Titration Problem

[LoLPoPs]

Advertisement - Members don't see this ad

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? 😀
Thanks!!!😍

 

[drm85]

could you provide the answer chioces?

 

[LoLPoPs]

could you provide the answer chioces?

Oooups sorry about that 😀

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.

 

[alanan84]

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]

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]

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! 😍