2014 final #8

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Ivanna_Tang_3B
Posts: 22
Joined: Wed Sep 21, 2016 2:58 pm

2014 final #8

Postby Ivanna_Tang_3B » Sat Dec 03, 2016 8:35 pm

A buffer solution of volume 300.0 mL is 0.200M CH3COOH and 0.300M NaCH3CO2. The pKa for acetic acid is 4.75.

In part A, the initial pH of the solution is found to be 4.93.

Part B asks: what mass of NaOH would have to be dissolved in this solution to bring the pH to 6.0?
the solution writes: 6.0 = 4.75 + log{(0.300L * 0.300M + x)/(0.300L * 0.200M - x)}

why are x moles being added to the base and x moles subtracted from the acid?

thank you!

Daniel Namgoong 3I
Posts: 10
Joined: Wed Sep 21, 2016 2:56 pm

Re: 2014 final #8

Postby Daniel Namgoong 3I » Sat Dec 03, 2016 10:08 pm

It is because the addition of NaOH puts in extra OH- concentration which leads to a higher pH.

Samuel_Vydro_1I
Posts: 21
Joined: Fri Jul 22, 2016 3:00 am

Re: 2014 final #8

Postby Samuel_Vydro_1I » Sun Dec 04, 2016 2:16 am

A higher pH corresponds to a higher amount of base as shown


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