Search found 91 matches

by Alison Perkins 2B
Mon Feb 22, 2021 12:49 pm
Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
Topic: Nernst Equation @ equilibrium
Replies: 6
Views: 22

Re: Nernst Equation @ equilibrium

from here if you know E° you can then solve for the equilibrium constant (K) with logK= (nE°)/(0.0592V)
by Alison Perkins 2B
Mon Feb 22, 2021 12:47 pm
Forum: Student Social/Study Group
Topic: We made it through Midterm 2!
Replies: 58
Views: 163

Re: We made it through Midterm 2!

congrats on surviving midterm 2
by Alison Perkins 2B
Mon Feb 22, 2021 12:47 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Spontaneous process
Replies: 4
Views: 15

Re: Spontaneous process

A spontaneous reaction always has a -ΔG, and since ΔG = -nFE, when there is a spontaneous reaction there will be a +E value for those negative symbols to cancel out.
by Alison Perkins 2B
Mon Feb 22, 2021 12:45 pm
Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
Topic: Units for delta G
Replies: 23
Views: 331

Re: Units for delta G

the moles will cancel between n (mol) and F (C/mol) so it will be in kJ
by Alison Perkins 2B
Mon Feb 22, 2021 12:44 pm
Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
Topic: n in NFE
Replies: 25
Views: 332

Re: n in NFE

n is the moles of electrons transferred in the reaction.
by Alison Perkins 2B
Sun Feb 14, 2021 9:30 pm
Forum: Concepts & Calculations Using Second Law of Thermodynamics
Topic: Sapling Question 6
Replies: 5
Views: 35

Re: Sapling Question 6

For this one you should solve for two ΔS values and sum them.
1. ΔS = nRln(V2/V1)
2. ΔS = Cv ln(T2/T1)

Before adding make sure you multiply the second value by the number of moles in the equation.
by Alison Perkins 2B
Sun Feb 14, 2021 9:28 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: What's the difference between delta G and delta G°
Replies: 7
Views: 23

Re: What's the difference between delta G and delta G°

ΔG = ΔG° + -RTln(Q)

The degrees on the delta G means that this is the standardized value.
by Alison Perkins 2B
Sun Feb 14, 2021 9:27 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: G° vs G
Replies: 22
Views: 67

Re: G° vs G

ΔG = ΔG° + -RTln(Q)

The degrees on the delta G means that this is the standardized value.
by Alison Perkins 2B
Sun Feb 14, 2021 9:26 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: Sapling week 5/6 #20
Replies: 12
Views: 71

Re: Sapling week 5/6 #20

I had the same problem, just make sure the inequalities are on the bottom and spontaniety is on the top!
by Alison Perkins 2B
Sun Feb 14, 2021 9:25 pm
Forum: Concepts & Calculations Using Second Law of Thermodynamics
Topic: qrev vs q
Replies: 19
Views: 56

Re: qrev vs q

Qrev is the Q of the reverse reaction, which is used for entropy. They're both heat transfer values.
by Alison Perkins 2B
Sun Feb 14, 2021 9:24 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: Sapling Week 5/6 HW 18
Replies: 11
Views: 72

Re: Sapling Week 5/6 HW 18

I am doing all of these steps and am still getting it wrong and don't know why. Can anyone help with C2H2(g) + 2H2(g) --> C2H6 ??
by Alison Perkins 2B
Sun Feb 07, 2021 11:38 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: Cv vs. Cp
Replies: 4
Views: 14

Re: Cv vs. Cp

Cv is the specific heat at a constant volume, and Cp is the specific heat at a constant pressure.
Since solids and liquids can't change volumes, we know for all that Cp = Cv.
by Alison Perkins 2B
Sun Feb 07, 2021 11:37 pm
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: Delta U
Replies: 6
Views: 41

Re: Delta U

ΔU refers to the change in the internal energy of a system.
This is the effect that the heat/work done on the system has on its initial internal energy state.
by Alison Perkins 2B
Sun Feb 07, 2021 11:35 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: Liquids and Solids
Replies: 7
Views: 20

Re: Liquids and Solids

Only gasses can change volumes, so for solids and liquids Cp = Cv.
by Alison Perkins 2B
Sun Feb 07, 2021 11:34 pm
Forum: Thermodynamic Systems (Open, Closed, Isolated)
Topic: Lecture wk5, Wednesday Question
Replies: 2
Views: 7

