## Search found 31 matches

Wed Jun 06, 2018 3:47 pm
Forum: Calculating pH or pOH for Strong & Weak Acids & Bases
Topic: H+ and H3O+
Replies: 1
Views: 233

### Re: H+ and H3O+

Yes, when you see H+ (aq) thats the same thing as hydronium
Wed Jun 06, 2018 3:45 pm
Forum: Calculating pH or pOH for Strong & Weak Acids & Bases
Topic: pH calculations on Final
Replies: 2
Views: 333

### Re: pH calculations on Final

I'm pretty sure we have to know the basics. Like if we are given that the concentration of an acid is 1.0 x 10-9 we would know the pH is 9. Beyond that, I don't think professor Lavelle indicated we would have to know more.
Tue Jun 05, 2018 10:10 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: 4.95
Replies: 1
Views: 141

### 4.95

So this homework problem asked what hybridizations exist with pi and sigma bonds. The answers said that the sigma bonds for a C-C double bond was 2sp3, which I understand. But then it said that the pi bond is 2p. Why is that? Does the pi bond have to be the first orbital in 2p? Can it not be 2s?
Thu May 31, 2018 3:55 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: 4.5 Confusion
Replies: 5
Views: 274

### Re: 4.5 Confusion

Hi! So trigonal planar is correct in that it is the general geometry of CLO2, but if you want to define its shape, the shape is bent due to the lone pair repulsion
Thu May 31, 2018 3:50 pm
Forum: Hybridization
Topic: VSEPR
Replies: 11
Views: 839

### Re: VSEPR

If a question asks you for the VSEPR formula, it is the formula written like: AXE
A stands for the central atom
X stands for number of electron regions
E stands for lone pairs of electrons
Tue May 29, 2018 4:41 pm
Forum: Bond Lengths & Energies
Topic: HW question 4.1
Replies: 5
Views: 361

### Re: HW question 4.1

The bent shape is due to the fact that lone pairs exert a higher electron repulsion than shared electrons, so the lone pair is pushing the two side atoms down
Thu May 24, 2018 10:36 pm
Forum: Dipole Moments
Topic: Dipole vs. london forces
Replies: 1
Views: 169

### Dipole vs. london forces

So i thought dipole-dipole forces were the same thing as london forces, but in homework problem 6.1 it has dipole-dipole and london forces as two separate answers. And CBr4 only has london forces and not dipole-dipole. Could someone explain the difference between the two?
Tue May 22, 2018 2:08 pm
Forum: Lewis Structures
Topic: problem 3.57 part b
Replies: 1
Views: 157

### problem 3.57 part b

this question asks about drawing the Lewis structure for a hydrogen sulfite ion. I drew it correctly, but when looking in the solutions manual, it notes that there are only two resonance structures. Yet, can't the hydrogen attached to the oxygen be moved to any of the oxygens surrounding sulfur? So ...
Mon May 21, 2018 11:08 pm
Forum: Lewis Acids & Bases
Topic: Boron and the octet rule [ENDORSED]
Replies: 7
Views: 547

### Re: Boron and the octet rule[ENDORSED]

I noticed this too. It can be explained in a lecture by Professor Lavelle when he mentioned that group 13 elements, like B and Al, are exceptions to the octet rule and mostly have 6 electrons. He noted that these reactions are called "lewis acid-base reactions"
Wed May 16, 2018 9:36 pm
Forum: Bond Lengths & Energies
Topic: test 3 [ENDORSED]
Replies: 3
Views: 195

### Re: test 3[ENDORSED]

Are all the homework problems from outline 3 going to be subjects on the test?
Wed May 09, 2018 10:27 pm
Forum: Empirical & Molecular Formulas
Topic: Question 3 on midterm [ENDORSED]
Replies: 8
Views: 626

### Re: Question 3 on midterm[ENDORSED]

Thank you so much for your response! It is interesting to see how you thought about it. I worked on this problem for a very long time and I was trying lots of different methods to see if I could make it work. I eventually settled on finding the ratio of the elements using the moles of N, H, and C I...
Wed May 09, 2018 9:06 pm
Forum: Empirical & Molecular Formulas
Topic: Question 3 on midterm [ENDORSED]
Replies: 8
Views: 626

