Search found 90 matches

by Wendy Perez 1E
Tue Feb 11, 2020 10:25 am
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Enthalpy and Heat
Replies: 1
Views: 8

Re: Enthalpy and Heat

Enthalpy (ΔH) is the measure of heat released or absorbed at a constant pressure. q is just heat under any conditions. ΔH would be equal to q only when the heat is released or absorbed at a constant pressure.
by Wendy Perez 1E
Tue Feb 11, 2020 12:12 am
Forum: Gibbs Free Energy Concepts and Calculations
Topic: spontaneity
Replies: 4
Views: 18

Re: spontaneity

If the ΔG is negative, then the reaction is spontaneous and favors the forward process.
by Wendy Perez 1E
Tue Feb 11, 2020 12:10 am
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: delta U = q + w
Replies: 6
Views: 27

Re: delta U = q + w

If work is done on the system by the surroundings, then work is positive. If work is done by the system onto the surroundings, then work is negative. This is because when work is done by the system, the system loses energy.
by Wendy Perez 1E
Tue Feb 11, 2020 12:05 am
Forum: Gibbs Free Energy Concepts and Calculations
Topic: Go=0
Replies: 5
Views: 20

Re: Go=0

In lecture today we learned that ΔG is zero at a reaction's boiling point.
by Wendy Perez 1E
Tue Feb 11, 2020 12:01 am
Forum: Thermodynamic Definitions (isochoric/isometric, isothermal, isobaric)
Topic: isothermal
Replies: 2
Views: 14

Re: isothermal

Yes, using the equation ΔU=(3/2)nRΔT, you can see that if ΔT is zero, so is ΔU.
by Wendy Perez 1E
Thu Feb 06, 2020 1:45 pm
Forum: Thermodynamic Systems (Open, Closed, Isolated)
Topic: Thermodynamics
Replies: 6
Views: 30

Re: Thermodynamics

When heat is transferred from the system and work is done by the system, both heat and work are negative. This is because when heat is transferred from the system, the system loses heat (hence the negative q). When work is done by the system, the system is losing energy (hence work is negative).
by Wendy Perez 1E
Thu Feb 06, 2020 1:41 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: -qsystem=qsurroundings
Replies: 2
Views: 14

-qsystem=qsurroundings

When I am doing calculations, I have a bit of trouble determining when to apply the "-qsystem=qsurroundings." How can you determine when to use this in a problem? Does anyone have any tips?
by Wendy Perez 1E
Tue Feb 04, 2020 4:40 pm
Forum: Administrative Questions and Class Announcements
Topic: Test 1 Distribution
Replies: 9
Views: 71

Re: Test 1 Distribution

Most likely not. We don't get distribution curves for tests.
by Wendy Perez 1E
Tue Feb 04, 2020 4:37 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: HW 4A.13
Replies: 1
Views: 14

Re: HW 4A.13

It is negative because the reaction is exothermic. The reaction is exothermic because heat is negative (reaction releases heat).
by Wendy Perez 1E
Tue Feb 04, 2020 4:22 pm
Forum: Calculating Work of Expansion
Topic: second equation
Replies: 8
Views: 25

Re: second equation

Unless asked to derive the equation, you would just use the -nRTln(v2/v1).
by Wendy Perez 1E
Wed Jan 29, 2020 7:19 pm
Forum: Thermodynamic Systems (Open, Closed, Isolated)
Topic: Increasing energy in an open system
Replies: 7
Views: 18

Re: Increasing energy in an open system

As discussed today in lecture, you can increase the energy of an open system by doing one of the following:
- adding or removing a substance
- heating or cooling the system
- doing work on the system or letting the system do work on its surroundings
by Wendy Perez 1E
Wed Jan 29, 2020 7:14 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: memorize
Replies: 6
Views: 17

Re: memorize

I would memorize the heat capacity of water, but other capacities most likely will be given in the equations sheet.
by Wendy Perez 1E
Wed Jan 29, 2020 7:11 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: Heat, Temperature, Enthalpy
Replies: 4
Views: 16

Heat, Temperature, Enthalpy

Can someone explain the difference between heat, temperature, and enthalpy? Thank you!
by Wendy Perez 1E
Wed Jan 29, 2020 4:31 pm
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: Endothermic vs Exothermic
Replies: 10
Views: 38