Re: Lecture wk5, Wednesday Question

I'm quite positive that the Boltzman Constant is always 1.3806 × 10-23 m^2 kg /s^2 K, it isn't dependent on the molecules you're dealing with.
by Alison Perkins 2B
Sun Feb 07, 2021 11:31 pm
Forum: Entropy Changes Due to Changes in Volume and Temperature
Topic: Different R Constants
Replies: 14
Views: 39

Different R Constants

I am confused on when to use which value for the gas constant: R = 8.3145 J/mol·K. and R= 0.08204 liter·atm/mol·K.
Can anyone help?
by Alison Perkins 2B
Sat Jan 30, 2021 2:10 pm
Forum: Student Social/Study Group
Topic: Worried About MT 1 Grades
Replies: 39
Views: 238

Re: Worried About MT 1 Grades

I felt the same way when I BOMBED the first 14A midterm, but it happens to everyone so don't get down on yourself...just study harder every time you think you can do better...because you can. All that matters is you do your best. I believe in you!
by Alison Perkins 2B
Sat Jan 30, 2021 2:08 pm
Forum: Phase Changes & Related Calculations
Topic: reaction shifts
Replies: 18
Views: 82

Re: reaction shifts

Increasing temp in an exothermic reaction will shift to the left, meaning it favors reactants.

Increasing temp in an endothermic reaction will shift to the right, meaning it favors products.
by Alison Perkins 2B
Sat Jan 30, 2021 2:06 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: How Does Temperature Affect the Equilibrium Constant?
Replies: 25
Views: 76

Re: How Does Temperature Affect the Equilibrium Constant?

In an exothermic reaction:
Increasing temperature will favor the reactants
Decreasing temperature will favor the products

In an endothermic reaction:
Increasing temperature will favor the products
Decreasing temperature will favor the reactants
by Alison Perkins 2B
Sat Jan 30, 2021 2:04 pm
Forum: Phase Changes & Related Calculations
Topic: when to assume x is insignificant
Replies: 83
Views: 191

Re: when to assume x is insignificant

When the equilibrium constant is less than 10^-4 in your ICE table, you can assume that x is negligent in K calculations.
by Alison Perkins 2B
Sat Jan 30, 2021 2:03 pm
Forum: Student Social/Study Group
Topic: Motivation
Replies: 34
Views: 175

Re: Motivation

I fill in every single assignment and test on the syllabus in a planner at the start of the quarter so that my schedule is already written out for me when each week begins. Having a schedule and mapping everything out definitely helped.
by Alison Perkins 2B
Sun Jan 24, 2021 10:59 am
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: 4.31 text [ENDORSED]
Replies: 2
Views: 47

Re: 4.31 text [ENDORSED]

a) to find out whether the reaction is endothermic or exothermic, take the ΔH°f(products) - ΔH°f(reactants). If you get a positive value, it is endothermic, and if negative it is exothermic.
b) now use these conditions to solve for ΔH (unsure about how exactly to do this step).
by Alison Perkins 2B
Sun Jan 24, 2021 10:57 am
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Sapling Week 2 Question 3
Replies: 5
Views: 33

Re: Sapling Week 2 Question 3

rather than approximating, make an ICE table, and use the Ka value and equation to solve for your x value.
Then, take [H+]/[HA] at equilibrium x 100% for percent ionization.
by Alison Perkins 2B
Sun Jan 24, 2021 10:55 am
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: 4D.15 Question
Replies: 2
Views: 22

Re: 4D.15 Question

ΔH° = ΔH°f(products) - ΔH°f(reactants).

