Q1 of 80 Page 115

Consider the following statements related to diamond and graphite.

I. Both diamond and graphite are used as abrasives.


II. Diamond and graphite have different arrangements of carbon atoms.


III. The carbon atoms in graphite have a different number of neutrons from those in diamond.


IV. The carbon atoms in both graphite and diamond have four single covalent bonds. The incorrect statement(s) is/are

Graphite is commonly used as an abrasive, but diamond is not used.


The number of neutrons in carbon atoms present in both graphite and diamond are the same. It only depends upon the nature of the element, and both are allotropes of the same element carbon.


In diamond, each carbon is covalently bonded to 4 other carbon atoms whereas in graphite, each carbon is covalently to 3 other carbon atoms.

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41

An organic compound A with molecular form C4H8O2 on alkaline hydrolysis gives two compound B and C. C on acidification with dil. HCl gives D. Oxidation of B with K2Cr2O7/H2SO4 also gives D. Identify A, B, C and D and explain all the reactions involved.

 42

Have you ever observed while cleaning cloth that foam is formed with difficulty and an insoluble substance (scum) remains after washing with water? This is caused by the reaction of soap with the calcium and magnesium salts, which cause the hardness of water. Hence, you need to use a larger amount of soap. This problem is overcome by using another class of compounds called detergents as cleansing agents. Detergents are generally ammonium or sulphonate salts of long chain carboxylic acids. The charged ends of these compounds do not form insoluble precipitates with the calcium and magnesium ions in hard water. Thus, they remain effective in hard water. Detergents are usually used to make shampoos and products for cleaning clothes.

(i) How will you test the hardness of water?


(ii) Why soap forms scum (insoluble substance) with hard water?


(iii) How one can overcome the problem of scum formation? What values do you identify in this context?

 2

What would happen if graphene is heated in sufficient supply of air?

 3

C4+ does not exist but Pb4+ exists although both belong to the same group. This is because

I. size of carbon is much smaller than Pb. II. large amount of energy is needed in case of carbon.


III. of inert pair effect.


IV. nucleus cannot hold such a large number of electrons.


The correct statement(s) is/are