Chemistry
State your observations in each of the following:
(a) Dilute hydrochloric acid is added to calcium hydrogen carbonate.
(b) At the cathode, acidified aqueous copper sulphate solution is electrolysed with copper electrodes.
(c) Moist starch iodide paper is introduced into chlorine gas.
(d) Calcium hydroxide is heated with ammonium chloride crystals.
Answer
(a) When dilute hydrochloric acid is added to calcium hydrogen carbonate, carbon dioxide gas is released with effervescence, and a solution of calcium chloride is formed along with water.
(b) Copper, a brownish pink metal is deposited at the cathode when acidified aqueous copper sulphate solution (CuSO4) is electrolysed with copper electrodes.
(c) The moist starch iodide paper turns blue-black when exposed to chlorine gas.
(d) When calcium hydroxide is heated with ammonium chloride crystals, the pungent smelling gas (ammonia) is given out.
Related Questions
(a) Name the other ion formed when ammonia gas dissolves in water.
(b) Give one test that can be used to detect the presence of the ion produced.
(c) Name the gaseous product formed when dilute nitric acid is added to copper.
Write balanced equations for the following reactions:
(a) Preparation of ethyne from ethylene dibromide.
(b) Preparation of ester using carboxylic acid.
(c) Conversion of alkyl halide to ethene.
Draw the structure of the stable positive ion formed when sulphuric acid dissolves in water.
Distinguish the following by your observations:
(a) Calcium nitrate solution and zinc nitrate solution (using NH4OH).
(b) Sodium carbonate and sodium sulphite (using HCl).