So for this, combine the ΔH°f for your products and reactants, and subtract for overall reaction enthalpy.
by Alison Perkins 2B
Sun Jan 24, 2021 10:52 am
Forum: Equilibrium Constants & Calculating Concentrations
Topic: hw question #5
Replies: 2
Views: 19

Re: hw question #5

to solve for OH-, make sure you are using an ICE table to solve for x from the Kb equation.
by Alison Perkins 2B
Sun Jan 24, 2021 10:51 am
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Bond Enthalpy on Midterm
Replies: 3
Views: 19

Re: Bond Enthalpy on Midterm

I am unsure, but in my TA Reid Wilson discussion slides from week 3, there is a table from the textbook (4D.1).
by Alison Perkins 2B
Sun Jan 24, 2021 10:47 am
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Sapling Acids/base equilibrium #5
Replies: 2
Views: 16

Re: Sapling Acids/base equilibrium #5

From the pH, you can solve for pOH because pH + pOH = 14.
From there, you can make an ICE table, and solve for your x with the Kb equation.
by Alison Perkins 2B
Fri Jan 15, 2021 5:24 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: Predominant Species
Replies: 3
Views: 30

Re: Predominant Species

The predominant species is just the strongest species present I believe.
by Alison Perkins 2B
Fri Jan 15, 2021 5:23 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Week 2 HW
Replies: 8
Views: 52

Re: Week 2 HW

Once you know the pH you can subtract this from 14 to get the pOH. Then, by doing 10^(-pOH) you will get [OH-]
by Alison Perkins 2B
Fri Jan 15, 2021 5:21 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: Classifying Salts
Replies: 2
Views: 17

Re: Classifying Salts

A salt will be basic if it contains the conjugate base of a weak acid
A salt will be acidic if it contains the conjugate acid of a weak base.
by Alison Perkins 2B
Fri Jan 15, 2021 5:19 pm
Forum: Calculating the pH of Salt Solutions
Topic: Sapling Week 2 (Question 5)
Replies: 1
Views: 18

Re: Sapling Week 2 (Question 5)

I wouldn't approximate, but rather set up an ICE table using another variable as the initial concentration. If you do 10^(-pOH) you will get an x value for your table. Then you can use the x and Kb to solve for an initial concentration, which you can use to set up the percent ionization equation. I ...
by Alison Perkins 2B
Fri Jan 15, 2021 5:12 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: the different Ks
Replies: 7
Views: 37

Re: the different Ks

Ka = [H+] [A-] / [HA] -> formula for the acidity constant of equilibrium, where HA is an acid and A- is it's conjugate base Kb = [BH+] [OH-] / [B] -> formula for the basicity constant of equilibrium, where B is a base and BH is it's conjugate acid Kw = [H3O+] [OH-] -> this is the formula for equilib...
by Alison Perkins 2B
Sun Jan 10, 2021 1:59 pm
Forum: Ideal Gases
Topic: Inert Gas
Replies: 20
Views: 99

Re: Inert Gas

An inert gas would be one that does not affect the outcome of the reaction. For instance, if you added Cl2 to a reaction that does not involve Cl2 and will not react with it, the same exact concentration of CL2 would be in the reactants as well as the products, only changing the volume and thus the ...
by Alison Perkins 2B
Sun Jan 10, 2021 1:57 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: I in ICE Chart
Replies: 11
Views: 56

Re: I in ICE Chart

If you are given the initial concentration for products, then the reactants could be zero for initial concentration if you are asked to find the concentration of the reactants.
by Alison Perkins 2B
Sun Jan 10, 2021 1:55 pm
Forum: Ideal Gases
Topic: Kc vs Kp
Replies: 109
Views: 989

Re: Kc vs Kp

When the problem contains all gases, you can use Kp if the pressure measurements are given. If you are given measurements for concentration rather than pressure, however, it is okay to use Kc.
by Alison Perkins 2B
Wed Jan 06, 2021 4:02 pm
Forum: Non-Equilibrium Conditions & The Reaction Quotient
Topic: names for reaction quotient Q
Replies: 19
Views: 86

Re: names for reaction quotient Q

They can all be calculated in the same way as you would calculate K with products over reactants. The difference between them is that Q is general, Qc is concentration specific, and Qp is partial pressure specific. Just as is with K, Kp, Kc. To calculate Qp or Qc, you would need to use the appropria...
by Alison Perkins 2B
Wed Jan 06, 2021 3:59 pm
Forum: Non-Equilibrium Conditions & The Reaction Quotient
Topic: Lecture 2 Ex) 1.5mol PCl5
Replies: 2
Views: 21

