[saratan]

This is a question that I am using to practice on from an old AP CHEM exam, its a seven part FRQ all the way from using titration graphs to using equation q=mc(deltaT) and also net ionic equations. Ill explain my questions as I go through these seperate problems...



So as you can see on the left hand side of the graph I worte "Temp C" and on the bottom of graph I wrote mL of HCL added, is this correct? Secondly when it asks for the "temprature change" how do I determine that and why do I determine that answer that way? In other words what is the logic behind this problem?

next..



B)     When it comes to the net ionic equation I personaly thought that it was writen like this- Cl- + Na+ => NaCl(s).      Unfortunately that answer was WRONG, turns out the answer sheet says that the net ionic equation for NaOH + HCl => NaCl(s) + H2O(l) is actually, H+ + OH- => H2O(l). Why is this the case? NaCl is the precipitant wouldent the net ionic equation have to show the creation of NaCl?

C)     I understand how to go about the problem but I cant because I first have to find the deltaT, which is answered in part a which I dont understand, so this can be glossed over with not much explanation...

D)     I would imagine since they replaced the HCL with HC2OOH, the new reaction would be NaOH + HC2OOH => NaC2OOH + H2O(l). What would the net Ionic equation look like for this reaction and if the net Ionic equation shows the creation of H2O please explain why because wouldent the formation of the salt be what the net Ionic equation would try to show?

E)     I dont understand this part of the FRQ at all, to start off what equation would I even use to solve for deltaH

F)     And finally, part F, this really threw me off... I would imagine that enthalpy of ionization of acetic acid is the same as the amount of energy required to remove an electron for the acid, I really dont know about this at all I need a good explination on this one.


If you feel inclined to share any resources I could use to try and understand that topics of this FRQ accompanied with you information, please let me know where I can learn specificly on this topic of chemistry.


Thanks,
Jay Sanc

 

[Borek]

Secondly when it asks for the "temprature change" how do I determine that and why do I determine that answer that way?

Can you read the initial and the final temperature from the plot?

When it comes to the net ionic equation I personaly thought that it was writen like this- Cl- + Na+ => NaCl(s).      Unfortunately that answer was WRONG, turns out the answer sheet says that the net ionic equation for NaOH + HCl => NaCl(s) + H2O(l) is actually, H+ + OH- => H2O(l). Why is this the case? NaCl is the precipitant wouldent the net ionic equation have to show the creation of NaCl?

Why do you think NaCl precipitates out from the solution?

Why do you think it is possible to have plenty of H⁺ and OH^- present in the solution at the same time?

I would imagine since they replaced the HCL with HC2OOH, the new reaction would be NaOH + HC2OOH => NaC2OOH + H2O(l). What would the net Ionic equation look like for this reaction and if the net Ionic equation shows the creation of H2O please explain why because wouldent the formation of the salt be what the net Ionic equation would try to show?

Large part of your problem here is based on the same misunderstanding of what the net ionic reaction is as before. Plus, your formula of the acetic acid is wrong.

I dont understand this part of the FRQ at all, to start off what equation would I even use to solve for deltaH

The same one you used in C).

And finally, part F, this really threw me off... I would imagine that enthalpy of ionization of acetic acid is the same as the amount of energy required to remove an electron for the acid, I really dont know about this at all I need a good explination on this one.

No, ionization here means the dissociation of the acid, not losing an electron.

This is a nice problem touching on many aspects. Any General Chemistry book should explain them all. Judging from your questions your best approach would be to study it systematically, as you have many holes in what you know.