pH and pOH in Reactions

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Jasmine 2C
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Joined: Wed Sep 18, 2019 12:18 am

pH and pOH in Reactions

Postby Jasmine 2C » Mon Jan 20, 2020 2:01 pm

Please correct my understanding if I'm wrong: in, say, a weak base reaction like NH3 + H20 ⇌ NH4+ + OH-, there are still H30 molecules in the reaction (to maintain autoprotolysis equilibrium Kw), but H30 is just not explicitly written.
Am I correct?
Reasoning: we can always calculate the pH from the pOH value of that reaction so there should be some H30 concentration?

Posts: 81
Joined: Fri Aug 09, 2019 12:17 am

Re: pH and pOH in Reactions

Postby madawy » Mon Jan 20, 2020 2:33 pm

There is no hydronium in the equation due to the fact that water is acting as an acid. Instead of gaining a proton to become H3O+, it transfers one to NH3 to become OH-.

Harry Zhang 1B
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Joined: Sat Sep 14, 2019 12:16 am

Re: pH and pOH in Reactions

Postby Harry Zhang 1B » Mon Jan 20, 2020 9:48 pm

Since the solvent here is water, there will be H3O+ due to the autoprotolysis of water.

Hannah Romeo 1J
Posts: 58
Joined: Thu Jul 11, 2019 12:16 am

Re: pH and pOH in Reactions

Postby Hannah Romeo 1J » Mon Jan 20, 2020 9:53 pm

In the equation ammonia is the base and water is the acid. When they react, only hydroxide will be sufficiently prevalent and the conjugate acid, ammonium, will be produced. This reaction further requires the use of a Kb to determine the equilibrium concentrations.

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