[jerrinl]

I've been looking at this problem, and the equations, but I'm not sure if I'm missing something here. Is the mass of the calorimeter merely the sum of the two substances?

You are profrming the calibration step of this experiment and you begin with 50g of water at 20C and 50g of water at 80C. AFter adding the two in your calorimeter setup and following procedure, you determine temperature to be 45C. What is the heat capacity of the calorimeter?

[Borek]

No, you have three things present - 50g of water (heat capacity 50g*4.18J/(gK)), another 50g of water(heat capacity 50g*4.18J/(gK)) and calorimeter itself (unknown heat capacity).

[jerrinl]

No, you have three things present - 50g of water (heat capacity 50g*4.18J/(gK)), another 50g of water(heat capacity 50g*4.18J/(gK)) and calorimeter itself (unknown heat capacity).

Ah so this is what I've gotten down so far

ive also forgotten to mention my lab book says to put the heat capacity of water int his experiment as 1.00 J/gK

-(SH warm * mass warm * dT warm) = (SH cool * mass cool * dT cool) + (C cal * dT cal)

I've plugged in the numbers for this to become

-(1.00 * 50 * 35) = (1.00 * 50 * 25) + (Ccal * dT cal)

and I've determined the q of the Calorimeter is 500K, and the equations tell me dT cal = dT cool

so C is equal to 20.

Now, Ccal is 20 and then that means (mass cal * SH cal) is how I find the SH.

But theres nothing listed in the lab procedures about the mass of the calorimeter

I'm sorry if i'm missing the obvious here.

[Borek]

ive also forgotten to mention my lab book says to put the heat capacity of water int his experiment as 1.00 J/gK

And not 1 cal/(gK)?

and I've determined the q of the Calorimeter is 500K

Heat is never measured in Kelvins, temperature is.

But theres nothing listed in the lab procedures about the mass of the calorimeter

You don't need mass for a heat capacity.

There is a specific heat capacity - cal/(g*K) or J/(g*K) - it can be used to calculate heat capacity of a given mass of the substance.

But if you have a well defined object - like the calorimeter - you can calculate just its heat capacity and don't worry about its mass, as the product of mass and specific heat capacity for this calorimeter will be always identical. Heat capacity of the calorimeter will be measured in cal/K (or J/K) - it doesn't contain the mass, as it is no longer important.

Or from different point of view. We know that

q = mcΔT

for a given calorimeter mc will be always identical, so we can rewrite the formula as

q = CΔT

where C is just a heat capacity of the calorimeter, which is a characteristic constant for a given device.

[jerrinl]

Ah damn, it all makes sense now. Thank you very much, you're quite helpful!