At a certain temperature the vapor pressure of pure heptane (C_7 H_16) is measured to be 170. torr. Suppose a solution is prepared by mixing 86.7 g of heptane and 125. g of acetyl bromide (CH_3 COBr). Calculate the partial pressure of heptane vapor above this solution. Round your answer to 3 significant digits. Note for advanced students: you may assume the solution is ideal.

Explanation:

The given data is as follows.

       Pressure (P) = 170 torr,      mass of heptane (m) = 86.7 g

First, we will calculate the number of moles as follows.

          No. of moles =

                        =

                        = 0.867 mol

Now, the number of moles of are calculated as follows.

     No. of moles =  

                           =      

                           = 1.07

Therefore, mole fraction of heptane will be calculated as follows.

     Mole fraction =

                           =

                           =

                           = 0.445

Now, we will calculate the partial pressure of heptane as follows.

                 =      

                 = 75.65 torr

Thus, we can conclude that the partial pressure of heptane vapor above this solution is 75.65 torr.