Posted by Sarah on Sunday, November 14, 2010 at 5:03pm.
q = mass brick x specific heat brick x delta T.
q = 4.62 kJ/C x delta T.
When I solved it the second problem it had a positive sign (23.2 KJ). Is that right or wrong because the problem wants heat of combustion?
#1. You are calculating the heat from heating bricks when N2H4 burns. You get a positive number because you are adding heat to the bricks; that is the same as the heat RELEASED by burning N2H4. Delta H for burning N2H4 is (heat released) negative.
#2. You are burning coal. The water absorbs the heat (same as the bricks in #1) so q comes out to be positive. However, the coal RELEASED heat so delta H for the combustion is negative.
Drbob you are wrong i got the question wrong doing what you told me to
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