Some Concepts to note

Two chemical properties of all alkalis include:

1. alkalis react with ammonium salts to produce salt, ammonia and water.

2. alkalis undergo neutralisation with acids to form salt and water. 

• True

• False

Answer explanation

Ensure you also know the chemical properties of acids.

Four metals were each added to an excess of acid in a conical flask.

The metals were labelled as metal 1, metal 2, metal 3 and metal 4.

The results of their investigation are displayed below. 

Describe the relationship shown by the graph for metal 3.

Answer explanation

From graph for metal 3, as time increases, the loss in mass of flask and contents increases.

• Iron is oxidised as the oxidation state of iron increases.

• Iron is reduced as the oxidation state of iron decreases.

• Iron is reduced as iron loses electrons to form iron ions.

Answer explanation

Note how you should make the phrasing to explain redox in terms of oxidation state clearly.

Draw the structure of ethanol after it is left in the open. Show all the bonds in the structure.

Answer explanation

Suggest the formula of organic acid when propanol is left open to the air.

Answer explanation

A carboxylic acid is formed when an alcohol is left open to air. When propanol is left open to air, propanoic acid is formed.

Suggest the identity of substances L, M, N, O and both substances in mixture P.

Suggest and explain a property of sodium oxide.

• A. Sodium oxide conducts electricity in aq or molten states as there are free-moving electrons.

• B. Sodium oxide has low melting point as little energy is needed to overcome weak intermolecular forces of attraction.

• C. Sodium oxide has high melting point & boiling point as a lot of energy is needed to overcome strong electrostatic forces of attraction.

• D. Sodium oxide conducts electricity in aq or molten states as the ions are free to move.

Answer explanation

A. Sodium oxide conducts electricity in aq or molten states as there are free-moving electrons. (should be ions instead of electrons)

B. Sodium oxide has low (high) melting point as little (a lot of) energy is needed to overcome weak intermolecular (strong electrostatic) forces of attraction.

Identify substances A, B, C, D, E and F.

Answer explanation

A is copper(II) hydroxide (cation test - light blue ppt formed using sodium hydroxide).

B is copper(II) nitrate (cation is copper(II) ion, anion is nitrate as it is a blue solution formed after reaction with nitric acid & C)

C is copper(II) oxide (cation is copper(II) ion, metal oxide)

D is iron(III) hydroxide (cation test - red-brown ppt formed using sodium hydroxide)

E is iron(III) oxide (cation is iron(III) ion, metal oxide)

F is water (colourless distillate after distillation of dilute nitric acid)