Wednesday, October 12, 2011

In class problem solving

Midterm from today's class, with short answers: http://web.uvic.ca/~mcindoe/101/2006midterm1.pdf

19 comments:

Anonymous said...

Hello,

I had a few questions:

1. for the uncertainty equation, how would you calculate the change in velocity if the questions gives you: a speed of 1.40m/s if the speed is known to within +- 0.01m/s
2.does the atomic radius increase MORE down or across? when we have to put atoms in order, how would you know which has a greater impact on the radius?
3.for the visible region of the electromagnetic spectrum, should we know the wavelength of the colors? (ie. that yellow is abou 580nm ect)
Thank you

Anonymous said...

Should we be able to remember all the experiments and the names of the researchers? Do we need to know the scientists name involved with each equation ect

Scott McIndoe said...

1. In this case, the ERROR in the velocity is given to you (0.01 m/s), so the 1.40 m/s is irrelevant.
2. You don't. The questions won't be asked in this sort of way, e.g. you wouldn't be expected to know whether O or Cl is biggest, but you would be expected to know both are bigger than F.
3. No.

You don't need to remember the names of scientists or experiments, but you DO need to understand the concepts they discovered.

Anonymous said...

For the midterm posted online, number 5 on the written part, I thought Lewis structures central atom was the least electronegative. For [CNO]-, the answer has it with N being in the middle, not C. Does it matter in this case?

Scott McIndoe said...

I think in this case N is specified as the central atom, but if it wasn't, you'd put C there.

Anonymous said...

On the practice midterm posted on the site (2010) written question 2c the question asks you to calculate the change in energy as an electron in a hydrogen atom moves from n=2 to n=1. I got the answer they got, but then in the answer key they made the answer positive rather than negative. Do we always neglect the negative when calculating the change in energy? Or why did they do that?

Thanks!

Anonymous said...

Today in class, when talking about the photoelectric effect, you said that the electrons will only be ejected when they have sufficient energy, and that we need to know what it is. How do we know what that energy is?
Thank you!

Anonymous said...

Hi professor, do we need to know how to calculate Zeff with Slater's rules for the midterm?

Anonymous said...

For number 12 in the practice midterm (http://web.uvic.ca/~chem101/C101Test1AFall2010Answers.pdf), why isn't the answer e instead of d?

Scott McIndoe said...

Re: change in energy - the negative sign implies energy is released. I think the positive value just means that the markers gave out marks if the answer had the wrong sign.

Re: photoelectric effect - the energy required was given in the question.

Re: Slater's rules - no, you don't need to know the values, but you do need to know how Zeff changes across the PT in a qualitative sense.

Anonymous said...

Why is ZrO2 the one with the greatest lattice energy between CaF2, ZrO2, and MgF2

Anonymous said...

do covalent molecules or ionic molecules have the greatest lattice energy?

Scott McIndoe said...

ZrO2 has charges of +4 and -2. The others are +2 and -1.

Covalent molecules don't have lattice energies. That's just for ionic compounds.

Anonymous said...

Could you explain number 11 on this midterm you did in class please

Scott McIndoe said...

The atomic number of an *element* is given by the number of electrons. So just add them up.

Anonymous said...

Hi, I was just wondering when and how we are going to be getting our midterm marks?

Scott McIndoe said...

Friday 9:31 am

Anonymous said...

Are we going to get that question from Graded Quiz 6 fixed? The one where there were two correct answers?

Scott McIndoe said...

This issue is in the hands of the course coordinator, who I'm waiting to hear back from on this matter. I'll let you know as soon as I find out.