## Search found 57 matches

Sun Dec 08, 2019 12:18 am
Forum: Interionic and Intermolecular Forces (Ion-Ion, Ion-Dipole, Dipole-Dipole, Dipole-Induced Dipole, Dispersion/Induced Dipole-Induced Dipole/London Forces, Hydrogen Bonding)
Topic: SF6 & NSF3 boiling points
Replies: 1
Views: 95

### Re: SF6 & NSF3 boiling points

NSF3 has dipole-dipole interactions that SF6 doesn't. SF6 is octahredral which means all the dipoles cancel out, but that is not the case in NSF3.
Sat Dec 07, 2019 5:36 pm
Forum: Calculating pH or pOH for Strong & Weak Acids & Bases
Topic: pH less than 0?
Replies: 1
Views: 36

### pH less than 0?

On homework problem 6B.9, you are given the concentration of H3O+ as 1.5M. The pH of this would be negative, making the pOH greater than 14. The textbook solution manual shows that the pH is positive. How is this true?
Fri Dec 06, 2019 6:40 pm
Forum: Shape, Structure, Coordination Number, Ligands
Topic: Finding Oxidation State of Cobalt in Vitamin B12
Replies: 3
Views: 63

### Re: Finding Oxidation State of Cobalt in Vitamin B12

I guess it would also depend on the charge of the R group attached to it, which you can't tell from the diagram.
Fri Dec 06, 2019 6:02 pm
Forum: Shape, Structure, Coordination Number, Ligands
Topic: Finding Oxidation State of Cobalt in Vitamin B12
Replies: 3
Views: 63

### Re: Finding Oxidation State of Cobalt in Vitamin B12

I think when the N's attached to the central metal have three bonds, they are neutral. One of the nitrogens attached to cobalt only has two bonds, so it probably has a negative charge. The cobalt oxidation state is probably +1
Thu Dec 05, 2019 4:32 pm
Forum: Dipole Moments
Topic: Polarity of Square Planar
Replies: 1
Views: 86

### Polarity of Square Planar

In a square planar molecule, say you have two different elements attached to the central atom, like Cl and H. If the two Cl molecule lie directly across each other, will these dipoles cancel out, making the entire molecule nonpolar? Since it is not tetrahedral, wouldn't the 90 degree angle allow the...
Thu Dec 05, 2019 4:26 pm
Forum: Shape, Structure, Coordination Number, Ligands
Topic: Chelating Ligands and Coordination Numbers
Replies: 4
Views: 75

### Re: Chelating Ligands and Coordination Numbers

I don't think it would necessarily be raised, but if a molecule chelates then less of that molecule is needed to bond to the metal. So there would just be less ligands needed in the coordinating complex. The coordinate number doesn't increase but there are less ligands, so the charge on the metal s...
Thu Dec 05, 2019 4:24 pm
Forum: Shape, Structure, Coordination Number, Ligands
Topic: EDTA
Replies: 3
Views: 86

### Re: EDTA

Also, the doubly-bonded oxygens are part of a carbonyl group, which is a very stable group that does not want to accept more electrons. A carbonyl group is a carbon atom double bonded to an oxygen with two other atoms bonded to the carbon via single bonds.
Wed Dec 04, 2019 9:38 am
Forum: Properties of Light
Topic: Light as a Wave
Replies: 8
Views: 233

### Re: Light as a Wave

Light has wave-particle duality, which means it technically has both wavelike and particlelike properties at all times. Light is essentially composed of photons, and the flow of these photons creates a wave. When you are presented with light in the form of electromagnetic radiation, you can treat it...
Wed Dec 04, 2019 12:14 am
Forum: Shape, Structure, Coordination Number, Ligands
Topic: Basic or Acidic
Replies: 2
Views: 38

### Re: Basic or Acidic

You can look at the lewis definition of an acid or base. Since this definition deals with the number of lone pairs present on an atom, you can look at whether or not the molecule would accept or donate electrons. If it look like it would accept electrons, such as BF3 which does not have a complete o...
Mon Dec 02, 2019 11:54 pm
Forum: Bronsted Acids & Bases
Topic: Relative Acid Strength
Replies: 1
Views: 56

