Pl 3 - Equilibria (Acid-Base)

Question 1

What is a carboxylic acid and why is a weak acid?

Answer 1

• A carboxylic acid is an organic compound with the -COOH functional group
• It is a weak acid because it partially dissociates in water to form -COO-

Question 2

How do carboxylic acids react with metals?

Answer 2

Carboxylic acids react with metals to form a salt and hydrogen gas
CH3COOH + Na –> CH3COO-Na+ + 1/2H2

Question 3

How do carboxylic acids react with alkalis?

Answer 3

Carboxylic acids react with alkalis to form a salt and water
CH3COOH + NaOH –> CH3COO-Na+ + H2O

Question 4

How do carboxylic acids react with carbonates?

Answer 4

Carboxylic acids react with carbonates to form a salt, water and carbon dioxide
2CH3COOh + Na2CO3 –> 2CH3COO-Na+ + H2O + CO2

Question 5

How do amino acids act as both an acid and a base?

Answer 5

The carboxylic acid group acts as an acid because it is a proton donor
The amine group acts as a base because it is a proton acceptor (has a lone pair)

Question 6

What is the structure of an amino acid zwitterion?

Answer 6

+H3N-RH-COO-

Question 7

How do amino acid zwitterions form?

Answer 7

The presence of both acidic and basic groups results in the transfer of a H+ ion from the carboxylic acid group to the nitrogen of the amine group. There is no overall charge

Question 8

How do amines react with acids?

Answer 8

They react with acids to form an alkylammonium salt
e.g. CH3CH2NH2 + HCl –> CH3CH3NH3+Cl-