Re: Endothermic vs Exothermic

This is correct. A negative value of q indicates that the system lost heat. Thus, the reaction is exothermic. A positive value of q indicates that the system gained heat. Thus, the reaction is endothermic.
by Wendy Perez 1E
Tue Jan 28, 2020 10:24 pm
Forum: Thermodynamic Systems (Open, Closed, Isolated)
Topic: Closed vs isolated systems
Replies: 24
Views: 64

Re: Closed vs isolated systems

Think of a closed system as a cup of coffee with a lid. It can exchange energy with its surroundings in the form of heat but cannot exchange matter because the lid is closed. Think of an isolated system, or something close to it, as a sealed hydro flask. You cannot exchange energy (hydro flasks esse...
by Wendy Perez 1E
Wed Jan 22, 2020 7:40 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Ice Box Question
Replies: 2
Views: 8

Re: Ice Box Question

Usually, we do subtract x from the reactants because the reactants are being used up. But, if the problem explicitly states that the products decreased in concentration or pressure, then you would subtract x from the products.
by Wendy Perez 1E
Wed Jan 22, 2020 7:34 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Strong Acids and Bases in Water
Replies: 1
Views: 15

Re: Strong Acids and Bases in Water

Strong acids and bases dissociate completely. Thus, if you know the concentration of a strong acid or base, you can find the hydronium and hydroxide concentration with molar ratios. You can then use this to find the pH or the pOH. For instance, if a problem says that you have 0.138 M HCl, then you k...
by Wendy Perez 1E
Wed Jan 22, 2020 7:30 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Autoprotolysis
Replies: 1
Views: 8

Re: Autoprotolysis

The reaction is endothermic because heat is required in order to break the hydrogen bonds between two water molecules.
by Wendy Perez 1E
Wed Jan 22, 2020 7:27 pm
Forum: General Science Questions
Topic: Test 1: Sig Figs
Replies: 7
Views: 62

Re: Test 1: Sig Figs

I am not sure if they count, but I would suggest knowing how they work. If pH=5.1 and you have to find the hydronium concentration, there are two significant figures total in the pH. Thus, you would put two numbers after the decimal point in your hydronium concentration answer. If you are asked to f...
by Wendy Perez 1E
Wed Jan 22, 2020 7:21 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: Exothermic vs. Endothermic reactions
Replies: 12
Views: 45

Re: Exothermic vs. Endothermic reactions

It is possible. All I suggest knowing is that when delta H is positive, the reaction is endothermic and when delta H is negative, the reaction is exothermic.
by Wendy Perez 1E
Thu Jan 16, 2020 10:25 am
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Quadratic
Replies: 6
Views: 25

Re: Quadratic

It will be given on tests. If you look at the "constants and equations" section on his website, you will see that the quadratic equation is given.
by Wendy Perez 1E
Wed Jan 15, 2020 7:33 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: 5.39
Replies: 2
Views: 21

Re: 5.39

I also came across this and was confused. I am sure it is just a typo. I would suggest doing the calculation with the value given in the textbook for extra practice.
by Wendy Perez 1E
Wed Jan 15, 2020 7:31 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Strong acids/weak acids
Replies: 3
Views: 17

Re: Strong acids/weak acids

Strong acids do have a Ka value. They have large Ka values because the higher the Ka, the more the acid dissociates. They have low pKa values.
by Wendy Perez 1E
Tue Jan 14, 2020 2:13 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Autoprolysis
Replies: 8
Views: 35

Re: Autoprolysis

Adding to this conversation, what does amphiprotic mean again?
by Wendy Perez 1E
Tue Jan 14, 2020 2:08 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: ICE charts on tests/exams
Replies: 8
Views: 35

Re: ICE charts on tests/exams

Since we spent almost an entire lecture learning about ice charts, it is safe to say that we will have to include them on exams as part of showing our work.
by Wendy Perez 1E
Sat Jan 11, 2020 10:16 am
Forum: Ideal Gases
Topic: Solids and Liquids [ENDORSED]
Replies: 10
Views: 64

Re: Solids and Liquids [ENDORSED]