Lecture 2 Ex) 1.5mol PCl5

"1.50 mol PCl5 is placed in a 500ml reaction vessel and decomposes at 250°C to form PCL3 and CL2. Kc= 1.80, all 3 compounds are gases at 250°C." Lavelle ended the second lecture today with this example and I have been trying to solve it, but am stuck on if I should be calculating Qc or Qp,...
by Alison Perkins 2B
Wed Dec 16, 2020 2:37 pm
Forum: Student Social/Study Group
Topic: Grades
Replies: 29
Views: 234

Re: Grades

Grades are saturday for the Final I believe! I would assume quarter grades would follow soon after.
by Alison Perkins 2B
Wed Dec 16, 2020 2:36 pm
Forum: Student Social/Study Group
Topic: 14B Groupme
Replies: 12
Views: 111

14B Groupme

Does anyone know if there is a Groupme for 14B next quarter yet? I was thinking that would be a good way to stay on top of chem and study/review so that I don't forget everything before 14B starts.
by Alison Perkins 2B
Wed Dec 16, 2020 2:34 pm
Forum: Lewis Acids & Bases
Topic: Acids & Bases
Replies: 9
Views: 81

Re: Acids & Bases

A Bronstead Acid, or just an acid, is a species that can donate a proton. A Lewis Acid is a species that accepts an electron pair.
A Bronstead Base, or just a base, is a species that accepts a proton. A Lewis Base is one that donates an electron pair.
by Alison Perkins 2B
Wed Dec 16, 2020 2:32 pm
Forum: Student Social/Study Group
Topic: Anxiety
Replies: 43
Views: 278

Re: Anxiety

Make some tea and tidy up your room! Or change study locations every so often. Keeping a fresh scenery is important especially when you're stuck at home.
by Alison Perkins 2B
Sun Dec 06, 2020 3:25 pm
Forum: Naming
Topic: Prefixes for parts outside of Coordination Compound
Replies: 7
Views: 58

Re: Prefixes for parts outside of Coordination Compound

I believe it is that it would be "dichloride" if the two chlorides were binding to the same central atom, but since they are not inside the brackets and thus not both binding to the same central atom these are just referred to as "chloride".
by Alison Perkins 2B
Sun Dec 06, 2020 3:22 pm
Forum: Bronsted Acids & Bases
Topic: bronsted vs. lewis acid
Replies: 10
Views: 79

Re: bronsted vs. lewis acid

Bronsted is concerned with proton presence/movement, and Lewis is concerned with electron presence/movement. I have found it helpful to remember that every Bronsted Base is a Lewis Base and every Bronsted Acid is a Lewis Acid, but these trends DONT work in reverse.
by Alison Perkins 2B
Sun Dec 06, 2020 3:17 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Lone Pair Locations
Replies: 6
Views: 76

Re: Lone Pair Locations

Lone pairs have significant stronger repulsion strength, so they occupy a larger region of electron density as they push down on other surrounding bonds to push away from themselves and thus the other bonds become closer together, reducing bond angles and forming a bent shape.
by Alison Perkins 2B
Sun Dec 06, 2020 3:10 pm
Forum: Lewis Acids & Bases
Topic: lewis vs bronsted
Replies: 8
Views: 98

Re: lewis vs bronsted

Bronsted defines based on proton characteristics and movement, while Lewis focuses on electron movement and characteristic.
by Alison Perkins 2B
Sun Nov 29, 2020 11:59 pm
Forum: Resonance Structures
Topic: Stable Resonance Structures
Replies: 4
Views: 36

Re: Stable Resonance Structures

I know that for resonance structures you must determine which has the most stable formal charge, to ensure that this is the most stable atom. I am not sure of what else.
by Alison Perkins 2B
Sun Nov 29, 2020 11:58 pm
Forum: Bond Lengths & Energies
Topic: London Dispersion Forces
Replies: 5
Views: 47

Re: London Dispersion Forces

Yes, more bonds would make London Dispersion Forces stronger, because a heavier atom with more bonds will have electrons extending further from the nucleus with a weaker connection, so they can temporarily form dipole connections.
by Alison Perkins 2B
Sun Nov 29, 2020 11:55 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Rings and cyclic structures
Replies: 2
Views: 30

Re: Rings and cyclic structures

A ring or cyclic structure is a combination of the resonance structure arrangements of double or triple bonds in a circular formation (C6H6 for example). I hope that helps!
by Alison Perkins 2B
Sun Nov 29, 2020 11:53 pm
Forum: *Molecular Orbital Theory (Bond Order, Diamagnetism, Paramagnetism)
Topic: Sigma and Pi Bonds
Replies: 31
Views: 429

