calorimetry

Question

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?

RankGuru · Accepted Answer

1. **Moles of KCl**: $n = 	ext{mass} / 	ext{molar mass} = 5.00 / 74.5 \approx 0.0671$ mol.
2. **Enthalpy of Dissolution**: The reaction absorbs $17.2$ kJ for every mole.
3. **Total Heat Absorption ($q$)**:
   - $q = n 	imes \Delta H_{sol}$
   - $q = 0.0671 	imes 17.2 	ext{ kJ} \approx 1.154 	ext{ kJ}$.
4. **Conversion**: $1.154 	ext{ kJ} = 1154$ J.
5. **Final Answer**: Approximately **$1150$ J**.

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