### Re: Question 3 on midterm[ENDORSED]

So i assumed oxygen was present in the compound as well, so I started solving for oxygen. I took each of the masses of the products, divided by the molar mass of that product so I could get the moles, then I used another conversion factor (mole of one element/the mole of each product) to get the mol...
Wed May 09, 2018 4:44 pm
Forum: Heisenberg Indeterminacy (Uncertainty) Equation
Topic: Delta X
Replies: 4
Views: 341

### Re: Delta X

I believe it would be the entire diameter because the electron can be within that entire diameter of an atom. It would not make physical sense for the electron to be limited to only half the atom.
Wed May 09, 2018 4:42 pm
Forum: Heisenberg Indeterminacy (Uncertainty) Equation
Topic: Uncertainty in Kinetic Energy
Replies: 1
Views: 179

### Re: Uncertainty in Kinetic Energy

Once you find the uncertainty in velocity, you can plug that value into the formula for kinetic energy, KE= .5mv2. Because your v was the uncertainty in v, the KE will be the uncertainty in kinetic energy
Tue May 08, 2018 6:09 pm
Forum: Heisenberg Indeterminacy (Uncertainty) Equation
Topic: Module #18
Replies: 3
Views: 288

### Re: Module #18

I worked this out in the following attachment. Hope it helps.
Wed May 02, 2018 9:34 pm
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: 2.19 part d
Replies: 2
Views: 181

### Re: 2.19 part d

so n=number of shells l=the subshell
n and l are related by this: l is any integer from 0 to (n-1)
so if n=4, there would be 4 values of l, or 4 subshells
those values would be 0, 1, 2, 3
It would not be 4 because l maxes out at (n-1)
hope that helps!
Wed May 02, 2018 9:29 pm
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: Question 2.13
Replies: 2
Views: 152

### Re: Question 2.13

My T.A. just mentioned that we only really need to know the axes that each lie on. I think anything more than that won't be tested.
Sat Apr 28, 2018 10:04 pm
Forum: Properties of Electrons
Topic: Hydrogen Levels and Energy [ENDORSED]
Replies: 3
Views: 258

### Re: Hydrogen Levels and Energy[ENDORSED]

Electrons in lower energy levels ex. n=1 have a lower energy than electrons at n=2,3,4,... because less energy had to be imputed into the electron. Electrons absorb energy in order to move to a higher energy level (absorbing photons) and they release energy when they fall to a lower energy level (em...
Sat Apr 28, 2018 1:40 pm
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: orbital values [ENDORSED]
Replies: 2
Views: 2843

### Re: orbital values[ENDORSED]

I'm a little shaky on questions 2-4 and I don't want to provide incorrect explanations, but I can help clarify number 1. n represents the energy levels when we went over atomic spectrum. n=whatever number represents the energy state an electron is at currently. n=0 represents when the electron is pr...
Sun Apr 22, 2018 1:31 pm
Forum: Properties of Light
Topic: frequency and wavelength [ENDORSED]
Replies: 5
Views: 341

### Re: frequency and wavelength[ENDORSED]

the speed of light equals the frequency times the wavelength for electromagnetic radiation. If the wavelength becomes larger, the frequency must become smaller and vice versa so that the product of the two can always equal approximately 3.00 x 10^8
Sun Apr 22, 2018 1:28 pm
Forum: Einstein Equation
Topic: constants [ENDORSED]
Replies: 2
Views: 207

### Re: constants[ENDORSED]

All the constants we have gone over as well as equations will be given to us on the front page of the test, like the first test. But you will need to know what the variables in the equations stand for and how to use them.
Sat Apr 21, 2018 1:54 am
Forum: Photoelectric Effect
Topic: Photoelectric effect pre-assessment module [ENDORSED]
Replies: 2
Views: 161

