4. A calorimeter contains 500 g of water at 25°C. You place a hand warmer containing 200 g of liquid sodium acetate inside the calorimeter. When the sodium acetate finishes crystallizing, the temperature of the water inside the calorimeter is 39.4°C. The specific heat of water is 4.18 J/g-°C. What is the enthalpy of fusion (Hf) of the sodium acetate? (Show your work.) Where necessary, use q = mHf.
First, we must calculate the energy released by the sodium acetate by assuming all the heat released is absorbed by the water. The heat absorbed by the water is given by: Q = mcΔT Q = 500 * 4.18 * (39.4 - 25) Q = 30,096 J = 30.096 kJ
The enthalpy of fusion is expressed in kJ/mol, so we must first calculate the moles of sodium acetate using: moles = mass / Mr moles = 200 / 82.03 moles = 2.44 mol
