3 (a) Which of the following is the formula of a cation? Put a cross (✗) in the box next to your answer - Edexcel - GCSE Chemistry - Question 3 - 2015 - Paper 1

To obtain a pure, dry sample of barium sulfate from the mixture:

1. Filter the Mixture: Use filter paper and a funnel to filter the mixture. This separates the solid barium sulfate precipitate from the liquid.

2. Wash the Precipitate: Rinse the solid barium sulfate with distilled water to remove any impurities that may be present.

3. Dry the Precipitate: Place the washed barium sulfate on filter paper and allow it to dry completely to achieve a pure sample.

Magnesium (Mg) has two electrons in its outer shell (2.8.2 configuration) and tends to lose these two electrons to achieve a stable electronic configuration, becoming a cation with a charge of +2 (Mg²⁺).

Oxygen (O), on the other hand, has six electrons in its outer shell (2.6 configuration) and tends to gain two electrons to complete its outer shell, becoming an anion with a charge of -2 (O²⁻).

In magnesium oxide (MgO), the magnesium cation (Mg²⁺) and oxygen anion (O²⁻) are held together by ionic bonds due to their opposite charges.

The relative formula mass of magnesium oxide (MgO) can be calculated using the atomic masses of magnesium and oxygen:

1. The atomic mass of magnesium (Mg) = 24
2. The atomic mass of oxygen (O) = 16

Thus, the relative formula mass of MgO is:

$ext{Relative formula mass} = 24 + 16 = 40$

Therefore, the relative formula mass of magnesium oxide is 40.