Help Gchm --dat Just In Just Over 24 Hrs!

[au5233]

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Hey Everyone,

so my day is about to come! I am writing the DAT on friday. I haven't had a lot of time to study this last month because I've gotten so busy with school, but I can't push it back any further if I want to be considered this cycle.

Neways enough mumble, I have a DAT question from I think TOPscore which I can't seem to figue out. Can someone clarify it for me? The question reads:

What volume of HCL was added if 20 mL of 1M NaOH is titrated with 1M HCL to produce a pH of 2?

The answer is 20.4 mL acid.

I understand that 20 mL of acid will neutralize 20 mL of bade to produce so far 40 mL solution, but after that I'm just lost and don't know how to incorporate pH.

Thank you SO much!

Cheers!

 

[ucla2134]

I also got stuck on this question too.

From what i understand is that to produce pH2 means that it already past the equivalence point (where 20ml HCL was used).
So pH=2 means that [H+]=0.01M. And i have no idea how to incorporate too.
SOMEONE PLEASE HELP US!!!!!!!!!!!!!

 

[barrett15]

First find how much HCl is needed to neutralize the solution.
N1V1=N2V2
Since both are 1 normality 20 ml HCl is needed to neutralize 20 ml NaOH. So the total solution is 40 ml.
Now use the dilution equation to find out how much more HCl is needed to get to pH = 2.
M1V1=M2V2
(1M HCl)(how much HCl you need to add) = (1.0x10^-2 which is the pH you want)(40 total volume + amount HCl you need to add)
In other words (1M HCl)(x ml) = (.01M HCl)(40 + x ml)
Solve for x get .404.
Now add that to the original amount of HCl added to get 20.4 ml HCl.

Good luck! I didn't have any problems this difficult on my DAT.

 

[ucla2134]

First find how much HCl is needed to neutralize the solution.
N1V1=N2V2
Since both are 1 normality 20 ml HCl is needed to neutralize 20 ml NaOH. So the total solution is 40 ml.
Now use the dilution equation to find out how much more HCl is needed to get to pH = 2.
M1V1=M2V2
(1M HCl)(how much HCl you need to add) = (1.0x10^-2 which is the pH you want)(40 total volume + amount HCl you need to add)
In other words (1M HCl)(x ml) = (.01M HCl)(40 + x ml)
Solve for x get .404.
Now add that to the original amount of HCl added to get 20.4 ml HCl.

Good luck! I didn't have any problems this difficult on my DAT.

Thank you so much!!!!!!!!!!👍

 

[au5233]

THANK YOU! That is a hige relief. I am hopeful the dat doesn't pound me with such questions.! I shall post my resullts sooN!

 

[barrett15]

good luck - don't stress out or panic and you'll do fine

 

[TheWiredNerv]

Stop studying the day before you test! Go do something fun.