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12th Grade > Physics

KINETIC THEORY OF GASES MCQs

Total Questions : 24 | Page 3 of 3 pages
Question 21. A vessel of volume V contains an ideal gas at absolute temperature T and pressure P. The gas is allowed to leak till its pressure falls to P. Assuming that the temperature remains constant during leakage, the number of moles of the gas that have leaked is
  1.    VRT(P + P′)
  2.    V2RT(P + P′)
  3.    VRT(P − P′)
  4.    V2RT(P − P′)
 Discuss Question
Answer: Option C. -> VRT(P − P′)
:
C
Number of moles present initially is n=PVRT. Let n be the number of moles of the gas that leaked till
the pressure falls to P. Since volume V of the vessel cannot change and temperature T remains
constant during leakage, we have
n=PVRT
Number of moles that leaked is
Δn=nn=PVRTPVRT=VRT(PP)
So the correct choice is (C)
Question 22. From the following V-T diagram we can conclude  From The Following V-T Diagram We Can Conclude 
  1.    P1=P2
  2.    P1>P2
  3.    P1
  4.    None of these
 Discuss Question
Answer: Option C. -> P1
:
C
In case of given graph, V and T are related as V = aT +b, where a and b are constants.
From ideal gas equation, PV = μRT
We find P = μRTaT+b = μa+bT
Since T2>T1, therefore P2>P1.
Question 23. One mole of an ideal monatomic gas requires 210 J heat to raise the temperature by 10 K, when heated at constant pressure. If the same gas is heated at constant volume to raise the temperature by 10 K then heat required is
  1.    238 J
  2.    126 J
  3.    210 J
  4.    350 J
 Discuss Question
Answer: Option B. -> 126 J
:
B
(Q)P = μCPT and (Q)V = μCVT
(Q)V(Q)P = CvCp = 32R52R = 35
[ (CV)mono=32R,(CP)mono=52R]
(Q)V = 35×(Q)P = 35×210=126J
Question 24. If the r.m.s. velocity of a gas at a given temperature (Kelvin scale) is 300 m/s, whathat will be the r.m.s. velocity of a gas having twice the molecular weight and half the temperature on Kelvin scale = 
  1.    300 m/sec  
  2.    600 m/sec
  3.    75 m/sec  
  4.    150 m/sec
 Discuss Question
Answer: Option D. -> 150 m/sec
:
D
vmax = 3RTMVmaxTM
v2v1 = M1M2×T2T112×12 v2=v12=3002=150m/sec

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