Question

The correct match is:

List-I	List-II
${O_3}$	Turns benzidine paper to brown
Hypo	Turns anhydrous $CuS{O_4}$to blue
${H_2}O$	Violet colour with $FeC{l_3}$
${H_2}S$	Rotten egg smell

A.A-2, B-3, C-1, D-4
B.A-4, B-2, C-3, D-1
C.A-1, B-3, C-2, D-4
D.A-3, B-4, C-2, D-1

Answer 1

To answer this question, you must recall the reactions shown by various inorganic chemicals with different reagents. Hypo is sodium thiosulphate $\left( {N{a_2}{S_2}{O_3}} \right)$ also known as hyposulphite of soda and in short hypo.

Complete answer:
Considering the first compound, that is ozone. Ozone is a triatomic allotropic form of oxygen and is highly oxidative in nature. It is an unstable compound and is much more reactive as compared to oxygen thus, shows a great number of characteristic reactions. One of those, is its reaction with benzidine. When added on benzidine paper, ozone turns it brown in colour. So, we can match A with 1.
Considering the second compound which is hypo. When sodium thiosulphate reacts with ferric chloride, thiosulphate ions and ferric ions form a dark- violet colour complex given as ${\left[ {Fe{{\left( {{S_2}{O_3}} \right)}_2}{{\left( {{H_2}O} \right)}_2}} \right]^ - }$.So we can match B with 3.
Considering the third compound, water. We know that copper sulphate is generally present in hydrated form in the form of blue crystals. Anhydrous copper sulphate is formed from the loss of those water molecules also known as the water of crystallization. It is a white powder like substance. When water is added, each molecule absorbs five molecules of water forming blue coloured crystals of copper sulphate pentahydrate. Thus, we can match C with 2.
Considering the last compound, hydrogen sulphide. It is a gas, which is colorless and has a characteristic unpleasant smell like rotten eggs. Thus, we can match D with 4.
The correct match is A-1, B-3, C-2, D-4.

Thus, the correct answer is C.
Note:
All these reactions show significant changes in colour and through smell and thus are used in qualitative analysis to detect the compounds present in a given unknown sample.