10.5: Kinetic Molecular Theory of Gases
- Page ID
- 170549
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Kinetic Molecular Theory
Exercise \(\PageIndex{1}\)
Which of the following statements is/are postulates of the kinetic–molecular theory of gases?
- Gas particles are in constant, random motion.
- The distance between gas particles is large in comparison to their size.
- The average kinetic energy of gas particles is proportional to the kelvin temperature of the gas.
a. 1 only b. 2 only c. 3 only d. 1 and 2 e. 1, 2, and 3
- Answer
-
e. 1, 2, and 3
Exercise \(\PageIndex{2}\)
Calculate the root-mean-square velocity for the O2 molecules in a sample of O2 gas at 35.9°C. (R = 8.3145 J/K⋅mol)
- Answer
-
2.41*105 J*kg-1
\(v = \sqrt{\frac{3RT}{M}}\)
R = 8.314 J/K*mol; T = 35.9 + 273.15 = 309.05 K; M = (O2) = 32*10-3 kg/mol
\(v = \sqrt{\frac{3*8.3145*309.05}{32*10-3}}=2.408*10^{5}\;J*kg^{-1}\)
Exercise \(\PageIndex{3}\)
Place the following gases in order of increasing average velocity at 300 K: Ar, CH4, N2, and N2O.
- Answer
-
N2O < Ar < N2 < CH4
Exercise \(\PageIndex{4}\)
At STP, as the molar mass of the molecules that make up a pure gas increases, the
- root mean square speed of the molecules increases.
- root mean square speed of the molecules decreases.
- root mean square speed of the molecules remains constant.
- root mean square speed increases to a maximum, then decreases.
- none of the above.
- Answer
-
b. root mean square speed of the molecules decreases.