a) (i) Balance the equation for the reaction between sodium and chlorine to produce sodium chloride by putting numbers in the spaces provided - Edexcel - GCSE Chemistry - Question 4 - 2014 - Paper 1

To calculate the percentage yield:

$\text{Percentage Yield} = \left( \frac{\text{Actual Yield}}{\text{Theoretical Yield}} \right) \times 100$

Substituting in the values:

$\text{Percentage Yield} = \left( \frac{2.5}{4.0} \right) \times 100 = 62.5\%$

The properties described indicate that sodium chloride is:

A ionic

The relative formula mass of sodium chloride is calculated as follows:

$\text{Relative Formula Mass} = \text{Na} + \text{Cl} = 23 + 35.5 = 58.5$

To calculate the percentage by mass of magnesium:

$\text{Percentage of Mg} = \left( \frac{\text{Mass of Mg}}{\text{Relative Formula Mass of MgSO}_4} \right) \times 100$

Substituting the values:

$\text{Percentage of Mg} = \left( \frac{24}{120} \right) \times 100 = 20\%$

The empirical formula of ethane (C₂H₆) is:

CH₃

Ethane has a low boiling point due to the weak intermolecular forces present between ethane molecules. These include:

• Van der Waals forces, which are relatively weak compared to covalent bonds.
• Little energy is required to break these forces, resulting in a low boiling point.