Re: Sigma and Pi Bonds

I don't believe there is a specific order in which these bonds need to be numbered, however one must be sigma and any remaining must be pi bonds.
by Alison Perkins 2B
Sun Nov 29, 2020 11:49 pm
Forum: Octet Exceptions
Topic: Which Elements have Expanded Octets
Replies: 3
Views: 35

Re: Which Elements have Expanded Octets

Do you know if we will need to know only specific ones or the trick to determine the elements with expanded octets for the final exam? Because I am still unsure how to determine this.
by Alison Perkins 2B
Sun Nov 22, 2020 9:01 pm
Forum: Bond Lengths & Energies
Topic: Melting Point
Replies: 12
Views: 106

Re: Melting Point

Melting points increase as the intermolecular strength of the atom increases. The more forces acting upon the nucleus to hold the atom together, the more energy required to break these.
by Alison Perkins 2B
Sun Nov 22, 2020 8:55 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Molecular Shape of Large Molecules
Replies: 3
Views: 13

Re: Molecular Shape of Large Molecules

To find the shape with more than one central atom, separate the large molecule into pieces by each of the central atoms. Then, after determining the shape of each portion, you combine these to describe the overall shape of the molecule.

I hope that helps !
by Alison Perkins 2B
Sun Nov 22, 2020 8:52 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Lone Pair E-
Replies: 47
Views: 305

Re: Lone Pair E-

Yes, each lone pair counts as its own region of electron density.
by Alison Perkins 2B
Sun Nov 22, 2020 8:51 pm
Forum: Bond Lengths & Energies
Topic: Higher Melting Point
Replies: 27
Views: 260

Re: Higher Melting Point

It has a higher melting point because it has more electrons, making it a larger molecule with more electronegative forces acting upon it, making it more difficult to break the bonds.
by Alison Perkins 2B
Sun Nov 22, 2020 8:50 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Incorrect Lewis Structure
Replies: 3
Views: 52

Re: Incorrect Lewis Structure

I'm pretty sure that it's because the number of regions of electron densities doesn't change when you draw different resonance structures. I am also confused by this because in the SO3 ^2- example in lecture, one structure had all single bonds and 4 regions of e- density, while the other structure ...
by Alison Perkins 2B
Sun Nov 22, 2020 8:47 pm
Forum: Lewis Structures
Topic: Electron Density
Replies: 14
Views: 132

Re: Electron Density

Electron density refers to the probability that an atom would be found in any given region of an orbital. And to answer your second question, I believe that any area where an electron could be found would be considered a region of electron density. Does electron density also contribute to the polar...
by Alison Perkins 2B
Sun Nov 22, 2020 8:29 pm
Forum: Student Social/Study Group
Topic: Big Sad: Midterm 2
Replies: 86
Views: 932

Re: Big Sad: Midterm 2

I totally feel you. I thought I had the first midterm in the bag....and i definitely did not.
Also felt like I had concepts for this midterm down and thought it was easier than the last... but I'm praying that the same thing doesn't happen. Scared for my grade.
by Alison Perkins 2B
Sun Nov 22, 2020 8:27 pm
Forum: Hybridization
Topic: Shape of Hybrid Orbital
Replies: 5
Views: 52

Re: Shape of Hybrid Orbital

sp orbitals have a linear shape
sp2 orbitals have a trigonal planer shape
sp3 orbitals have a tetrahedral shape
sp3d orbitals have a trigonal bi- pyramidal shape
sp3d2 orbitals have octahedral or square bi-pyramid shape

Hope this helps!
by Alison Perkins 2B
Sun Nov 22, 2020 8:24 pm
Forum: Administrative Questions and Class Announcements
Topic: Extra Credit
Replies: 11
Views: 126

Extra Credit

Are there any extra credit opportunities offered for this course?

