Give reasons for the following :

(a) Sulphuric acid forms two types of salts with NaOH,

(b) Red brown vapours are produced when concentrated sulphuric acid is added to hydrogen bromide,

(c) A piece of wood becomes black when concentrated sulphuric acid is poured on it,

(d) Brisk effervescence is seen when oil of vitriol is added to sodium carbonate.

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Solution

(a) Two types of salts are formed when sulphuric acid reacts with NaOH because sulphuric acid is dibasic.

(b) When hydrogen bromide reacts with sulphuric acid the bromine gas is obtained which produce red brown vapours.

(c) A piece of wood becomes black when concentrated sulphuric acid is poured on it because it gives a mass of carbon.
(d) When sulphuric acid is added to sodium carbonate it liberates carbon dioxide which produces brisk effervescence.

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Similar questions

Give reasons for the following:
(i) In the contact process, sulphur trioxide formed is dissolved in 98% sulphuric acid and not in water.
(ii) When solution of sulphur dioxide is exposed to air, it gets converted to sulphuric acid.
(iii) When diluting concentrated sulphuric acid, the acid should be added to water and not water to the acid.
(iv) When concentrated sulphuric acid is exposed to air, its volume increases and it becomes slightly dilute.
(v) Sulphuric acid can form two kinds of salts with sodium chloride.
(vi) When barium chloride is added to dilute sulphuric acid, a white precipitate is formed.
(vii) When carbon is heated with concentrated sulphuric acid, carbon dioxide is formed.
(viii) Ammonia gas cannot be dried by passing through concentrated sulphuric acid.
(ix) When concentrated sulphuric acid is added to sugar/glucose, a black mass is left behind.
(x) Concentrated sulphuric acid should not be added to oxalic acid or formic acid in the open laboratory.
(xi) When concentrated sulphuric acid is added to blue crystalline copper sulphate, it turns powdery white.
(xii) Concentrated sulphuric acid must be stored in airtight bottles.
(xiii) Cotton clothes get burnt with concentrated sulphuric acid.
(xiv) H₂SO₄ cannot be prepared by heating sodium sulphate with conc. HCl or HNO₃.

Q. When concentrated sulphuric acid is added to copper sulphate it gives :

Q. (a) When carbon is heating with concentrated sulphuric acid, carbon dioxide is formed. Why?
(b) Why the wooden shelves on which concentrated sulphuric acid bottles are kept are stained black? [4 MARKS]

Q. When a mixture of solid sodium chloride,potassium dichromate is heated with concentrated sulphuric acid orange red vapours are formed, then compound formed is :

Q. 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. Tabulate your answers in the format given below:
(i) When silver nitrate solution is added to a solution of A, a white precipitate, insoluble in dilute nitric acid, is formed.
(ii) Addition of dilute hydrochloric acid to B produces a gas which turns lead acetate paper black.
(iii) 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.
(iv) When dilute sulphuric acid is added to D, a gas is produced which turns acidified potassium dichromate solution from orange to green.
(v) Addition of dilute hydrochloric acid to E produces an effervescence. The gas produced turns limewater milky but does not affect acidified potassium dichromate solution.

Salt	Anion
A
B
C
D
E

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