Calculate the mole fraction of benzene in a mixture that contains 45.2 g of benzene and 115.8 g of toluene.

molecular weight of toluene = 92 g/mol  

C6 = 12 x 6 = 72  

H5 = 1 x 5 =5  

CH3 = 12 + 1 x 3 =15  

molecular weight of benzene = 78 g/mol  

C6 = 12 x 6 = 72  

H6 = 1 x 6 = 6  

moles toluene:  

115.8 / (92 g/mol) = 1.25 mol  

moles benzene:  

45.2/ (78 g/mol) = 0.57mol  

total moles: 1.25  + 0.57= 1.82 moles  

mole fraction of toluene:  

1.25 mol  / 1.82 moles  = 0.68

the answer is barium and copper bromide