9 replies to this topic

[Jar Jar D'oh!]

Hey so I'm confused about the topic. I have two research question and I don't know which one is better.

A)How can the heat of hydration of Copper (II) Sulfate be found using Hess’s law ? How effectively can experimental values estimate the heat of hydration of Copper (II) Sulfate as compared to theoretical values?
B)How can the heat of hydration of Copper (II) Sulfate be found using Hess’s law ? How effectively can experimental values estimate the heat of hydration of Copper (II) Sulfate as compared to theoretical values?

If you're wondering what its about, well basically I performed two experiments that gave me two values of enthalpy changes and using Hess's Law I calculated the third one, simple. Do ask for clarifications if necessary.

[Desy Glau]

this is an IA, right? a design one? if it's a design then both RQ are not appropriate.

[Summer Glau]

I agree with Desy. You should phrase your RQ in terms of your independent/dependent variables.

[Jar Jar D'oh!]

Is that so... hmm, thanks for bringing it to my notice! All right, so conclusively this would be suitable for a Design, DCP and CE Lab? but not a Design solely.

The thing is I designed it and carried it out, so its not just design, now what do you think?

I really didn't know the way questions were framed differed, are there any other such odd balls? Excuse my ignorance, but my school's relatively new to IB and such details tend to slip them at times!

[Jar Jar D'oh!]

Independent variable: The experimental enthalpies of the alternate path
Dependent variable: ∆H_reaction for the hydration of Copper (II) Sulfate.

Clarification: experimental implying that I carried out those reactions and calculated the enthalpy change.

New RQ (hope this passes):an the experimental enthalpies of the alternate path of Copper (II) Sulfate’s hydration accurately determine the heat of hydration of Copper (II) Sulfate.

I have a tendency to complicate stuff, can you make any suggestions on simplifying this?

[Desy Glau]

that sounds complicated lol but this is the formula:

X: independent variable
Y: dependent variable
RQ --> How does Y change when X is varied?

example:
X: concentration of HCl
Y: volume of H2 gas collected
RQ --> When hydrochloric acid is reacted with excess magnesium metal, how does the volume of H2 gas collected change when the concentration of HCl is varied from 0.2 M, 0.4 M, 0.6 M, 0.8 M and 1.0 M?


note that you need at least 5 different values for your indep variable, in case if you're not aware of that. and 3 repeats for each value.

[Jar Jar D'oh!]

Where's that written? Is it an established rule? Lol, I wish I could change your name to the harbinger of bad news! xP.



How do your 5 diff values make any sense in my exp?

[Desy Glau]

that's the problem, your design lacks of that aspect. you can't get a 'complete' without that.

and, it's one of the "must have"s that our teacher taught us in the beginning of the course. I think she got that from the IB teachers forum.

[Jar Jar D'oh!]

And I don't even see anyway around it  except by doing the same exp with diff masses of CuSO4 to obtain the same values(roughly)

[Jar Jar D'oh!]

Hi all! Yet another RQ puzzles me, its that common lab on concentration Vs. Rate of reaction: How is the time taken for the Sulfur precipitate to obscure the ‘X’ Mark affected by the concentration of the Sodium Thiosulfate?

The reaction occurring is between Sodium thiosulfate and HCl (both dil.) and sulfur(solid- hence it is assumed to be a ppt.) is produced among some other products. So basically each time I dilute the Sodium thiosulfate more and measure the time taken for the 'X' on a sheet o paper below the beaker, to be obscured.

I really appreciate your help so far!