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Chemistry doubts.

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thecandydoll:
I need help solving the enthalpy questions.
How do we do it.
Any tips?

CHEMMASTER6000:
entalphy = heat evolved / moles of reactant

heat evolved =m.c. temp change

m mass of soln total soln

c= specific heat capacity

temp change = well temp change

so devide heat evolved by moles of ractants gives you enaltalphy change

thecandydoll:
I meant chemical energetics.
Like find the enthalpy change of reaction.
THat is enthalpy change of products- reactants.
yoohoo :)

destructor:
so listen
while doing these enthalpy reactions
u wil be given the kj/mol for the formation of two bonds like for example if u want to find the enthalpy for the formation of HCl
it would be like this
H-H =678 kj
Cl-Cl = 343 kj
and  H-Cl = 478kj
then u add H-H and Cl-Cl
and subtract from H-Cl
over here it will be (478-(678+343))
which will result in a -ve value
hence when the value is negative it is an exothermic reaction
dont worry lol
u will be given the table for the energies
so yeah thats basically it!

beacon_of_light:
Are you talking about hess's law??

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