Question

A 500.0 ml buffer solution is 0.10 m benzoic acid and 0.10 m sodium benzoate has an initial ph of 4.19. what is the ph of the buffersolution upon addition of 0.010 mol ofnaoh? the kafor benzoic acid is 6.5 • 10-5

Answer 1

To calculate the pH of a buffer solution, you can use the Henderson-Hasselbalch equation. In this case, you can calculate the initial concentration of the conjugate base and acid using the equation. Then, find the new pH of the buffer solution after adding NaOH.

Step-by-step explanation:

To calculate the pH of a buffer solution, you can use the Henderson-Hasselbalch equation:

pH = pKa + log([conjugate base]/[acid])

In this case, the initial pH of the buffer is 4.19, so you can calculate the initial concentration of the conjugate base and acid using the equation.

Then, you can calculate the new concentrations of the conjugate base and acid after adding 0.010 mol of NaOH and use the Henderson-Hasselbalch equation again to find the new pH of the buffer solution.

Using the given Ka value of 6.5 x 10^-5 for benzoic acid and the initial concentrations of the buffer solution, you can calculate the initial pH and the new pH after adding NaOH.

Answer 2

new pH = 4.27

Adding 0.01 mol of NaOH would increase the amount (in mol, 0.10) of sodium benzoate and decrease the amount (in mol, 0.10) of benzoic acid. This is because NaOH would react with benzoic acid to form more sodium benzoate. NaOH would get used up in the solution. Adding (sodium benzoate + NaOH) and subtracting (benzoic acid + NaOH) would give you 0.11 mol of sodium benzoate and 0.09 mol of benzoic acid. New pH = pKa + log [mol of sodium benzoate/mol of benzoic acid]. Hope this helps!