### Relative Acid Strength

In homework question 6C.21, we are asked to say why there is a difference in acid strengths of formic acid (HCOOH) and acetic acid (C3COOH). Why is formic acid stronger? Shouldn't acetic acid be stronger as it has a carbon atom (not including the carboxyl group) with higher electronegativity which m...
Mon Dec 02, 2019 9:25 pm
Forum: Identifying Acidic & Basic Salts
Topic: Electron withdrawing to identify acids
Replies: 2
Views: 46

### Re: Electron withdrawing to identify acids

When you look at these cations in a salt, you should look at their ability to lose a proton or to gain electrons. Something that is positively charged and small will pull electrons closer to it and thus accept electrons from something with more electrons. In water, these cations attract the slightly...
Mon Dec 02, 2019 9:08 pm
Forum: Acidity & Basicity Constants and The Conjugate Seesaw
Topic: pKa
Replies: 2
Views: 51

### Re: pKa

pKa is the negative log of the Ka value. The Ka value is the concentration of the products of acid dissociation (so the two ions that make up said acid) divided by the concentration of the reactants (which is just the acid in molecular form). pKa can be assigned to all acids technically, but since s...
Wed Nov 27, 2019 10:10 pm
Forum: Bronsted Acids & Bases
Topic: Lewis and Bronsted
Replies: 4
Views: 46

### Re: Lewis and Bronsted

Yes, a Lewis acid and Bronsted acid describe an acid, just in different ways and in terms of different types of behavior. The Bronsted definition of an acid is proton (H+) donor, while the Lewis definition of an acid is an electron-pair acceptor. Essentially, acids are electron deficit species that ...
Tue Nov 26, 2019 1:00 pm
Forum: Naming
Topic: Problem #3 part d, from 9C
Replies: 1
Views: 42

### Re: Problem #3 part d, from 9C

It doesn't matter which ligand comes first as long as they are within the brackets (in the coordination sphere). It may be to emphasize the bonding sites of the water, but as long as all ligands are included, it is written properly.
Tue Nov 26, 2019 12:53 pm
Forum: Hybridization
Topic: Delocalized Hybridization
Replies: 2
Views: 18

### Re: Delocalized Hybridization

Even with delocalized electron pairs, there is still a bond that exists there so hybridization will still occur. For this reason, these electrons must still be included in hybridization of orbitals.
Tue Nov 26, 2019 12:49 pm
Forum: Shape, Structure, Coordination Number, Ligands
Topic: Oxidation state
Replies: 3
Views: 37

### Re: Oxidation state

An oxidation state is essentially the charge of the metal ion, which you determine by looking at the charges of the ligands and the overall charge of the coordination compound. Because transition metals can have multiple oxidation states due to their empty d-orbitals, you have to use the charges of ...
Tue Nov 26, 2019 11:22 am
Forum: Shape, Structure, Coordination Number, Ligands
Topic: HW Question 9C.5
Replies: 4
Views: 42

### Re: HW Question 9C.5

This question is asking you how many lone pairs on the ligand can bind to a metal. This is known as chelation, where one ligand binds to a metal on multiple sites. You need to draw the lewis structures to determine how many bonding sites there are on the ligand. Table 9C.1 also lists some common pol...
Thu Nov 21, 2019 6:38 pm
Forum: Hybridization
Topic: Hybridization with lone pairs on central atom
Replies: 6
Views: 82

### Re: Hybridization with lone pairs on central atom

Atoms with lone pairs can be hybridized, such as the example NH3 that Dr. Lavelle gave in class. This is because the final hybridization state must reflect the number of electron density regions around the central atom, which includes any lone pairs. Going back to the NH3 example, the two lone pairs...
Thu Nov 21, 2019 6:36 pm
Forum: Hybridization
Topic: Hybridization
Replies: 1
Views: 31

