You plan to prepare a buffer solution of pH 5.75 from sodium acetate (NaCH3COO)

Question

You plan to prepare a buffer solution of pH 5.75 from sodium acetate (NaCH3COO) and acetic acid (CH3COOH, Ka= 1.8x10^-5).

a) Write a chemical equation for the addition of acetic acid to water

b) Identify the conjugate acid/base pairs

c) How much solid NaCH3COO (n-grams) must be added to 2.50 L of 0.55M CH3COOH to make a buffer solution with pH 5.75 (assume solid does not change volume).

d) You add a volume of 2.0 M HCl to the buffer solution prepared in c above. Will pH increase or decrease? Explain

e) The pH changed by 0.25 pH units. How much HCl did you add?

Explanation / Answer

In order to calculate the pH of the buffer solution you need to know the amount of acid and the amount of the conjugate base combined to make the solution. These amounts should be either in moles or in molarities. The Ka of the acid also needs to be known.

PH=-log[H+]

-5.75=log[H+]

[H+]= anti log (-5.75)=

all the information you requested available in following site.

https://www.chem.purdue.edu/gchelp/howtosolveit/Equilibrium/Buffers.htm#BufferpH

If you still have any more doubt, let me know.

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