Deduce Bronsted-Lowry Base

Let's take a look at our discussion question this week!

We want to determine if the underlined species are acting as Bronsted-Lowry bases.

Let us first understand what is an acid and base according to the Bronsted-Lowry theory.

Bronsted acid is a proton (H⁺) donor.

Bronsted base is a proton (H⁺) acceptor.

The biggest difference between Bronsted-Lowry theory and Arrhenius theory is in the base.

Arrhenius base must dissolve in water to give OH^-, while Bronsted base just need to accept H⁺.

Check out this video lesson for a detailed comparison of the 3 different acid-base theories.

Let's look at the 3 options and determine the Bronsted acid and base.

NH₄⁺ donates proton to form NH₃, hence NH₄⁺ is the Bronsted acid.

Underlined species H₂O accepts proton to form H₃O⁺, hence H₂O is the Bronsted base.

Hence option 1 is correct.

H₂SO₄ donates proton to form HSO₄^-, hence H₂SO₄ is the Bronsted acid.

Underlined species HNO₃ accepts proton to form H₂NO₃⁺, hence HNO₃ is the Bronsted base.

Hence option 2 is correct.

It will be easier to deduce the acid and base if we separate NaNH₂ into Na⁺ and NH₂^-.

CH₃COCH₃ donates proton to form CH₃COCH₂^-, hence CH₃COCH₃ is the Bronsted acid.

Underlined species NH₂^- accepts proton to form NH₃, hence NH₂^- is the Bronsted base.

Hence option 3 is correct.

Therefore all options are correct and the answer to this question is option D.

Topic: Ionic Equilibria, Physical Chemistry, A Level Chemistry, Singapore

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