Preparation of Standard Solution by dilution

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 1The 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?

Vi =

Ci =

Vf =

Cf =

Example 1The 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)Vi = 10mL

Ci = 5M

(Solution we are making)Vf =

Cf =

Example 1The 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)Vi = 10mL

Ci = 5M

(Solution we are making)Vf = 250mL

Cf = X (unknown)

Calculations

CiVi = CfVf

(5M)(10mL) = (X)(250mL)

Rearrange so it looks more familiar

50 = 250XDivide both sides by 250 (solve for X)

50 = X 250

X = 0.2M

Example 2The 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?

Vi =

Ci =

Vf =

Cf =

Example 2The 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?

Vi = 100mL

Ci = X

Vf = 500mL

Cf = 0.1M

Calculations

CiVi = CfVf

(X)(100mL) = (0.1M)(500mL)

Rearrange so it looks more familiar

100X = 50Divide both sides by 100 (solve for X)

X = 50 100

X = 0.5M

Assignment

See note handout