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

Aluminium is more expensive than carbon because more energy is required to obtain aluminium from its ore (aluminium oxide). The extraction process for aluminium is more complex and involves electrolysis, making it costlier compared to the relatively simpler extraction of carbon.

Both magnesium oxide and silicon are solid products, making it challenging to separate them physically after the reaction.

First, we find the molar mass of silicon dioxide (SiO₂):

$M_{SiO_2} = 28 + (2 \times 16) = 60 \text{ g/mol}$

Now, we convert 1.2 kg to grams:

$1.2 kg = 1200 g$

Next, we calculate the number of moles of SiO₂:

$\text{Number of moles of } SiO_2 = \frac{1200 g}{60 g/mol} = 20 ext{ mol}$

From the reaction, we see that 2 moles of magnesium (Mg) react with 1 mole of silicon dioxide:

$2Mg + SiO_2 \rightarrow Si + 2MgO$

Thus, 20 moles of SiO₂ will require:

$\text{Number of moles of Mg} = 20 \times 2 = 40 \text{ mol}$

Finally, we calculate the mass of magnesium required:

$\text{Mass of Mg} = 40 \text{ mol} \times 24 g/mol = 960 g$

In Figure 9, each silicon atom (Si) has 4 outer shell electrons and each hydrogen atom (H) has 1 outer shell electron. The diagram should show a central bond between the silicon atoms with hydrogen atoms bonded to each silicon, reflecting the covalent bonds formed.

First, we find the volume of oxygen reacted for 30 cm³ of Si₂H₆:

$\text{Volume of oxygen} = 30 cm³ \times 3.5 = 105 cm³$

Since 150 cm³ of oxygen is used (in excess), the volume of excess oxygen is:

$\text{Volume of excess oxygen} = 150 - 105 = 45 cm³$

Next, we calculate the volume of water vapor produced:

$\text{Volume of water vapor} = 3 \times 30 cm³ = 90 cm³$

Finally, the total volume of gases present after the reaction is:

$\text{Total volume of gases} = 45 cm³ + 90 cm³ = 135 cm³$