It does not make sense for solids to have a concentration since the units for concentration are mol/L. For liquids, the change in concentration is insignificant because the change is very small.
by Wendy Perez 1E
Thu Jan 09, 2020 10:30 pm
Forum: Ideal Gases
Topic: 5G1 true/false
Replies: 8
Views: 55

Re: 5G1 true/false

Instead of looking at K as Kc look at it as Kp. Kp= (partial pressure of products) / (partial pressure of reactants) according to this equation, an increase in the partial pressure of reactants would lead to a decrease in the equilibrium constant instead of an increase in the equilibrium constant, ...
by Wendy Perez 1E
Thu Jan 09, 2020 10:27 pm
Forum: Ideal Gases
Topic: 5G1 true/false
Replies: 8
Views: 55

Re: 5G1 true/false

Your reasoning that "if there is higher pressure of reactant, it will shift towards product" is correct. However, this does not mean that K will change. Here, only Q is changing because initially Q<K. K is not changing. This is because the temperature is constant. Only when the temperature...
by Wendy Perez 1E
Wed Jan 08, 2020 11:21 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Homework Question 5I.13
Replies: 2
Views: 51

Homework Question 5I.13

In an experiment, 2.0 mmol Cl2(g) was sealed into a reaction vessel of volume 2.0 L and heated to 1000. K to study its dissociation into Cl atoms. Use the information in Table 5G.2 to calculate the equilibrium composition of the mixture. (b) If 2.0 mmol F2 was placed into the reaction vessel instead...
by Wendy Perez 1E
Wed Jan 08, 2020 12:03 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Reverse reaction
Replies: 6
Views: 34

Re: Reverse reaction

The reverse reaction occurs when Q>K. This occurs when there is an abundance of products and not enough reactants.
by Wendy Perez 1E
Tue Jan 07, 2020 1:05 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Keq vs Kc
Replies: 6
Views: 39

Re: Keq vs Kc

Also relevant to this discussion is how Kc is different than Kp. Kp is the equilibrium constant found using partial pressures. The method of calculating Kp is essentially the same as Kc, except Kp is calculated by the partial pressure of products/the partial pressure of the reactants.
by Wendy Perez 1E
Tue Jan 07, 2020 12:58 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: ICE Table Variables
Replies: 2
Views: 17

Re: ICE Table Variables

I would use the variable x for the change concentration. Putting the variable x for the change concentration makes it clearer and easier to find the value of x as opposed to putting numbers for the change concentration.
by Wendy Perez 1E
Wed Dec 04, 2019 10:34 am
Forum: Shape, Structure, Coordination Number, Ligands
Topic: Drawing structures on the final
Replies: 3
Views: 38

Re: Drawing structures on the final

I don't believe that we have to know how to draw coordination compounds or chelating coordination compounds because it was not thoroughly discussed in the lecture. However, make sure you thoroughly understand the concepts of each and make sure you know how to draw cisplatin, EDTA, myoglobin, ethylen...
by Wendy Perez 1E
Wed Dec 04, 2019 10:29 am
Forum: Properties & Structures of Inorganic & Organic Acids
Topic: Acid or Base
Replies: 2
Views: 27

Re: Acid or Base

SO3 is a nonmetal oxide and nonmetal oxides are acidic
by Wendy Perez 1E
Wed Dec 04, 2019 10:24 am
Forum: Bronsted Acids & Bases
Topic: Neutralizations
Replies: 3
Views: 38

Re: Neutralizations

In a neutralization reaction, acids and bases always produce salt and water.
by Wendy Perez 1E
Wed Dec 04, 2019 10:14 am
Forum: Calculating pH or pOH for Strong & Weak Acids & Bases
Topic: 6C 21 part b
Replies: 2
Views: 27

Re: 6C 21 part b

Formic acid is stronger than acetic acid because acetic acid has a CH3 that is e- donating. This means that CH3 contributes electron density to the O-H bond. This makes it harder to remove the H. Thus it is weaker acid compared to formic acid.
by Wendy Perez 1E
Wed Dec 04, 2019 10:05 am
Forum: Biological Examples
Topic: Cisplatin
Replies: 6
Views: 50

Re: Cisplatin

Unlike trans-diamine-dichloro-platinum, Cisplatin has two Cls on the same side of the molecule that allows the Cls to bind to the same DNA strand to form 2 bonds. This blocks the enzymes used in DNA replication from replicating the DNA strand. Thus, it blocks DNA replication.
by Wendy Perez 1E
Wed Dec 04, 2019 9:59 am
Forum: Properties of Light
Topic: Light as a Wave
Replies: 8
Views: 72

Re: Light as a Wave

Light has wave-like properties all the time, along with particle-like properties.
by Wendy Perez 1E
Mon Nov 25, 2019 11:43 am
Forum: Hybridization
Topic: When does hybridization occur?
Replies: 7
Views: 46

Re: When does hybridization occur?

