Acids

Question 1

Give the formula of the 7 weak acids you need to know

Answer 1

• Hydrochloric acid = HCl
• Sulfuric acid = H2SO4
• Nitric acid = HNO3
• Phosphoric acid = H3PO4
• Methanoic acid = HCOOH
• Ethanoic acid = CH3COOH
• Propanoic acid = CH3CH2COOH

Question 2

Give the definition of an acid

Answer 2

(Proton doner)
- Release H+ ions in aqueous solutions

Question 3

Give the definition of a strong acid

Answer 3

(one way reaction)
- Completely dissociate when dissolved in water.

Question 4

Give the definition of a weak acid

Answer 4

(reversible reaction)
- Only slight dissociate when dissolved in water, giving an equilibrium mixture

Question 5

What is formed when an acid dissociates in water?

Answer 5

A proton (H+ ion) and a negative anion.

Question 6

Are carbonates, hydroxides and oxides bases? Could they also be alkalis?

Answer 6

Yes, anything that reacts with an acid is a base, however to be an alkali it must react or dissolve in water to form OH- ions and react with acids.

Question 7

Give the definition of a base

Answer 7

A substance which neutralises an acid (proton acceptor)

Question 8

Give the definition of an alkali

Answer 8

A soluble substance that releases OH- ions in aqueous solutions

Question 9

State whether soluble metal oxides, soluble hydroxides and ammonia reacts or dissolves in water and if so what does it form?

Answer 9

• Soluble metal oxides react with water as the oxide ions react with water to form OH- ions e.g. Na2O + H2O –> 2Na+ + 2OH-
• Soluble hydroxides just dissociate in water to form OH- ions e.g. NaOH —> Na+ + OH-
• Ammonia reacts with water to form ammonium ions and OH- ions e.g. NH3 + H2O —> NH4+ + OH-

Question 10

Give the definition of a salt

Answer 10

• A chemical compound formed from the reaction of an acid and a base, with all or part of the hydrogen of the acid is replaced by a metal or other cation e.g. NH4+

Question 11

Give the reaction of when an acid reacts with a base, when an acid reacts with an alkali, when an acid reacts with a carbonate and when an acid reacts with ammonia

Answer 11

1. acid + base —> salt + water
2. acid + alkali —> salt + water
3. acid + carbonate —> salt + carbon dioxide + water
4. acid + ammonia —> ammonium salt

Question 12

Does salt dissolve in water; if so what does it form?

Answer 12

• Yes
• It will dissolve to form aqueous ions e.g. NaCl —> Na+ + Cl-

Question 13

What is an ionic equation and give all the steps to creating an ionic equation

Answer 13

• An ionic equation will only show the ions or species that change state in a reaction, and they omit (leave out) those ions that are not involved in the reaction

1. assign correct state symbols
2. separate anything aqueous into its ions
3. cancel out anything that appears on the side of the equation (anything that stays the same)
4. write the ionic equation