Calorimetry
Mediumchemistry
In a coffee-cup calorimeter, dissolution of 5.00 g KCl (ΔHsol = +17.2 kJ mol⁻¹) in 100.0 g water causes temperature drop. Molar mass KCl ≈ 74.5 g mol⁻¹. Approximate q (J) absorbed from solution?
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Solution
Incorrect! Answer:
1150 J
- Moles of KCl: n=mass/molar mass=5.00/74.5≈0.0671 mol.
- Enthalpy of Dissolution: The reaction absorbs 17.2 kJ for every mole.
- Total Heat Absorption (q):
- q=n×ΔHsol
- q=0.0671×17.2 kJ≈1.154 kJ.
- Conversion: 1.154 kJ=1154 J.
- Final Answer: Approximately 1150 J.
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About This Question
- Subject
- chemistry
- Chapter
- chemical thermodynamics
- Topic
- calorimetry
- Difficulty
- Medium
- Year
- 2025
Solution
Correct Answer:
1150 J
- Moles of KCl: n=mass/molar mass=5.00/74.5≈0.0671 mol.
- Enthalpy of Dissolution: The reaction absorbs 17.2 kJ for every mole.
- Total Heat Absorption (q):
- q=n×ΔHsol
- q=0.0671×17.2 kJ≈1.154 kJ.
- Conversion: 1.154 kJ=1154 J.
- Final Answer: Approximately 1150 J.
This medium difficulty chemistry question is from the chapter chemical thermodynamics, covering the topic of calorimetry. It appeared in the 2025 exam.
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