A solution has 25% of water, 25% ethanol and 50% acetic acid by mass. The mole fraction of water,ethanol and acetic acid respectively will be

Since 18 g of water = 1 mole 

25 g of water $=\frac{25}{18}=1.38$ mole 

Similarly, 46 g of ethanol = 1 mole 

25 g of ethanol $=\frac{25}{46}=0.55$ moles 

Again, 60 g of acetic acid = 1 mole 

50 g of acetic acid $=\frac{50}{60}=0.83$ mole 

$\therefore$ Mole fraction of water $=\frac{1.38}{1.38+0.55+0.83}=0.50$

Similarly, Mole fraction of ethanol $=\frac{0.55}{1.38+0.55+0.83}=0.19$

Mole fraction of acetic acid $=\frac{0.83}{1.38+0.55+0.83}=0.3$