For gaseous state, if most probable speed is denoted by C*,average speed by C and mean square speed by C,then for a large number of molecules the ratios of these speeds are :

C* : \(\bar{C}\) : C = 1.225 : 1.128 : 1
C* : \(\bar{C}\) : C = 1.128 : 1.225 : 1
C* : \(\bar{C}\) : C = 1 : 1.128 : 1.225
C* : \(\bar{C}\) : C = 1 : 1.225 : 1.128

Solution

For one mole of a van der Waals gas when b = 0 and T = 300 K, the PV vs, 1/V plot is shown below.The value of the van der Waals constant a(atm. liter²mol^-2) is :

Solution

The molecular velocity of any gas is

inversely proportional to absolute temperature.
directly proportional to square of temperature.
directly proportional to square root of temperature.
inversely proportional to the square root of temperature.

Solution

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 area under the distribution curve remains the same as under the lower temperature
The distribution becomes broader
The fraction of the molecules with the most probable speed increases
The most probable speed increases

Solution

As temperature rises the most probable speed increases and the fraction of molecules possessing most probable speed decreases.

A certain gas takes three times as long to effuse out as helium. Its molecular mass will be :

27 u
36 u
64 u
9 u

Solution

A gaseous mixture was prepared by taking equal mole of CO and N₂. If the total pressure of the mixture was found 1 atmosphere, the partial pressure of the nitrogen (N₂) in the mixture is :

0.5 atm
0.8 atm
0.9 atm
1 atm

Solution

Two gases A and B having the same volume diffuse through a porous partition in 20 and 10 seconds respectively. The molecular mass of A is 49 u. Molecular mass of B will be :

50.00 u
12.25 u
6.50 u
25.00 u

Solution

The pressure exerted by 6.0 g of methane gas in a 0.03 m³ vessel at 129°C is (Atomic masses : C = 12.01, H = 1.01 and R = 8.314 Kpa dm³K^-1mol^-1)

31684 Pa
215216 Pa
13409 Pa
41777 Pa

Solution

If a gas expands at constant temperature, it indicates that :

kinetic energy of molecules decreases
pressure of the gas increases
kinetic energy of molecules remains the same
number of the molecules of gas increases

Solution

At any constant temperature the K.E. of gaseous molecules remains same (K.E. ∝ T). Thus option (c) iscorrect answer.

A weather ballon filled with hydrogen at 1 atm and 27°C has volume equal to 12000 litres. On ascending it reaches a place where the temperature is –23°C and pressure is 0.5 atm. The volume of the balloon is

24000 litres
20000 litres
10000 litres
12000 litres

Solution

\(V_{2} = \frac{P_{1}}{P_{2}}\frac{T_{2}}{T_{1}}\cdot V_{1} = \frac{1}{0.5} \times \frac{250}{300} \times 12000 \; lit. = 20000 \; lit\)

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