## Search found 48 matches

Thu Jun 14, 2018 3:07 am
Forum: Calculating pH or pOH for Strong & Weak Acids & Bases
Topic: French Toast Number 27 Part B
Replies: 4
Views: 284

### Re: French Toast Number 27 Part B

Lily Emerson 1I wrote:you just need to do 14-(-log(1.1)) since you already know that the concentration of the new mixture is .55 - just multiply that by 2 moles of HO- to get the concentration

Where did you get 1.1 from?
Thu Jun 14, 2018 12:47 am
Forum: Bronsted Acids & Bases
Topic: Glycine
Replies: 1
Views: 198

### Glycine

How does glycine act as a proton acceptor? I read that H can dissociate from O in a solution, so therefore that makes it able to be a proton acceptor, but what does this mean? How do you go about thinking if something can be a proton acceptor?
Wed Jun 13, 2018 11:52 pm
Forum: Sigma & Pi Bonds
Topic: Composition of a Bond [ENDORSED]
Replies: 1
Views: 200

### Composition of a Bond[ENDORSED]

How do you identify the composition of a bond? I know how to figure out if the bond is a pi or sigma bond, and I know what hybridization an atom would have. For example, sigma(C2sp 2 , C2sp 2 ). I know the sigma refers to a sigma bond, and the Cs refer to a bond between two carbon atoms. The sp 2 re...
Wed Jun 13, 2018 11:46 pm
Forum: Molarity, Solutions, Dilutions
Topic: French Toast #27a
Replies: 1
Views: 169

### French Toast #27a

In a sicence lab, you created a stock soluiton of 1.50 M Na2O.
How many milliliters of this stock solution would you need to make 210 mL of a .550 M Na2O solution?

How do you go about solving this?
Wed Jun 06, 2018 11:32 pm
Forum: Lewis Structures
Topic: Lowest energy lewis structure
Replies: 5
Views: 1762

### Re: Lowest energy lewis structure

This thread might help. https://lavelle.chem.ucla.edu/forum/viewtopic.php?f=33&t=31624&p=103217&hilit=Lewis+structures&sid=450ab185a9474d380218e0e88a8cc6d7#p103217 "formal charge purpose" is the title of the thread. Basically you draw a Lewis structure and then calculate th...
Wed Jun 06, 2018 11:18 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: molecular shape-seesaw
Replies: 2
Views: 142

### Re: molecular shape-seesaw

6 regions of electron density = 5 bonded atoms + 1 lone pair. ex. SF4. Tetrahedral has 4 regions of electron density.
Tue Jun 05, 2018 8:30 pm
Forum: Acidity & Basicity Constants and The Conjugate Seesaw
Topic: pH in changing temperature
Replies: 4
Views: 368

### Re: pH in changing temperature

If it has the same amount, how does pH decrease? What effect does temperature have in this situation?
Tue Jun 05, 2018 3:23 pm
Forum: Hybridization
Topic: strength of sigma and pi bonds
Replies: 10
Views: 440

### Re: strength of sigma and pi bonds

Yes, a sigma bond is stronger than a pi bond. This is because the length of a sigma bond is shorter than a pi bond, and it takes more energy to break a sigma bond. Because a double bond is a sigma bond and a pi bond and every type of chemical bond has to have at least one sigma bond, how are double...
Tue Jun 05, 2018 3:18 pm
Forum: Naming
Topic: Coordination Compound confusion [ENDORSED]
Replies: 4
Views: 317

### Re: Coordination Compound confusion[ENDORSED]

Which parts of the textbook you should read, what topics pertaining to it,and problems you should be able to solve are all listed in the syllabus: Coordination Compounds and their Biological Importance (oxidation states, coordination number, shape and structures of coordination compounds; biological...
Tue Jun 05, 2018 2:51 pm
Forum: Bond Lengths & Energies
Topic: sp2 and sp3 hybridization- the bond lengths
Replies: 1
Views: 785

### sp2 and sp3 hybridization- the bond lengths

I would like some clarification on the bond lengths in sp2 and sp3 orbitals. Are the bond lengths in sp2 orbitals shorter because the orbitals have more s-orbital character (33% as opposed to 25% in sp3) and more s-orbital character means the electrons are closer to the nucleus? Also, in regards to ...
Tue Jun 05, 2018 1:44 pm
Forum: Hybridization
Topic: BF3
Replies: 1
Views: 132

