The vapor pressure of benzene is 53.3 k P a at 603 o C , but it falls to 51 .5 kP a when 19 g of a non-volatile organic compound is dissolved in 500 g benzene. The molar mass of the non-volatile compound is

Step-by-step solution

P 0   =   53 .3   kPa P s = 51.5   kP a P 0 - P s P s = n N = 19 × 78 M × 500 53.3 - 51.5 51.5 = n N = 19 × 78 M × 500 M = 19 × 78 × 51.5 ( 53.3 - 51.5 ) × 500 M = 85 g