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Knowing which equation to use when finding q

Posted: Thu Jan 18, 2018 2:51 pm
by Abigail Urbina 1K
We've seen so many different equations that can be used to calculate q such as q=nCdeltaT or q=mCdeltaT. How do we know when to not take mass or moles into account and just use the equation q=C*deltaT? I was having a hard time finding why this equation was used in 8.53 when a mass was given.

Re: Knowing which equation to use when finding q

Posted: Thu Jan 18, 2018 3:17 pm
by Justin Chang 2K
I think because 8.53 says the reaction took place in a bomb calorimeter, so you would use q=C(cal)*deltaT, which relates the heat to the specific heat capacity of the calorimeter.

Re: Knowing which equation to use when finding q

Posted: Thu Jan 18, 2018 4:30 pm
by Ammar Amjad 1L
When heat capacity is given you don’t need to take number of moles or mass into account. However, when specific heat capacity is given you would use the mass in the equation, and when molar heat capacity is given you would use the number of moles. You are essentially multiplying by the number moles or the mass in both situations to acquire the heat capacity. Recall from lecture, when you divide heat capacity by the amount of substance present (g), you get specific heat capacity.