Question

The density of a solution of 3.69g NaCl in 21.70g H₂O is 1.11g/mL. Calculate the molarity of NaCl in the solution

		2.02 M
		2.24 M
		1.90 M
		3.04 M
		2.76 M
		3.17 M

Answer 1

density of solution = 1.11 g/mL

mass of solution = 3.69 g + 21.70 g = 25.39 g

so,

volume of solution = mass of solution / density of solution

= 25.39 g / 1.11 g/mL

= 22.87 mL

= 2.287*10^-2 L

Molar mass of NaCl,

MM = 1*MM(Na) + 1*MM(Cl)

= 1*22.99 + 1*35.45

= 58.44 g/mol

mass(NaCl)= 3.69 g

number of mol of NaCl,

n = mass of NaCl/molar mass of NaCl

=(3.69 g)/(58.44 g/mol)

= 6.314*10^-2 mol

Molarity,

M = number of mol / volume in L

= 6.314*10^-2/(2.287*10^-2)

= 2.76 M

Answer: 2.76 M