Formulae for ionic compounds

4 marks · Normal

For each of the following, state the ions present, their charges, and the correct formula for the compound:

(a)

potassium nitrate

(i)

State the ions and their charges.

[1 mark]

(ii)

Write the formula for potassium nitrate.

[1 mark]

(b)

magnesium chloride

(i)

State the ions and their charges.

[1 mark]

(ii)

Write the formula for magnesium chloride.

[1 mark]

Work this out on paper, then compare with the answer and worked solution below. With a free account you can submit written answers for marking.

Show answer

(a.i) K+ and NO3–

(a.ii) KNO3

(b.i) Mg2+ and Cl–

(b.ii) MgCl2

Common mistakes: wrong charge for magnesium or nitrate; not balancing number of chloride ions

Show mark scheme and worked solution

Marking points

B1 (a(i)) · 1 mark · Correctly states ions for potassium nitrate (K+ and NO3–)

A1 (a(ii)) · 1 mark · Correct formula for potassium nitrate: KNO3

B2 (b(i)) · 1 mark · Correctly states ions for magnesium chloride (Mg2+ and Cl–)

A2 (b(ii)) · 1 mark · Correct formula for magnesium chloride: MgCl2

Worked solution

a.i) K+ and NO3–; a.ii) KNO3 b.i) Mg2+ and Cl–; b.ii) MgCl2