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Phosphorus can exist as P₄ molecules - OCR Gateway - GCSE Chemistry - Question 21 - 2022 - Paper 3
Question 21
Phosphorus can exist as P₄ molecules. Phosphorus trichloride, PCl₃, is made in the reaction of phosphorus, P₄, and chlorine as shown in the equation. P₄ + 6Cl₂ → 4... show full transcript
Worked Solution & Example Answer:Phosphorus can exist as P₄ molecules - OCR Gateway - GCSE Chemistry - Question 21 - 2022 - Paper 3
Step 1
Calculate the mass of phosphorus.
Answer
To calculate the mass of 2.0 mol of phosphorus (P₄), we first need to find the molar mass of P₄:
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The atomic mass of phosphorus (P) is approximately 31 g/mol.
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The molecular formula for tetraphosphorus is P₄, thus:
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Next, we calculate the total mass for 2.0 mol:
Therefore, the mass of phosphorus is 248 g.
Step 2
Calculate the maximum mass of phosphorus trichloride.
Answer
To determine the maximum mass of phosphorus trichloride (PCl₃) made from 2.0 mol of phosphorus (P₄), we need to analyze the balanced chemical equation:
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The reaction indicates that 1 mole of P₄ produces 4 moles of PCl₃.
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Therefore, from 2.0 mol of P₄, the moles of PCl₃ produced will be:
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We now calculate the molar mass of PCl₃:
- Molar mass of chlorine (Cl) is approximately 35.5 g/mol, thus:
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Finally, we find the maximum mass of PCl₃ produced:
Thus, the maximum mass of phosphorus trichloride produced is 1100 g.
Step 3
Which is the limiting reactant? Explain your answer.
Answer
To identify the limiting reactant, we assess the quantities of both reactants:
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Starting moles of P₄:
- We have 2.0 mol of phosphorus (P₄).
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Chlorine needed for the reaction:
- According to the balanced equation, 6 moles of Cl₂ are required for every 1 mole of P₄. Thus:
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Available chlorine:
- The given amount of chlorine is 866.2 g. The moles of Cl₂ can be calculated by:
ightarrow rac{866.2 ext{ g}}{35.5 ext{ g/mol}} ext{ ≈ 24.4 mol}$$
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Since only 12.0 moles of Cl₂ are needed for 2.0 moles of P₄, P₄ is the limiting reactant.
Thus, the limiting reactant is phosphorus (P₄), because it produces a smaller amount of product compared to chlorine.