You are Here: Home

# Acids Question Watch

1. Hey I've done this question and just want to make sure I followed it correctly. I can't get the markscheme as the OCR site is down and my files have been mixed up but here's my method:

n=m/M so do 72.9/45 = 1.58mol

apply n=c*v/1000 to get the concentration by rearranging therefore c = 2.10moldm^-3

Apply the Ka formula:
Ka = [CH3OO-][H+]/[CH3COOH]

Plugged the values in and got [H+] to be 5.97*10^-3
Converted it into pH and got the pH of 2.22

If anyone can be kind enough to check it for me, I'll really appreciate it
2. (Original post by LifeIsGood)

Hey I've done this question and just want to make sure I followed it correctly. I can't get the markscheme as the OCR site is down and my files have been mixed up but here's my method:

n=m/M so do 72.9/45 = 1.58mol

apply n=c*v/1000 to get the concentration by rearranging therefore c = 2.10moldm^-3

Apply the Ka formula:
Ka = [CH3OO-][H+]/[CH3COOH]

Plugged the values in and got [H+] to be 5.97*10^-3
Converted it into pH and got the pH of 2.22

If anyone can be kind enough to check it for me, I'll really appreciate it
Error in red.

NOTE : Your method is correct.... Just change that small error in the beginning
3. (Original post by LifeIsGood)

Hey I've done this question and just want to make sure I followed it correctly. I can't get the markscheme as the OCR site is down and my files have been mixed up but here's my method:

n=m/M so do 72.9/45 = 1.58mol
the relative mass of ethanol is 46

79.2/46 = 1.72 mol

apply n=c*v/1000 to get the concentration by rearranging therefore c = 2.10moldm^-3
if 1.72 mol is in 0.75 litres the concentration is 1.72/.75 = 2.30 M

Apply the Ka formula:
Ka = [CH3OO-][H+]/[CH3COOH]

Plugged the values in and got [H+] to be 5.97*10^-3
Converted it into pH and got the pH of 2.22

If anyone can be kind enough to check it for me, I'll really appreciate it
4. Thanks for the quick replies! Small error on my part, glad I got it right. Thanks again!

Updated: April 22, 2012
TSR Support Team

We have a brilliant team of more than 60 Support Team members looking after discussions on The Student Room, helping to make it a fun, safe and useful place to hang out.

This forum is supported by:
Today on TSR

### Stuck for things to do this summer?

Come and get some inspiration.

### Accidentally received rude picture...

Poll
Study resources

The Student Room, Get Revising and Marked by Teachers are trading names of The Student Room Group Ltd.

Register Number: 04666380 (England and Wales), VAT No. 806 8067 22 Registered Office: International House, Queens Road, Brighton, BN1 3XE

Reputation gems: You get these gems as you gain rep from other members for making good contributions and giving helpful advice.