### BF3

Just to confirm: BF3 would have an sp2 hybridization, but it has an empty p-orbital (can accept a lone pair and have an octet). When BF3 undergoes an acid-base reaction, Boron can accept a lone pair from a Lewis base, and that bond is called a coordinate covalent bond? And that coordinate covalent b...
Wed May 30, 2018 11:13 pm
Forum: Hybridization
Topic: Hybridization purpose
Replies: 3
Views: 156

### Re: Hybridization purpose

I agree. The atoms wouldn't need to have hybridized orbitals when it's not bonding. When the orbitals are hybridized, the electron(s) is/are moved to a higher energy orbital. For example, carbon alone is at a 2s 2 2p 2 . That is a lower energy state than if it had 1 unpaired electron in its s orbita...
Wed May 30, 2018 11:03 pm
Forum: Lewis Structures
Topic: Central Atom(s)
Replies: 6
Views: 228

### Re: Central Atom(s)

To add on, there are a few compounds that the central atom isn't the least electronegative because the formal charges are best that way.
Wed May 30, 2018 11:00 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Resonance structure effect on molecular shape
Replies: 3
Views: 153

### Re: Resonance structure effect on molecular shape

You also have to keep in mind that the actual structure of the compound is a hybrid of all the resonance structures. So one resonance structure wouldn't have a greater effect on the shape or anything. As stated above, since resonance structures is basically shifting double bonds around, the bonds ar...
Wed May 23, 2018 11:47 pm
Forum: Lewis Structures
Topic: 3.45
Replies: 2
Views: 148

### 3.45

3.45 asks us to draw the resonance structures for ClNO2. I drew that N would have a double bond with an oxygen atom and a single bond with the other oxygen atom. With the oxygen with a single bond with Nitrogen, I drew chlorine bonded to it so that that oxygen would now have two bonds. This way the ...
Wed May 23, 2018 1:40 pm
Forum: Lewis Structures
Topic: 3.35
Replies: 1
Views: 143

### 3.35

3.35 states "Write the Lewis structure of (a) tetrahydridoborate ion, BH4"; (b) hypobromite ion, BrO"; (c) amide ion, NH2" I don't understand how you can use covalent bonds for molecules like BH4- or NH2- if they're ions. I know ionic bonds, you gain or lose electrons, and for co...
Wed May 23, 2018 1:17 am
Forum: Resonance Structures
Topic: Kekulé Structures??
Replies: 6
Views: 355

### Re: Kekulé Structures??

Kekule structures is in Chapter 3, but it's just a fancier version of a Lewis structure that shows its shape. We would be told if the molecule would have a cyclic/ring structure, and then we can form our Lewis structures based on that.
Wed May 23, 2018 1:10 am
Forum: Ionic & Covalent Bonds
Topic: Polyatomic Ions
Replies: 1
Views: 106

### Polyatomic Ions

The cations and anions have to be treated separately as they aren't linked by shared pairs (stated in the textbook). So what would they be linked by so that the ions are together? For example, ammonium bicarbonate, what links the three ions together so that they aren't just separate ions floating ar...
Wed May 23, 2018 1:02 am
Forum: Ionic & Covalent Bonds
Topic: Fluorine
Replies: 1
Views: 137

### Fluorine

In the textbook, it says, "As well as a bonding pair of electrons, a fluorine molecule also possesses lone pairs of electrons; that is, pairs of valence electrons that do not take part in bonding. The lone pairs on one F atom repel the lone pairs on the other F atom, and this repulsion is almos...
Mon May 21, 2018 12:39 am
Forum: Lewis Structures
Topic: Formal Charge
Replies: 4
Views: 190

### Re: Formal Charge

Other than just memorizing it, practice makes you know it and then calculate them faster.
Mon May 21, 2018 12:35 am
Forum: Ionic & Covalent Bonds
Topic: condensed phase
Replies: 2
Views: 113

### Re: condensed phase

Not the gas phase. Condensed phase = liquid or solid state.
Mon May 21, 2018 12:32 am
Forum: Octet Exceptions
Topic: Expanded Octet Rules
Replies: 7
Views: 534

### Re: Expanded Octet Rules

For the third row of the periodic table, we don't put any d-orbital electrons in their ground state configurations as they don't have any in the d orbital. However, since their energy level is 3 (n=3), they are able to have more electrons. They have a whole new shell rather than be just n=2, so the...
Mon May 21, 2018 12:27 am
Forum: Octet Exceptions
Topic: Octet Rules
Replies: 4
Views: 264

### Re: Octet Rules

No. Group 3 elements in general often have incomplete octets.
Sun May 20, 2018 12:46 am
Forum: Lewis Structures
Topic: Exception to Lewis Structure?
Replies: 4
Views: 174

