Question

Molarity & Dilutions Worksheet
mols = (L)(M)
1. What is the molarity of 0.96 mols of MgCl 2 in 500 mL of solution?

2. What is the volume of 9.33mols Na 2 S in 4.50 M solution?

3. What is the molarity of 2.48 mols CaF2 in .375 L of solution?

4. How many moles of solute are in 15.25 L of 2.0M CaCl 2 ?

Diluting solutions
M 1 V 1 = M 2 V 2
1. How many L of a 7.5M H 2 SO 4 stock solution would you need
to prepare a dilute solution 100 L of 0.25M H 2 SO 4 ?

2. How many L of 0.48M HBr dilute solution can be made from
a stock solution of .5 L of 3.5M HBr solution?

3. A chemist starts with 0.83 L of a 0.27M NaCl solution and
dilutes it. What is the Molarity of NaCl in the new solution of
3.00 L?

4. A chemist starts with 1.5 L of a 0.75M KCl solution and
dilutes it. What is the Molarity of KCl in the new solution of
5.00 L?

Answer 1

Molarity & Dilutions Worksheet — answers

Mols = (L)(M)

1) Molarity of 0.96 mol MgCl2 in 500 mL:
500 mL = 0.500 L
M = n / V = 0.96 mol / 0.500 L = 1.92 M

2) Volume of 9.33 mol Na2S in 4.50 M solution:
V = n / M = 9.33 mol / 4.50 M = 2.07 L

3) Molarity of 2.48 mol CaF2 in 0.375 L:
M = n / V = 2.48 mol / 0.375 L = 6.61 M

4) Moles in 15.25 L of 2.0 M CaCl2:
n = M · V = 2.0 M · 15.25 L = 30.5 mol

Diluting solutions (M1V1 = M2V2)

1) Volume of 7.5 M H2SO4 needed to make 100 L of 0.25 M:
V1 = M2V2 / M1 = (0.25·100 L) / 7.5 = 3.33 L

2) Volume of 0.48 M HBr that can be made from 0.5 L of 3.5 M stock:
V2 = (M1V1) / M2 = (3.5·0.5 L) / 0.48 = 3.65 L

3) Molarity after diluting 0.83 L of 0.27 M NaCl to 3.00 L:
M2 = (M1V1) / V2 = (0.27·0.83) / 3.00 = 0.0747 M (≈ 0.075 M)

4) Molarity after diluting 1.5 L of 0.75 M KCl to 5.00 L:
M2 = (0.75·1.5) / 5.00 = 0.225 M

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