Question

The mole fraction of NaCl in an aqueous solution is 0.132. How many moles of water are present in 1 mole of this solution?

Answer 1

You could look at it this way.
1 mole of solution = 0.132 of NaCl + x
1 - 0.132 = 0.868 mols of water.

answer: 0.868 <<<< answer

Answer 2

Answer: The number of moles of water in the solution is 0.868 mole.

Explanation:

• The summation of mole fractions of different components in solution is equal 1.0.

• If a solution composed of different components (a, b, c, d, ...., n) and each component has its mole fraction (Xa, Xb, Xc, Xd, ......,Xn) then Xa + Xb + Xc + Xd + ... + Xn = 1.0

• For the mentioned NaCl solution; the solution composed of NaCl and water: XNaCl + XH2O = 1.0

• Also, it is important to define the mole fraction: XNaCl = nNaCl/ntotal and ntotal = nNaCl + nwater; where n id the number of mole (n = mass/molar mass)

• XNaCl + XH2O = 1.0 and XNaCl = 0.132

• then Xwater = 1.0 - 0.132 = 0.868