✔ 最佳答案
Mole ratio C : H = (100 - 20)/12 : 20/1 = 6.67 : 20 = 1 : 3
Hence, empirical formula = CH3
Pressure, P = (640/760) x 101000 = 85050 Pa
Volume, V = 250 cm³ = 250 x 10¯⁶ m³
No. of moles, n = ?
Gas constant, R = 8.314 J mol¯¹ K¯¹
Absolute temperature, T = 273 + 27 = 300 K
PV = nRT
(85050)(250 x 10¯⁶) = n(8.314)(300)
n = 0.008525 mol
Let (CH3)y be the molecular formula of the compound.
Molar mass: (12 + 1x3)y = 0.256/0.008525
15y = 30
y = 2
Hence, molecular formula = C2H6