Reactivity 3.1—Proton transfer reactions SL

Question 2

What defines a Brønsted–Lowry acid?

Answer 2

A Brønsted–Lowry acid is defined as a substance that donates a proton (H+) in a reaction. It is known as a proton donor.

Question 3

What defines a Brønsted–Lowry base?

Answer 3

A Brønsted–Lowry base is defined as a substance that accepts a proton (H+) in a reaction. It is known as a proton acceptor.

Question 4

How is a hydrogen ion (H+) represented in aqueous solutions?

Answer 4

In aqueous solutions, a hydrogen ion (H+) is often represented as a hydronium ion (H3O+).

Question 5

In the reaction between hydrogen chloride gas and water, which is the Brønsted–Lowry acid, and which is the base?

Answer 5

In the reaction between hydrogen chloride gas and water, hydrogen chloride (HCl) is the Brønsted–Lowry acid because it donates a proton, and water (H2O) is the Brønsted–Lowry base because it accepts a proton.

Question 6

What must all Brønsted–Lowry acids contain?

Answer 6

All Brønsted–Lowry acids must contain hydrogen, as they need to be able to donate a hydrogen ion to another species.

Question 7

What is the conjugate acid of NH3?

Answer 7

NH4+ (The ammonium ion is the conjugate acid of ammonia, as it has gained a proton.)

Question 8

How does water act as an amphiprotic species with NH3?

Answer 8

Water donates a proton to NH3, acting as an acid. NH3 + H2O ⇌ NH4+ + OH−.

Question 9

Conjugate acid

Answer 9

Has one more proton than the base.

Question 10

Conjugate base

Answer 10

Has one less proton than the acid.

Question 11

Is water (H2O) capable of acting as both an acid and a base? Give an example reaction where it acts as a base.

Answer 11

Yes, water is amphiprotic. As a base, it can accept a proton from HCl: HCl + H2O ⇌ Cl− + H3O+.

Question 12

Ionic product of water.

Answer 12

The ionic product of water is the product of the [H^+] and [OH^−] in water at a particular temperature.

Kw=[H+][OH−]

Question 13

Name two common acid-base indicators

Answer 13

Litmus paper and Universal indicator

Question 14

What’s the main difference between Litmus paper and Universal indicator?

Answer 14

Litmus paper cannot determine the pH value unlike the universal indicator

Question 15

What distinguishes strong acids/bases from weak acids/bases in aqueous solutions?

Answer 15

Strong acids/bases completely dissociate/ionise in solution, while weak acids/bases only partially dissociate/ionise.

Question 16

Name three common strong acids

Answer 16

Hydrochloric acid, sulfuric acid, and nitric acid

Question 17

What are examples of weak acids

Answer 17

Ethanoic acid and carbonic acid

Question 18

What characterizes weak bases

Answer 18

Weak bases partially dissociate in water

Question 19

How do the pH and electrical conductivity differ between strong and weak acids?

Answer 19

Strong acids have a lower pH and higher electrical conductivity compared to weak acids at the same concentration.

Question 20

How do the strengths of conjugate acids and bases compare between strong and weak acids?

Answer 20

Strong acids have relatively weak conjugate bases, while weak acids have relatively strong conjugate bases.

Question 21

What are neutralisation reactions?

Answer 21

Reactions where an acid reacts with a base, moving the pH towards neutral.

Question 22

Reaction of acids with metal hydroxides produces?

Answer 22

Salt and water.

Question 23

How can you test for carbon dioxide in reactions involving acids and carbonates?

Answer 23

By bubbling the gas through limewater; if CO₂ is present, the limewater turns milky due to calcium carbonate formation.

Question 24

How do acids react with ammonia and amines?

Answer 24

They undergo neutralisation reactions to produce a salt.

Question 25

What is titration used for?

Answer 25

To determine the unknown concentration of an acid or base by using a solution of known concentration.

Question 26

What signifies the equivalence point in a titration?

Answer 26

It is the point where the acid and base have been reacted in stoichiometrically equivalent amounts, typically indicated by a color change of an indicator.

Question 27

Describe the pH change in a neutralisation reaction between a strong acid and a strong base.

Answer 27

The pH decreases from a high value to a lower value as the concentration of H⁺ ions increases.

Question 28

What is the significance of the equivalence point on a pH curve?

Answer 28

It indicates the volume at which the acid and base have reacted completely, resulting in a solution containing only salt and water.

Question 29

What is the typical pH at the equivalence point for a titration between a strong acid and a strong base?

Answer 29

The pH at the equivalence point is typically around 7.