General Chemistry Question

[flin5845]

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This was from a topscore exam, and I do not really understand their explanation.

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

I know that since there is a strong acid and strong base, if we added 20mL of HCl we would have 40mL of a neutral solution with a pH of 7. This is where I do not know where to go next. I thought that since we wanted to have a pH that is 5 pH units below what the current pH is then I could add 50 times more acid since 10 times as much acid would be 1 pH unit.

 

[Josh779]

This was from a topscore exam, and I do not really understand their explanation.

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

I know that since there is a strong acid and strong base, if we added 20mL of HCl we would have 40mL of a neutral solution with a pH of 7. This is where I do not know where to go next. I thought that since we wanted to have a pH that is 5 pH units below what the current pH is then I could add 50 times more acid since 10 times as much acid would be 1 pH unit.

http://forums.studentdoctor.net/showthread.php?t=837213

I posted the same question a couple of days ago. I think it's the second or 3rd post when you scroll down.

 

[flin5845]

Thank you!