[Frederick95]

Please help me answer this quesiton. I have been at it for well over two days now.


Three calorimetry experiments are performed, with the choice of chemical systems such that the enthalpy changes of two of the reactions should equal the enthalpy change of the third.  The three thermochemical reactions are:

1.  HBr(aq) + KOH(aq) → H2O(l) + KBr(aq)            DH1 = ? kJ
2.  KOH(s) → KOH(aq)                                           DH2 = ? kJ
3.  KOH(s) + HBr(aq) → H2O(l) + KBr (aq)                 DH3 = ? kJ

a)  Use Hess's law to show how two of these equations can be added to yield the third equation.



God bless

[LQ43]

What do you know about Hess's Law?

This can be solved if you choose one of the equations as your target (or third equation) to solve for.

Remember that if a compound appears both on the left and the right hand side, it can be cancelled out.

[Frederick95]

Does this mean I need to cross out KOH(s) → KOH(aq)?

[LQ43]

cross out compounds, not whole equations

KOH (s)  not the same as KOH (aq)

choose one equation to be your target equation. Add the other two to show that you would form the target equation.


http://dbhs.wvusd.k12.ca.us/webdocs/Thermochem/HessLawIntro1.html