Calorimetry SAC

[HarveyD]

haha alright

btw does anyone know if adding too much/more reactants will affect the enthalpy/calibration factor?
it'd just be in excess so it wouldnt have an effect right?

just asking cause i was reading up on the prac and i came upon this info
Take care to note:
the effect on calculated calibration factor if too much of one of the reactants has been added
the effect on calculated enthalpy value of a reaction if one reactant is added more.

but I dont really know why...

[kenhung123]

Adding more of both reactants won't do anything because essentially your trying to find the enthalpy value which you would only use ratios to get the correct value for. E.g. 1 mole produces 10kj then 2 mole produces 20kj
If your only adding excess of 1 reactant then of course use the limiting reactant.

[HarveyD]

ah k thats what i thought

for the reaction of NaOH and HCl
if you were to decrease the number of mol equally (i.e. decrease the volume for both)
would the heat of neutralization change?

i was thinking that it would increase from the formula, but then wouldnt decreasing the volume also decrease the temperature rise  proportionally, meaning that it wouldnt change at all :S

[HarveyD]

ah sorry to bother everyone again :S
but would anyone be able to check my explanations for errors relating to this experiment

CF (Too High)/ Would also apply to enthalpy being less then expected -
1) Poor Insulation – If the calorimeter is not properly insulted this, it will result in a loss of heat to the surroundings, hence it will reach a lower temperature than it should.  This will therefore mean that the change in temperature will also be lower, and since this is on the denominator for the formula of the Calibration Factor, a poorly insulted calorimeter will thus lead to a higher calibration factor.

2) Parallax Errors – If the temperature readings are taken from above, then this will result in a lower temperature being recorded after the reaction has taken place. Hence this will mean that the change in temperature obtained will be lower and since this value is on the denominator for the formula of the Calibration Factor, such parallax errors will thus lead to a higher calibration factor.

3) Uneven stirring/slow stirring

CF (Too Low) / Enthalpy more then expected
1) Parallax Errors – Basically the same explanation for too high, except when readings are taken from below etc

Can’t think of another others for this :/
I guess that means there’s a less chance of it happening...

[Graphite]

Contamination, incomplete rxn etc

[azn_dj]

Dodgy wiring in the electrics?