Some Basic Concepts of Chemistry - Result Question 33

####31. Ratio of Cp and Cv of a gas ’ X ’ is 1.4. The number of atoms of the gas ’ X ’ present in 11.2 litres of it at NTP will be

(a) 6.02×1023

(b) 1.2×1023

(c) 3.01×1023

(d) 2.01×1023

[1989]

[1988]

(a) 1.8224×1022 atoms

(b) 6.0222400×1023 molecules

(c) 1.32224×1023 electrons

(d) all the above

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Solution:

  1. (a) Cp/Cv=1.4 shows that the gas is diatomic. 22.4 litre at NTP 6.02×1023 molecules

11.2L at NTP =3.01×1023 molecules

No. of atoms in gas =3.01×1023×2 atoms =6.02×1023 atoms

r=CpCv=1+2F, where F= degree of freedom of the gas molecules For mono atomic gas, F=3

γ=CpCv=1+23=53=1.67

For diatomic gas, F=5

γ=CpCv=1+25=75=1.40

For triatomic gas, F=6 or 7 (depending upon the nature of the gas)

γ=CpCv=1+26=1.33γ=CpCv=1+27=1.29



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