A sample of chloroethane, C2H5Cl, absorbs 0.185 kJ and begins to vaporize at its normal boiling point of 12.3°C. What is the mass of the chloroethane sample? The molar heat of vaporization for chloroethane is 24.7kJ/mol.
Heat absorbed (q) = 0.185 kJ Molar heat of vaporization (ΔH) = 24.7 kJ/ mol Molar mass of chloroethane = 64.51 g/mol q = (ΔH) * (n) where n is the number of moles. so n = q / ΔH = 0.185 / 24.7 = 7.5 x 10⁻³ mole number of moles = mass(g) / Molar mass mass (g) = number of moles * molar mass = (7.5 x 10⁻³) * (64.51) = 0.48 g
