CHEMISTRY COMMUNITY

Nawaphan Watanasirisuk 3B

Thank you Dr. Lavelle! You explained each topic so well I was able to really understand the material logically and how they come together despite not having taken chemistry in high school. You certainly made Chemistry interesting, Thank you prof! :)

Nawaphan Watanasirisuk 3B

one of the examples was [Mn(en)2(NH3)2I2]+2

I'm a bit confused because I thought en is a shorthand for ethylenediamine which already includes (NH3)2 ? Why should there still be (NH3)2 in the formula in it is already shorthanded as en?

Please help!

Nawaphan Watanasirisuk 3B

For seesaw, the bonds in the axial plane are <90 degrees right? How about the bonds in the equatorial planes, are those 120 degrees apart or <120 ? For T-shape, are 2 bonds in the axial plane are <90 degree? Would they be even less than the axial plane bonds in seesaw since there are 2 lone pairs pu...

Nawaphan Watanasirisuk 3B

I also want to know this as well if anyone knows please explain

Nawaphan Watanasirisuk 3B

Does anyone know why AX3E2 is t shape instead of trigonal bipyramidal? That is, why are the 2 lone pairs on the equatorial plane and not on opposite sides of the axial plane? Since lone pair-lone pair e- repulsion is the strongest, wouldn't it make more sense for the 2 lone pairs to be as far from o...

Nawaphan Watanasirisuk 3B

I am also confused about this. If anyone knows why the answer for So2 lewis isnt the one with 2 double bonds on oxygen please explain the reason!

Nawaphan Watanasirisuk 3B

We learned 2 rules that tell us an acid is strong— 1. Weaker [longer] bonds = stronger acid because loses H+ easier 2. Resulting anion must be stable i.e. resonance or high electronegativity pulls the - charge to it and away from H+. How do we know which rule to to apply if an acid have a stronger b...

Nawaphan Watanasirisuk 3B

Why do electrons in the s orbitals have lower energy than those in the p orbital if the e- in s orbital shield the nuclear pull from those in p. Why do the e- in p orbitals have more energy if it experiences less nuclear attachment/pull since they are further from the nucleus and are shielded? Is it...

Nawaphan Watanasirisuk 3B

Can someone explain why these 2 answers are wrong?

The first picture is 3b. Kinetic energy is 2x10^-19

Nawaphan Watanasirisuk 3B

HI has longer bond than HCl, making its bond weaker. Therefore it is easier for HI to lose H+, making it a stronger acid.

Nawaphan Watanasirisuk 3B

I think just knowing the ones he went over in lecture should be fine

Nawaphan Watanasirisuk 3B

Is it possible to ever have a negative oxidation number? If so how would that be reflected in the name because there is no +/- sign in the brackets

Nawaphan Watanasirisuk 3B

On the question 9C.1 part c) why is the answer aquapentacyanocobaltate and not pentacyanoaquacobaltate ? I thought we rank the ligands based on their name on the periodic table. Did I remember wrong and we actually rank the alphabetical order based on their actual name?

Nawaphan Watanasirisuk 3B

-ate is added to the end of the metal name if the complex has an overall negative charge but not when the the complex has an overall positive charge or if the complex is neutral.

Nawaphan Watanasirisuk 3B

Yes, it is "universal".

Nawaphan Watanasirisuk 3B

The sp^3 hybridization would occur when you have 4 regions of e- density

Nawaphan Watanasirisuk 3B

The homework doesnt necessarily have to be from the immediate week. It can be from the older weeks as long as the content has already been covered in class.

Nawaphan Watanasirisuk 3B

Test 3 covers: End of Bonding from 3.12 (6 Ed.) and from 2D (7 Ed.); and all of Molecular Shape and Structure (see Syllabus and Outlines for details) <-- from the class website

Nawaphan Watanasirisuk 3B

Does it matter which way (horizontal or vertical) we draw the VSEPR model as long as theh indicate the same arrangement & shape? For example the one on the left shows that the O bonds are being pushed down because of the lone pair but in the solution manual the structure is as on the right.

Nawaphan Watanasirisuk 3B

The book asks to explain why AsF3 has significantly higher boiling point than AsF5 and in the solution its because AsF3 is a polar molecule. What makes AsF3 polar? Is it because the lone pair pushes the 3 F bonds down and so the vectors don't cancel out whereas in AsF5 all 5 bonds are spread out aro...

Nawaphan Watanasirisuk 3B

Initially on the syllabus test 3 was listed during week 8 but it has since changed. Test 3 will start on the 27th [after thanksgiving break].

Nawaphan Watanasirisuk 3B

Approximately yes, the accurate number I believe will be calculated after taking into account the class' average

Nawaphan Watanasirisuk 3B

We do have discussions but we dont have to hand in any homework this week

Nawaphan Watanasirisuk 3B

It depends on the difference in electronegativity of the atoms. C-H for example have similar electronegativity and therefore is nonpolar because electrons are shared equally between the 2 atoms.

Nawaphan Watanasirisuk 3B

Negative charge should be on the more electronegative atom such as oxygen and positive charge should be on the less electronegative atom. However this comes seconds to filling up octets or getting the overall charge to 0.

Nawaphan Watanasirisuk 3B

I believe we don't need to be able to draw the wedge and shape model, and I dont think which atom goes to the front/back matters as long as their positions don't affect the angle/structure of the molecule.

Nawaphan Watanasirisuk 3B

https://i.pinimg.com/originals/8c/76/d0/8c76d0df9e1d578b46a2d8fb02bf7f24.png here's a chart I've been using. you probably don't want to rely on it since we won't have it on the test but its been helpful for me to double check my answers with it before looking in the solutions manual Thank you so mu...

