- #1
pooker
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Homework Statement
1. How much energy does it take to heat 95.3 grams of water from -10 degrees celcius to 35 degrees celcius?
2. How much energy does it take to cool water from 125 degrees celcius to 75 degrees celcius?
Homework Equations
specific heat of water in solid is 2.06 j/g c
liquid is 6.01 j/g c
gas is 1.84 j/g c
delta h of fusion is 6.01 kj/mol
delta h of vap is 44 kj/mol
The Attempt at a Solution
1.
95.7(2.067)(10) = 1093.18 j = 10.93 kj
5.29(6.01) = 31.79 kj
95.3(4.184)(35) = 13955.77 j = 13.95 kj
answer is 56.7 kj
2
95.3(25)(1.84) = 4384 j = 43.84 kj
5.29(44) = 232.9 kj
25(95.3)(4.184) = 9968.38 j = 99.68 kj
answer is -376.42 kj
Now here is where I am confused. Is it -376.42 kj since it is an endothermic reaction? Or is only part of the reaction negative meaning my answer is completely different? Like when calculating delta h of evaporation would that be positive and the others negative? Or is it right that anytime you cool something off it is all completely negative? My book does not go into detail at all with this. It just gives one answer.