December 14, 2024, 03:05:30 AM
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Topic: How could I make a buffer solution if I only had the weak base NH3 and HCl?  (Read 2255 times)

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Offline LackOfNames34

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I'm not sure how to answer this. Someone briefly explained that adding 1 mol of HCl and 2 mol of NH3 would lead to an NH3/NH4 buffer. But I don't really understand that. Any help?

Offline Babcock_Hall

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A good place to start is to write a balanced chemical equation.

Offline LackOfNames34

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Ok so a balanced equation would be NH3+HCl = NH4 + Cl

Offline penta-d

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Offline LackOfNames34

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I'm still a little bit lost. So we would react the NH3 and HCL to form NH4Cl. But how does this lead to NH3 +H2O = NH4 +OH?

Offline Meter

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I'm still a little bit lost. So we would react the NH3 and HCL to form NH4Cl. But how does this lead to NH3 +H2O = NH4 +OH?
1 mole of HCl reacts with 2 moles of NH3. By the end, all your HCl will be gone but you will have an equilibrium mixture of NH3 and it's conjugated acid, NH4+.

Offline LackOfNames34

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Ohh so by doing so, I would be reacting the HCl w NH3 to completion. And the equilibriums for the NH3 and the conjugate acid Nh4+ would be

NH3 + H2O <—> NH4+ + OH-

Or

NH4+ <—> NH3 + H+


Offline Meter

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Ohh so by doing so, I would be reacting the HCl w NH3 to completion. And the equilibriums for the NH3 and the conjugate acid Nh4+ would be

NH3 + H2O <—> NH4+ + OH-

Or

NH4+ <—> NH3 + H+
So you are adding a strong acid to an aqueous solution of ammonia. What exactly is happening?

Offline LackOfNames34

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Wouldn't the added acid be consumed in the buffer solution? Did I make an error?

Offline Meter

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Wouldn't the added acid be consumed in the buffer solution? Did I make an error?
The protons from the acid would react with ammonia to form NH4+, but after the reaction is over, an equilibrium will be reached. Your question is which equilibrium is reached, correct?

Offline LackOfNames34

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Yes, furthermore the pH would not have changed much if im not mistaken since NH4+/NH3 is a buffer solution

Offline Borek

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Wouldn't the added acid be consumed in the buffer solution?

Why would that matter?

What is the acid in your buffer solution? What is the base?
ChemBuddy chemical calculators - stoichiometry, pH, concentration, buffer preparation, titrations.info

Offline Babcock_Hall

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Yes, furthermore the pH would not have changed much if im not mistaken since NH4+/NH3 is a buffer solution
This seems like the key point to me.

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