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22 (a) In an experiment, a mixture of ammonium chloride and calcium hydroxide is heated - OCR Gateway - GCSE Chemistry - Question 22 - 2019 - Paper 4
Question 22
22 (a) In an experiment, a mixture of ammonium chloride and calcium hydroxide is heated. Ammonia gas, NH₃, is made. 2NH₄Cl + Ca(OH)₂ → CaCl₂ + 2NH₃ + 2H₂O A studen... show full transcript
Worked Solution & Example Answer:22 (a) In an experiment, a mixture of ammonium chloride and calcium hydroxide is heated - OCR Gateway - GCSE Chemistry - Question 22 - 2019 - Paper 4
Step 1
Calculate the concentration of the potassium hydroxide solution in mol/dm³.
Answer
To calculate the concentration of the potassium hydroxide solution:
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Using the balanced reaction: 2 KOH + H₂SO₄ → K₂SO₄ + 2 H₂O.
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Calculate moles of H₂SO₄ used:
- Volume = 24.80 cm³ = 0.02480 dm³
- Moles of H₂SO₄ = 0.200 mol/dm³ × 0.02480 dm³ = 0.00496 mol.
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From the balanced equation, 2 moles of KOH react with 1 mole of H₂SO₄.
- Therefore, moles of KOH = 2 × moles of H₂SO₄ = 2 × 0.00496 mol = 0.00992 mol.
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Concentration of KOH = ( \frac{moles}{volume} = \frac{0.00992 ext{ mol}}{0.025 ext{ dm}³} = 0.3968 ext{ mol/dm}³ )
Thus, the concentration of the potassium hydroxide solution is approximately 0.397 mol/dm³.