Question

how could you use 1.0M lactic acid and 1.0M NaOH (instead of lactate) to make 200ml of a 0.25M lactate buffer, ph 4.0?
i dont know where to start

Answer 1

Start by looking at how much lactic acid and sodium lactate you would need for the buffer (200ml of a 0.25M lactate buffer, ph 4.0).

Then you're going to find what proportions of lactic acid and NaOH you should mix to get the sodium lactate and lactic acid (because its not a strong acid and won't fully dissociate).

\(CH_3CH(OH)COOH+ NaOH \rightarrow CH_3CH(OH)COO^-Na^+ + H_2O \)

\(+\; CH_3CH(OH)COOH\)

Answer 2

how would tou calculate for what you will need

Answer 3

I'm pretty sure you can use the henderson-hasslebach equation

Answer 4

yh i did i got 0.11 lactic acid, 0.14 lactate then i got stuck

Answer 5

M

Answer 6

Now find how much lactic acid and NaOH you need to mix to achieve that mixture.

Answer 7

thats where i am confused

Answer 8

You gotta think like a chemist. To get an idea, mix any amount and see what you end up with.

Answer 9

HINT: you have to do it in 2 parts, use the dissociation of lactic acid (equilibrium expression), and the neutralization to make sodium lactate.

Answer 10

so the first thing will be 1.0M under the eq. then under it will be 0.11M on the left side of the eq. and the right side will be 0.14 m..then i substracted both sides by 1.0M naoh .. however i got a - num on the left i am kind of puzzled

Answer 11

can you write it as an equation, i don't know what you mean.
if you got a negative number you're doing i wrong.