A student carries out an experiment to measure the temperature change when ammonium nitrate dissolves in water.
The student uses 100 g100\text{ g}100 g of water. The thermometer readings before and after adding the ammonium nitrate are:
Calculate the temperature change in ∘C^\circ\text{C}∘C.
Calculate the heat energy change, in joules, using the expression:
heat energy change (J)=mass of water (g)×4.2×temperature change (∘C) \text{heat energy change (J)} = \text{mass of water (g)} \times 4.2 \times \text{temperature change (}^\circ\text{C)} heat energy change (J)=mass of water (g)×4.2×temperature change (∘C)The student used 4.0 g4.0\text{ g}4.0 g of ammonium nitrate. Calculate the amount, in moles, of ammonium nitrate dissolved (Mr of NH4NO3=80M_r\text{ of NH}_4\text{NO}_3 = 80Mr of NH4NO3=80).
Calculate the molar enthalpy change, in kJ/mol\text{kJ/mol}kJ/mol, for dissolving ammonium nitrate. Since the temperature decreased, include the appropriate sign (+++ or −-−) with your value.
