If you add 5.0 mL of 0.50 M NaOH solution to 20.0 mL to Buffer C, what is the change in pH of
the buffer?
(where buffer C is 8.203 g sodium acetate with 100.0 mL of 1.0 M acetic acid)

I have calculated the pH of buffer C to be 4.74.
Now what? =\

  1. 👍
  2. 👎
  3. 👁
    I am a , I have figured this out

    1. 👍
    2. 👎
  2. couple someone please still explain? and explain how the 4.74 pH was found? thanks

    1. 👍
    2. 👎
  3. could someone please still explain? and explain how the 4.74 pH was found? thanks

    1. 👍
    2. 👎
  4. pH = pKa + log ([A-]/[HA])
    We ned to determine the concentration of the sodium acetate:
    Molar mass CH3COONa = 82.0340 g/mol
    Therefore you are adding 1mol CH3COOH per litre = 1.00M
    pKa CH3COOH = 4.75
    pH = 4.75 + log (1/1)
    pH = 4.75 as you got - OK.

    Question 2: If you add 5 ml of 0.50M NaOH solution to 20ml of the buffer, what is the change in pH?

    The answer should be that the pH does not change very much - that is what a buffer solution is all about. I am sure that there is a simple way to make this calculation - but I do not know it. So let us try and do it from first principles:

    You have a buffer solution that is 1.00M in CH3COOH and 1.00M in CH3COONa.
    If you add some NaOH you react with the CH3COOH , reducing its concentration and increasing the concentration of CH3COONa

    Mol CH3COOH in 20 mL of 1.00M = 20/1000*1 = 0.02mol CH3COOH
    Mol CH3COONa in 20mL of 1.00M = 0.02mol CH2COONa
    Mol NaOH in 5.0mL of 0.50M = 5/1000*0.5 = 0.0025mol NaOH
    The NaOH reacts with the CH3COOH to form 0.0025 mol CH3COONa and 0.0025 mol CH3COOH is removed
    You end up with
    CH3COOH = 0.02mol - 0.0025 mol = 0.0175mol CH3COOH in 25mL total solution:
    Molarity of CH3COOH = 0.0175/25*1000 = 0.70M CH3COOH
    CH3COONa = 0.02mol + 0.0025mol = 0.0225 mol CH3COONa in 25mL total solution
    Molarity of CH3COONa = 0.0225/25*1000 = 0.9M CH3COONa

    pH = pKa + log([A-]/[HA])
    pH = 4.75 + log( 0.9/0.7)
    pH = 4.75 + log 1.286
    pH = 4.75 + 0.11
    pH = 4.86

    1. 👍
    2. 👎

Respond to this Question

First Name

Your Response

Similar Questions

  1. Chemistry

    Which of the following pairs would make a good buffer solution in an aqueous solution? A) H2SO4 and NaHSO4 B) Ca(NO3)2 and HNO3 C) HCl and NaCl D) HF and NaOH E) none of them I know the answer is D but I don't understand why. I


    HOW CAN U TELL IF HNO3 +KNO3 IS A BUFFER SOLUTION A buffer solution must contain a weak acid and its conjugate base OR a weak base and its conjugate acid. HNO3 is a strong base and KNO3 is the salt of a strong base (KOH) and a

  3. Chemistry Help! Thank you :)

    Assuming the final solution will be diluted to 1.00 , how much more should you add to achieve the desired pH? Information: Imagine that you are in chemistry lab and need to make 1.00 L of a solution with a pH of 2.80. You have in

  4. chemistry

    Consider a buffer solution consisting of CH3NH3Cl and CH3NH2. Which of the following statements are true concerning this solution? (Ka for CH3NH3+ = 2.3 x 10 -11). 1. A solution consisting of 0.1 M CH3NH3Cl and 0.1 M CH3NH2 would

  1. Chemistry

    A 500 mL buffer solution is 0.1 M benzoic acid and 0.10 M in sodium benzoate and has an initial pH of 4.19. What is the pH of the buffer upon addition of 0.010 mol of NaOH?

  2. Chemistry

    You are asked to prepare 500. mL of a 0.150 M acetate buffer at pH 5.00 using only pure acetic acid, 3.00 M NaOH, and water. Calculate the quantities needed for each of the following steps in the buffer preparation. 1. Add acetic

  3. Chemistry

    What would happen if you add HCl to a buffer solution of HNO2 and KNO2 and result. WHat about adding NaOH?

  4. chemistry

    2. A 350 mL buffer solution containing 0.15 M HF and 0.150 M NaF is reacted with sodium hydroxide. What mass of NaOH can this buffer neutralize before the pH rises above 4.0? If the same volume of buffer was 0.35 M in HF and 0.35

  1. chemistry

    Chemist needs a buffer with pH of 4.5. how many milliliters of pure CH3COOH (density;1.049g/ml) must be added to 500ml of 0.1M NaOH solution to obtain such a buffer?

  2. Chemistry

    You need to prepare 1.0 L of a buffer with a pH of 9.15. The concentration of the acid in the buffer needs to be 0.100 M. You have available to you a 1.00 M NH4Cl solution, a 6.00 M NaOH solution, and a 6.00 M HCl solution.

  3. Quantitive Analysis

    You are asked to prepare 500. mL of a 0.250 M acetate buffer at pH 4.90 using only pure acetic acid (MW=60.05 g/mol, pKa=4.76), 3.00 M NaOH, and water. Answer the following questions regarding the preparation of the buffer.

  4. chemistry

    Prepare 500mL of a 0.200 M acetate buffer at pH 4.90 using only pure acetic acid, 3M NaOH, and water. 1) Add acetic acid to ~400mL of water in a 500 mL beaker. How many grams of acetic acid are needed? 2)Add 3 M NaOH solution

You can view more similar questions or ask a new question.