LoLPoPs

10+ Year Member
7+ Year Member
Mar 31, 2008
110
0
Status
  1. Dental Student
What volume of HCl was added if 20mL of 1 M NaOH is titrated with 1 M HCl to produce a pH=2?

This problem is from TopScore Exam#2. I understand that 20mL of HCl will react with 20mL of NaOH. But where do I go from here? Can someone explain this in detail please? :D
Thanks!!!:love:
 

LoLPoPs

10+ Year Member
7+ Year Member
Mar 31, 2008
110
0
Status
  1. Dental Student
could you provide the answer chioces?

Oooups sorry about that :D

A) 10.2 mL

B) 20.2 mL

C) 30.4 mL

D) 35.5 mL

E) None of these

The answer is E) None of these...20.4mL.
But I'm not sure how to tackle these types of Q. :idea:
 
About the Ads

alanan84

D1
10+ Year Member
5+ Year Member
Mar 17, 2008
1,387
5
Status
  1. Dental Student
Use M1V1=M2V2

M1=1M HCl, V1=x, M2=.01 (concentration of H+ at pH of 2), V2=40mL + x

(1M)(x)=(.01M)(40+x)
x=0.4mL

40.4 total mL - 20mL NaOH = 20.4mL HCl
 

alanan84

D1
10+ Year Member
5+ Year Member
Mar 17, 2008
1,387
5
Status
  1. Dental Student
Use M1V1=M2V2

M1=1M HCl, V1=x, M2=.01 (concentration of H+ at pH of 2), V2=40mL + x

(1M)(x)=(.01M)(40+x)
x=0.4mL

40.4 total mL - 20mL NaOH = 20.4mL HCl

I guess I could be a little clearer. You know that 20mL of HCl will react with 20mL NaOH to give a neutral pH. So with the equation you are finding x which is the volume of needed to bring it down to a pH of 2. Then you just add that to the amount of HCl added.

I need to go to sleep...
 

LoLPoPs

10+ Year Member
7+ Year Member
Mar 31, 2008
110
0
Status
  1. Dental Student
I guess I could be a little clearer. You know that 20mL of HCl will react with 20mL NaOH to give a neutral pH. So with the equation you are finding x which is the volume of needed to bring it down to a pH of 2. Then you just add that to the amount of HCl added.

I need to go to sleep...


The more I think about it, I'm realizing this question requires some critical thinking. But it makes total sense now after reading your explanation. Thanks so much for your help! :love:
 
This thread is more than 11 years old.

Your message may be considered spam for the following reasons:

  1. Your new thread title is very short, and likely is unhelpful.
  2. Your reply is very short and likely does not add anything to the thread.
  3. Your reply is very long and likely does not add anything to the thread.
  4. It is very likely that it does not need any further discussion and thus bumping it serves no purpose.
  5. Your message is mostly quotes or spoilers.
  6. Your reply has occurred very quickly after a previous reply and likely does not add anything to the thread.
  7. This thread is locked.
About the Ads