Bases and Alkalis

IGCSE Edexcel Chemistry
2.38 Bases: metal oxides, hydroxides and ammonia
Key Concept: Bases neutralise acids. Metal oxides, metal hydroxides and ammonia act as bases; soluble bases are alkalis.

Section A: Identifying Bases

1. State which of these are bases: MgO, HCl, NaOH, NH3. [2]
2. Explain why metal oxides are bases. [2]

Section B: Alkalis and Neutralisation

3. Define the term alkali. [1]
4. Write a word equation for ammonia solution reacting with hydrochloric acid. [2]

Total marks: 7

Mark Scheme

1. Bases: MgO, NaOH, NH3 [2]
2. They neutralise acids to form salts and water [2]
3. A soluble base that produces OH- in water [1]
4. Ammonia + hydrochloric acid -> ammonium chloride [2]