An environmental scientist investigates the energetics of dissolving anhydrous calcium chloride in water to design a portable self-heating pack.
The scientist uses 150.0 g150.0\text{ g}150.0 g of water in a polystyrene cup. The temperature of the water is recorded before and after adding the anhydrous calcium chloride:
Calculate the temperature change of the mixture in ∘C^\circ\text{C}∘C.
Calculate the heat energy change, in joules, using the expression:
heat energy change (J)=mass of water (g)×4.18×temperature change (∘C) \text{heat energy change (J)} = \text{mass of water (g)} \times 4.18 \times \text{temperature change (}^\circ\text{C)} heat energy change (J)=mass of water (g)×4.18×temperature change (∘C)The scientist used 6.66 g6.66\text{ g}6.66 g of anhydrous calcium chloride. Calculate the amount, in moles, of calcium chloride dissolved (Mr of CaCl2=111M_r\text{ of CaCl}_2 = 111Mr of CaCl2=111).
Calculate the molar enthalpy change, in kJ/mol\text{kJ/mol}kJ/mol, for dissolving anhydrous calcium chloride. Since the temperature increased, include the appropriate sign (+++ or −-−) with your value.
