IGCSE Ionic Formulae Quiz

Which is the correct formula for Sodium chloride?

• NaCl₂

• Na₂Cl

• NaCl₃

• NaCl

Answer explanation

The correct formula for Sodium chloride is NaCl, which consists of one sodium (Na) atom and one chloride (Cl) atom. The other options incorrectly represent the ratio of sodium to chloride.

Which is the correct formula for Magnesium oxide?

• Mg₂O

• MgO₂

• MgO

• Mg₃O₂

Answer explanation

The correct formula for Magnesium oxide is MgO. Magnesium (Mg) has a +2 charge and oxygen (O) has a -2 charge, resulting in a 1:1 ratio, hence MgO is the correct representation.

Which is the correct formula for Aluminium oxide?

• AlO

• Al₂O₃

• Al₃O₂

• AlO₃

Answer explanation

The correct formula for Aluminium oxide is Al₂O₃, which indicates that there are two aluminium atoms and three oxygen atoms in the compound. The other options do not accurately represent the composition of Aluminium oxide.

Which is the correct formula for Potassium iodide?

• K₂I

• KI₂

• KI

• K₂I₂

Answer explanation

The correct formula for Potassium iodide is KI, which consists of one potassium (K) atom and one iodide (I) atom. The other options either misrepresent the ratio of elements or are incorrect chemical formulas.

Which is the correct formula for Iron(II) sulfide?

• Fe₂S₃

• FeS

• Fe₃S₂

• Fe₂S

Answer explanation

Iron(II) sulfide consists of iron in the +2 oxidation state and sulfide ions. The correct formula is FeS, indicating one iron atom and one sulfide ion, while the other options represent different compounds.

Which is the correct formula for Iron(III) oxide?

• FeO₂

• Fe₃O

• Fe₂O (missing subscript)

• Fe₂O₃

Answer explanation

Iron(III) oxide has the formula Fe₂O₃, indicating it contains two iron (Fe) atoms and three oxygen (O) atoms. The other options do not correctly represent the oxidation state of iron in this compound.

Which is the correct formula for Copper(II) sulfate?

• CuSO₂

• Cu₂SO₄

• CuSO₄

• CuS₂O₄

Answer explanation

Copper(II) sulfate is represented by the formula CuSO₄, where Cu indicates copper with a +2 oxidation state and SO₄ is the sulfate ion. The other options do not correctly represent this compound.

Which is the correct formula for Zinc chloride?

• ZnCl₂

• Zn₂Cl

• ZnCl

• ZnCl₃

Answer explanation

The correct formula for Zinc chloride is ZnCl₂, which indicates one zinc atom and two chloride atoms. The other options do not accurately represent the compound's composition.

Which is the correct formula for Calcium hydroxide?

• CaOH₂

• Ca(OH)₂

• Ca₂(OH)₂

• CaOH

Answer explanation

The correct formula for Calcium hydroxide is Ca(OH)₂. This indicates one calcium ion (Ca²+) and two hydroxide ions (OH⁻), which is the proper way to represent this compound.

Which is the correct formula for Ammonium nitrate?

• NH₄NO₂

• NH₂NO₃

• NH₄(NO₃)₂

• NH₄NO₃

Answer explanation

The correct formula for Ammonium nitrate is NH₄NO₃. It consists of the ammonium ion (NH₄⁺) and the nitrate ion (NO₃⁻). The other options either represent different compounds or incorrect formulas.