I'm Monday and Wednesday (11:30) lecture... I'm not taking 126 this semester. There's a msg board for the 122 capa... I don't know about the 126 though. We should make a group on facebook or.... use this forum as a help section or something.
i'm not in either of these classes, but have looked into them...
correct me if i'm wrong, but isn't Chem 126 the lab component to Chem 122?
this is taken from the Chem 122 course outline, "Students who intend to take further courses in physical or inorganic chemistry should take the laboratory course CHEM 126 concurrently with 122."
126 isn't required to be in the same semester. However, IF you take it in the same semester, and you drop 122, you will be dropped from 126. Be aware of this.
I e-mailed Ken MacFarlene the advisor of the chem department.. he said it was ok.. It's only a suggested corequisite because the things in 126 and 122 go together so it'll be easier if you take in the same semester.
For loncapa exp 3 last question...the slope..i graphed the thing..and use excel to gimme the slope of the line that average the points... but its wrong.. WHY!!!!
You have to be careful about how many sig. figs you put in. I had a similar situation where a guy used some program other than Excel to graph the points and get the slope and intercept and it kept rejecting the slope. When I had him redo it with Excel it worked fine.
In addition be careful to let Excel carry all the sig figs internally so the errors don't magnify too much when you plot with the Add Trendline bit (You need to make it an X-Y scatter plot, don't force through zero).
Make sure you've got the right axes, too. If your axes are flipped your slope will be wrong.
Had to miss this whole week of chem to make up for loss time at work (had to line up for a passport). Looks like I better do some extra reviewing.
I noticed on this week's capa theres a few ppl that is talking about their aurora calculators. Did anyone of you actually get one? Are we only allowed to use these calcs for the MT/Final? If so I better get one ASAP.
Lab 6 is potassium bitartrate. Be aware of statistical techniques for eliminating outliers in a collection of data points, and understand the difference between solubility and the equilibrium constant (the first is concentration dependent and the second is temperature dependent).
And do yourselves a favor and look up the molar mass of potassium bitartrate. :)
Lab 7 will focus on simple acid-base equilibria. Read the Appendixes regarding acids and bases and be familiar with the graphs showing the different titration shapes.
In addition, be conscious of the fact that in a mixture of acids with one strong and the other weak, the weak acid is in equilibrium. Consider the effect on a weak acid when you flood the solution with a large amount of H+ ions. You did something similiar to this in the bitartrate lab where the common ion effect shifted the position of the equilibrium.
Also, when you titrate, try not to overshoot the endpoint. The most common problem in manual titrations is going too fast and not being careful enough with adding dropwise from the buret. In such situations you may find that twisting the orange nut on the stopcock to increase the resistance to turning will help you.
Lab 8's already been posted on the CHEM 126 website for next week, so I'll make a few notes about it now --
WRITE THOSE VALUES IN YOUR LAB BOOK. Writing them in your lab manual is not acceptable. IN YOUR BOOK, PLEASE. Additionally, there is no such thing as the pKa or pKb for a strong acid or base. As well, pKa + pKb = 14. Use this to get BOTH the pKa and pKb for the weak acids/bases/salts that you have been asked to work out.
I will update this when I have a little more time as I've got to rush off somewhere.
An update - for lab 8, you'll more than likely need to use the analytical balance to weigh your samples, as otherwise you just won't have the accuracy needed for subsequent calculations.
As well, you have probably learned that using the computer to do pH titrations involves a compromise between getting a good curve and taking too much time acquiring the data. In general the rule of thumb is in the flat range, go 0.5 mL between points, and in sharp transition ranges, 0.1 mL between points.
Comments
I'm not taking 126 this semester.
There's a msg board for the 122 capa... I don't know about the 126 though.
We should make a group on facebook or.... use this forum as a help section or something.
and yep that's the plan, this is the help section for this subject/course for term 1071 winter.
whaaaaaaaaat...
uh oh... =/
why would it let me enrol just in 122 then..?
hopefully i can take it in the summer :S
correct me if i'm wrong, but isn't Chem 126 the lab component to Chem 122?
this is taken from the Chem 122 course outline,
"Students who intend to take further courses in physical or inorganic chemistry should take the laboratory course CHEM 126 concurrently with 122."
he said it was ok.. It's only a suggested corequisite because the things in 126 and 122 go together so it'll be easier if you take in the same semester.
but yeah, i'll take it in summer. :)
and a four hour lab just looks so unappealing on top of the class and tutorial!
anyone in chem122 tutorial on wednesday130. see you there foos.
For loncapa exp 3 last question...the slope..i graphed the thing..and use excel to gimme the slope of the line that average the points... but its wrong.. WHY!!!!
In addition be careful to let Excel carry all the sig figs internally so the errors don't magnify too much when you plot with the Add Trendline bit (You need to make it an X-Y scatter plot, don't force through zero).
Make sure you've got the right axes, too. If your axes are flipped your slope will be wrong.
Anyway this week it's a whack of equlibrium stuff so make sure you all understand equilibrium! :smile:
OMFG....
I noticed on this week's capa theres a few ppl that is talking about their aurora calculators. Did anyone of you actually get one? Are we only allowed to use these calcs for the MT/Final? If so I better get one ASAP.
Iron thiocyanate is fun. It's also blood-red in color. :tongue:
Anyway, remember - K values are dimensionless. And again, please be aware of equilibrium, its temperature dependence and Le Chatelier.
And do yourselves a favor and look up the molar mass of potassium bitartrate. :)
In addition, be conscious of the fact that in a mixture of acids with one strong and the other weak, the weak acid is in equilibrium. Consider the effect on a weak acid when you flood the solution with a large amount of H+ ions. You did something similiar to this in the bitartrate lab where the common ion effect shifted the position of the equilibrium.
Also, when you titrate, try not to overshoot the endpoint. The most common problem in manual titrations is going too fast and not being careful enough with adding dropwise from the buret. In such situations you may find that twisting the orange nut on the stopcock to increase the resistance to turning will help you.
WRITE THOSE VALUES IN YOUR LAB BOOK. Writing them in your lab manual is not acceptable. IN YOUR BOOK, PLEASE. Additionally, there is no such thing as the pKa or pKb for a strong acid or base. As well, pKa + pKb = 14. Use this to get BOTH the pKa and pKb for the weak acids/bases/salts that you have been asked to work out.
I will update this when I have a little more time as I've got to rush off somewhere.
As well, you have probably learned that using the computer to do pH titrations involves a compromise between getting a good curve and taking too much time acquiring the data. In general the rule of thumb is in the flat range, go 0.5 mL between points, and in sharp transition ranges, 0.1 mL between points.
Saw a bunch of you folks outside the 122 classroom waiting for the midterm. How 'bout the inevitable post-mortem? :)
(and PS, if it helps, I was wishing good karma on you all. :smile: )