Hybridization doesn't always occur when forming bonds. It only occurs when an atom needs to form more bonds than it would be able to in a ground state.
by Wendy Perez 1E
Mon Nov 25, 2019 11:41 am
Forum: Naming
Topic: Correct naming conventions
Replies: 5
Views: 36

Re: Correct naming conventions

You add the suffix -ate to the metal name in a coordination compound when the net coordination compound has a net negative charge.
by Wendy Perez 1E
Mon Nov 25, 2019 11:29 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: Hydrogen Bonding Sites
Replies: 2
Views: 25

Re: Hydrogen Bonding Sites

We can determine the number of hydrogen bonding sites between two molecules if there is an F, O, or N with an available lone pair. A hydrogen must be bonded to a F, O, or N.
by Wendy Perez 1E
Mon Nov 25, 2019 9:28 am
Forum: Hybridization
Topic: Sigma and Pi Bonds
Replies: 5
Views: 31

Re: Sigma and Pi Bonds

Sigma bonds are also made from hybridized orbitals, whereas pi bonds are made only from leftover p orbitals.
by Wendy Perez 1E
Mon Nov 25, 2019 9:21 am
Forum: Naming
Topic: Coordination shape
Replies: 3
Views: 31

Re: Coordination shape

Lavelle did not go into too much depth about this but I believe that you have to draw the Lewis structure. If the molecule has a tetrahedral shape, it is a tetrahedral complex. If the molecule has a square planar shape, it is a square planar complex.
by Wendy Perez 1E
Sun Nov 24, 2019 1:43 pm
Forum: Hybridization
Topic: d-orbitals
Replies: 7
Views: 38

Re: d-orbitals

D-orbitals do get involved in hybridization. This is why there are sp^3d orbitals and sp^3d^2 orbitals.
by Wendy Perez 1E
Wed Nov 20, 2019 10:09 am
Forum: Determining Molecular Shape (VSEPR)
Topic: Lone Pairs for AX4E
Replies: 3
Views: 35

Re: Lone Pairs for AX4E

When the lone pair is in the equatorial plane, it is only perpendicular to two atoms. If the lone pair was in the axial plane, it would be perpendicular to three atoms. Therefore, having a lone pair in the equatorial plane would minimize the repulsions created by the lone pair.
by Wendy Perez 1E
Wed Nov 20, 2019 9:38 am
Forum: Determining Molecular Shape (VSEPR)
Topic: cancelling dipoles
Replies: 2
Views: 27

Re: cancelling dipoles

You are correct in that the dipole moments only cancel for a tetrahedral if all the atoms bonded to the central atom are the same. This would make the molecule nonpolar. If one atom is different, the dipole moments do not cancel and the molecule is polar. However, it is possible for different atoms ...
by Wendy Perez 1E
Wed Nov 20, 2019 9:31 am
Forum: Dipole Moments
Topic: Hydrogen Bonds
Replies: 3
Views: 27

Re: Hydrogen Bonds

This is correct. But, you also have to remember that F, O, and N also must have an available lone pair in order to be able to form a hydrogen bond.
by Wendy Perez 1E
Tue Nov 19, 2019 10:36 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: kJ/mol
Replies: 1
Views: 13

Re: kJ/mol

I do not believe that we need to know these exact values. Just know the strength of each intermolecular force in comparison with other intermolecular forces. You should know that ion-ion forces are the strongest followed by hydrogen bonds, ion-dipole forces, dipole-dipole forces, and london dispersi...
by Wendy Perez 1E
Tue Nov 19, 2019 10:32 am
Forum: Determining Molecular Shape (VSEPR)
Topic: Figuring Out Bond Angle
Replies: 3
Views: 18

