Magnesium and calcium are in group 2 of the periodic table - Edexcel - GCSE Chemistry - Question 2 - 2016 - Paper 1

The balanced equation for the reaction between magnesium and steam is:

Calcium is more reactive than magnesium because it has a higher atomic number, which means it has more electron shells. Specifically, magnesium has an electronic configuration of 2.8.2, while calcium has 2.8.8.2. The extra electron shell in calcium means that its outer electrons are further away from the nucleus and are less tightly held. This makes it easier for calcium to lose its two outer electrons compared to magnesium, making calcium more reactive.

To calculate the empirical formula of calcium bromide, we first divide the mass of each element by its relative atomic mass:

• For calcium: $\frac{0.2 \text{ g}}{40 \text{ g/mol}} = 0.005 \text{ mol}$

• For bromine: $\frac{0.8 \text{ g}}{80 \text{ g/mol}} = 0.01 \text{ mol}$

Next, we find the simplest ratio:

• Calcium: $\frac{0.005}{0.005} = 1$
• Bromine: $\frac{0.01}{0.005} = 2$

Thus, the empirical formula for calcium bromide is CaBr₂.