### Hybridization

Can someone explain why orbitals need to hybridize? I understand it lowers the energy of the orbitals, but wouldn't the original orbitals already be stable?
Tue Nov 19, 2019 12:55 pm
Forum: Interionic and Intermolecular Forces (Ion-Ion, Ion-Dipole, Dipole-Dipole, Dipole-Induced Dipole, Dispersion/Induced Dipole-Induced Dipole/London Forces, Hydrogen Bonding)
Topic: H2SeO4
Replies: 2
Views: 33

### Re: H2SeO4

The tetrahedral shape of this compound means that the dipoles do not actually cancel out. They are at a 109.5 degree angle on 3D planes, not the 2D plane that Lewis structures look like. This means that the dipoles will not line up in space to cancel out.
Mon Nov 18, 2019 10:32 pm
Forum: Interionic and Intermolecular Forces (Ion-Ion, Ion-Dipole, Dipole-Dipole, Dipole-Induced Dipole, Dispersion/Induced Dipole-Induced Dipole/London Forces, Hydrogen Bonding)
Topic: hydrogen bonds
Replies: 4
Views: 33

### Re: hydrogen bonds

Hydrogen bonds are essentially just extremely strong dipole-dipole forces. They occur when a hydrogen bonded to an N, O, or F comes near a lone pair on another molecule. They are classified as their own time of intermolecular force because the bonds created are much stronger than regular dipole-dipo...
Mon Nov 18, 2019 2:48 pm
Forum: Sigma & Pi Bonds
Topic: Orbitals in sigma and pi bonds
Replies: 1
Views: 39

### Orbitals in sigma and pi bonds

I'm confused by which orbitals are involved in sigma and pi bonding. Do sigma bonds exist only between s orbitals and pi bonds exist between 2pz orbitals?
Sat Nov 16, 2019 4:55 pm
Forum: Interionic and Intermolecular Forces (Ion-Ion, Ion-Dipole, Dipole-Dipole, Dipole-Induced Dipole, Dispersion/Induced Dipole-Induced Dipole/London Forces, Hydrogen Bonding)
Topic: strongest intermolecular forces
Replies: 7
Views: 119

### Re: strongest intermolecular forces

The strongest intermolecular force is hydrogen bonding, followed by dipole-dipole interactions, and then Van der Waals forces. Van der Waals are the same as induced dipole-induced dipole and London dispersion forces.
Sat Nov 16, 2019 2:18 pm
Forum: Interionic and Intermolecular Forces (Ion-Ion, Ion-Dipole, Dipole-Dipole, Dipole-Induced Dipole, Dispersion/Induced Dipole-Induced Dipole/London Forces, Hydrogen Bonding)
Topic: Dipole-dipole in H2SeO4
Replies: 3
Views: 51

### Re: Dipole-dipole in H2SeO4

I think because oxygen is much more electronegative than Se, it exerts a greater pull on the electrons and pulls out. The dipoles may not cancel out because there are multiple resonances of H2SeO4. For example, if the OH and O are not symmetrically bonded to the Se (like an O across and O and an OH ...
Wed Nov 13, 2019 10:12 pm
Forum: Dipole Moments
Topic: Bonds in Pentane vs 2-2 dimethylbutane?
Replies: 2
Views: 34

### Re: Bonds in Pentane vs 2-2 dimethylbutane?

Rod shaped molecules have more potential points of interaction in the electron clouds when you lay them flat against each other the long way. Spherical molecules, however, have limited points of interaction because they can only experience dipoles on one point on the surface of their electron cloud.
Wed Nov 13, 2019 10:04 pm
Forum: Interionic and Intermolecular Forces (Ion-Ion, Ion-Dipole, Dipole-Dipole, Dipole-Induced Dipole, Dispersion/Induced Dipole-Induced Dipole/London Forces, Hydrogen Bonding)
Topic: Electron distortion
Replies: 4
Views: 46

### Re: Electron distortion

To expand upon this definition, electron distortion has to do with how easily the electron cloud surrounding an atom can be pulled. The polarizability of an atom refers to how easily its electron regions can be distorted. It is easier for them to be distorted when the atom is larger, because the ele...
Wed Nov 13, 2019 10:00 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: VSEPR Bond and Regions
Replies: 2
Views: 46

