When 2.80 g of CaCl2 dissolves in 100.0 g of water, the temperature of the water rises from 20.50 oC to 25.4 oC. Assuming that all the heat is absorbed by the water, calculate the enthalpy change (ΔH) per mole of CaCl2 dissolved.
2007-04-17 10:47:51 · 2 answers · asked by Special K 1 in Science & Mathematics ➔ Chemistry
Two part calculation.
First calculate the heat gained by the water
q = m Cp delta T
q = (100.0g) (1 cal /g oC) ( 25.4-20.5)
Now take that q and make it negative (exothermic) and calulate the heat of reaction (the dissolving)
- q = m delta H
-q = (2.80g) delta H.
Solve for delta H, but this is cal /gr.
Multiply by the MM of CaCl2 and you will have delta H per mole
2007-04-17 11:35:22 · answer #1 · answered by reb1240 7 · 0⤊ 0⤋
For (a) you pick q = mHv on condition that a hundred*C is that magical factor at which H2O may be the two steam OR water, looking on its whim. For (b) you pick q = mHf by way of fact it suggested "fusion" that tells you to apply Hf (fusion is what the little bitty f stands for) and then the only equation you need to apply it to is q = mHf. you will might desire to bypass from mol -> g on your individual. None of those problems pick "c". you purely use "c" once you have a metamorphosis in temperature.
2016-12-26 11:53:33 · answer #2 · answered by ? 3 · 0⤊ 0⤋