1. After absorbing 1.850 kJ of heat, the temperature of a 0.500 kg block of copp
ID: 548545 • Letter: 1
Question
1. After absorbing 1.850 kJ of heat, the temperature of a 0.500 kg block of copper metal is 37 °C. What
was the initial temperature of the copper?
2. Pioneers used to reheat their coffee by placing and iron poker from the fire directly into their cup. If
the cup initially held 0.50 L of coffee at 20.0°C, what would be the final temperature of the coffee
when a 5.00 x 102 g iron poker at 2.00 x 102
°C was placed in it? Assume that no heat is lost to the
surroundings during the process, and that the heat capacity and density of coffee is that same as that
of water (I’m sure it wasn’t very good coffee!).
3. Hydrogen peroxide is often used as an oxidizing agent in rocket fuel mixtures. The reaction below
details the decomposition of hydrogen peroxide.
2 H2O2(l) 2 H2O(l) + O2(g) Hrxn = -196.1 kJ
a. How much heat is released when 732 g of peroxide is decomposed?
b. If the peroxide started at 19.6°C, what is the final temperature of the system? (Assume a
“closed” system that does not interact with the surroundings, and that peroxide has the
same specific heat capacity of water).
c. At that “final” temperature and 1 atm of pressure, what volume of oxygen gas is
generated? (hint: which moles do you need for the ideal gas law?)
Explanation / Answer
1)
we have:
Q = 1.850 KJ = 1850 J
m = 0.500 Kg = 500 g
specific heat capacity of copper, C = 0.385 J/g.oC
Tf = 37 oC
we have below equation to be used:
Q = m*C*(Tf-Ti)
1850.0 = 500.0*0.385*(37.0-Ti)
37.0 - Ti = 9.61 oC
Ti = 27.39 oC
Answer: 27.39 oC
Feel free to comment below if you have any doubts or if this answer do not work
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