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sarah1004 · Nov 18, 2009, 11:06 PM

Calculate the quantity of heat lost when 52g of S is cooled from 85C to 60C.
The specific heat of sulfur is 0.736J/g C.

Do I have to find mole of S first?

Please help the step to solve this problem.Thanks

Perito · Nov 19, 2009, 05:56 AM

Calculate the quantity of heat lost when 52g of S is cooled from 85C to 60C.
The specific heat of sulfur is 0.736J/g C.

Do I have to find the number of moles of S first?

No. You don't have to calculate the number of moles of sulfur. The reason is that your specific heat is given in Joules / (gram Celsius). If your specific heat were given in Joules/(mole Celsius), you would have to convert to moles.

Note the units of your specific heat: $\frac {0.7361\,J}{g\,C}$

The temperature difference is $85C - 60C = 15C = \frac {15\,C}{1}$

The weight of S is $52 \, g = \frac {52\,g}{1}$

I've divided the temperature difference and the weight by 1 to make the following clearer:

$\frac {0.7361\, J}{\cancel{g} \,\cancel {C}}\,\times\,\frac {52\,\, \cancel{g}}{1} \times \frac {15 \, \cancel{C}}{1} = 0.7361\, \times \, 52 \, \times \, 15\, \times \, Joules$

sarah1004 · Nov 19, 2009, 11:41 AM

So, this answer going to be 574.08J

Correct?

Thanks

Unknown008 · Nov 19, 2009, 11:51 AM

No...

What you did is only take from what Perito said. I suggest to you that you look at the explanations themselves, not the values.

For you see, anyone can makes mistakes, and you'll see that there is an error in the calculation of the temperature change. Try again, and next time, do the work all from the start. It will be a good practice, plus it will show where you get really stuck, or even point out possible errors from our members :)

sarah1004 · Nov 19, 2009, 12:00 PM

ohh okay Thanks^^

sarah1004 · Nov 20, 2009, 06:09 PM

Do you know any formula for this problem?

Thanks

Unknown008 · Nov 21, 2009, 01:34 AM

It remains the same. I have already told you in previous threads:

$Q = mc\theta$

Q is the amount of heat involved
m the mass involved
c the specific heat capacity
theta the change in temperature.