Subject

Chemistry

Class

NEET Class 12

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 Multiple Choice QuestionsMultiple Choice Questions

1.

1 mole of H2SO4 is mixed with 2 moles of NaOH .The heat evolved will be :

  • 57.3 kJ

  • 2 x 57.3 kJ

  • 57.3/2 kJ

  • Cannot be predicted


B.

2 x 57.3 kJ

1 mole of H2SO4 = 2g-equivalent of H2SO4 .Hence , when 1 mole of H2SOis mixed with 2 moles of NaOH , the heat evolved will be 2 x 57.3 kJ .


2.

27Co60 is radioactive because :

  • its atomic number is high

  • it has high pn ratio

  • it has high np ratio

  • None of the above


C.

it has high np ratio

Co2760 is radioactive and unstable due to high np ratio .

i.e. , np > 1

Number of protons = 27

Number of neutrons = 33

 np for Co2760 = 3327 = 1.22


3.

One mole of which of the following has the highest entropy ?

  • Liquid nitrogen

  • Hydrogen gas

  • Mercury

  • Diamond


B.

Hydrogen gas

Entropy is the measure of degree of disorder (or randomness) of a system . The greater the disorder in a system , the higher is the entropy . Hence , entropy is highest for hydrogen gas .


4.

Conjugate acid of CH3NH2 is :

  • CH3OH

  • CH3NH3+

  • CH2NH2+

  • CH3N-H


B.

CH3NH3+

Conjugate acid is obtained , when a base accepts a proton .

CH3NH2base + H+proton CH3NH3+conjugate acid


5.

If the mass defect of 40X is 0.090 u , then binding energy per nucleon is :

(1 u = 931.5 MeV)

  • 9.315 MeV

  • 931.5 MeV

  • 83.0 MeV

  • 8.38 MeV


A.

9.315 MeV

m = 0.090 u

Number of nucleons = 9

 Binding energy per nucleon

total binding energynumber of nucleon

 m × 931.5number of nucleon

0.090 × 931.59 = 9.315 MeV


6.

Amines behave as :

  • Lewis acid

  • Lewis base

  • aprotic acid

  • neutral compound


B.

Lewis base

The substance which. can donate a pair of electrons is called Lewis base .

Amines contain a lone pair of electrons on nitrogen atom which is available for donation , so they behave as Lewis base .


7.

One mole. of a perfect gas expands isothermally to ten times of its original volume. The change in entropy is :

  • 0.1 R

  • 2.303 R

  • 10.0 R

  • 100.0 R


B.

2.303 R

ΔS = 2.303nR log V2V1

n = 1

 S = 2.303 R log 101

S = 2.303R              (log 10 = 1)


8.

100 cc of 0.6 N H2SO4 and 200 cc of 0.3 N HCl were mixed together .The normality of the solution will be :

  • 0.2 N

  • 0.4 N

  • 0.8 N

  • 0.6 N


B.

0.4 N

Normality of the mixed solution 

N1V1 + N2V2V1 + V2

0.6 × 1001000 + 0.3 × 2001000100 + 2001000

0.6 × 0.1 × 0.3 × 0.20.3

0.06 + 0.060.3 

0.120.3 = 0.4 N


9.

For the reaction :

N2 + 3H2  2NH3H = ?

  • E + 2RT

  • E - 2RT

  • E + RT

  • E - RT


B.

E - 2RT

N2 + 3H2  2NH3

H = E + ngRT

ng = np - nr = 2 - 4 = -2

 H = E + (-2)RT

H = E - 2RT


10.

50 mL of 0.1 M HCl and 50 mL of 0.2 M NaOH are mixed .The pH of the resulting solution is :

  • 1.30

  • 4.2

  • 12.70

  • 11.70


C.

12.70

50 mL of0.1 M HCl = 0.1 × 501000 = 5 x 10-3

50 mL of 0.2 M NaOH = 0.2 × 501000 = 10 x 10-3

Hence , after neutralisation NaOH left 

= 10 x 10-3 - 5 x 10-3 = 5 x 10-3

Total volume = 100 cc

The concentration of NaOH

5 x 10-3 x 1000100 = 0.05 M

[OH-] = 0.05 M = 5 x 10-2 M

pOH = - log [OH-]

= - log [5 x 10-2]

= 1.3010

pH + pOH = 14

pH = 14 - 1.3010

= 12.699

= 12.70