Asolution is prepared by adding 16 g of ch3oh (molar mass 32 g) to 90 g of h2o (molar mass 18 g). the mole fraction of ch3oh in this solution is closest to which of the following?
(a) 0.1
(b) 0.2
(c) 0.3
(d) 0.4
(e) 0.6

The mole fraction of CH3OH in this solution is closest to 0.1.

Explanation:

The mole fraction of CH3OH can be calculated by dividing the number of mole of CH3OH by the sum of all moles present in the solution. In our example, we have 16 g CH3OH and 90 g H2O. Let´s see how many mols of each constituent we have:

1 mol CH3OH = 32 g ⇒ 16 g CH3OH = 0.5 mol.

1 mol H2O = 18 g ⇒ 90 g H20 = 5 mol

Then, the mole fraction is:

X = mol CH3OH / (mol H2O + mol CH3OH)

X= 0.5 mol / (5 mol + 0.5 mol) ≅ 0.1

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