Question

If 85g LiCl is dissolved in water to 2.00L, what is the molarity?

What is the new concentration of 5.00 mL of the above solution is diluted with water to 0.25L?

Answer 1

1)

Molar mass of LiCl,

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

= 1*6.968 + 1*35.45

= 42.418 g/mol

mass(LiCl)= 85 g

number of mol of LiCl,

n = mass of LiCl/molar mass of LiCl

=(85.0 g)/(42.418 g/mol)

= 2.004 mol

volume , V = 2.00 L

Molarity,

M = number of mol / volume in L

= 2.004/2

= 1.002 M

Answer: 1.00 M

2)

use dilution formula

M1*V1 = M2*V2

1---> is for stock solution

2---> is for diluted solution

Given

M1 = 1.00 M

V1 = 5.00 mL

V2 = 0.25L = 250 mL

Use:

M1*V1 = M2*V2

M2 = (M1*V1)/V2

M2 = (1.00*5.00)/250

M2 = 0.020 M

Answer: 0.020 M