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Author Topic: Calorimeter Constant problem help  (Read 255 times)
AwesomOne
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« on: February 01, 2010, 08:10:39 PM »

I am stuck on how to do this problem:

       A calorimeter is to be calibrated 51.203 g of water at 55.2 degrees C is added to a calorimeter containing 49.783g of water at 23.5 degress C. After stirring and waiting for the system to equilibrate, the final temperature reached is 37.6 degrees C. Calculate the calorimeter constant.

I think that you have to 55.2- 37.6 and 37.6- 23.5  and I also know that you need the 4.184 constant for specific heat of water... I am stuck what to do next.
Thanks  Cheesy       
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kingchemist
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« Reply #1 on: February 02, 2010, 06:21:05 AM »

I assume you will have to find the temperature of mixing the two sample of water, assuming no heat is absorbed by the calorimeter. I expect the temperature will be >37.6 degrees C. The difference in temp will be the result of heat being absorbed by the calorimeter.
Let the temperature of water on mixing be w degrees

As c is constant, then m1[delta]T = m2[delta]T
                              51.203 x (55.2-w) = 49.783 x (23.5 + w)

Solve for w.

Find q at this temperature using g = cm[delta]T where m=the combined mass of water and c is the specific heat of water in the right units.
Find q at 37.6 degrees C and the difference in the two values is the amount of heat absorbed by the calorimeter.

I expect the constant will be this difference in the amount of heat/the difference in temperature and so will have units of J (or kJ) per degree C
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valdorod
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« Reply #2 on: February 02, 2010, 12:28:25 PM »

qhot = -(qcold+qcal)

qhot = mhot*swater*ΔThot = 51.206*4.184*(-17.6)

qcold = mcold*swater*ΔTcold = 49.783*4.184*14.1

qcal) = C*ΔTcold = C*14.1

plug in and solve for C

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