Re: Figuring Out Bond Angle

If the central atom has lone pairs, it will cause more electron-electron repulsion, which will result in a molecule having a bond angle that is smaller than usual (i.e. less than 120 degrees). You can think of this as if the electrons are "pushing away" the other bonds, which results in a ...
by Wendy Perez 1E
Sun Nov 17, 2019 12:32 am
Forum: Electronegativity
Topic: Symbols for partial charge
Replies: 4
Views: 37

Re: Symbols for partial charge

The symbols represent partial charge. The negative partial charge goes on the most electronegative atom in a molecule, while the positive charge goes on the other atom. The dipole moments, which represent the arrows used, point from a positive partial charge to a negative partial charge (towards the...
by Wendy Perez 1E
Thu Nov 14, 2019 12:19 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: H-bonds
Replies: 4
Views: 19

Re: H-bonds

Hydrogen bonds do have dipole moments because they typically form when a hydrogen atom bonds to a highly electronegative atom (F,O,N). When bonded to these specific highly electronegative atoms, the hydrogen bonds will have a dipole moment.
by Wendy Perez 1E
Wed Nov 13, 2019 10:13 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Memorization
Replies: 15
Views: 109

Re: Memorization

We do have to memorize the different shapes. However, Lavelle said that we are not required to memorize all of the bond angles as we will never be specifically asked to state them. The main thing that he wants us to remember are the shapes.
by Wendy Perez 1E
Wed Nov 13, 2019 9:35 am
Forum: Determining Molecular Shape (VSEPR)
Topic: Intermolecular Forces
Replies: 2
Views: 20

Intermolecular Forces

If given a molecule, how can you determine whether it has dipole-dipole interactions, dipole-induced dipole interactions, or induced dipole-induced dipole interactions?
by Wendy Perez 1E
Wed Nov 13, 2019 9:20 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: Determining Polarity
Replies: 5
Views: 54

Re: Determining Polarity

In order to determine if a molecule is polar, you have to look at the shape and the differences in electronegativity. There is no cutoff in electronegativity. If the dipole moments all cancel, the molecule is nonpolar. If the dipole moments do not cancel, the molecule is polar.
by Wendy Perez 1E
Mon Nov 11, 2019 8:40 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Interactions between Ions and Molecules
Replies: 1
Views: 14

Interactions between Ions and Molecules

What is the difference between ion-ion, ion-dipole, dipole-dipole, and dipole-induced dipole interactions?
by Wendy Perez 1E
Mon Nov 11, 2019 8:37 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Induced dipole-induced dipole interactions
Replies: 2
Views: 13

Induced dipole-induced dipole interactions

How does induced dipole-induced dipole interactions relate to polarizability and electron distortion?
by Wendy Perez 1E
Mon Nov 11, 2019 8:33 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Hydrogen Bonding
Replies: 3
Views: 23

Hydrogen Bonding

How does hydrogen bonding affect the melting points of compounds?
by Wendy Perez 1E
Tue Nov 05, 2019 7:04 pm
Forum: Electronegativity
Topic: Homework Question 2D.5 Part a
Replies: 2
Views: 28

Homework Question 2D.5 Part a

For each pair, determine which compound has bonds with greater ionic character: (a) HCl or HI; (b) CH4 or CF4; (c) CO2 or CS2?

For part a, I was wondering why HI has a lower ionic character than HCl. I am just confused as to why HCl has a larger difference in electronegativity than HI.
by Wendy Perez 1E
Mon Nov 04, 2019 11:52 pm
Forum: Lewis Structures
Topic: Valence Electrons in D Subshell
Replies: 5
Views: 35

Valence Electrons in D Subshell

How do you determine the number of valence electrons in the d subshell? On A.1 part c, they asked for the number of valence electrons in Manganese and the answer was 7. How did they get to this answer?
by Wendy Perez 1E
Mon Nov 04, 2019 9:47 am
Forum: Octet Exceptions
Topic: octet exceptions
Replies: 11
Views: 104

Re: octet exceptions

Boron is also an exception to the octet rule as it can be content with 6 valence electrons, instead of an octet.
by Wendy Perez 1E
Sun Nov 03, 2019 1:25 am
Forum: Heisenberg Indeterminacy (Uncertainty) Equation
Topic: Which equations can be used for what topics
Replies: 2
Views: 32