### Re: VSEPR Bond and Regions

Even though there are more electrons, the electrons are also being shared between two atoms, which weakens their repulsive effects and allows us to treat them as one unit. Only lone bonding pairs are more repulsive than any bond order because they take up more space, while shared electrons in a bond...
Wed Nov 06, 2019 10:29 pm
Forum: Dipole Moments
Topic: Hydrogen Dipoles
Replies: 3
Views: 31

### Hydrogen Dipoles

When we draw dipole moments on molecules, why does hydrogen not receive a dipole? For example, in CH3Br, the dipole is only drawn on the carbon and bromine, and not on the hydrogens.
Wed Nov 06, 2019 10:27 pm
Forum: Electronegativity
Topic: Electron affinity
Replies: 4
Views: 53

### Re: Electron affinity

Electron Affinity refers to the energy released when an electron is added to a gas-phase atom. It is essentially the opposite of ionization energy, where you're calculating the energy needed to remove an electron. Both are important in understanding the ionic behavior of an atom.
Wed Nov 06, 2019 4:05 pm
Forum: Trends in The Periodic Table
Topic: Electrostatic Forces vs Effective Nuclear Charge
Replies: 1
Views: 67

### Re: Electrostatic Forces vs Effective Nuclear Charge

Electrostatic force is related more to electron-electron repulsion while effective nuclear charge has to do with the nucleus' pull on electrons being reduced by shielding. Both deal with electron-electron repulsion but effective nuclear charge looks more at the pull of the nucleus.
Tue Nov 05, 2019 4:11 pm
Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
Topic: Atomic vs Molecular Spectroscopy
Replies: 1
Views: 60

### Re: Atomic vs Molecular Spectroscopy

Both deal with absorption of light at different energy levels and both can yield a line spectrum. Atomic spectra only deal with the energy transition of a valence electron in that atom, which molecular spectra deal with the different valence electrons of the different atoms in the molecule. In both,...
Tue Nov 05, 2019 4:07 pm
Forum: Lewis Structures
Topic: Favorable Bonds
Replies: 5
Views: 75

### Re: Favorable Bonds

Nitrogen would want 3 and oxygen would want 2. However, depending on the molecule and formal charge distribution this can change. Neither of these elements can accommodate anything less or more than an octet, however.
Sat Nov 02, 2019 11:00 am
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: Nodal Planes
Replies: 1
Views: 34

### Re: Nodal Planes

Nodal planes are areas where there is 0 probability of finding an electron. Nodal planes also help us figure out the shape and symmetry of orbitals. Electron density refers to the probability of an electron being found in a certain area. It will never be negative, and when it is 0, that is a nodal p...
Sat Nov 02, 2019 10:55 am
Forum: Octet Exceptions
Topic: Odd number of valence electrons
Replies: 2
Views: 47

### Re: Odd number of valence electrons

Put the electron on the atom where it will give it the lowest formal charge. Usually this is the central atom, but you have to calculate formal charges to know which configuration is the most stable.
Thu Oct 31, 2019 3:59 pm
Forum: Resonance Structures
Topic: Difference between Resonance and Lewis structures
Replies: 5
Views: 80

### Re: Difference between Resonance and Lewis structures

A resonance is a type of Lewis structure in which a double bond can be moved around. In benzene, for example, there are two possible resonance structures because the three double bonds can be between different carbon atoms; the electrons are delocalized, meaning they are not attached to just one pai...
Thu Oct 31, 2019 3:54 pm
Forum: Octet Exceptions
Topic: En
Replies: 3
Views: 48

### Re: En

En (the electronegativity) represents an atoms ability to attract a shared pair of electrons toward it. The difference in electronegativity between two atoms in a molecule determines whether it exhibits more ionic or covalent character. More ionic character means there is a large difference in elect...
Mon Oct 28, 2019 2:55 pm
Forum: Ionic & Covalent Bonds
Topic: Homework 2B.11
Replies: 1
Views: 20

