1-propanol (p*1 = 20.9 torr at 25 °C) and 2-propanol (p*2 = 45.2 torr at 25 °C) form ideal solutions in all proportions. Let x1 and x2 represent the mole fractions of 1-propanol and 2-propanol, respectively, in a liquid mixture and y1 and y2 represent the mole fractions of each in the vapor phase For a solution of these liquids with x1 = 0.510, calculate the composition of the vapor phase at 25 °C if the vapor above the liquid phase is composed only of 1-propanol and 2-propanol.

answer : third trial had the contaminated sample and the correct value for dhrxn should be 1000 kj/mol

explanation :

let us write down the given equations

equation 1 :

equation 2 :

equation 3 :

let us use hess's law to find out which 2 equations can be added to get the third equation.

let us reverse equation 2 and multiply it by 2. the new equation that we get is,

equation 4 :

let us add equation 1 & 4

the above equation is similar to equation 3 but has different value for dhrxn.

therefore third trial had the contaminated sample and the correct value for dhrxn should be 1000 kj/mol