### Re: Photoelectric effect pre-assessment module[ENDORSED]

Hm the only way I've been able to check which answers I got wrong was by completing the post-assessment. It'll let you review your answers at the end.
Sat Apr 21, 2018 1:51 am
Forum: Significant Figures
Topic: Sig Fig Accuracy [ENDORSED]
Replies: 6
Views: 502

### Re: Sig Fig Accuracy[ENDORSED]

I'm not sure if this is entirely accurate, so please correct me if I'm wrong, but the way I've always done it is to keep track of how many sig figs I have while I'm solving equations and whatnot BUT I don't round at all in my calculator until my final answer where I can see how many sig figs it is s...
Sun Apr 15, 2018 9:24 pm
Forum: Photoelectric Effect
Topic: Planck's Constant
Replies: 4
Views: 330

### Re: Planck's Constant

If you'd like to see professor Lavelle explain this exact concept I found 16:30 on his photoelectric effect video/module very helpful in clearing up what Planck's constant is
Thu Apr 12, 2018 9:55 pm
Forum: SI Units, Unit Conversions
Topic: writing out conversions in one long line vs. steps
Replies: 16
Views: 877

### Re: writing out conversions in one long line vs. steps

I do my conversions using dimensional analysis, which I believe is the way most people were taught, so I find it most helpful to do all my conversions in a long line so I can continually cancel out my units until I end up with an answer in the units I wanted.
Thu Apr 12, 2018 9:53 pm
Forum: Empirical & Molecular Formulas
Topic: Order of elements in molecule
Replies: 1
Views: 172

### Re: Order of elements in molecule

For chemical formulas containing carbon:
1. Carbon
2. Hydrogen
3. Other elements in alphabetical order
example: C7H4Br2O2
For elements containing no carbon:
Elements in alphabetical order
example: H2O4S
Thu Apr 12, 2018 9:49 pm
Forum: Significant Figures
Topic: Sig fifs in 750 [ENDORSED]
Replies: 6
Views: 549

### Re: Sig fifs in 750[ENDORSED]

Yes! So 750 only has two sig figs because of that 0 at the end. It would be 3 if it was 751 because it is ambiguous whether that 0 is there due to rounding or if it is exactly 750, so it can be said that only two numbers are significant figures. In 750.01 and even 750.00, there would be 5 significan...
Thu Apr 12, 2018 9:41 pm
Forum: Molarity, Solutions, Dilutions
Topic: Review worksheet from week 1, question 8 [ENDORSED]
Replies: 1
Views: 457

### Re: Review worksheet from week 1, question 8[ENDORSED]

start with the 702 grams of octane, multiply that by the molar mass of octane (in moles/grams so the units cancel out), then multiply by 25 moles of oxygen gas/ 2 moles of octane (this is directly from the balanced chemical equation), then multiply by the molar mass of oxygen in grams/moles so the m...
Thu Apr 12, 2018 7:20 pm
Forum: Molarity, Solutions, Dilutions
Topic: Finding the molarity concentration of one type of atom from a molecule
Replies: 3
Views: 154

### Re: Finding the molarity concentration of one type of atom from a molecule

I also did it the same way the previous answer mentioned. Since there is 1 mole of Na+ in 1 mole of NaCl, you would use that information as a conversion factor if you want to solve for something else or you'd know that there is .2 M of Na+.
Thu Apr 12, 2018 7:07 pm
Forum: Properties of Light
Topic: Units of speed of light [ENDORSED]
Replies: 2
Views: 185

### Units of speed of light[ENDORSED]

Just a little confused about the units for the constant in the equation v(lamda) = C
if v is frequency in units of cycles/sec
and lamda is wavelength in units of m
then how is speed of time in m/sec?
Maybe I wrote my notes wrong, please correct me if that is the case and thank you!
Mon Apr 09, 2018 6:43 pm
Forum: Properties of Light
Topic: Homework? [ENDORSED]
Replies: 10
Views: 530

### Re: Homework?[ENDORSED]

I believe it's the questions in outline 2 on the 14A website, titled "The Quantum World". We haven't covered much of that section yet so our homework this week can come from the homework problems from last week as well, outline 1.