Question

A diprotic acid (H,A) has Kal = 4.38 x 10-7 and Ka2 = 5.37 x 10-11. What is the pH of a 0.327 M H,A solution? pH =

0 0
Add a comment Improve this question Transcribed image text
Answer #1

Solution-

The reaction can be writeen as

H2A ----> H+ + HA- (Ka1 = 4.38x10^-7)

HA- ---> H+ + A2- ... (Ka2 = 5.37x10^-9)

=>4.38*10^-7 = [H+][HA-]/[H2A] = (x)(x)/(0.327 - x)

x2 = 1.43*10^-7 - 4.38*10^-7x

x2 + 4.38*10^-7x - 1.43*10^-7 = 0

Solving the quadratic equation we get

x = 0.00037 M = H+ = HA- (after 1st ionization)

HA- ---> H+ + A2-

I 0.00037 0.00037 0   

C- x +x +x   

E 0.00037-x 0.00037+x x

5.37*10^-11 = (0.00037 + x)(x)/(0.00037 - x)

=> 5.37*10^-11(0.00037 - x)= 0.00037x + x^2

=> x^2 +1.9869*10^-14- 5.37*10^-11 x-0.00037x=0

=> x^2 -0.0003699x +1.9869*10^-14=0
x = 0.00036 M = [H+] = [A2-] (second ionization)

The ph is determined by first ionization h+=0.00037

[H+] = 0.00037 M

pH = -log 0.00037
= 3.43

Add a comment
Know the answer?
Add Answer to:
A diprotic acid (H,A) has Kal = 4.38 x 10-7 and Ka2 = 5.37 x 10-11....
Your Answer:

Post as a guest

Your Name:

What's your source?

Earn Coins

Coins can be redeemed for fabulous gifts.

Not the answer you're looking for? Ask your own homework help question. Our experts will answer your question WITHIN MINUTES for Free.
Similar Homework Help Questions
ADVERTISEMENT
Free Homework Help App
Download From Google Play
Scan Your Homework
to Get Instant Free Answers
Need Online Homework Help?
Ask a Question
Get Answers For Free
Most questions answered within 3 hours.
ADVERTISEMENT
ADVERTISEMENT
ADVERTISEMENT