Final answer:
The relative molecular mass of the hydrocarbon X, with a vapor density of 20.83, is calculated to be 41.66 g/mol.
Step-by-step explanation:
The vapor density of a substance is defined as half the relative molecular mass (molar mass) of a gas compared to that of hydrogen gas. Since the vapor density of the hydrocarbon X is given as 20.83, we need to calculate its relative molecular mass.
To calculate the relative molecular mass (Mr) of the hydrocarbon X, we simply multiply the vapor density by two (because vapor density is half the molar mass):
Mr(X) = Vapor Density of X × 2 = 20.83 × 2
Therefore, the relative molecular mass of the hydrocarbon X is:
Mr(X) = 41.66 g/mol