### Re: Homework 2B.11

The order that the formula is written in is essentially the order that the lewis structure should be drawn in. For instance, the two H molecules are bonded to carbon, and the NH2 is also bonded to carbon as a separate group. This is three bonds for carbon. Finally, the last COOH group is the last bo...
Wed Oct 23, 2019 7:04 pm
Forum: Photoelectric Effect
Topic: Focus 1.31
Replies: 3
Views: 53

### Re: Focus 1.31

This question is essentially asking you which laser has enough energy to eject electrons from the lithium cell. Because you know the work function of the lithium cell, you can convert that to joules and find the energy of the two given wavelengths and determine which one is high enough to eject elec...
Wed Oct 23, 2019 7:00 pm
Forum: Electron Configurations for Multi-Electron Atoms
Topic: 1E25 b
Replies: 2
Views: 28

### Re: 1E25 b

The problem asks specifically for the valence-shell configuration, and because the energy of the d block drops lower than s once you start adding electrons to it, the d block will not participate in chemical bonding. That's why you only consider the s and p block electrons that can be shared or tran...
Mon Oct 21, 2019 10:07 pm
Forum: Trends in The Periodic Table
Topic: Ionization Energies Trend
Replies: 5
Views: 49

### Ionization Energies Trend

In lecture, we learned that ionization energies increase across a period because the effective nuclear charge increases. I understand this, but since more electrons are added across a period, shouldn't the shielding effect from those electrons also increase? And wouldn't this prevent the ionization ...
Mon Oct 21, 2019 10:05 pm
Forum: Properties of Electrons
Topic: Diffraction Patterns
Replies: 2
Views: 48

### Re: Diffraction Patterns

Diffraction patterns are a result of high and low wave patterns that vary based on wave intensity (amplitude). When the peaks and troughs of one wave interfere with those of another, you get a diffraction pattern. It can either be constructive (meaning that the combined wave has a higher final peak ...
Mon Oct 21, 2019 7:51 pm
Forum: Heisenberg Indeterminacy (Uncertainty) Equation
Topic: Hw 1B.25 and ℏ symbol
Replies: 1
Views: 81

### Re: Hw 1B.25 and ℏ symbol

That symbol, h bar, is a constant used widely in quantum mechanics. The equation you'd plug your numbers into is (delta v=ℏ/2*m*delta x). You get ths equation because (delta p = m x delta v), which states that minimum uncertainty in momentum equals mass times minimal uncertainty in speed. Since you'...
Fri Oct 18, 2019 5:05 pm
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: Hund's Rule
Replies: 4
Views: 56

### Re: Hund's Rule

They cannot have different energies because they are degenerate. In multi-electron atoms, energy is dependent on the shell and orbital of the electron. If the two electrons have the same principal and magnetic quantum number, and thus occupy the same orbital, they must have the same energy.
Fri Oct 18, 2019 12:06 pm
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: Orbitals and Probability
Replies: 2
Views: 42

### Re: Orbitals and Probability

psi by itself represents a wave function, or the position of a wave at (x,y,z). In simpler terms, one can just think of it as the height of a wave, or its position. psi^2 represents the probability of finding an e-. Also, Professor Lavelle mentioned in class that psi^2 is always positive because, #...
Thu Oct 17, 2019 7:36 pm
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: Atomic Orbitals
Replies: 1
Views: 33

### Re: Atomic Orbitals

Each of the quantum numbers corresponds to a different state of the electron, whether it be energy level, orientation, plane or spin. The orbital notation (ex. 2s) corresponds with these numbers and tells you the principal and angular momentum quantum numbers (n and l). However, for the other two, y...
Thu Oct 17, 2019 7:32 pm
Forum: Photoelectric Effect
Topic: Wave Properties vs. Particle Properties
Replies: 3
Views: 56

### Re: Wave Properties vs. Particle Properties

The reason that electrons are not ejected when higher intensity light is aimed at a metal is because intensity of light doesn't correspond with the amount of energy in a particle model. Intensity, which is dependent on amplitude, is confined solely to the wave model. However, the particle model tell...
Mon Oct 14, 2019 8:31 pm
Forum: Electron Configurations for Multi-Electron Atoms
Topic: Radii
Replies: 2
Views: 34

