# Specific Heat

## Homework Statement

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?

## Homework Equations

Cs=$\frac{q}{m * ΔT}$

## 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.

tiny-tim
Homework Helper
Hi FTCC.student! (b) What temperature change would these rocks undergo if they emitted 450 kJ of heat?

Part B, however, all I could think to do was try and rearrange the equation again by solving for ΔT.

Should work.

Show us how far you got.
… Am I allowed to create a new thread for each question …

yes quick! 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

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