I am concerned since we cannot make up Chemistry Community posts if we miss the hard midnight deadline, and because the midterms have been more difficult than I had expected.
by Alison Perkins 2B
Sun Nov 22, 2020 8:22 pm
Forum: Student Social/Study Group
Topic: post midterm 2
Replies: 27
Views: 306

Re: post midterm 2

I thought this midterm was much easier than the last...however I thought the first midterm was fairly doable ... and really did not do well.
Does anyone know when the grades will be released?
by Alison Perkins 2B
Sun Nov 22, 2020 8:12 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Linear Strucutres
Replies: 6
Views: 28

Re: Linear Strucutres

Linear structures should have bonds of 180 degrees
by Alison Perkins 2B
Sun Nov 22, 2020 8:11 pm
Forum: General Science Questions
Topic: # of chem posts
Replies: 27
Views: 334

Re: # of chem posts

jasmineculilap_2J wrote:You need 5 posts per week, so 35 posts are needed.

Do general questions and jokes count? Or strictly chemistry material?
by Alison Perkins 2B
Sun Nov 22, 2020 8:10 pm
Forum: General Science Questions
Topic: # of chem posts
Replies: 27
Views: 334

Re: # of chem posts

Summer_Corona 3F wrote:By this Sunday you should have 35 posts.


If we missed a week can we make extra posts in the next week to make up for it?
by Alison Perkins 2B
Sun Nov 22, 2020 8:08 pm
Forum: Shape, Structure, Coordination Number, Ligands
Topic: shape, structure
Replies: 4
Views: 15

Re: shape, structure

I am not really sure...but what may help is to know the structures that go with different VSEPR notations...because if molecules have the same VSEPR structure they have the same shape.

Ex: CH4 and CCl4 are both notated as AX4...which always has a tetrahedral shape.

I hope that helps somewhat !
by Alison Perkins 2B
Sun Nov 22, 2020 8:05 pm
Forum: Student Social/Study Group
Topic: Post All Chemistry Jokes Here
Replies: 8753
Views: 1489546

Re: Post All Chemistry Jokes Here

Why do chemists like nitrates so much?
They're cheaper than day rates!
by Alison Perkins 2B
Sun Nov 22, 2020 8:05 pm
Forum: Student Social/Study Group
Topic: Post All Chemistry Jokes Here
Replies: 8753
Views: 1489546

Re: Post All Chemistry Jokes Here

What's the dullest element? Bohrium!
by Alison Perkins 2B
Sun Nov 22, 2020 8:04 pm
Forum: Sigma & Pi Bonds
Topic: Pi bonds and Sigma bonds
Replies: 3
Views: 22

Re: Pi bonds and Sigma bonds

I don't exactly know the theory but... sigma bond: when 2 orbitals with 1 electron each interact end to end ... that is on their internuclear axes. these bonds are also cylindrically symmetric. pi bond: when 2 orbitals with 1 electron each interact side to side. These also occur in any case where th...
by Alison Perkins 2B
Sun Nov 22, 2020 7:56 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: polarity of trans-dichlorethene
Replies: 4
Views: 26

Re: polarity of trans-dichlorethene

Yes, however since the Chlorines are on opposite sides the dipole moments cancel in terms of direction. It is different for cis-dichlorethene because the Chlorines are on the same side, so their dipole moments do not cancel. Hope that helps !!
by Alison Perkins 2B
Sun Nov 22, 2020 7:53 pm
Forum: Administrative Questions and Class Announcements
Topic: Thanksgiving
Replies: 26
Views: 206

Re: Thanksgiving

I believe we will still have them seeing as they are pre recorded.
Also will there be discussions on thursday or friday?
by Alison Perkins 2B
Sun Nov 22, 2020 7:48 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: memorizing molecular shapes
Replies: 3
Views: 13

Re: memorizing molecular shapes

Will Dr. Lavell be telling us which ones we should memorize for the final then or should we assume all?
by Alison Perkins 2B
Sun Nov 22, 2020 7:46 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Lecture 20 Example 2
Replies: 1
Views: 12

Lecture 20 Example 2

I am confused as to how we are supposed to find the structure of SO3 ^-2 One resonance structure with all single bonds has a lone pair in a 4th region of electron density, however with a double bond there are only 3 regions. Why is it that it is still trigonal pyramidral instead of trigonal planar ....
by Alison Perkins 2B
Mon Nov 16, 2020 3:35 pm
Forum: Octet Exceptions
Topic: Xenon Textbook 2C.11
Replies: 2
Views: 21