Re: Which equations can be used for what topics

E=hv is used for the energy of a photon, or in this case, electromagnetic radiation.
by Wendy Perez 1E
Sun Nov 03, 2019 1:19 am
Forum: Dipole Moments
Topic: Dipole Moments
Replies: 3
Views: 30

Dipole Moments

Can someone please explain to me what dipole moments are and what they have to do with electronegativity?
by Wendy Perez 1E
Thu Oct 31, 2019 1:40 am
Forum: Student Social/Study Group
Topic: Equation sheet
Replies: 1
Views: 31

Re: Equation sheet

Here's the link to the constants and equations sheet that Lavelle has on his website: https://lavelle.chem.ucla.edu/wp-content/supporting-files/Chem14A/constants_equations.pdf If you cannot access the sheet through this link, you can find it on Lavelle's Chem14A classroom page. It is under the title...
by Wendy Perez 1E
Wed Oct 30, 2019 9:36 am
Forum: Trends in The Periodic Table
Topic: Summary of Periodic Trends [ENDORSED]
Replies: 2
Views: 33

Re: Summary of Periodic Trends [ENDORSED]

I find it useful to remember that most periodic trends increase going upper right on the periodic table. This includes, ionization energy, electron affinity, and electronegativity. The only periodic trend that increases to the lower left is atomic radii and ionic radii.
by Wendy Perez 1E
Wed Oct 30, 2019 9:32 am
Forum: Resonance Structures
Topic: Delocalization vs. Resonance
Replies: 8
Views: 71

Re: Delocalization vs. Resonance

A molecule with resonance refers to the fact that it has multiple bonds that can be placed in different locations within the molecule, without moving the individual atoms in the molecule. When a molecule has resonance, the electrons aren't localized at one particular atom, but rather they are deloca...
by Wendy Perez 1E
Sat Oct 26, 2019 10:37 pm
Forum: Trends in The Periodic Table
Topic: atomic Radii
Replies: 11
Views: 43

Re: atomic Radii

This is correct. The addition of an electron adds more electrons to the outermost shell. This increases the radius because there are now more electrons farther away from the nucleus.
by Wendy Perez 1E
Sat Oct 26, 2019 10:35 pm
Forum: Quantum Numbers and The H-Atom
Topic: Ms and ML
Replies: 6
Views: 48

Re: Ms and ML

I believe that you have ms and ml confused. Ms, which stands for the spin magnetic quantum number, is always either +1/2 or -1/2. +1/2 indicates that the electron's spin is up. -1/2 indicates that the electron's spin is down. Ml stands for the magnetic quantum number and refers to the orientation of...
by Wendy Perez 1E
Sat Oct 26, 2019 10:25 pm
Forum: Electron Configurations for Multi-Electron Atoms
Topic: Shorthand Notation
Replies: 4
Views: 24

Re: Shorthand Notation

I believe that for most electron configurations, we will have to write the entire configuration. However, if an element has an excessively long electron configuration, such as Strontium, we most likely will be able to use the shorthand notation.
by Wendy Perez 1E
Fri Oct 25, 2019 1:13 am
Forum: Administrative Questions and Class Announcements
Topic: Powerpoint Slides
Replies: 5
Views: 43

Re: Powerpoint Slides

Unfortunately, we do not. Luckily, professor Lavelle gives us enough time in class to take notes, and he doesn't rush us.
by Wendy Perez 1E
Fri Oct 25, 2019 1:11 am
Forum: Ionic & Covalent Bonds
Topic: Electron Affinity
Replies: 5
Views: 44

Re: Electron Affinity

Why does electron affinity increase as we go towards the noble gasses? Electron affinity increases as we go towards the noble gases because the elements near the noble gases have the tendency to gain an electron due to their higher nuclear charge. In order for these elements to fill their shells, i...
by Wendy Perez 1E
Tue Oct 22, 2019 11:00 pm
Forum: Electron Configurations for Multi-Electron Atoms
Topic: Electron Configurations
Replies: 4
Views: 28

Re: Electron Configurations

As to your question on how many electrons will fit into a specific orbital, each orbital consists of two electrons. There is one s-orbital, thus there are 2 electrons in the s-sublevel. There are 3 p-orbitals, thus there are 6 electrons in the p-sublevel (3 p-orbitals* 2 e- per orbital). There are a...
by Wendy Perez 1E
Tue Oct 22, 2019 10:50 pm
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: s, p, d, f orbitals
Replies: 15
Views: 90