### Re: Exception to Lewis Structure?

This relates to "expanded octets." Chlorine is an element that can have an expanded octet. There are discussions on Chemistry Community about expanded octets.
Sun May 20, 2018 12:43 am
Forum: Octet Exceptions
Topic: Expanded Octet Rules
Replies: 7
Views: 534

### Re: Expanded Octet Rules

For the third row of the periodic table, we don't put any d-orbital electrons in their ground state configurations as they don't have any in the d orbital. However, since their energy level is 3 (n=3), they are able to have more electrons. They have a whole new shell rather than be just n=2, so ther...
Sun May 20, 2018 12:17 am
Forum: Resonance Structures
Topic: How does a resonance structure work?
Replies: 10
Views: 368

### Re: How does a resonance structure work?

If you can draw more than one Lewis structure that is equivalent to each other, then it displays resonance. This usually occurs in molecules that have double bonds and single bonds. For example, benzyne has double bonds on every other bond between two carbons (and single bonds for the other carbons)...
Sun May 20, 2018 12:09 am
Forum: Ionic & Covalent Bonds
Replies: 9
Views: 338

I don't think radicals are necessarily made from atoms giving up or gaining electrons. If they do that, they would make bonds. I think radicals are made because of combustion or if something breaks a bond. Some examples would be gas from a muffler or broken bonds because of UV rays.
Thu May 10, 2018 5:43 pm
Forum: Ionic & Covalent Bonds
Topic: Octet
Replies: 7
Views: 369

### Re: Octet

An extra detail is that the first four elements never have an octet.
Thu May 10, 2018 5:33 pm
Forum: Photoelectric Effect
Topic: Intensity of Photon
Replies: 8
Views: 386

### Re: Intensity of Photon

To add onto the other replies, increasing the intensity/brightness/amplitude of the photons would mean more electrons can be emitted (since there is a 1:1 ratio with one photon ejecting one electron). However, if the threshold energy isn't even reached per photon, an electron would not be emitted. T...
Mon May 07, 2018 9:09 pm
Forum: Properties of Light
Topic: Keywords for Work Function or E_photon?
Replies: 4
Views: 231

### Re: Keywords for Work Function or E_photon?

I don't think you should necessarily memorize keywords in order to use different equations. Different problems have different contexts. In the example you gave for last Friday's midterm session, you had to use the work function + the kinetic energy to eventually find the wavelength because in the fi...
Mon May 07, 2018 9:01 pm
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: Ground state elec. config.
Replies: 3
Views: 163

### Re: Ground state elec. config.

You take away the electrons from the outer shell (the valence electrons). In this case, the electrons in the s and p orbitals are the outermost electrons.
Wed May 02, 2018 12:20 am
Forum: Trends in The Periodic Table
Replies: 3
Views: 164

I'm confused on how the covalent radius can be different than atomic radius between two atoms. I thought a covalent radius would just be the atomic radius between two atoms that have a covalent bond. Same with an ionic radius but with two atoms with an ionic bond. Is the difference because the coval...
Mon Apr 30, 2018 7:45 am
Forum: Einstein Equation
Topic: Difference between diffraction patterns and interacting waves
Replies: 2
Views: 149

### Re: Difference between diffraction patterns and interacting waves

Interacting waves produce diffraction patterns. Particles do not. When two waves interact, their amplitudes are combined. If two waves are in sync with each other, then the resulting amplitude is the sum of the two amplitude of the waves. If the two waves are not in sync (or in phase) with each othe...
Mon Apr 30, 2018 7:29 am
Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
Topic: test
Replies: 3
Views: 174

### Re: test

In my version of the test and if I'm thinking of the same problem, it did say the electrons were excited from a ground state to an excited state. It did not say which energy level it was excited to though. However, you do not need to know the energy level to solve this problem. It gave you a wavelen...
Mon Apr 30, 2018 7:20 am
Forum: Properties of Electrons
Topic: ejecting electrons
Replies: 4
Views: 193

### Re: ejecting electrons

To add on to the replies above,

A greater amplitude would mean more photons. If all these photons had a high enough frequency, then more electrons can be emitted.
Mon Apr 30, 2018 7:13 am
Forum: Photoelectric Effect
Topic: Test 2 final question [ENDORSED]
Replies: 15
Views: 617

### Re: Test 2 final question[ENDORSED]

In my version of the test, it was said that the photons were absorbed . That's why lines appear. Because we know this, it would mean the photons had the correct amount of energy in order to be excited to another energy level. It was given on the test that it had enough energy. We did not have to ass...
Mon Apr 30, 2018 6:53 am
Forum: Student Social/Study Group
Topic: Post All Chemistry Jokes Here
Replies: 7742
Views: 1060752

### Re: Post All Chemistry Jokes Here

How do you find a mole?

