Brønsted-Lowry acids and bases
A Brønsted-Lowry acid gives away a proton (H⁺). A base accepts one. When an acid loses a proton, it becomes its conjugate base. When a base gains one, it becomes its conjugate acid.
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Analogy
Passing a ball in a game: the acid throws the proton, the base catches it, and now each holds the other's role.
Example
HCl: acidH₂O: baseCl⁻: conjugate base of HClH₃O⁺: conjugate acid of H₂O
In practice
In a cup of lemon juice, citric acid passes protons to water molecules, making H₃O⁺ that tastes sour.
Practice
Flashcards
- What is a Brønsted-Lowry acid?A proton (H⁺) donor.
Questions people ask
What makes an acid strong?
A strong acid ionizes almost completely in water, so nearly every molecule gives up its proton. HCl, HBr, HI, HNO₃, H₂SO₄ and HClO₄ are the common examples. The stronger the acid, the weaker its conjugate base, because a weak base holds on poorly to the proton it just lost.
What is an amphoteric substance?
An amphoteric substance can act as an acid or a base depending on what it meets. Water is the classic example: it gives a proton to ammonia and accepts a proton from HCl. Species like HCO₃⁻ and H₂PO₄⁻ also behave this way.