Question 11 

You have a stock solution of 2.00 mol/L potassium iodide, KI(aq). What volume of the stock solution do you need to prepare each of the following solutions?SHOW CALCULATIONS PLEASE.

a) 50.0 mL of 1.00 mol/L

b) 150.0 mL of 0.500 mol/L

Question 12 

A pharmaceutical assistant has a 50.0 g/L solution of glucose, C₆H₁₂O₆(aq).

a) What is the concentration of the solution in mol/L? 

b) What volume of the glucose solution should the pharmaceutical assistant use to make 500.0 mL of a 0.050 mol/L glucose solution?

Question 11 

You have a stock solution of 2.00 mol/L potassium iodide, KI(aq). What volume of the stock solution do you need to prepare each of the following solutions?SHOW CALCULATIONS PLEASE.

a) 50.0 mL of 1.00 mol/L

C₁V₁ = C₂V₂ where:

V₁ = Volume of stock solution needed to make the new solution

C₁ = Concentration of stock solution

V₂ = Final volume of new solution

C₂ = Final concentration of new solution

C₁₌2.00 mol/L

V₁ = X

 C₂= 1.00 mol/L

V₂= 50.0 mL

2.00 mol/L × X = 1.00 mol/L ×50.0 mL

X =(1.00 mol/L ×50.0 mL) ÷ 2.00 mol/L

= 25.0 mL

b) 150.0 mL of 0.500 mol/L

C₁₌2.00 mol/L

V₁ = X

 C₂= 0.500 mol/L

V₂= 150.0 mL

2.00 mol/L × X = 0.500 mol/L ×150.0 mL

X =(0.500 mol/L ×150.0 mL) ÷ 2.00 mol/L

= 37.5 mL

Question 12 

A pharmaceutical assistant has a 50.0 g/L solution of glucose, C₆H₁₂O₆(aq).

a) What is the concentration of the solution in mol/L? 

Start by converting grams per litre into moles per litre.

Molar mass of glucose = 180.156 g/mol

Moles of glucose present in a litre solution = mass present/molar mass

=50.0 g ÷ 180.156 g

= 0.278 moles/L

b) What volume of the glucose solution should the pharmaceutical assistant use to make 500.0 mL of a 0.050 mol/L glucose solution?

C₁V₁ = C₂V₂

C₁₌ 0.278 moles/L

V₁ = X

 C₂= 0.050 mol/L

V₂= 500.0 mL

0.278 moles/L × X = 0.050 mol/L × 500.0 mL

X =(0.050 mol/L × 500.0 mL) ÷ 0.278 moles/L

= 89.9 mL

To make a fixed amount of a dilute solution from a stock solution, you can use the formula: C₁V₁ = C₂V₂ where:

V₁ = Volume of stock solution needed to make the new solution

C₁ = Concentration of stock solution

V₂ = Final volume of new solution

C₂ = Final concentration of new solution