Energy Day 3 - Representing Enthalpy Change

Four ways to represent enthalpy changes are to be considered.
-see the four ways outlined on page 319 of Nelson Chemistry 12

A nice review of thermochemical equations is found at"
http://chemistry.about.com/od/physicalchemistrythermo/a/thermochemlaws.htm

This next link has some questions with answers - available after you answer the question. The answer does not require units, but include a negative sign if required. One other tidbit for the questions, you need to ensure that you have calculated the molar enthalpy of the substance of interest. [That is, you may need to divide the stated enthalpy of the equation by the moles (coefficient) associated with the desired reactant.]
http://chemistry.csudh.edu/lechelpcs/thermoequationscsn7.html

From today: Page 319-320 [2,3,4,5]  and page 320 [1 to 4]

A helpful hint for #4 page 320 (the eicosane question), the surroundings that are heated as a result of the burning candle are the copper container and the water in the copper container.
So -      nH combustion eicosane = -[mcTwater  +  mcTcopper]   ...once again, 'delta' represented by 

One other thing with this question - in (d) a percentage error calculation is requested - consider the %difference calculation outlined on page 778 of Nelson Chemistry 12. [% difference/ % error - the calculation will work for both. In this case the predicted value = actual value = -13.3 MJ  ...watch the units]

Now should you have to use a similar approach with a 'tin can' (~ iron) and a burning cheesie/chip/marshmallow/peanut/cracker......all the better. :<)

A few closing thoughts in honour of the potential cheesie burn - some cheesie jokes: (1) What do you call a fish with no eyes? A fsh  (2) I went to buy some camouflage trousers the other day but I couldn't find any.   (3) And finally, there was the person who sent twenty different puns to his friends, with the hope that at least ten of the puns would make them laugh.     No pun in ten did.