This question is about silicon and compounds of silicon - AQA - GCSE Chemistry - Question 7 - 2022 - Paper 1
Question 7
This question is about silicon and compounds of silicon.
07.1
The reactivity series sometimes includes non-metals such as carbon, hydrogen, and silicon.
Silicon ca... show full transcript
Worked Solution & Example Answer:This question is about silicon and compounds of silicon - AQA - GCSE Chemistry - Question 7 - 2022 - Paper 1
Step 1
Explain what this reaction shows about the position of silicon in the reactivity series.
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Answer
The reaction indicates that silicon is less reactive than carbon because carbon can displace silicon from silicon dioxide. This implies that silicon is positioned below carbon in the reactivity series.
Step 2
Explain why aluminium is more expensive than carbon.
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Answer
Aluminium is more expensive than carbon because more energy is needed to extract aluminium from its ore, which is done through electrolysis, making the process costlier than obtaining carbon from materials such as coal.
Step 3
Give one reason why the products are difficult to separate if magnesium is used to reduce silicon dioxide.
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Answer
Both products (silicon and magnesium oxide) formed in the reaction are solid, making it difficult to separate them due to potential formation of a solid mixture.
Step 4
Calculate the minimum mass in grams of magnesium needed to completely reduce 1.2 kg of silicon dioxide.
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Answer
First, calculate the moles of SiO₂:
Relative formula mass of SiO₂ = 28 + (2 × 16) = 60 g/mol.
Moles of SiO₂ = rac{1200g}{60g/mol} = 20 moles.
From the balanced equation, 2 moles of Mg are needed for 1 mole of SiO₂.
Mass of Mg = Moles × Atomic mass = 40 moles × 24 g/mol = 960 g.
Step 5
Complete Figure 9 to show the outer shell electrons in a molecule of Si₂H₆.
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Answer
In the molecule of Si₂H₆, each silicon atom should have four outer shell electrons, and each hydrogen atom should have one. Draw the electrons as dots around the silicon and hydrogen atoms appropriately.
Step 6
Calculate the total volume of gases present after the reaction.
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Answer
The volume of oxygen used for 30 cm³ of Si₂H₆ is calculated as follows:
30 cm³ Si₂H₆ reacts with 105 cm³ of O₂.
With 150 cm³ of excess O₂, the leftover is 150 cm³ - 105 cm³ = 45 cm³.
The water vapour formed from the reaction is 90 cm³.
Therefore, the total volume of gases = volume of excess oxygen + volume of water vapour = 45 cm³ + 90 cm³ = 135 cm³.
