## Search found 31 matches

Thu Jun 07, 2018 1:11 am
Forum: Calculating pH or pOH for Strong & Weak Acids & Bases
Topic: pH calculations on Final
Replies: 2
Views: 335

### Re: pH calculations on Final

Yea I am a bit worried as to what we need to know about the calculations as well. I thought I heard him say in class that the calculations are part of chem 14B but I might have misunderstood.
Tue Jun 05, 2018 10:03 pm
Forum: Sigma & Pi Bonds
Topic: Sigma and Pi bonds
Replies: 3
Views: 312

### Re: Sigma and Pi bonds

I think the most important thing you need to know about them is that single bonds are sigma bonds, double bonds are a sigma bond and a pi bond, and a triple bond is a sigma bond and two pi bonds.
Tue Jun 05, 2018 9:56 pm
Forum: Lewis Acids & Bases
Topic: Protons are lewis acids?
Replies: 5
Views: 1705

### Protons are lewis acids?

Why is it that lewis acids are H+ (protons) and are protons the only lewis acid there is?
Tue Jun 05, 2018 9:53 pm
Forum: Lewis Acids & Bases
Topic: Weak vs strong acids [ENDORSED]
Replies: 7
Views: 533

### Weak vs strong acids[ENDORSED]

So I understand the difference between what makes a strong acid (the fact that it fully becomes deprotonated) vs a weak acid (not fully deprotonated). However, I don't understand how we can conclude this from looking at an equation because that will always shows us that it becomes fully deprotonated...
Fri Jun 01, 2018 12:18 am
Forum: Determining Molecular Shape (VSEPR)
Topic: Problem 4.9
Replies: 3
Views: 207

### Re: Problem 4.9

Trigonal pyramidal takes on the form of A-X3-E, with 3 atoms bonded to a central atom and a lone pair of the central atom.
ICl3, when you draw the lewis structure, has 2 lone pairs and 3 atoms bonded to the central atom, which takes on the form of A-X3-E2, which is T-Shaped.
Fri Jun 01, 2018 12:12 am
Forum: Determining Molecular Shape (VSEPR)
Topic: lone pairs
Replies: 5
Views: 332

### Re: lone pairs

think of the ball and stick module that Dr. Lavelle showed us in class when he asked someone to pull out an atom and make it a lone pair. Since lone pair repulsion is stronger than the repulsion of a bonded pair of electrons, the lone pair pushes the other atoms away from it and causes bond angles t...
Fri Jun 01, 2018 12:01 am
Forum: Determining Molecular Shape (VSEPR)
Topic: 4.5 Confusion
Replies: 5
Views: 277

### Re: 4.5 Confusion

Since we count lone pairs and atoms connected to the central atom as 1 region of electron density for each one, then there are 3 regions of electron density, meaning that this has to be trigonal. It is confusing though so I definitely understand.
Thu May 24, 2018 1:34 am
Forum: Lewis Structures
Topic: HW 3.45
Replies: 1
Views: 151

### Re: HW 3.45

Hey!
I think you misread the formula. There are only two O atoms, one to the left and one above it, there is no O to the right of it (instead, its Cl). Having a double bond on the Cl would mess up all the formal charges! Hopefully that helps and I hope I didn't misread your question :)
Thu May 24, 2018 1:16 am
Forum: Octet Exceptions
Topic: Help on 3.59 in homework?
Replies: 2
Views: 187

### Help on 3.59 in homework?

Hello, So 3.59 asks us to find the lewis structure of the radical ClO, and the answer key shows us Cl----O with 5 valence electrons (or dots) around the Cl and 6 Valence e- (or dots) around the O. However, this gives us the formal charges of +1 and -1, but why is it not switched (where Cl has 6 dots...
Wed May 23, 2018 11:16 pm
Forum: Lewis Structures
Topic: 3.45 quick question
Replies: 3
Views: 212

### 3.45 quick question

Draw the Lewis structures that contribute to the resonance hybrid of nitryl chloride, ClNO2 (N is the central atom).

Hello, I get this problem but I was just wondering why N is the central atom instead of Cl, when N has a higher electronegativity than Cl (FONCl).

