The mole fraction is the ratio of the number of moles of a component of a solution to the total number of moles. For example:
mole fraction of H₂O = number of moles of H₂O/(total number of moles)
To find the mole fraction of each component we only have to find the total number of moles and then apply the formula.
total number of moles = moles of H₂O + moles of C₂H₅OH
total number of moles = 6.8 moles + 1.5 moles
total number of moles = 8.3 moles
mole fraction of H₂O = moles of H₂O/total number of moles
mole fraction of H₂O = 6.8 moles/(8.3 moles)
mole fraction of H₂O = 0.82
mole fraction of C₂H₅OH = moles of C₂H₅OH/total number of moles
mole fraction of C₂H₅OH = 1.5 moles/(8.3 moles)
mole fraction of C₂H₅OH = 0.18
Answer: the mole fraction of H₂O is 0.82 and the mole fraction of C₂H₅OH is 0.18.