Eenie meenie minie mole.

-an original
Tue Apr 24, 2018 1:41 pm
Forum: Properties of Light
Topic: Rydberg Formula for Atomic Hydrogen [ENDORSED]
Replies: 4
Views: 292

### Rydberg Formula for Atomic Hydrogen[ENDORSED]

On the front page of Test 1, the Rydberg Formula is $E_{n} = -hRhn^{2}$. In lecture, it is $E_{n}=\frac{-hR}{n^{2}}$. I was wondering how the formula on Test 1 is equivalent to the one given in lecture.
Tue Apr 24, 2018 1:36 pm
Forum: Properties of Light
Topic: Amplitude and Intensity
Replies: 6
Views: 248

### Re: Amplitude and Intensity

The brighter the light is, the more intense it is. In regards to the amplitude, then there is a larger amplitude. Let's say I shine a flashlight at you: When the waves of light are in sync with each other, they create a constructive diffraction pattern. This means the waves overlap together, and the...
Thu Apr 19, 2018 10:04 pm
Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
Topic: Lyman and Balmer Series
Replies: 3
Views: 176

### Re: Lyman and Balmer Series

If I understand correctly, the names of each series refers to the range that the electron moves from energy to energy level. So for example, when an electron transitions from n=2 to n=1, that is called the Lyman Series. The Balmer series represents the drop from higher energy levels to n=2. These di...
Thu Apr 19, 2018 9:52 pm
Forum: General Science Questions
Topic: Notation
Replies: 3
Views: 367

### Notation

I noticed how the textbook uses "s^-1" instead of "/s" (like Js^-1 instead of J/s). Also, ms^-1 is the same as m/s. However, I was wondering if there was any special reason that it's notated with specifically a negative exponent. Is the reason chemistry-related or is it just a pr...
Mon Apr 16, 2018 9:42 pm
Forum: Properties of Light
Topic: Reference Point
Replies: 1
Views: 90

### Reference Point

I would like clarification for something Dr. Lavelle explained during lecture. We were on the slide for calculating deltaE using the empirical equation for an H-atom (-hR/n^2) Dr. Lavelle explained that the reference point is when the electron is fully removed, and the ground states for elements sho...
Sun Apr 15, 2018 9:26 pm
Forum: Student Social/Study Group
Topic: Post All Chemistry Jokes Here
Replies: 7742
Views: 1060752

### Re: Post All Chemistry Jokes Here

People always say all the good chemistry jokes Argon, but NO3-, they're not.
Sun Apr 15, 2018 9:24 pm
Forum: Student Social/Study Group
Topic: Post All Chemistry Jokes Here
Replies: 7742
Views: 1060752

### Re: Post All Chemistry Jokes Here

If you're not part of the solution, you're part of the precipitate.
Sun Apr 15, 2018 9:23 pm
Forum: Student Social/Study Group
Topic: Post All Chemistry Jokes Here
Replies: 7742
Views: 1060752

### Re: Post All Chemistry Jokes Here

What do you call an acid with an attitude?

A-mean-oh acid.
Sun Apr 15, 2018 9:20 pm
Forum: Student Social/Study Group
Topic: Post All Chemistry Jokes Here
Replies: 7742
Views: 1060752

### Re: Post All Chemistry Jokes Here

What kind of dogs do chemists have?

Laboratory Retrievers
Fri Apr 13, 2018 12:28 am
Forum: Limiting Reactant Calculations
Topic: M.2 Example in Textbook
Replies: 1
Views: 109

### M.2 Example in Textbook

Hello, I was going over the example problem in the textbook and was confused on Step 3 (b). The equation is CaC2(s) + 2 H2O(l) -> Ca(OH)2(aq) + C2H2(g). It's balanced. We are asked if either 100g of water or 100g of calcium carbide is the limiting reactant, what mass of ethyne is produced, and what ...
Thu Apr 12, 2018 10:39 pm
Forum: Empirical & Molecular Formulas
Topic: F.21
Replies: 5
Views: 975

### Re: F.21

I understand how the answer is so, but if the problem asked to find the empirical formula of the compound didemnin-A, how can the ratio for Carbon be 8.143 when the number of atoms should/is always a whole number?