A buffer solution?

Question

a buffer solution is prepared by taking 0.400 moles of acetic acid (pKa= 4.76) and 0.250 moles of calcium acetate in suffecient water to make 1,400 liters of solution. calculate the pH of this solution

can some one explain me this how to do it i am really lost..

Answer 1

This is all you need to know:

Ka = [H+] . [salt] / [acid]

-You can calculate Ka:

Ka =10^-4.76 = 1.738*10^-5 M

- 0.250 mol calcium acetate (salt) in 1400 L, [salt] = 0.250/1400 = 1.786 * 10^-4 M

-0.400 mol acetic acid in 1400 L, [acid]= 0.4/1400= 2.857*10^-4 M

Hence:

1.738*10^-5  = [H+] . 1.786 * 10^-4 /  2.857*10^-4

[H+] = 2.78 * 10^-5 M

pH = - log  (2.78 * 10^-5 ) = 4.56

Answer 2

use the simle eqn.

ph=pka+log[salt]/[acid].moles of salt and acid hv been given,so is the volume.