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Secondary 5 • December 6, 2025

Hello!
I do not get Bronsted Lowry theory well. I just get that an acid is H+ donor while a base is a H+ acceptor.
My teacher wrote the following on the board but I do not get, are both equation the same? Why is one an equilibirum while the other isnt. I thought its the same .
A base accepts H+ in water
NH3(base) + H+ -> NH4+
NH3 + H2O <-> NH4+ + OH-

Answer (1)

Alloprof Answer

December 6, 2025

Hello there, learning supernova! 😁
We're delighted that you're using Alloprof!

You already understand the basic Bronsted–Lowry idea :
Acid = H⁺ donor
Base = H⁺ acceptor.

In the first equation,
NH₃ (ammonia) is acting as a base and accepts H⁺.
H⁺ is just “given” to NH₃.
It's a complete reaction.

In the second equation, at equilibrium,
NH₃ is still the base.
But H⁺ doesn’t exist freely in water. Instead, water donates H⁺ (acting as an acid) and becomes OH⁻.
This reaction doesn’t go 100% to products because NH₃ is a weak base. Most ammonia molecules stay as NH₃ in water. That’s why it’s an equilibrium.

I suggest this worksheet for your revision.
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