Page 1 of 1

### #39 from Chapter 8

Posted: Thu Jan 11, 2018 2:01 pm
On number 39 from chapter 8, the specific heat of water is multiplied with the grams of water present with the final temperature minus the initial. My question is: how do we know when to use the specific heat? Is it always used in problems when they are asking for q?

### Re: #39 from Chapter 8

Posted: Thu Jan 11, 2018 2:14 pm
I learned in discussion that the formula for this kind of problem is q= m*C*deltaT or q=n*C*deltaT.
m= mass
n=moles
C= heat capacity
deltaT= change in temperature (final- initial)

Sometimes the heat capacity will be specific heat capacity (in grams) or molar heat capacity (moles).

### Re: #39 from Chapter 8

Posted: Thu Jan 11, 2018 3:53 pm
You would use the specific heat capacity when you have the mass, while you would use molar heat capacity when you know the amount of moles because specific heat capacity measures the joules of heat needed to raise one gram of a substance by one degree C, while molar heat capacity measure the joules of heat needed to raise 1 mole of a substance by one degree C.

### Re: #39 from Chapter 8

Posted: Thu Jan 11, 2018 5:17 pm
Another mistake I ran into while solving this question was forgetting to convert the enthalpy of fusion into Joules because in the tables, it is given in kJ.