6th ed: Fundamentals J.1

[Hannah Morales 1D]

How do you determine whether a compound is a bronsted base or acid?
a) NH3 b) HBr c)KOH d) H2SO3, e) Ca(OH)2

Are there any tips when deciding whether something is an acid or base (Bronsted)?

[Edward Xie 2E]

A Bronsted acid is a proton donor, and a Bronsted base is a proton acceptor.

In this case, NH₃ is a base, HBr is an acid, KOH is a base, H₂SO₃ is an acid, and Ca(OH)₂ is a base.

One tip I generally use is I look at the chemical equation and see which substance loses a proton and which one gains a proton, which determines which is an acid or base.

[Alma Carrera 3C]

But how would you know which ones lose a proton and which ones gain a proton?

[Edward Xie 2E]

But how would you know which ones lose a proton and which ones gain a proton?

See which chemical gains/loses an H⁺.

For example: HCl(aq) + NH₃(aq) → Cl⁻(aq) + NH₄⁺(aq)
HCl would be the acid because it donates a proton to NH₃ and becomes Cl^-.
NH₃ would be the base because it accepts the proton from HCl and becomes NH₄⁺.

[Jeremy_Guiman2E]

If something can produce/donate an H⁺ ion, it is probably a Bronsted acid. But, if it can accept one, it is a Bronsted base. The base is often OH^-, but as you can seen, ammonia (NH₃) can also act as a Bronsted base (proton acceptor) to produce ammonium ion, NH₄⁺.