+91-8076753736 support@wiredfaculty.com
Wired Faculty Logo
Wired Faculty Logo Wired Faculty

NEET chemistry

Sponsor Area

Question
CBSEENCH11008436
Wired Faculty App

Identify the correct statement for the change of Gibbs energy for a system (ΔGsystem) at constant temperature and pressure

  • If ΔGsystem > 0, the process is spontaneous

  • If ΔGsystem =0, the system has attained equilibrium

  • If ΔGsystem < 0, the system is still moving in a particular direction

  • If ΔGsystem < 0, the process is not spontaneous

Solution

B.

If ΔGsystem =0, the system has attained equilibrium

If the Gibbs free energy for a system (ΔGsystem) is equal to zero, then system is present in equilibrium at a constant temperature and pressure.

Sponsor Area

Question
CBSEENCH11008437
Wired Faculty App

Assume each reaction is carried out in an open container. For which reaction will ΔH = ΔE?

  • H2 (g) + Br2 (g) →2HBr (g)

  • C (s) + 2 H2O (g) → 2 H2 (g) + CO2 (g)

  • PCl5 (g) →PCl3 (g) + Cl2 (g) 

  • 2CO (g) + O2 (g) → 2 CO2 (g)

Solution

A.

H2 (g) + Br2 (g) →2HBr (g)

As we know that
 ΔH = ΔE + PΔV
ΔH = ΔE +ΔnRT ..(1)
where ΔH → change in enthalpy of the system (standard heat at constant pressure)
Δ E → change in internal energy of system (Standard heat at constant volume)
Δn → no. of gaseous moles of product - no. of gaseous moles of reactant
R → gas constant
T → absolute temperature
If Δ n = 0 for reactions which is carried out in an open container, therefore, Δn = 0 for reactions which are carried out in an open container, therefore, ΔH  =ΔE
so for reaction (1) Δn = 2-2 = 0
Hence, for reaction (1) , ΔH =ΔE 

Question
CBSEENCH11008438
Wired Faculty App

Given: The mass of electron is 9.11 x 10-31 kg
Planck constant is 6.626 x 10-34 Js,
the uncertainty involved in the measurement of velocity within a distance of 0.1 A is:

  • 5.79 x 106 ms-1

  • 5.79 x 107 ms-1

  • 5.79 x 108 ms-1

  • 5.79 x 105 ms-1

Solution

A.

5.79 x 106 ms-1

By Heisenberg's uncertainty principle
WiredFaculty

Question
CBSEENCH11008439
Wired Faculty App

The enthalpy and entropy change for the reaction:

Br2 (l) + Cl2 (g)→ 2BrCl (g)

are 30 kJ mol-1 and 105 JK-1 mol-1 respectively. The temperature at which the reaction will be in equilibrium is:

  • 285.7 K 

  • 273 K

  • 450 K

  • 300 K

Solution

A.

285.7 K 

At equilibrium, Gibbs free energy change (ΔGo) is equal to zero. The following thermodynamic relation is used to show the relation of ΔGo with the enthalpy change (ΔHo) and entropy change (ΔSo)
ΔGo  = ΔHo - ΔSo
0 = 30 x 103 (J mol-1) - T x 105 (J K-1) mol-1
WiredFaculty

Question
CBSEENCH11008441
Wired Faculty App

For the reaction,

CH4  (g) + 2 O2 (g) ⇌ CO2 (g) + 2H2O (l), 

ΔrH = - 170. 8 kJ mol-1

Which of the following statements is not true? 

  • At equilibrium, the concentrations of CO2 (g) and H2O (l) are not equal

  • The equilibrium constant for the reaction is given by Kp = fraction numerator left square bracket CO subscript 2 right square bracket over denominator left square bracket CH subscript 4 right square bracket left square bracket straight O subscript 2 right square bracket end fraction

  • Addition of CH4 (g) or O2 (g) at equilibrium will cause a shift to the right

  • The reaction is exothermic

Solution

B.

The equilibrium constant for the reaction is given by Kp = fraction numerator left square bracket CO subscript 2 right square bracket over denominator left square bracket CH subscript 4 right square bracket left square bracket straight O subscript 2 right square bracket end fraction

For the reaction,
CH4  (g) + 2 O2 (g) ⇌ CO2 (g) + 2H2O (l), 
ΔrH = - 170. 8 kJ mol-1
This equilibrium is an example of heterogeneous chemical equilibrium.Hence, for it
WiredFaculty
not correct expression.
In addition of CH4 (g) or O2 (g) at equilibrium Kc = will be decreased according to expression (i) but Kc remains constant at constant  at constant temperature fro a reaction, so for maintaining the constant value of Kc, the concentration of CO2 will increase in same order. Hence, on the addition of CH4 or O2 equilibrium will cause to the right.
This reaction is an example of an exothermic reaction.

Sponsor Area

Mock Test Series

Mock Test Series

NCERT Sample Papers

Entrance Exams Preparation