A student performs a titration of 25.0 mL of 0.100 M lactic acid (HC3H5O3), using 0.050 M sodium hydroxide (NaOH). The Ka for lactic acid is 1.4 x 10-4. a) (10 points) What is the pH of the solution after the addition of 23.5 mL of sodium hydroxide solution

The pH of resulting solution is 3.815

Explanation:

To calculate the number of moles for given molarity, we use the equation:

Molarity of lactic acid solution = 0.100 M

Volume of solution = 25.0 mL

Putting values in above equation, we get:

Molarity of NaOH solution = 0.050 M

Volume of solution = 23.5 mL

Putting values in above equation, we get:

The chemical reaction for NaOH and lactic acid follows the equation:

Initial:        0.0025    0.0012      

Final:         0.0013          -               0.0012          

Volume of solution = 25 + 23.5 = 48.5 mL = 0.0485 L    (Conversion factor:  1 L = 1000 mL)

To calculate the pH of acidic buffer, we use the equation given by Henderson Hasselbalch:

We are given:

= negative logarithm of acid dissociation constant of lactic acid = 3.85

pH = ?

Putting values in above equation, we get:

Hence, the pH of resulting solution is 3.815

if the concentration of products is decreased, the equilibrium will shift toward the products). add an inert gas (one that is not involved in the reaction) to the constant-volume reaction mixture: this will increase the total pressure of the system, but will have no effect on the equilibrium condition.

explanation: