1.

The vapour pressure of acetone at `20^(@)C` is 185 torr. When `1.2 g` of non-volatile substance was dissolved in `100g` of acetone at `20^(@)C` its vapour pressure was 183 torr. The moalr mass `(g mol^(-1))` of the substance is:A. 488B. 32C. 64D. 128

Answer» Correct Answer - C
For dilute solutions,
`(Deltap)/(p_(0))=(w_(B)xxm_(A))/(m_(B)xxw_(A))`
`(185-183)/(185)=(1.2xx58)/(m_(B)xx100)`
`m_(B)=64.38`
`~~ 64 g mol^(-1)`]


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