Xenon Textbook 2C.11

This is probably a simple answer ... but I forget why Xe is allowed to have 12 valence e- in molecules.
What makes Xe and As and other elements like this able to have more than 8 valence e- ?
by Alison Perkins 2B
Sun Nov 15, 2020 6:48 pm
Forum: Electron Configurations for Multi-Electron Atoms
Topic: Textbook 1E.19
Replies: 1
Views: 21

Textbook 1E.19

This problem asks for the ground state of listed ions.
I am confused as to why Sb^(3+) = [Kr]4d^10 5s^2, while Sn^(4+) = [Kr]4d^10...is this because 5s would be filled after 4d?
by Alison Perkins 2B
Sun Nov 15, 2020 6:43 pm
Forum: Electron Configurations for Multi-Electron Atoms
Topic: Textbook 1E.23
Replies: 4
Views: 37

Re: Textbook 1E.23

Hi! Correct me if I'm wrong, but I think you have confused unpaired electrons with valence electrons. Since Ga, Ge, As, Se, and Br are all p-block elements, the number of unpaired electrons for each element respectively is 1,2,3,2,1. If you are looking for the number of valence electrons for each e...
by Alison Perkins 2B
Sun Nov 15, 2020 6:42 pm
Forum: Ionic & Covalent Bonds
Topic: Textbook 2A.23
Replies: 1
Views: 10

Textbook 2A.23

"On the basis of the expected charges on the monatomic ions, give the chemical formula of each of the following compounds: (a) magnesium arsenide; (b) indium(III) sulfide; (c) aluminum hydride; (d) hydrogen telluride; (e) bismuth(III) fluoride."

Can someone explain a, b, and e please?
by Alison Perkins 2B
Sun Nov 15, 2020 6:39 pm
Forum: Ionic & Covalent Bonds
Topic: Textbook 2A.5
Replies: 4
Views: 46

Textbook 2A.5

Can someone please explain how to find the ground-state e- configurations for Bi^(3+) and P^(3-)?
by Alison Perkins 2B
Sun Nov 15, 2020 6:34 pm
Forum: Electron Configurations for Multi-Electron Atoms
Topic: Textbook 1E.23
Replies: 4
Views: 37

Textbook 1E.23

The question reads: "The elements Ga, Ge, As, Se, and Br lie in the same period in the periodic table. Write the electron configuration expected for the ground-state atoms of these elements and predict how many unpaired electrons, if any, each atom has. Seeing as these all go across the period ...
by Alison Perkins 2B
Sun Nov 15, 2020 6:28 pm
Forum: Electron Configurations for Multi-Electron Atoms
Topic: Textbook 1E.25
Replies: 1
Views: 15

Textbook 1E.25

The textbook question reads: "Give the notation for the valence-shell configuration (including the outermost d-electrons) of (a) the alkali metals; (b) Group 15 elements; (c) Group 5 transition metals; (d) the “coinage” metals (Cu, Ag, Au)." I know how to give a notation for a single atom,...
by Alison Perkins 2B
Wed Nov 04, 2020 3:02 pm
Forum: Trends in The Periodic Table
Topic: Nuclear Charge
Replies: 6
Views: 30

Re: Nuclear Charge

The atomic radius decreases because of the increasing amount of protons in the nucleus, which creates a more polar charge and pulls electrons closer to the nucleus in their orbit due to increased stability.
by Alison Perkins 2B
Wed Nov 04, 2020 3:00 pm
Forum: Lewis Structures
Topic: Coordinate Covalent Bonds & Lewis Acid-base Reactions
Replies: 6
Views: 47

Re: Coordinate Covalent Bonds & Lewis Acid-base Reactions

I know that a Lewis Acid is an atom that can accept a pair of electrons, and a Lewis Base is an atom that can donate a pair of electrons. For instance, F + BF3 --> BF4 is a Lewis Acid-Lewis Base reaction, creating an acid-base adduct. I am unsure if we need to label these concepts in our Lewis Struc...
by Alison Perkins 2B
Wed Nov 04, 2020 2:54 pm
Forum: Ionic & Covalent Bonds
Topic: Electron spin in bonds
Replies: 8
Views: 76

