There are two separate experiments done in this problem. First experiment
106.6 gram of water at 23.28 C and 8.56 gram of sodium sulfate places into a foam cup (a calorimeter) the temperature to 24.97C. The product are sodium sulfate decahydrate.
105.4 g of water at 24.4C and 19.3 grams of sodium sulfate decahydrate. The temp this time rises lowers to 17.34.(the question didn't state what the product is of this reaction, but I guess it's Na2SO3•20H2O)
Note the specific heat of both solutions is that of water-4.18. And that heat of reaction is -heat of calorimeter
The question is what the molar enthalpy of hydration of sodium sulfate is. also one more questionhow to determine the theoretical value?(after yomen answered my question I realized it is basically a reaction from sodium sulfate 10-hydrate to 20 hydrate as product, if you were to combine the two reaction as one(Hess Law)but the thing is i can't find the heat of formation of any hydrate compounds!?)
Now the question refers to the first experiment, so I multiply the the total mass of water of and sodium sulfate by the specifc heat of water and then multiply the product by the change in temperature and I got 813.513J
Because this is the enthalpy for 0.060263 moles of sodium sulfate so Divide 813.513 by 0.060263 and I got 13499.37J.
Before starting solving for the value of molar enthalpy I knew I am probably gonna get a wrong answer because:
By doing this way, I render the second experiment completely useless.
The final answer I knew I was gonna get is way too big.
(Chances are I may read the question wrong...).