Saturday

April 19, 2014

April 19, 2014

Posted by **Petty** on Thursday, September 22, 2011 at 7:33am.

Ka = [H3O+][CH3COO-]\[CH3COOH]

Starting from this relationship show that

pH = pKa + log [base]\[acid]

urgently need assistance

- CHEMISTRY LAB urgent assistance -
**Dr Russ**, Thursday, September 22, 2011 at 7:52amStart with the acid dissociation equation:

HAc -> H+ + Ac-

Ka is then

[H+][Ac-]/[HAc] {given in the question}

at the start

HAc -> H+ + Ac-

and we start from A mole/L and B mol/L for the acid and buffer

A M ___0__ B M

at the end

HAc -> H+ + Ac-

A-x____x___B+x

so Ka is

Ka=(x)(B+x)/(A-x)

Assume that x is small wrt A and wrt B so that the equation reduces to

Ka=x(B)/(A)

which we can rearrange to

x=Ka(A)/(B)

take logs of each side

log(x)=log(Ka(A)/(B))

which is

log(x)=log(Ka) + log((A)/(B))

multiply through by -1

-log(x)=-log(Ka) - log((A)/(B))

which is

-log(x)=-log(Ka) + log((B)/(A))

or

pH = pKa + log((B)/(A))

or

pH = pKa + log [base]\[acid]

- CHEMISTRY LAB urgent assistance -
**DrBob222**, Thursday, September 22, 2011 at 12:31pmAs an added note (perhaps picky but I think needed) is that / is used as a divide sign while \ is used for other purposes.

**Related Questions**

Biology Lab gr 12 - hi, i did this lab, from this website and I was wondering if...

Chemistry (URGENT) - Hello! Does anyone know where to find the solubility of Ca(...

Discrete Math - Which of these relations on {0, 1, 2, 3} are equivalence ...

Repost bio - hi, i did this lab, from this website and I was wondering if anyone...

English - Original sentence: The urgent care center offers a variety of services...

chemistry - A student prepared 5.00 mL of borax solution at 59.2 C. He diluted ...

Discrete Math - a) Show that the relation R on Z x Z defined by (a , b) R (c, d...

Socials Studies *URGENT* - Research Territory, Food, Shelter, Transportation and...

Math - Let R1 be a binary relation on the set of integers defined as follows: R1...

Chemistry - I did a lab in chemistry about weighing table salt and sand and ...