Q24 of 26 Page 1

(a) A solution is prepared by dissolving 5.0 g of a non-volatile solute in 95 g of water. It has a vapour pressure of 23.375 mmHg at 25°C. Calculate the molar mass of the solute. Vapour pressure of pure water at 25°C is 23.75 mmHg.

(b) Give reasons for the following :


(i) Osmotic pressure is considered to be a colligative property.


(ii) Molality is a better option to express concentration in comparison to molarity.


OR


(a) Calculate the amount of CaCl2 (molar mass = 111 g/mol) which must be added to 500 g of water to lower its freezing point by 2K, assuming CaCl2 is completely dissociated.


(Kf For water = 1.86 K kg /mol )


(b)


(i) What happens when blood cells are placed in distilled water?


(ii) Why is increase in temperature observed on mixing chloroform with acetone?


(a) Given:

Mass Of Solute (W1) = 5.0 g


Mass of solvent (W2) = 95g


Vapour pressure of solution (p)=23.375mm Hg


Vapour pressure of pure water (P° = 23.75 mm Hg)


Molar mass of solute (M1) = ?


Acc to Raoults Law


P=P° A

More from this chapter

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22

(a) Why is it safer to use soaps from the environmental point of view?


(b) What is the basic difference between antiseptics and disinfectants?


(c) Pickles have a long shelf life and do not get spoiled for months. Why?


 23

Sanjay, a peon working in Mr. Pamil’s office, fainted while standing outside his room. Mr. Pamil took him to the nearby hospital where he was diagnosed to be severely 'anaemic’. The doctor prescribed an iron rich diet and multivitamin supplement to him. Mr. Pamil supported his family to get the medicines. After 20 — 25 days he was diagnosed to be normal.

Answer the following questions:


(a) What values (two) are displayed by Mr. Pamil ?


(b) Name the vitamin whose deficiency causes ‘Pernicious


Anaemia'.


(c) Give an example of a water soluble vitamin.


(d) Name two sources of vitamins needed to treat Pernicious Anaemia.


 25

Account for the following:

(a) Chlorine water on standing loses its yellow colour.


(b) F2 has lower bond dissociation enthalpy than Cl2.


(c) BiH3 is the strongest reducing agent amongst all the


hydrides of group 15.


(d) Noble gases have low boiling points.


(e) On addition of ozone to KI solution, violet vapours are Obtained.


OR


(a) Give balanced chemical equations for the following reactions :


(i) XeF2 + H2O →


(ii) XeF6 + NaF →


(iii) XeF4 + SbF5 →


(b) Draw the structures of the following :


(i) H4P2O7


(ii) XeF4


 26

(a) How are the following conversions carried out ?

(i) Benzoic acid to Benzene


(ii) Ethanoyl Chloride to Acetone


(iii) Acetophenone to Ethyl Benzene


(b) Give chemical tests to distinguish between the following pairs of compounds


(i) Benzaldehyde and Acetophenone


(ii) Ethanal and Propanal


OR


(a) Give reasons for the following :


(i) Chloro acetic acid is stronger than acetic acid.


(ii) Aldehydes are more reactive than ketones towards nucleophilic reagents.


(iii) Formaldehyde does not take part in Aldol condensation.

(b) Write the structures of A and B in the following reactions :


(i)CH3COCl


(ii) CH3MgBr