# Specific Heat

1. Nov 4, 2013

### FTCC.student

1. The problem statement, all variables and given/known data
Large beds of rock are used in some solar-heated homes to store heat. Assume that the specific heat of the rocks is 0.82 J/g-K. (a) Calculate the quantity of heat absorbed by 50.0 kg of rocks if their temperature increases by 12.0°C. (b) What temperature change would these rocks undergo if they emitted 450 kJ of heat?

2. Relevant equations

Cs=$\frac{q}{m * ΔT}$

3. The attempt at a solution

For part a, I have rearranged the formula to give me q=Cs X m X ΔT, and got an answer of 4.9*105 J. Part B, however, all I could think to do was try and rearrange the equation again by solving for ΔT. Either I cannot figure out how to rearrange it (this is probably the case, I was never very good at that), or I am on the wrong track completely. Either way, I'm probably also over-thinking it.

Also, a question about forum rules, I am studying for a test that is tomorrow afternoon and will probably have several other questions tonight on a variety of subjects (such as ΔH, electron config, net ionic equations, concentrations of solutions/molarity etc). Am I allowed to create a new thread for each question or should I stick to this thread?

Thanks for the help.

2. Nov 4, 2013

### tiny-tim

Hi FTCC.student!
Should work.

Show us how far you got.
yes

quick!

3. Nov 4, 2013

### FTCC.student

Well okay, this is what I got when I tried to solve for delta-T (I tried twice and did something wrong, I can't remember how to isolate it because it is in the denominator...) the -x- represents that variable being cancelled.

ΔT = $\frac{Cs*m}{q}$

Which gave me: ΔT=(0.82 J/g-K)(50.0g)/450kJ

That answer was far from correct. I also tried multiplying all my given variables, also far from correct :(

So what I'm really confused on here probably isnt the actual chemistry portion, just how to rearrange the dang formula

4. Nov 4, 2013

### haruspex

(Your LaTex was messed up because you used "" inside $. That doesn't work. You have to use _ for subscript, ^ for superscript, etc.) Let's try that one step at a time: Cs=[itex]\frac{q}{m * ΔT}$​
Multiply both sides by ΔT
ΔT*Cs=$\frac{q}{m}$​
What next?