Question

At 300 K and 1.00 atm. pressure, the density of gaseous HF is 3.17 `gL^(-1)`. Which of the following facts, is supported by the given data ?
A. Gaseous HF under these conditions is lighter than Alr
B. There is no hydrogen bonding in gaseous HF under these conditions
C. There is extensive hydrogen bonding in gaseous HF under these conditions
D. None of these

Answer 1

Correct Answer - C
T=300 K, P=1.00 atm, V=1.00 L
`therefore n=(PV)/(RT)`
`=(("1.00 atm")("1.00 L"))/(("0.0821 L atm" K^(-1) mol^(-1))("300 K"))`
=0.0406 mol
Mass of 1 L of HF under these conditions =3.7 g
`therefore` Formula mass of HF under these conditions =`(3.17 g)/(0.0406 mol)=78.1 g mol^(-1)`
The formula mass of HF =`19 g mol^(-1)`