6.1.9: Carboxylic acids

Question 1

Which functional group do carboxylic acids contain?

Answer 1

-COOH

Question 2

What is the solubility of small carboxylic acids?

Answer 2

-Small carboxylic acids are very soluble in polar solvents like water. This is because hydrogen bonds can be formed between the carboxylic acid functional group and water.

Question 3

What happens the hydrocarbon chain of the carboxylic acid increases in size?

Answer 3

• The solubility decreases.
• This is because only the polar carboxylic acid functional group can form hydrogen bonds with the water.
• So, as more of the molecule becomes non-polar, then solubility will decrease.

Question 4

Carboxylic acids are weak acids. What does this mean?

Answer 4

They partially ionise in solution producing H+ ions from the carboxylic acid group.

Question 5

Why do carboxylic acids happen at a slower rate than with a strong acid?

Answer 5

The pH is higher and therefore the concentration of H+(aq) will be lower.

Question 6

Describe how Carboxylic will react with metals.

Answer 6

Carboxylic acids will react with metals above hydrogen in the reactivity series to make hydrogen and a metal salt.

Question 7

Sodium +ethanoic acid —> ?

Answer 7

Sodium +ethanoic acid-> sodium ethanoate + hydrogen

2Na + 2CH3COOH -> 2CH3COONa +H2

Question 8

Why can metal oxides be classified as bases?

Answer 8

Metal oxides react with acids and can therefore be classified as bases.

Question 9

Describe how Carboxylic will react with metal oxides.

Answer 9

Carboxylic acids will react with metal oxides to make water and a metal salt.

Question 10

Magnesium oxide + methanoic acid -> ?

Answer 10

Magnesium oxide + methanoic acid ->
Magnesium methanoate + water

MgO(s) + HCOOH(aq) –> (HCOO)2Mg (aq) +H2O(l)

Question 11

What are group 1 metal hydroxides?

Answer 11

Soluble bases that release OH- (aq)

Question 12

Describe how Carboxylic will react with metal hydroxides.

Answer 12

Carboxylic acids will react with metal hydroxides to make water and a metal salt.

Question 13

Potassium hydroxide + propanoic acid –> ?

Answer 13

Potassium hydroxide + propanoic acid –>
Potassium propanoate + water

KOH(aq) + CH3CH2COOH(l) –> CH3CH2COOK(aq) + H2O

Question 14

Metal carbonates are also bases, how do carboxylic acids react with metal carbonates?

Answer 14

Carboxylic acids will react with metal carbonates to form water, carbon dioxide and a metal salt.

Question 15

Sodium carbonate + methanoic acid –> ?

Answer 15

Sodium carbonate + methanoic acid –>
sodium methanoate + water + carbon dioxide
Na2CO3(s)+2HCOOH (aq) ->2HCOONa + H2O (l)+ CO2

Question 16

Group 1 metals can also form metal hydrogencarbonates. When does this happen?

Answer 16

This is when the carbonic acid (H2CO3) has only one proton exchanged for a metal ion to form the metal hydrogencarbonate (MHCO3) Where M is a group 1 metal.

Question 17

How do acids react with metal hydrogencarbonates?

Answer 17

To form a salt, water and carbon dioxide.