Question
Say for example, that you had prepared a Buffer C, in whichyou mixed 8.203 g of sodium acetate,NaC2H3O2, with 100.0 mL of 1.0 Maetic acid. a. What would be the initial pH of Buffer C b. If you add 5.0mL of 0.5 M NaOH solution to 20.0 mL each ofBuffer B( initial pH of Buffer B is 3.92), andBuffer C, Which buffer's pH would change less? explain Please use steps so I can fully understand. Thank you :) Say for example, that you had prepared a Buffer C, in whichyou mixed 8.203 g of sodium acetate,NaC2H3O2, with 100.0 mL of 1.0 Maetic acid. a. What would be the initial pH of Buffer C b. If you add 5.0mL of 0.5 M NaOH solution to 20.0 mL each ofBuffer B( initial pH of Buffer B is 3.92), andBuffer C, Which buffer's pH would change less? explain Please use steps so I can fully understand. Thank you :)
Explanation / Answer
Molar mass of sodium acetate = 82.03 g / mol Mass of sodium acetate = 8.203 g Number of moles of sodium acetate = 8.203 g / 82.03 g /mol =0.1 mol Number of moles of aceticacid = 0.1 L * 1.0 M =0.1 mols pKa = 4.74 As the number of moles of both are equal , pH = pKa Number of moles of NaOH = 0.0025 moles When a strong base is added to the acidic buffer, number ofmoles of acid decreases and number of moles of saltincreases. Number of moles of salt = 0.1 mol + 0.0025 moles = 0.1025 moles Number of moles of acid= 0.1 mol - 0.0025 moles =0.0975 moles pKa = 4.74 pH = 4.74 + log ( 0.1025 / 0.0975) = 4.77 pH = 0.03 pH = 0.03 Change in pH for the buffer B and C depends upon thecompositions of the buffer.