2 turns potassium iodide (KI) solution blue black
Cl2 + 2KI ⟶ 2KCl + I2
(e) Water vapour turns blue cobalt chloride paper pink.
CoCl2 + 2H2O ⟶ CoCl2.2H2O