### Re: Radii

Ionic radius refers to the radius of an ion, which is an atom that has gained or lost electrons. Because they have a unique number of electrons which can occupy more or less shells, the radius of the ion will be different than the radius of the original atom, which is referred to as the atomic radius.
Fri Oct 11, 2019 5:51 pm
Forum: Properties of Electrons
Topic: Circular Standing Wave
Replies: 4
Views: 71

### Circular Standing Wave

Can someone explain how in the diagram today about a circular standing wave, what is and isn't allowed for a circular standing wave? What does it mean for the wave around the nucleus to be in phase?
Thu Oct 10, 2019 11:22 am
Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
Topic: Photoelectric Effect
Replies: 4
Views: 77

### Photoelectric Effect

In Monday's lecture, Dr. Lavelle talked about the photoelectric effect where even with high intensity light, an electron will not be emitted from metal unless the energy of the incoming photon of light is greater than the energy required to remove the electron. What exactly does intensity of light r...
Thu Oct 10, 2019 11:06 am
Forum: Properties of Electrons
Topic: Atomic Spectra and Energy Levels
Replies: 5
Views: 62

### Re: Atomic Spectra and Energy Levels

Going along with what was said above, light is also quantized, so it exists in discrete units. This is why you see jumps in energy levels and lines on an emission spectra—each element has a unique number of electrons with different sets of energy levels. These unique energy levels cause different el...
Mon Oct 07, 2019 2:04 pm
Forum: Properties of Light
Topic: Planck's Law
Replies: 4
Views: 73

### Re: Planck's Law

Quanta are packets of energy, while a photon is a packet of light from electromagnetic radiation, or a type of quanta. Both are forms of energy distilled into a "packet" and both imply that energy exists in discrete units. Quanta is just a broader term for all energy but a photon refers sp...
Mon Oct 07, 2019 1:58 pm
Forum: Limiting Reactant Calculations
Topic: Question about Calculating Limiting Reactants
Replies: 5
Views: 77

### Re: Question about Calculating Limiting Reactants

If you just want to compare moles to find the limiting reactant, you can find the moles of each reactant, divide each by their stoichiometric coefficient, and the smaller value is the limiting reactant.
Wed Oct 02, 2019 5:00 pm
Forum: Significant Figures
Topic: Rounding Sig Figs
Replies: 4
Views: 69

### Re: Rounding Sig Figs

You should definitely try to preserve the maximum amount of sig figs in every step in your calculations. You can try storing them in your calculator as you do the entire problem so it's easier to access the unrounded number! This way you'll always have very accurate answers that are actually reflect...
Wed Oct 02, 2019 4:42 pm
Forum: Molarity, Solutions, Dilutions
Topic: E15
Replies: 3
Views: 30

### Re: E15

When they ask for the molar mass of the sulfide, they mean that you have to swap out the hydroxide - the OH - for a sulfur atom. Because you're given the molar mass of the metal hydroxide, you can figure out the molar mass of the metal 'M' by subtracting the molar mass of two hydroxide molecules (17...
Wed Oct 02, 2019 12:40 am
Forum: Molarity, Solutions, Dilutions
Topic: Fundamentals #G5
Replies: 2
Views: 52

### Re: Fundamentals #G5

I believe you would multiply the molarity of Na2CO3 that you find by two because there are two Na+ atoms in every molecule of Na2CO3. By doing this, you are able to account for the individual moles of NA+ rather than the entire compound.
Mon Sep 30, 2019 2:27 pm
Forum: Balancing Chemical Reactions
Topic: Equations
Replies: 5
Views: 168

### Re: Equations

When you say extra elements, you imply something else has to be added to the reaction to balance it. However, balancing a reaction just means preserving the Law of Conservation of Mass. By making the number of atoms in the reactants equal the number of atoms in the products, you get a balanced equat...
Sun Sep 29, 2019 10:00 pm
Forum: Limiting Reactant Calculations
Topic: Lecture Question
Replies: 5
Views: 83

### Re: Lecture Question

That's a really interesting question! My guess is that the excess reactant is just leftover there because there's nothing for it to react with.

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