EK Heat Capacity

[sparkleys]

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In an experiment, it was found that 6 kJ of heat were required to raise the temperature of a sample of copper by 15 degrees C. If the experiment was repeated with a gold sample of the same mass, how much heat would be required to achieve the same temperature change?

Specific Heat of Au = 0.13 J / g-C
Specific Heat of Cu = 0.39 J / g-C

Answer choice A was 2kJ while D was 18kJ. I chose D, but the correct answer is A. Where am I going wrong?

Using c = q / mT

First I found the mass from the copper:
.39 = 6000 / (m * 15)
m = 160g

Next I plugged this in for gold:
.13 = X / (160 * 15)

X = 18KJ

 

[ljc]

Without even doing any equations, you can see that Gold has a specific heat one third that of copper, so it will take one third as much energy to experience the same temperature change. Thus, 1/3rd of 6 is 2.

And your math is going down the way wrong path. You don't need to find mass of copper, because you know it is the same as gold. Here's the math in case you need it, though you should try to use the above approach to avoid the math altogether:

Q=mcT, where m can be ignored because it is the same in both copper and gold, and T is 15
Q=0.13*15
Q=1.95 is approximately 2

Edit: Also, your math is off somewhere regardless. You should have gotten a mass of 1025g. If you plug this back into Q=mcT, you get Q=2000J, or 2kj