Correct Answer - Option 1 : 6.4 x 10
17
CONCEPT:
BEHAVIOUR OF GASES:
- In gases, the molecules are far apart and mutual interactions amongst the molecules are negligible except when they collide.
- At low pressures and high temperatures (much above the temps at which gases liquefy or solidify), the gases follow a simple relation
⇒ PV = KT ------ (1)
Where P = pressure, V = volume, and T = temperature of a given mass of gas. K = constant that varies with the volume of the gas or with a number of atoms/molecules of the gas in the sample.
We can write, K = NkB ------ (2)
Where N = number of molecules and kb = Boltzmann constant = 1.38 × 10-23 JK-1, which is the same for every gas.
Combining equation 1 and 2, we get
\(⇒ PV=Nk_BT\)
EXPLANATION:
Given - Volume (V) = 1 cm3 = 10-6 m3, Pressure (P) = 20 mm of Hg = 2666.45 Pa, and temperature (T) = 27°C = 300 K
- The number of molecules present in a cubic centimeter of the volume is
\(\Rightarrow N=\frac{PV}{k_BT}\)
\(\Rightarrow N=\frac{2666.45\times 10^{-6}}{1.38\times 10^{-23}\times 300}=6.4 \times 10^{17}\)