About us | Feedback

pH calculation - questions

pH questions

BATE pH calculator

operating systems:
XP, Vista, 7, 8, 10

single user license price:
€24.95 - approximately $25

Buy Now!

By clicking Buy Now! you will continue to the FastSpring checkout page where payment will be taken, and your order fulfilled by FastSpring, our trusted reseller, and Merchant of Record.

download 30-day free trial!
30-day money back guarantee!

pH calculation questions » pH of weak acid

Calculate pH of 0.001M solution of benzoic acid, pKa=4.19.

We will start with the simplified formula 8.13.

eq. 8.138.13

From formula we get [H+]=2.54×10-4 M and pH=3.60. Is it correct? To be sure we have to check if the 5% rule is obeyed, that is if the dissociation fraction is less than 5%.

eq. 1.31.3

Dissociated acid concentration is the same as [H+], thus dissociation fraction is 2.54×10-4/0.001 - above 25%. We can't use simplified formula 8.13! We have to use more precise equation 8.10:

eq. 8.108.10

This time we get pH=3.65, exactly the same result as from our pH calculator.


Chemical calculator software for pH calculation, concentration conversion solution preparation and chemical equation balancing chemical calculator