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This question is about citric acid, a hydrated tricarboxylic acid - AQA - A-Level Chemistry - Question 8 - 2020 - Paper 2
Question 8
This question is about citric acid, a hydrated tricarboxylic acid. Its formula can be represented as HₓY·zH₂O. 1. A 1.50 g sample of HₓY·zH₂O contains 0.913 g of ox... show full transcript
Worked Solution & Example Answer:This question is about citric acid, a hydrated tricarboxylic acid - AQA - A-Level Chemistry - Question 8 - 2020 - Paper 2
Step 1
2. Show, using these data, that the value of x = 1.
Answer
Using the mass of the hydrated compound and the remaining mass:
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Initial and final mass of HₓY·zH₂O:
- Initial mass = 3.00 g
- Final mass = 2.74 g
- Mass of water lost = 3.00 g - 2.74 g = 0.26 g
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Moles of H₂O lost:
- Moles of H₂O = ( \frac{0.26 , g}{18.02 , g/mol} \approx 0.014 ) mol
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Moles of anhydrous HₓY produced:
- Moles of HₓY = ( \frac{2.74 , g}{210.0 , g/mol} \approx 0.013 ) mol
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Establishing the ratio:
- The molar ratio of H₂O to anhydrous HₓY is approximately 1:1, thus confirming that x = 1.
Step 2
Step 3