Midterm Q3

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Marina Gollas 1A
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Joined: Fri Sep 28, 2018 12:20 am

Midterm Q3

Postby Marina Gollas 1A » Thu Mar 14, 2019 3:36 am

In Q3 of the Midterm, part D, it states Phosphoric acid is used to acidify foods and beverages such as various colas and jams and provides a tangy or sour taste. Write the reaction that represents Ka2 for phosphoric acid (H3PO4). What would've been the correct answer?

Jeannine 1I
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Joined: Fri Sep 28, 2018 12:27 am

Re: Midterm Q3

Postby Jeannine 1I » Thu Mar 14, 2019 9:46 am

So the is the second deprotonation of phosphoric acid, which means two ions will be gone.

The first deprotonation () would be:
The second deprotonation () would be:

There were 4 points in total for the correct equation, phases, and oxidation numbers.

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Re: Midterm Q3

Postby Lynsea_Southwick_2K » Thu Mar 14, 2019 10:08 am

What section covers deprotonation?

Joonsoo Kim 4L
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Re: Midterm Q3

Postby Joonsoo Kim 4L » Thu Mar 14, 2019 10:57 pm

Deprotonation is just the dissociation of an acid when it reacts with H2O to produce H3O+. Polyprotic acids like H3PO4 have multiple hydrogens which it can give off, hence the possibility for a Ka2 value.

Xinyi Zeng 4C
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Re: Midterm Q3

Postby Xinyi Zeng 4C » Fri Mar 15, 2019 6:25 pm

Lynsea_Southwick_2K wrote:What section covers deprotonation?

Just to add on to the previous reply, it is covered in the acid-base equilibrium section. It is related to the definition of acids and bases with respect to loss/gain of hydrogen.

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