3. 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.

Question

3.	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.

matt101 · Answer

You know that whatever heat produced by the crystallization reaction is transferred to water. Therefore you can say:

$$\Delta H_{f}n=mc \Delta T$$
ΔH(f) is the enthalpy in fusion
n is the moles of NaAc (in your question, I think your equation should be q = nHf)
m is the mass of water
c is the specific heat of water
ΔT is the temperature change

You have everything you need in the question (you can find n by dividing the mass of NaAc by it's molar mass), so plug in your numbers and solve for ΔHf!

aaronq · Answer

both equations, $q = mH_f$and  $q = nH_f$, are fine. They just spit out different units.