Solid, Liquid, Gas Phases - 21 - Fill Blanks Type

1. Cp – Cv for an ideal gas is ____________.
(JEE 1984)

Answer : R
(See page No. 67 H C Verma part 2)

2. The rate of diffusion of gas is ______________________ proportional to the square root of molecular mass.
(JEE 1986)

Answer: inversely
(Graham’s law of diffusion: The rate of diffusion of a gas is inversely proportional to the square root of its density or molar mass.)

3. The value of PV for 5.6 litres of an ideal gas is _________________ RT at STP.
(JEE 1987)

Answer: ¼ or 0.25
1 mole of an ideal gas at STP has a volume of 22.4 litres

4. Eight grams of oxygen and hydrogen at 27°C will have the total kinetic energy in the ratio of __________________.
(JEE 1989)

Answer: 1:16

Reason: For a mixture of gases, in thermal equilibrium, average kinetic energy of all molecules is same.

(½)*m1* v1² = (1/2)*(m2*v2²

Oxygen’s molecular weight is 32 and hence 8 grams will have 8/32 = ¼ moles.
Hydrogen’s molecular weight is 2 and hence 8 grams will have 8/2 = 4 mols

Total kinetic energy of oxygen moleculues = (¼ )* (½)*m1* v1²
Total kinetic energy of hydrogen molecules = 4*(1/2)*(m2*v2²

The ratio will be (1/4)/4 = 1/16 as remaining terms or equal in both cases.

5. The shape of [CH3] ⁺ is ___________________.
(JEE 1990)

Answer: Planar

6. Among N₂0, S0₂, I₃3⁺, I₃^-, the linear species are ____________ and __________ .
(JEE 1997).

Answer: N₂0, I₃3^-

7. A liquid which is permanently supercooled is frequently called as ___________.
(JEE 1997)

Answer: glass