## q=mc∆t vs q=c∆t? (chapter 8)

Zoe Robertson 2H
Posts: 28
Joined: Fri Jun 17, 2016 11:28 am

### q=mc∆t vs q=c∆t? (chapter 8)

Hi! Could anyone clarify when to use q=mc∆t vs q=c∆t? I was working on question 8.53 and I was going to use q=mc∆t but the 'm' wasn't included in the solution. Thank you!!

Jessica Huang 1M
Posts: 26
Joined: Wed Sep 21, 2016 2:59 pm

### Re: q=mc∆t vs q=c∆t? (chapter 8)

The C given in the problem is in units of kJ/C.

You want your q to be in units of Joules or kJ.

If you used the q=mC(delta T) with your given C, your q would be in units of (grams)(kJ).

In the problem, you were given the heat capacity, not the specific heat capacity. Therefore, you don't need mass to calculate q.

Laura Rabichow 1J
Posts: 29
Joined: Fri Jun 17, 2016 11:28 am

### Re: q=mc∆t vs q=c∆t? (chapter 8)

In general, you can figure it out based on the units of the given C. You typically want q to be in kJ or J. Like Jessica said, in your example problem the C was given in kJ/˚C, so you would only multiply by the temperature. If your C was given in kJ/(˚C*mol), you would use q = nC∆T. If your C was given in kJ/(˚C*g), you would use q = mC∆T. Also, don't forget to convert moles of substance to grams or vice versa if it doesn't match the C given!