A mixture of $CO$ ( $28 g/mol$ ) and $CO X_{2}$ ( $44 g/mol$ ) has vapour density $17.2$ . Find the mass percent of $CO X_{2}$ in the mixture, to the nearest integer.

Numerical answer type, answer in %, tolerance 0.5.

Answer: 51 %

Average molar mass = 2 x 17.2 = 34.4. With mole fraction x of

CO

: 28x + 44(1-x) = 34.4, so x = 0.60. Per mole:

CO

= 16.8 g,

CO X_{2}

= 17.6 g. Mass % of

CO X_{2}

= 17.6/34.4 x 100 = 51.16, i.e. 51%.