This question is about silicon and compounds of silicon - AQA - GCSE Chemistry - Question 7 - 2022 - Paper 1

Aluminium is more expensive than carbon primarily because more energy is required to extract aluminium from its ore, requiring electrolysis, while carbon can be obtained more cheaply from sources like coal.

Both products of the reaction are solid, making it challenging to separate them due to the lack of a clear phase difference that would assist in the separation process.

First, calculate the number of moles of SiO2 using its molar mass:

$M(MgO) = 28 + 2 \times 16 = 60 \, \text{g/mol}$

For 1.2 kg of SiO2:

$1.2 \, \text{kg} = 1200 \, \text{g}$

$\frac{1200 \, \text{g}}{60 \, \text{g/mol}} = 20 \, \text{moles of SiO2}$

Since two moles of Mg are required for each mole of SiO2:

$20 \, \text{moles SiO2} \times 2 \, \text{moles Mg} = 40 \, \text{moles Mg}$

The mass of Mg needed is:

$\text{Mass} = 40 \, \text{moles} \times 24 \, \text{g/mol} = 960 \, \text{g}$

In Figure 9, each silicon atom (Si) is at the center connected to three hydrogen atoms (H) with the appropriate number of outer shell electrons drawn around each atom to indicate bonding pairs and lone pairs.

To calculate the volume of oxygen consumed by Si2H6:

For 30 cm³ of Si2H6:

$\frac{30 \, \text{cm³}}{30} \times 105 = 105 \, \text{cm³}$

The volume of excess oxygen:

$150 - 105 = 45 \, \text{cm³}$

The volume of water vapor formed:

$3 \times 30 = 90 \, \text{cm³}$

Total volume of gases:

$45 + 90 = 135 \, \text{cm³}$