In four calorimetry trials

CHEMISTRY · Single correct · A Level · Chemistry · Energetics · Energetics

Problem

In four calorimetry trials, 2000 g2000\,\text{g} of water at 25.0 ∘C25.0\,^{\circ}\text{C} surrounds the reacting mixture. Each trial uses a different reaction and number of moles, as listed below. Assume no heat is exchanged with anything other than the water (cwater=4.18 J g−1 ∘C−1c_{\text{water}} = 4.18\,\text{J g}^{-1}\,^{\circ}\text{C}^{-1}). • Trial I: 0.60 mol0.60\,\text{mol}, ΔH=−250 kJ mol−1\Delta H = -250\,\text{kJ mol}^{-1} • Trial II: 1.20 mol1.20\,\text{mol}, ΔH=−120 kJ mol−1\Delta H = -120\,\text{kJ mol}^{-1} • Trial III: 0.40 mol0.40\,\text{mol}, ΔH=+300 kJ mol−1\Delta H = +300\,\text{kJ mol}^{-1} • Trial IV: 0.80 mol0.80\,\text{mol}, ΔH=−170 kJ mol−1\Delta H = -170\,\text{kJ mol}^{-1} Which ranking correctly orders the final water temperatures from highest to lowest after the reactions have gone to completion? (a) III > I > II > IV (b) I > IV > II > III (c) I > II > IV > III (d) II > I > IV > III

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