Preparation of Standard Solution by dilution

Dilution: Decreasing the concentration of a solution by adding more solvent Stock Solution: The solution you start with (A higher concentration)

Example 1 The concentration of the stock solution is 5M. If we use 10mL of this solution to make a 250 mL solution what will the new concentration be? V i = C i = V f = C f =

Example 1 The concentration of the stock solution is 5M. If we use 10mL of this solution to make a 250 mL solution what will the new concentration be? (Stock solution) V i = 10mL C i = 5M (Solution we are making) V f = C f =

Example 1 The concentration of the stock solution is 5M. If we use 10mL of this solution to make a 250 mL solution what will the new concentration be? (Stock solution) V i = 10mL C i = 5M (Solution we are making) V f = 250mL C f = X (unknown)

Calculations CiVi = CfVf (5M)(10mL) = (X)(250mL) Rearrange so it looks more familiar 50 = 250X Divide both sides by 250 (solve for X) 50 = X 250 X = 0.2M

Example 2 The concentration of the stock solution is unknown. We use 100mL of this solution to make a 500 mL solution. If this new solution was tested to be 0.1M what was the concentration of the stock solution? V i = C i = V f = C f =

Example 2 The concentration of the stock solution is unknown. We use 100mL of this solution to make a 500 mL solution. If this new solution was tested to be 0.1M what was the concentration of the stock solution? V i = 100mL C i = X V f = 500mL C f = 0.1M

Calculations CiVi = CfVf (X)(100mL) = (0.1M)(500mL) Rearrange so it looks more familiar 100X = 50 Divide both sides by 100 (solve for X) X = X = 0.5M

Assignment See note handout