Re: s, p, d, f orbitals

As to the first part of your question, 3d orbitals have slightly higher energy than 4s orbitals, thus, the 4s orbitals get filled first. This is only true if there are no electrons in the 3d orbitals. If the 3d orbitals are filled, then the 4s orbitals will be higher in energy.
by Wendy Perez 1E
Wed Oct 16, 2019 1:01 pm
Forum: Properties of Electrons
Topic: Properties of P momentum
Replies: 3
Views: 27

Re: Properties of P momentum

p = mv (v is the greek letter nu for frequency here, NOT velocity) lamda = h/p (lamda = wavelength) (h is Planck's constant) using these two equations, you can calculate the frequency, wavelength, and even the energy you can also use the uncertainty in momentum (Delta p) to find the uncertainty in ...
by Wendy Perez 1E
Wed Oct 16, 2019 10:28 am
Forum: Heisenberg Indeterminacy (Uncertainty) Equation
Topic: 1B 27 [ENDORSED]
Replies: 1
Views: 23

Re: 1B 27 [ENDORSED]

You are correct, the uncertainty would be 10 m/s. There is an error in the solution manual. If you go to the chem14A class website and scroll down to "Solution Manual Errors 7th Edition," you will see the corrected version.
by Wendy Perez 1E
Wed Oct 16, 2019 10:17 am
Forum: Heisenberg Indeterminacy (Uncertainty) Equation
Topic: Which equation to use for determining uncertainty?
Replies: 4
Views: 22

Re: Which equation to use for determining uncertainty?

h bar is a simplified form of Planck's constant, in which h bar is equal to h/2π. If you use the equation given in the textbook and substitute h bar as h/2π, you will see the equation that professor Lavelle gave us. This is because (h bar/2π)/2 is equal to h/4π. In regards to your question of which ...
by Wendy Perez 1E
Wed Oct 16, 2019 9:05 am
Forum: Heisenberg Indeterminacy (Uncertainty) Equation
Topic: Why divide h by 4pi?
Replies: 5
Views: 48

Re: Why divide h by 4pi?

Through experimentation, scientists determined that the minimum uncertainty of knowing both a particles momentum and position simultaneously is this value: h/4pi.
by Wendy Perez 1E
Tue Oct 15, 2019 9:13 pm
Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
Topic: Rydbergs Equation
Replies: 3
Views: 37

Re: Rydbergs Equation

Use the equation that Lavelle gave us in the lecture E=(-hR/n^2) as the Rydberg equation. Lavelle didn't want us to use a different version of this equation that was given in the textbook, which is v=R{(1/n^2)-(1/n^2)}. He said that if we use this equation, we will just be plugging in numbers and we...
by Wendy Perez 1E
Sun Oct 13, 2019 11:41 am
Forum: Bond Lengths & Energies
Topic: Bond lengths
Replies: 15
Views: 141

Re: Bond lengths

I believe that Dr. Lavelle mentioned this once in his lectures. A bond length between two molecules is about 10^-10m, which is equal to 1 Angstrom.
by Wendy Perez 1E
Sat Oct 12, 2019 3:02 pm
Forum: DeBroglie Equation
Topic: De Broglie equation
Replies: 5
Views: 29

Re: De Broglie equation

Within the De Broglie equation, the mass should be in kg instead of grams in order to cancel out with the units of Planck's constant. The units for Planck's constant are J.s. The SI units of J is kg*m^2*s^-2. Thus, the units for Planck's constant are also (kg*m^2*s^-2)*s. In order to cancel out kg i...
by Wendy Perez 1E
Sat Oct 12, 2019 2:30 pm
Forum: Properties of Electrons
Topic: Diffraction
Replies: 4
Views: 23

Re: Diffraction

Diffraction patterns result from interacting waves. For instance, light waves, such as x-rays, show diffraction patterns. Since electrons passing though a crystal also show diffraction waves, they must have wavelike properties.
by Wendy Perez 1E
Sat Oct 12, 2019 2:14 pm
Forum: Photoelectric Effect
Topic: Energy in Photoelectric Effect
Replies: 5
Views: 29

