Calorimetry errors

[chewybacca]

Okay I'm confused.

During the calibration process, if I added more vol. of water than usual, would the temp. change be higher or lower than expected (and hence CF would be lower or higher respectively)? Seems TSFX (notes) and STAV 08 MC Q1 are conflicting each other... (one states that CF is lower if less water was added, while the other states the CF is lower if MORE water was added - unless I'm misunderstanding things...)

Also, would the temp. change be higher or lower (than expected) if I added more amount (mol) of the substance I'm using the calibrate (as opposed to water)?

Thanks!

[Collin Li]

There's more stuff to heat up, so you would require more energy per degree of temperature, meaning you would have a higher calculated CF than actual CF.

[chewybacca]

There's more stuff to heat up, so you would require more energy per degree of temperature, meaning you would have a higher calculated CF than actual CF.

Hmm...does that consequently mean, if you applied the same amount of energy (i.e. VIt = constant) and you filled up the calorimeter with LESS water than what was required, that the change in temp. would be higher (how is that possible?) (hence CF is lower), as you would require less energy per deg. of temp.?
Sorry if that sounds confusing

[bec]

I think so...
It's like when you're boiling water - if the kettle's basically empty, it takes much less time than if it's full. Same deal here - VIt (ie, the electricity you're putting into the kettle) hasn't changed, just the amount of water.

So yeah, the CF would end up being lower if you used less water.


Oh and just a note...I'm probably wrong. Someone else?

[roly182]

Remember the Stav exam is asking for the CORRECT calibration factor, not the incorrect one..

[chewybacca]

Remember the Stav exam is asking for the CORRECT calibration factor, not the incorrect one..

Ahh...so that explains the STAV problem...my bad!

[roly182]

hahah yeah i spent about half an hour on this question with my teacher trying to figure out what was wrong with it, then i realised that night that we didnt even read the question properly. It helps!