Final answer:
To find the molecular formula of a compound with a known empirical formula, determine the molar mass using the ideal gas law and compare it to the empirical formula mass. This process can be applied to any gaseous sample, like chloroform, by using the sample's mass, volume, temperature, and pressure. The number of empirical units making up the molecular formula is deduced from this comparison.
Step-by-step explanation:
Determining the Molecular Formula of a Gas
To determine the molecular formula of an unknown vapor with an empirical formula of CH2, we need to find its molar mass and compare it to the empirical formula mass. To find the molar mass, we can use the ideal gas law PV = nRT, where P is pressure, V is volume, n is moles, R is the ideal gas constant, and T is temperature in Kelvin. For the given sample, we convert temperatures to Kelvin and pressures to atmospheres. Then solve for n (moles) and multiply by the molar mass of the empirical formula to get the molar mass of the compound. From there, we can determine how many times the empirical formula must be multiplied to reach the actual molar mass.
For chloroform, the process is similar. Given a sample's mass, volume, temperature, and pressure, we apply the ideal gas law to find its molar mass. Chloroform's molar mass would be crucial when comparing with its empirical formula to deduce the molecular formula.
Finally, to check your understanding, for ethane's volume at different conditions, you would use Charles's Law, assuming that the pressure remains constant, to find the new volume V2 using the relation V1/T1 = V2/T2.