Thanks!
Thu May 17, 2018 7:17 pm
Forum: Lewis Structures
Topic: HW 3.41 part c)
Replies: 1
Views: 124

### HW 3.41 part c)

Hello, I have a quick question about part c in hw 3.41 Write the complete Lewis structure for each of the following compounds:(c) glycine, H2C(NH2)COOH, the simplest of the amino acids, the building blocks of proteins. So I was wondering if the chemical formula helps us in determining the groupings ...
Thu May 17, 2018 6:31 pm
Forum: Ionic & Covalent Bonds
Topic: HW 3.39
Replies: 1
Views: 122

### HW 3.39

Write the complete Lewis structure for each of the following compounds: (a) ammonium chloride; (b) potassium phosphide; (c) sodium hypochlorite. Hello, I am very confused on this question and how to determine if I need to draw a lewis structure for an ionic or covalent bond, and in the case of A and...
Thu May 17, 2018 6:14 pm
Forum: Ionic & Covalent Bonds
Topic: What do the roman numerals mean?
Replies: 2
Views: 839

### What do the roman numerals mean?

For example, (Hw 3.27) manganese(IV) oxide is MnO2. What do the roman numerals mean and how does that influence the answer of the chemical formula of it?
Thu May 10, 2018 6:43 pm
Forum: Trends in The Periodic Table
Topic: electron affinity [ENDORSED]
Replies: 15
Views: 785

### Re: electron affinity[ENDORSED]

Electron affinity is the energy released when an electron is added, so it makes sense when we think about its trend on the periodic table. The energy released when an electron is added increases across a period because elements are always trying to reach the most stable configuration. They want to b...
Thu May 10, 2018 11:52 am
Forum: Trends in The Periodic Table
Topic: Relationship between Ionic Radius, Atomic RdiuIonization Enrgy, Electron Affinity
Replies: 3
Views: 420

### Re: Relationship between Ionic Radius, Atomic RdiuIonization Enrgy, Electron Affinity

They are all related and intertwined as part of the explanation for the trends in the periodic table. Yes, ionic and atomic radius follow the same trend (increases down a group and decreases across) while electron affinity and ionization energy follow the opposite trend (increases across and decreas...
Thu May 10, 2018 11:48 am
Forum: Trends in The Periodic Table
Replies: 2
Views: 234

Ionic radius follows the same pattern of atomic radius on the periodic table (increases down a group and decreases across a period). However they are different in that in ionic radius, the periodic table is separated into anions and cations. Cations are going to be smaller than anions since they los...
Wed May 02, 2018 7:33 pm
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: 2.21
Replies: 2
Views: 158

### Re: 2.21

Basically, these are the fancy words for n,l,ml,ms:
Principle quantum number = n
orbital angular momentum = l (or n-1)
Magnetic = ml
spin magnetic = ms
This is straight from Table 2.2 on page 36 from the textbook!
Hope that helps :)
Wed May 02, 2018 7:28 pm
Forum: Electron Configurations for Multi-Electron Atoms
Topic: Valence Shell Configuration (2.55)
Replies: 2
Views: 215

### Valence Shell Configuration (2.55)

Hello,

What is the valence shell configuration and how is it different than the ground state electron configuration (if it is any different at all)?

Thanks!
Tue May 01, 2018 12:53 am
Forum: Electron Configurations for Multi-Electron Atoms
Topic: 2.37
Replies: 2
Views: 132

### 2.37

Which of the following statements are true for many- electron atoms? If false, explain why. (a) The effective nuclear charge Z-eff is independent of the number of electrons present in an atom. (b) Electrons in an s-orbital are more effective than those in other orbitals at shielding other electrons ...
Fri Apr 27, 2018 12:37 am
Forum: Photoelectric Effect
Topic: homework 1.25 part b
Replies: 3
Views: 150

### Re: homework 1.25 part b

Since you know that the photoelectric effect, as well as in general, that all photon-electron interactions are one-to-one. So, you have to ask yourself how do I determine how many atoms of Sodium are in 5mg, and that is when you use the atomic mass to find the moles, and then from moles you multiply...
Fri Apr 27, 2018 12:05 am
Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
Topic: Wavelengths and their corresponding electromagnetic spectrum
Replies: 2
Views: 168

### Wavelengths and their corresponding electromagnetic spectrum

Hello,
Will we need to know which wavelengths correspond to gamma, x-rays, visible light, etc..? I know that very small wavelengths are toward the gamma ray side and very large wavelengths are toward the radio waves side, but do we need to know more than that?
Thanks!!
Thu Apr 26, 2018 11:16 pm
Forum: Photoelectric Effect
Topic: Photoelectric Effect Module Question [ENDORSED]
Replies: 5
Views: 348