Re: Energy in Photoelectric Effect

In order for electrons to be emitted, the energy of the photon has to be greater than OR equal to the threshold energy.
by Wendy Perez 1E
Wed Oct 09, 2019 11:48 pm
Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
Topic: Photon Absorption/Emission
Replies: 8
Views: 108

Re: Photon Absorption/Emission

Absorption of a photon does always lead to a later emission of a photon. The emitted photon has the same energy as the photon that was first absorbed due to the law of conservation of energy.
by Wendy Perez 1E
Wed Oct 09, 2019 10:04 am
Forum: Photoelectric Effect
Topic: Photon [ENDORSED]
Replies: 6
Views: 83

Re: Photon [ENDORSED]

A photon is essentially a packet of electromagnetic energy. Photons are unique in that they are both, a particle and a wave. A photon must have enough energy (high enough frequency) in order to remove an electron from a metal. In other words, the photon's energy must be greater than or equal to the ...
by Wendy Perez 1E
Wed Oct 09, 2019 9:50 am
Forum: Photoelectric Effect
Topic: h and c
Replies: 2
Views: 41

Re: h and c

Both, "h" and "c" are constants that are given. "h" in the equation E=hv refers to Planck's constant (6.62608*10^-34 J.s). In other words, the equation means that the energy of a photon is equal to Planck's constant multiplied by the frequency of the light source. "...
by Wendy Perez 1E
Thu Oct 03, 2019 2:03 pm
Forum: Balancing Chemical Reactions
Topic: HW question L35
Replies: 2
Views: 40

Re: HW question L35

I came across this problem before, and it is an error. On the Chem14A class website, professor Lavelle has a link to a section titled, "Solution Manual Errors 7th Edition." On there, it is confirmed that there is an error, and you can see any other typos that the book has.
by Wendy Perez 1E
Tue Oct 01, 2019 8:36 pm
Forum: Empirical & Molecular Formulas
Topic: Typo on L.35
Replies: 3
Views: 43

Typo on L.35

Hey everyone! Homework problem L.35 states, "Sodium bromide, NaBr, which is used to produce AgBr for use in photographic film, can itself be prepared as follows: Fe + Br2 --> FeBr2 FeBr2 + Br2 --> Fe3Br8 FeBr2 + Na2CO3 --> NaBr + CO2 + Fe3O4 What mass of iron, in kilograms, is needed to produce...
by Wendy Perez 1E
Tue Oct 01, 2019 8:32 pm
Forum: Limiting Reactant Calculations
Topic: Homework Problem M.5
Replies: 2
Views: 34

Homework Problem M.5

Hi everyone! I am not sure where to start on homework problem M.5 in the textbook. I specifically need help with part (a) of the problem. The question reads, "Solve this exercise without using a calculator. The reaction 6 ClO2(g) 1 2 BrF3(l) S 6 ClO2F(s) 1 Br2(l) is carried out with 12 mol ClO2...
by Wendy Perez 1E
Mon Sep 30, 2019 10:08 pm
Forum: Accuracy, Precision, Mole, Other Definitions
Topic: Understanding Titrations
Replies: 3
Views: 66

Understanding Titrations

Hi everyone!

I am having a bit of trouble understanding what a titration is from Fundamentals Section L. The textbook has a definition but makes it very wordy and confusing. Can anyone provide a simple definition of what a titration is?
by Wendy Perez 1E
Mon Sep 30, 2019 9:58 pm
Forum: Significant Figures
Topic: Determining significant figures on HW and quizzes/exams
Replies: 3
Views: 50

Re: Determining significant figures on HW and quizzes/exams

We most likely will be marked down points since significant figures are important in chemistry. It is important to understand them in order to be a good chemist.
by Wendy Perez 1E
Mon Sep 30, 2019 9:55 pm
Forum: Molarity, Solutions, Dilutions
Topic: Homework Problem G.17
Replies: 4
Views: 57

Homework Problem G.17

Hi everyone! I was having some trouble figuring out part b of homework problem G.17. The problem asks to "(b) Determine the mass of CuSO4*5H2O that must be used to prepare 250 mL of 0.20 m CuSO4(aq)." I am not sure how I can cancel out the molar units of CuS04 and CuSO4*5H20 if they are di...

Go to advanced search