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Chemistry Forums for Students => High School Chemistry Forum => Topic started by: tiny101 on July 01, 2008, 12:42:24 AM

Title: Using acetic acid to prepare a buffer solution?
Post by: tiny101 on July 01, 2008, 12:42:24 AM

How would you calculate the volume of 0.100M of acetic acid required to prepare a 60.0mL of a buffer solution with a pH of 4.6?

I've tried calculating the number of moles of H+, then dividing that by the concentration of acetic acid. With that, I got an answer of 0.02 mL which doesn't seem right.

Also, if acetic acid is not used and instead, SODIUM ACETATE is used... would the method of calculation change?

Thanks in advance.

Title: Re: Using acetic acid to prepare a buffer solution?
Post by: Borek on July 01, 2008, 02:43:04 AM

You have to use Henderson-Hasselbalch (http://www.chembuddy.com/?left=pH-calculation&right=pH-buffers-henderson-hasselbalch) equation, and just acetic acid or just sodium acetate are not enough to prepare buffer - you need them both  in the solution. It doesn't mean you have to use them both in preparation - acetic acid plus sodium hydroxide will do.

Quote from: tiny101 on July 01, 2008, 12:42:24 AM

How would you calculate the volume of 0.100M of acetic acid required to prepare a 60.0mL of a buffer solution with a pH of 4.6?

With buffer calculator ;)

Title: Re: Using acetic acid to prepare a buffer solution?
Post by: chrisf on July 03, 2008, 06:16:49 PM

A weak acid with a strong base will product a buffer solution. Like Borek says, use the Henderson-Hasselbach equation.

pH = pKa + log ([A^-]/[HA])