Subject

Chemistry

Class

NEET Class 12

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 Multiple Choice QuestionsMultiple Choice Questions

1.

In the reaction of sodium thiosulphate with I2 in aqueous medium, the equivalent weight of sodium thiosulphate is equal to

  • molar mass of sodium thiosulphate

  • the average of molar masses of Na2S2O3 and I2

  • half the molar mass of sodium thiosulphate

  • molar mass of sodium thiosulphate × 2


A.

molar mass of sodium thiosulphate

In the reaction of sodium thiosulphate with I2 in aqueous medium, the equivalent weight of sodium thiosulphate is equal to molar mass of sodium thiosulphate.

2Na23S2+2O + I2 → Na26S4+2.5O + 2NaI

n factor = 1

E = M1 = M


2.

If a species has 16 protons, 18 electrons and 16 neutrons, find the species and its charge.

  • S1-

  • Si2-

  • P3-

  • S2-


D.

S2-

The species with 16 protons, 18 electrons (2 unit negative charge is present) and 16 neutrons is S2-.  


3.

In Sommerfeld's modification of Bohr's theory, the trajectory of an electron in a hydrogen atom is

  • a perfect ellipse

  • a closed ellipse-like curve, narrower at the perihelion position and flatter at the aphelion position

  • a closed loop on spherical surface

  • a rosette


C.

a closed loop on spherical surface

In Sommerfeld's modification of Bohr's theory, the trajectory of an electron in a hydrogen atom is a closed loop on spherical surface. 


4.

Dipole moment of  is 1.5 D. The dipole moment of  is

  • 1.5 D

  • 2.25 D

  • 1 D

  • 3 D


A.

1.5 D

Given for this molecule  μ1 = 1.5 D

For  μ = 0 (as it is symmetrical)

Hence for   μ will be 1.5 D.


5.

Calculate Kc for the reversible process given below if Kp = 167 and T = 800°C

CaCO3 (s)  CaO (s) + CO2 (g)

  • 1.95

  • 1.85

  • 1.89

  • 1.60


C.

1.89

Kp = Kc(RT)ng

For Eq. CaCO3 (s)  CaO (s) + CO2 (g), ng = 1

KcKp(RT)ng = 167(0.0821 × 1073)1 = 1.89


6.

At identical temperature and pessure, the ratio of diffusion of hydrogen gas is 33 times that of a hydrocarbon having molecular formula CnH2n-2. What is the value of 'n'?

  • 1

  • 4

  • 3

  • 8


B.

4

rH2rCnH2n-2 = MCnH2n-2MH2 = MCnH2n-22 MCnH2n-22 = 33 = 27MCnH2n-2 = 27 × 2 = 54

Hence, 12n + (2n - 2) × 1 = 54 

14n = 56

n = 4

Thus, hydrocarbon is C4H6.


7.

0.1M HCl and 0.1M H2SO4 each of volume 2 mL are mixed and the volume is made upto 6 mL by adding 2 mL of 0.01N NaCl solution. The pH of the resulting mixture is

  • 1.17

  • 1.0

  • 0.3

  • log 2 - log 3


B.

1.0

Millimoles of H+ = 0.1 × 2 + 0.1 × 2 × 2 = 0.6

Total volume in mL = 6

pH = -log10[H+] = - log0.66 = -log 0.1 = 1


8.

The molarity of a NaOH solution by dissolving 4 g of it in 250 mL water is

  • 0.4 M

  • 0.8 M

  • 0.2 M

  • 0.1 M


A.

0.4 M

The molarity of a NaOH solution by dissolving 4 g of it in 250 mL water can be calculated using

Molarity = 4402501000 = 0.4 M


9.

For a reversible chemical reaction where the forward process is exothermic, which of the following statements is correct ?

  • The backward reaction has higher activation energy than the forward reaction.

  • The backward and the forward processes have the same activation energy.

  • The backward reaction has lower activation energy

  • No activation energy is required at all since energy is liberated in the process.


A.

The backward reaction has higher activation energy than the forward reaction.

The energy profile diagram for a exothermic reaction is as

 (Ea)b > (Ea)f

Among all the statements given, correct option is a.


10.

Which of the following thermodynamic relation is correct ?

  • dG = Vdp- SdT

  • dE = pdV + TdS

  • dH = -Vdp + Tds

  • dG = Vdp + SdT


A.

dG = Vdp- SdT

The correct thermodynamic relation is

dG = dH - TdS - SdT (as G = H - TS)

Again, H = E + pV

 dH = dE +pdV +Vdp and dE = TdS - pdV

Thus, dG = (TdS - pdV) +pdV + Vdp - TdS - SdT

              = Vdp - SdT