Re: Electron spin in bonds

Forgive me if I am wrong, but isn't spin a constant property of the electron or am I completely missing something. I believe youre right in that it is a constant property of an electron...meaning it always has some sort of spin. I think this spin can change depending on bonding, but I also think th...
by Alison Perkins 2B
Wed Nov 04, 2020 2:53 pm
Forum: Ionic & Covalent Bonds
Topic: Electron spin in bonds
Replies: 8
Views: 76

Re: Electron spin in bonds

I also have a question. If they cannot change spin, then does that inhibit what kinds of atoms are able to bond together? I am actually not sure ... I am also wondering this. I thought this just depended on the kind of bond, so a borrowed or shared electron would fall into place in terms of spin wi...
by Alison Perkins 2B
Wed Nov 04, 2020 2:49 pm
Forum: Formal Charge and Oxidation Numbers
Topic: Lecture O Formal Charge Ex
Replies: 4
Views: 20

Lecture O Formal Charge Ex

In lecture when Prof. Lavell was calculating the individual formal charges of S and O in SO4 I was very confused by the FC of the Oxygen in the molecule.Can someone explain how he did that ?
by Alison Perkins 2B
Wed Nov 04, 2020 2:45 pm
Forum: Resonance Structures
Topic: Resonance Structures
Replies: 10
Views: 62

Re: Resonance Structures

Yes! A resonance structure can be any of the possible structures (ex: In C6H6 there are 2 resonance structures bc of double bond placement. A resonance hybrid is the combination of all of these structures (ex: in C6H6 the diagram with the circle in the middle represents the resonance of those placem...
by Alison Perkins 2B
Wed Oct 21, 2020 5:12 pm
Forum: Photoelectric Effect
Topic: Sapling 2 Problem 3
Replies: 5
Views: 31

Sapling 2 Problem 3

Why is it that when we are given an energy of E, frequency of v, and wavelength of λ,
E=100 while λ and v are not altered when applied to 100 photons??
by Alison Perkins 2B
Sun Oct 11, 2020 9:38 pm
Forum: Empirical & Molecular Formulas
Topic: Difference In Formula Types
Replies: 4
Views: 27

Re: Difference In Formula Types

What is the easiest way to think about the difference between chemical, molecular and empirical formulas? I feel like I know how to figure out each one but I don't really know what each one is used for and when/where to apply it. I was also wondering this, because in problem 9 the empirical formula...
by Alison Perkins 2B
Sun Oct 11, 2020 9:36 pm
Forum: Empirical & Molecular Formulas
Topic: Formula Units [ENDORSED]
Replies: 3
Views: 114

Re: Formula Units [ENDORSED]

Hi, I'm pretty sure that when we are completing calculations, we don't necessarily have to worry about the differences between formula units and molecules. From my understanding and from what I can recall from high school chemistry, formula units are used to describe ionic compounds while molecules...
by Alison Perkins 2B
Sun Oct 11, 2020 9:31 pm
Forum: Empirical & Molecular Formulas
Topic: E15 Sulfide of a Metal
Replies: 2
Views: 35

Re: E15 Sulfide of a Metal

The molar mass of the metal hydroxide M(OH) 2 is 74.10 g/mol 21 What is the molar mass of the sulfide of this metal? What is the sulfide of a metal? A similar question asked what the chloride of a metal is. Did we learn this in class? Does anyone know the actual meaning of "sulfide of a metal&...
by Alison Perkins 2B
Sun Oct 11, 2020 9:27 pm
Forum: Empirical & Molecular Formulas
Topic: Sapling Homework 1 Q#9
Replies: 21
Views: 254

Re: Sapling Homework 1 Q#9

In the step by step answers listed, no one lists the step of multiplying each element by the smallest number to get an integer after dividing the mols by the smallest number of the three elements. I thought this was an essential step to do from the audio visual focus topics and lecture. Is everyone...
by Alison Perkins 2B
Sun Oct 11, 2020 9:21 pm
Forum: Empirical & Molecular Formulas
Topic: Sapling Hw #10
Replies: 10
Views: 101

Re: Sapling Hw #10

Hey! I was definitely stuck on this problem for a while too. The first thing I did was write out a chemical equation and check that it was balanced. The next step is to convert the mL of 2-butanone to grams. There should be a given g/mL underneath each molecule in the formula (in my question it was...

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