pH Question

I have a question which states that the Ka value for ethanoic acid is 1.74x10^-5. Sodium hydroxide is added to the beaker containing ethanoic acid, forming a salt. The questions asks to calculate the value of [salt]/[acid] at a pH of 4.84.

So far, I have calculated [H+] by doing 10^-4.84 which I'm assuming will be equal to the concentration of ethanoic acid. I wasn't sure how to get the concentration of the salt, so I looked at the mark scheme and it took the value of Ka to be equal to the salt concentration. Why can Ka be equal to the concentration of the salt?

Can you post the whole question please?

You need to divide Ka by h+ to get the salt/acid ratio- just rearranging ka equation, h+=10^-4.84
h+=1.4454*10^-5

ka=1.74*10^-5

ka/h+ =1.21

This is because Ka=[H+][A-]/[HA] so divide both sides by [H+]
to get Ka/[H+] = [A-]/[HA]

You need to divide Ka by h+ to get the salt/acid ratio- just rearranging ka equation, h+=10^-4.84
h+=1.4454*10^-5

ka=1.74*10^-5

ka/h+ =1.21

This is because Ka=[H+][A-]/[HA] so divide both sides by [H+]
to get Ka/[H+] = [A-]/[HA]

thank you!!

it isn't.

Ka = [h+][a-]/[ha]

the hydrogen ion concentration does not equal the concentration of the ethanoic acid (it is only partially dissociated)

the moles of salt will be equal to the moles of base added to the excess acid.

The ethanoic acid concentration is the moles remaining divided by the total volume.

anyone please help with this q

anyone please help with this q