Question

If 5.85 g of nacl are dissolve in 90 g of water the mole fraction of nacl is

Answer 1

5.85g of nacl ,
molecular mass of nacl is 58.44 approx.
therefore no. of moles of nacl are 0.1

and 90g of water,
molecular mass of water is 18
therefore no. of moles are 5

mole fraction=no.of moles of nacl / no. of moles of nacl +no. of moles of water.

mole fraction = 0.1 / 0.1+5

=0.1/5.1
= 1 / 51. ( Ans )

Answer 2

Moles = Weight / Molar mass

Moles of NaCl = 5.85 g / (58.5 g/mol) = 0.1 mole
Moles of H₂O = 90 g / (18 g/mol) = 5.0 mole

Mole fraction of NaCl = (Moles of NaCl) / (Total number of moles in solution)
= (Moles of NaCl) / (Moles of NaCl + Moles of H₂O)
= 0.1 mole / (0.1 mole + 5.0 mole)
= 0.1 / 5.1
= 1 / 51

Mole fraction of NaCl in solution is 1 / 51