### Photoelectric Effect Module Question[ENDORSED]

24. In photoelectric experiments, typically what part of the electromagnetic spectrum is the incoming light? A. Ultraviolet B. Infrared C. Visible light D. Gamma rays E. None of the above I'm not sure what the answer is. I thought it was gamma rays since those have the highest energy and would surel...
Fri Apr 20, 2018 6:54 pm
Forum: DeBroglie Equation
Topic: HW 1.39 [ENDORSED]
Replies: 8
Views: 583

### Re: HW 1.39[ENDORSED]

The way I went about this is just noticed what values we are given. We are given mass and velocity (which must first be converted to kg and m/s of course). I then knew that we must use de Broglie's equation, which gives us the wavelength of any particle. We then solve for wavelength using the equati...
Fri Apr 20, 2018 5:35 pm
Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
Topic: Rydberg’s formula
Replies: 1
Views: 143

### Rydberg’s formula

Hello, We did this question in class. Calculate the frequency of light emitted by a hydrogen atom when an electron makes a transition from fourth to second principal quantum level. I noticed that using Rydberg's formula gives us the same answer as the answer we got using professor Lavelle's way, whi...
Fri Apr 20, 2018 5:20 pm
Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
Topic: Balmer Series vs Lyman Series
Replies: 4
Views: 619

### Balmer Series vs Lyman Series

Hello, I am confused about the difference between the balmer series and lyman series and what they are? Do we need to know this for the test? Also why are the lines in the visible light region of balmer series only red and blue? Are those the only two wavelengths that can be emitted by electrons in ...
Thu Apr 12, 2018 2:13 am
Forum: Limiting Reactant Calculations
Topic: Knowing if it's Limiting Reactions
Replies: 6
Views: 364

### Knowing if it's Limiting Reactions

Hello, On the test, or in general, will the questions asked indicate that the problem is a limiting reactions problem by either mentioning yields or stating to find the limiting reactant or the reactant in excess? In other words, will there be limiting reaction questions that will be disguised as si...
Thu Apr 12, 2018 12:07 am
Forum: Molarity, Solutions, Dilutions
Topic: When to use MiVi=MfVf
Replies: 8
Views: 1434

### When to use MiVi=MfVf

Hello,
I'm having some difficulty determining when to use the M(initial) x V(initial) = M(final) x V(final) equation in problems. Is there any way to know to use this equation in a type of problem? What kind of problems is it used for?
Thanks!
Wed Apr 11, 2018 9:36 pm
Forum: Properties of Light
Topic: Atomic Spectra Electron Emission
Replies: 2
Views: 163

### Atomic Spectra Electron Emission

Hello, I was wondering about how the electron, when returning from its excited state and down the energy levels following the absorption of light and I have a couple of questions. 1. Do the electrons physically absorb the photon or just its energy? 2. What are the effects of electrons emitting the p...
Sun Apr 08, 2018 11:17 pm
Forum: Empirical & Molecular Formulas
Topic: L.39 [ENDORSED]
Replies: 1
Views: 123

### L.39[ENDORSED]

Hello, I'm having a lot of trouble understanding this problem and its solution. A 1.50-g sample of metallic tin was placed in a 26.45-g crucible and heated until all the tin had reacted with the oxygen in air to form an oxide. The crucible and product together were found to weigh 28.35 g. (a) What i...
Sun Apr 08, 2018 11:07 pm
Forum: Balancing Chemical Reactions
Topic: Balancing equations with fractions [ENDORSED]
Replies: 13
Views: 736

### Re: Balancing equations with fractions[ENDORSED]

I think it is best to have the coefficients be whole numbers and not fractions. However, it is also important to remember that if you are asked something like how many moles of the other reactant (oxygen) are needed when there are only two moles of ammonia the answer would then be (5/2) or 2.5 .
Sun Apr 08, 2018 10:39 pm
Forum: Balancing Chemical Reactions
Topic: L.35
Replies: 1
Views: 203

### L.35

Sodium bromide, NaBr, which is used to produce AgBr for use in photographic lm, can itself be prepared as follows. Fe + Br2 --> FeBr2 FeBr2 + Br2 --> Fe3Br8 Fe3Br8 + Na2CO3 --> NaBr + CO2 + Fe3O4 What mass of iron, in kilograms, is needed to produce 2.50 t of NaBr? Note that these equations must fir...