PV = nRT
n = PV/RT
P = 40k Pa = 40 x 103 Pa V = 2 m3
T = 298 K, R = 8.314 J K - 1 mol-1
\(n = \frac{(40\times 10^3\ Pa)\ (2\ m^3)}{(8.314JK^{-1}\ mol^{-1})\times (298\ K)}\)
n = 32.28 mol (1 Pa = 1 J m3)
अणुओं की संख्या = मोल x आवोगाद्रो संख्या
= 32.28 × 6.022 x 1023
= 1.94 × 1025