JEE Chemistry

Question 1

Which one of the following species is diamagnetic in nature?

  • He2+

  • H2

  • H2+

  • H2-

Solution

B.

H2

H2 σ1s2 σ* 1s0 , no unpaired so diamagnetic.

Question 2

For a spontaneous reaction the ∆G, equilibrium constant (K) and Eocell will be respectively 

  • -ve, >1, +ve

  • +ve, >1, -ve

  • -ve, <1, -ve

  • -ve, >1, -ve

Solution

A.

-ve, >1, +ve

Question 3

Consider the reaction: N2 +3H2 → 2NH3 carried out at constant temperature and pressure. If ∆H and ∆U are the enthalpy and internal energy changes for the reaction, which of the following expressions is true? 

  • ∆H = 0

  • ∆H = ∆U

  • ∆H < ∆U

  • ∆H >∆U

Solution

C.

∆H < ∆U

∆H = ∆U + ∆nRT
∆n = -2
∆H = ∆U - 2RT
∆H < ∆U

Question 4

Which one of the following statements is NOT true about the effect of an increase in temperature on the distribution of molecular speeds in a gas?

  • The most probable speed increases

  • The fraction of the molecules with the most probable speed increases

  • The distribution becomes broader

  • The area under the distribution curve remains the same as under the lower temperature

Solution

B.

The fraction of the molecules with the most probable speed increases

Most probable velocity increase and a fraction of a molecule possessing most probable velocity decreases.

Question 5

The exothermic formation of ClF3 is represented by the equation
Cl subscript 2 left parenthesis straight g right parenthesis space plus space 3 straight F subscript 2 space left parenthesis straight g right parenthesis space rightwards harpoon over leftwards harpoon with space space space space space space space on top space 2 ClF subscript 3 space left parenthesis straight g right parenthesis space semicolon space increment rH space equals negative 329 space kJ
Which of the following will increase the quantity of ClF3 in an equilibrium mixture of Cl2, F2 and ClF3?

  • Increasing the temperature

  • Removing Cl2

  • Increasing the volume of the container

  • Adding F2

Solution

D.

Adding F2

straight M subscript 3 straight V subscript 3 space equals space straight M subscript 1 straight V subscript 2 space plus space straight M subscript 2 straight V subscript 2
straight M space equals space fraction numerator 480 space left parenthesis 1.5 right parenthesis space plus space 520 space left parenthesis 1.2 right parenthesis over denominator 1000 end fraction space equals space 1.344 space straight M