Nawaphan Watanasirisuk 3B

The "everything you need to know about SigFigs" section on Lavelle's website is really clear and helpful you should definitely check it out!

Nawaphan Watanasirisuk 3B

Q: Why do chemists call helium, curium, and barium the medical elements?
A: Because if you can't helium or curium, you barium!

Nawaphan Watanasirisuk 3B

They are related because if an element has a tendency to take electron (high electron affinity), then it would take a lot of energy to remove one from that element, since the element likes/tends to gain an electron rather than lose an electron. This follows the trend that elements on the right on th...

Nawaphan Watanasirisuk 3B

Can someone explain 1. to me?

Thanks in advance!

Nawaphan Watanasirisuk 3B

On test 2 #4 a) the question says at the threshold level light is emitted with energy equal to 3.61x10^-22 kJ. Find the frequency of the emitted photon.

How do I find the frequency of the emitted photon? Is it just the normal E=hV? --> E/h = V ?

Nawaphan Watanasirisuk 3B

Does anyone know if the 3 review sessions will cover the same practice problems? Because they are during normal lecture times that professor Lavelle teaches I think they might be the same but am not sure. If anyone could clarify that would be helpful!

Nawaphan Watanasirisuk 3B

Happy Birthday prof!!

Nawaphan Watanasirisuk 3B

Are we suppose to be able to write the chemical formula for sodium hypochloride? Is there another way of figuring out it's ClO- without memorizing? Because in order to write the Lewis structure we need its chemical formula.

Nawaphan Watanasirisuk 3B

I also want to know if we were expected to know the chemical formula when given a less obvious compound name like ammonium chloride?

Nawaphan Watanasirisuk 3B

Are the 2 exceptions the only ones we need to know? It seems there are more as you go down the periodic table.

Nawaphan Watanasirisuk 3B

I think you only need to to know that both the Lyman and Balmer series are spectral line for H atoms and that Balmer series is the visible region in which the final n [n1] is 2. For Lyman series n1 is 1 and it lies in the ultraviolet region.

Nawaphan Watanasirisuk 3B

The 4s subshell is lower in energy than the 3d subshell, so it fills up first. The 4s becomes higher in energy after filling up, so if you ionize the atom, electrons are lost from the 4s subshell before the 3d subshell. But that's not how I learned it so it just confuses me to think of it that way....

Nawaphan Watanasirisuk 3B

I know 6s should be filled first before electrons can start filling 5d orbitals. The textbook states that after 6s is filled, 4f will start to be filled, and only after 4f is filled then electrons can start filling 5d? This is the case with the example of ytterbium [Xe]4f^14 6s^2. However, Cerium's ...

Nawaphan Watanasirisuk 3B

saw this on facebook

Nawaphan Watanasirisuk 3B

Did he mention particle in a box in lecture briefly and I missed it or is it just in the textbook?

Nawaphan Watanasirisuk 3B

It also depends on what values you are given/asked

Nawaphan Watanasirisuk 3B

Materials that should only be in test 1 [i.e. not related to the quantum world section] will not be on but the test is still kind of cumulative in a way that you would need to apply some knowledge from test 1 to be able to fully do test 2.

Nawaphan Watanasirisuk 3B

The pull of the remaining electrons also becomes stronger after each electron removal because the pull is now divided/distributed among less electrons

Nawaphan Watanasirisuk 3B

In 1D.9 in the 7th edition part c of the question asks about the number of radial nodes and angular nodal surfaces. I recognize only nodal planes from the lecture. For this our purposes for this class what are the significant differences [if any] of radial nodes, angular nodal surfaces, and nodal pl...

Nawaphan Watanasirisuk 3B

You're a 10? On the pH scale maybe, cuz you're basic.

Nawaphan Watanasirisuk 3B

I find it helpful, especially when balancing equations with many different elements, to keep track of the amount of each element on the side. It might be a bit tedious if you have to update them each time you change the amount in the equation but usually it works well for me.

Nawaphan Watanasirisuk 3B

If your answer is 200 and need to write your answer in 3 sigfigs you can write 200, but if the lowest given value from the question has 4 sigfigs you would need to answer in 4 sigfigs as well. You would write 200.0 which has 4 sigfigs.

Nawaphan Watanasirisuk 3B

Judging from the homework and examples in class I believe we on tests would get answers that would be obvious. For example 10^-12 [picometer] would be detectable and 10^-24 would not.

Nawaphan Watanasirisuk 3B

You can turn homework from the high school review section as well as the new topic as long as it has been covered. So if your discussion is on Thursday you would have a little bit more questions to choose for the homework.

Nawaphan Watanasirisuk 3B

I've thought about it and I don't think it is extra credit, since Prof Lavelle hasn't mentioned anything about it at all and it is not even on the syllabus.

Nawaphan Watanasirisuk 3B

I think one of the TAs mentioned the maximum point we could lose on sig fig related errors are 4 points. You're supposed to apply the sig fig rules at the very end of calculation, I usually keep a longer sig fig during calculations to avoid any errors.

Nawaphan Watanasirisuk 3B

No it's on Sapling Learning where you can access your etextbook: http://www.saplinglearning.com/ibiscms/ ... p?id=87018

Nawaphan Watanasirisuk 3B

I noticed the practice assignments or quizzes on Sapling Learning are labelled 'extra credits'. However on the syllabus there isn't a grade for it and the website itself says the practice assignments are optional. Does this mean they aren't really extra credits?

Nawaphan Watanasirisuk 3B

It should either be given or information should be given for you to find out on your own but you need both the actual and theoretical values to find the percent yield.

Nawaphan Watanasirisuk 3B

I also got 4.57x10^-2, but I think both answers should be fine

Nawaphan Watanasirisuk 3B

How often do I tell chemistry jokes?

Periodically.

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