Solve this :
11. What is the molarity of a solution of sodium chloride (At. wts. Na = 23, Cl = 35.5) which contains 60 g of sodium chloride in 2000 cm3 of a solution ?
12. Calculate the mole fraction of ethyl alcohol and water in a solution in which 46 g of ethyl alchol and 180 g of warter are mixed together.
Molarity of NaCl = no of moles of NaCl / volume of solution in litres.
Volume of solution = 2000cm^3 = 2000ml= 2L
Given mass of NaCl = 60g.
Molar mass = 23+35.5=58.5g.
No of moles = 60/ 58.5 = 1.026 moles.
Hence molarity = 1. 026/ 2 = 0.513 M
2)
2)
Ethyl alcohol,
Given mass = 46g
Molar mass = 46.
No of moles = given mass / molar mass = 46/46= 1 mole
Water,
Given mass = 180g
Molar mass = 18.
No of moles = 180/18 = 10 moles.
Hence , total moles = 10+1 = 11 moles.
Mole fraction of ethyl alcohol = 1 / 11 = 0.0909.
Mole fraction of water = 10/11 = 0.9090