Enthalpy of Formation of ZnO lab

[cutielollipop]

Homework Statement

I'm having trouble understanding whether q stays constant? If it does, then for part b) does q stay the same?

Relevant Equations

q = mcdeltaT

Experiment equation: Zn(s) + 2HCL(aq) -> 2ZnCl(aq) + H2(g)

a) If the the mass of zinc solid used was doubled, what effect would this have on temperature change?

Answer: if mass of zinc increases, there will be an increase in zinc particles which increases the collisions between particles and increases the average kinetic energy therefore giving higher temperature change

b) What would have been the number of joules evolved (q)?

c)What effect would this have on delta H?
delta H would increase by a factor of 2 since the mass is doubled, so the number of mols has also doubled.

 

[Borek]

Question is a bit poorly worded or you posted it incomplete, as the answer depends on several other factors - mainly on what is the limiting reagent in the setup.

Amount of heat produced is directly proportional to the amount of zinc that reacted.

Q is not much different from ΔH in that regard (see your answer to c.) - assuming there was a sufficient excess of acid.

 

[cutielollipop]

Thx for your reply. I have figured out the answer as I realized that zinc was the limiting reagant.

 

[chemisttree]

Yes, q is an extensive property.