5.1.9: Bronsted-Lowry acids and bases

Question 1

What is a Bronsted-Lowry acid?

Answer 1

A proton, H+, donor

Question 2

What is a Bronsted-Lowry base?

Answer 2

A proton, H+, acceptor

Question 3

What are conjugate aid-base pairs?

Answer 3

Two species related to each other by the loss or gain of a proton.

Question 4

What did Joseph Priestly and Karl Scheele do?

Answer 4

They both reported findings that suggested the existence of oxygen.

Question 5

What did Antonie-Laurent de Lavoisier do?

Answer 5

• He found, among other things, that gas was important in the rusting of metal.
• In 1778, he proposed that it was the source of acidity. This was wrong but a step in understanding acids.

Question 6

In 1815, what did Humphrey Davy do?

Answer 6

Showed that some acidic substances, such as HCl, did not actually contain oxygen.

Question 7

In 1832 what did Justus Liebig define an acid as?

Answer 7

-A substance containing hydrogen that could be replaced by a metal. (very close to today’s definition)

Question 8

In the late 1880s, what did Svante Arrhenius propose?

Answer 8

• That acids dissociated in water to form hydrogen ions, H+, and that bases dissociated in water to form hydroxide ions, OH-.
• This is true for many acids and bases and they can be referred to as Arrhenius acids and bases.
• The model breaks down when the acids and bases are not solutions in water or when bases are not soluble in hydroxides.

Question 9

When did the Danish chemist Johannes Brosted and the British chemist Thomas Lowry propose the Bronsted-Lowry definition od acids?

Answer 9

In 1929

Question 10

The Bronsted-Lowry model can also break down, the Americal chemist Gilbert Lewis proposed a more general theory to describe acids and bases, what is this?

Answer 10

• Lewis acid- Electron pair acceptor
• Lewis base- An electron base donor

Question 11

Write the ionic equation for the reaction between HCl and NaOH.

Answer 11

HCl_(aq) + NaOH_(aq) → NaCl_(aq) + H2O_(l)

H⁺_(aq) + OH^-_(aq) → H2O_(l)

Question 12

Why is HCl a monobasic acid?

Answer 12

Each molecule can release one proton:

HCl_(aq) → H+_(aq) + Cl^-_(aq)

Question 13

Why is H2SO₄ a dibasic acid?

Answer 13

Each molecule can release two protons:

H2SO_4(aq) → H⁺_(aq) + HSO₄^-_(aq)

HSO₄^-_(aq) → H⁺_(aq) + SO₄^2-_(aq)

Question 14

Why is H₃PO₄ a tribasic acid?

Answer 14

Each molecule can release three protons:

H₃PO_4(aq) → H⁺_(aq) + H₂PO₄^-_(aq)

H₂PO₄^-_(aq) → H⁺_(aq) + HPO₄^2-_(aq)

HPO₄^2-_(aq) → H+_(aq) + PO₄^3- _(aq)

Question 15

What are the conjugate acid-base pairs?

HNO_2(aq) + H2O_(l) ↔ H3O⁺_(aq) + NO₂^-_(aq)

Answer 15

• HNO₂ (acid 1) and NO₂^- (base 1)
• H₂O (base 2) and H3O⁺ (acid 2)