Chemistry [3 Mark Question Answer]

Sodium hydroxide solution is added first in a small quantity, then in excess to the aqueous salt solution of copper (II) sulphate, zinc nitrate, lead nitrate, calcium chloride and iron (III) sulphate. Copy of the following table and write the colour of the precipitate in (i) to (v) and the nature of the precipitate (soluble or insoluble) in (vi) to (x).

Aqueous salt solution	Colour of the precipitate when NaOH is added in small quantity	Nature of the(soluble or insoluble) when NaOH is added in excess
copper (II) sulphate zinc nitrate lead nitrate calcium chloride Iron (III) sulphate	(i) (ii) (iii) (iv) (v)	(vi) (vii) (viii) (ix) (x)

Use the information given in (a) to (h) to identify the substances P to W selecting your answers from the given list.
List:

Calcium	Oxygen	Copper (II) Oxide
Carbon	Calcium hydroxide	Copper (II) Nitrate
Lead (II) Oxide	Hydrogen chloride	Chlorine
Lead (II) Nitrate	Calcium Oxide	Ammonium chloride

(a) P is white solid. When heated produces white fumes (sublime).
(b) P and R on warming produce an alkaline gas.
(c) On adding water to T, heat is evolved and R is formed.
(d) Q burns brightly in the air to form T.
(e) When S is heated, it gives off brown fumes and leaves a black residue of U.
(f) A solution of S is formed by warming U with dilute nitric acid.
(g) V is a gaseous non-metallic element that reacts with hydrogen to form W.
(h) A solution of W will neutralize the solution of R.

Identify the following substances:
(i) An alkaline gas A which gives dense white fumes with hydrogen chloride.
(ii) A dilute acid B which does not normally give hydrogen when reacted with metals but does give a gas when it reacts with copper.
(iii) Gas C has an offensive smell like rotten eggs
(iv) Gas D is a colourless gas which can be used as a bleaching agent
(v) Liquid E can be dehydrated to produce ethene

Salts A, B, C, D, and E undergo reactions (i) to (v) respectively. Identify the anion present in these salts on the basis of these reactions.
(a) When silver nitrate solution is added to a solution of A, a white precipitate, insoluble in dilute nitric acid, is formed.
(b) The addition of dilute hydrochloric acid to B produces a gas which turns lead acetate black paper.
(c) When a freshly prepared solution of ferrous sulphate is added to a solution of C and concentrated sulphuric acid is gently poured from the side of the test-tube, a brown ring is formed.
(d) When dilute sulphuric acid is added to D, a gas is produced which turns acidified potassium dichromate solution from orange to green.
(e) The addition of dilute hydrochloric acid to E produces effervescence. The gas produced turns lime water milky but does not affect acidified potassium dichromate solution.

Mention the colour changes observed when the following indicators are added:

Solution	Acids	Alkalies
(a) Alkaline phenolphthalein solution (b) Methyl orange solution (c) Neutral litmus solution

State your observation when:
Zinc chloride solution, zinc nitrate solution, and zinc sulphate solutions are added individually to
(i)Barium chloride solution
(ii)Lead nitrate solution.