Class 12 CBSE Chemistry Test Paper

1

Blood cells collapse when suspended in saline water. Account for it.

(1)

2

Name any two neutral oxides.

(1)

3

a) What is the principle behind reverse osmosis?

b) Which substance is usually added into water in the car radiator to act as antifreeze?

(2)

4

State Raoult’s law for a solution containing non-volatile solute.

(2)

     

5

Complete the following equations and also balance them.

i) NH4Cl + Ca(OH)2 clip_image002

ii) Zn + HNO3 clip_image004

iii) P4 + SOCl2clip_image004[1]

iv) MnO4 + HClclip_image006

(2)

6

Draw the structures of the following compounds.

i) Peroxodisulphuric acid

ii) Phosphorous acid and account for the basicity of phosphorous acid.

(2)

7

45 g of ethylene glycol ( C2H6O2) is mixed with 600g of water. Calculate (a) the freezing point depression and (b) the freezing point of the solution.

(3)

8

2 g of benzoic acid (C6H5COOH) dissolved in 25 g of benzene shows a depression in freezing point equal to 1.62 K. Molal depression constant for benzene is 4.9 K Kgmol-1. What is the percentage association of acid if it forms dimer in solution?

(3)

9

Arrange the following in the order indicated.

i) MF, MCl, MBr, MI – Decreasing ionic character.

ii)HOCl, HOBr, HOI – increasing acidic strength

iii)NH3, AsH3, SbH3, PH3 – Decreasing bond dissociation enthalpy

(3)

10

Give reasons for the following observations.

i)Halogens are strong oxidizing agents

ii)Noble gases have large positive electron gain enthalpy.

iii)Sulphur shows paramagnetic character in vapour phase.

(3)

11

How do you prepare XeO3 from XeF4? Write equation. Draw the structure of XeF6. Mention any two applications of He gas.

(3)

12

i) How is O3 estimated quantitatively?

ii)H2SO4 is a moderately strong acid. Give evidence.

ii)Though N2 exhibits +5 oxidation state, it doesnot form pentahalide. Why?

iv)Mention the conditions required for the maximum yield of NH3.

v)What happens when Cl2 reacts with excess NH3 and NH3 reacts with excess Cl2. Give equations.

(5)

13

i) With the help of a graph explain positive deviation.

ii)The vapour pressure of pure liquids A & B are 450 & 700mm Hg respectively at 350K. Find out the composition of the liquid mixture if total vapour pressure is 600mm Hg. Also find the composition of the vapour phase.

(5)

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