Search found 61 matches

Sun Jan 17, 2021 10:25 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: ICE table troubles
Replies: 16
Views: 43

Re: ICE table troubles

In one of the lectures, Lavelle gave us a list of things to keep in mind when going into a problem like the ICE table ones, and it included tips like finding what you know, what you don't know, etc. and I think that it's helpful to go through a mental inventory of these things before filling out you...
Sun Jan 17, 2021 10:23 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: Total Pressure
Replies: 12
Views: 22

Re: Total Pressure

Total pressure is all of the PARTIAL pressures added together, which can usually be solved using Kp and the rest of the given partial pressures
Sun Jan 17, 2021 10:21 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Sapling Week 1 #10
Replies: 8
Views: 26

Re: Sapling Week 1 #10

the products over reactants should equal the Kc you need to find for the question
Sun Jan 17, 2021 10:20 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Sapling #10
Replies: 4
Views: 16

Re: Sapling #10

One thing that tripped me up when I tried to solve this question was how I had to add x to the initial concentrations in order to get the answer that you plug into the program. Hope this helps!
Sun Jan 17, 2021 10:17 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Total pressure calculation
Replies: 8
Views: 23

Re: Total pressure calculation

When solving with Kp, you can set up your ICE table to solve with the equation you use to solve for concentrations to solve for individual partial pressures. From there you can find all of them and add them together for total pressure.
Sun Jan 10, 2021 6:06 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Sapling hw 5
Replies: 14
Views: 77

Re: Sapling hw 5

For this question I chose the first equation and multiplied K by 3, and took the inverse of the 3rd K, but it still comes up as wrong. Is there a problem with how I calculated it or is there a problem with the question?
Sun Jan 10, 2021 6:05 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Sapling hw 5
Replies: 14
Views: 77

Re: Sapling hw 5

AlyssaMaynard1C wrote:Is the week 1 homework due tonight or next sunday, I'm slightly confused.

The homework is due on the 17th, hope this helps!
Sun Jan 10, 2021 6:01 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: K vs Kc
Replies: 9
Views: 26

Re: K vs Kc

Kc is just K that uses the concentrations of the variables involved. Hope this helps!
Sun Jan 10, 2021 6:01 pm
Forum: Ideal Gases
Topic: Difference between real and ideal gas
Replies: 10
Views: 75

Re: Difference between real and ideal gas

As a follow-up question, if real and ideal gasses are so different than each other, why is it helpful to treat real gasses the same as ideal gasses? Would this assumption not cause problems? I have the same question, because wouldn't the violations of the ideal gas law that the real gas law present...
Sun Jan 10, 2021 5:58 pm
Forum: Ideal Gases
Topic: Kc vs Kp
Replies: 109
Views: 907

Re: Kc vs Kp

You would use Kc if the moles are given, and if the partial pressures are given, use Kp. If both are given then you would have to use the Ideal Gas Law along with given information to convert between the two. Hope this helps!
Wed Dec 16, 2020 12:55 am
Forum: SI Units, Unit Conversions
Replies: 12
Views: 70

In a more general sense, Avogadro's number is just the amount of objects in one mole. So if you were to set up a dimensional analysis table to solve a question, you should be using Avogadro's number as (6.0221*10^23)objects/mole
Wed Dec 16, 2020 12:46 am
Forum: Student Social/Study Group
Topic: Changing Study Habits
Replies: 35
Views: 166

Re: Changing Study Habits

I think that UA/TA step ups and workshops are what made my final experience bearable in this class. These people are seriously so knowledgeable and so helpful. I'm going to at least one every week starting in 14B!
Wed Dec 16, 2020 12:30 am
Forum: Student Social/Study Group
Topic: Final Exam
Replies: 49
Views: 289

Re: Final Exam

I had enough time, but only because I rushed the questions and probably got a lot more wrong than is good for me
Wed Dec 16, 2020 12:13 am
Forum: Student Social/Study Group
Topic: Plans for Relaxing After Finals
Replies: 97
Views: 443

Re: Plans for Relaxing After Finals

Probably trying to fix the "sleep schedule" that I currently am running
Wed Dec 16, 2020 12:10 am
Forum: Acidity & Basicity Constants and The Conjugate Seesaw
Topic: Finding PH and POH
Replies: 6
Views: 54

Re: Finding PH and POH

The [OH-] is actually the concentration of OH- ions in the solution, and the pOH is the indication of the "power" of the hydroxide ions, so the number for pOH will be the negative log of [OH]-, which means it will be bigger
Tue Dec 15, 2020 11:31 pm
Forum: Empirical & Molecular Formulas
Topic: Empirical Formulas
Replies: 4
Views: 34

Re: Empirical Formulas

In order to find the empirical formula given the molecular formula, the best way is to divide each number of atoms by the greatest common denominator. Ex. C3H6O3 becomes CH2O
Sun Dec 06, 2020 7:00 pm
Forum: Naming
Topic: Sapling 1
Replies: 34
Views: 166

Re: Sapling 1

The ligand's "other name" will take priority in ordering the compounds in alphabetical order. Hope this helps!
Sun Dec 06, 2020 6:55 pm
Forum: Naming
Topic: Ferrate
Replies: 5
Views: 38

Re: Ferrate

These elements are just differently named due to the original Roman name. Elements like Lead are instead Plumbum, and Tin Stannum. Hope this helps!
Sun Dec 06, 2020 6:49 pm
Forum: Naming
Topic: Naming Coordination Compounds
Replies: 5
Views: 59

Re: Naming Coordination Compounds

As said above, I think the best way is to partition the ligands, transition metal, then the anion afterwards, and then arrange/add the extra parts afterwards.
Sun Dec 06, 2020 6:46 pm
Forum: Naming
Topic: -ate
Replies: 17
Views: 83

Re: -ate

Only use -ate for negative charge, and neutral/positive compounds will just end in the name of the last part
Sun Dec 06, 2020 6:43 pm
Forum: Naming
Topic: Naming [Co(CN)5(OH2)]2-
Replies: 5
Views: 24

Re: Naming [Co(CN)5(OH2)]2-

I think this is still aqua and not hydroxo, since the OH2 would signify water just in a different order. Hope this helps!
Sun Nov 29, 2020 11:02 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Shape Names
Replies: 50
Views: 282

Re: Shape Names

2 lp and 2 bonds is bent, as well as 2 lp and 1 lp. Hope this helps!
Sun Nov 29, 2020 11:01 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Equatorial and Axial
Replies: 2
Views: 8

Re: Equatorial and Axial

I think the general rule is that there is less crowding in equatorial bonds rather than axial ones, so atoms will tend towards equatorial first, but I'm not sure and he will probably cover it in lecture at some point. Hope this helps!
Sun Nov 29, 2020 10:58 pm
Forum: Hybridization
Topic: Sapling #12
Replies: 27
Views: 171

Re: Sapling #12

to find the hybridization for the oxygen, you have to count the bonded ATOMS (not just bonds!) and the lone pairs as well, so it would come out to 2 atoms and 2 lone pairs, which is an sp3 orbital
Sun Nov 29, 2020 10:55 pm
Forum: Hybridization
Topic: Sapling #11
Replies: 19
Views: 109

Re: Sapling #11

This example specifies hybridization for the Phosphorus atoms, so you would count the three bonded atoms, the three O atoms, and then the lone pair, and that would lead to 4 groups, which means it's an sp3 orbital
Sun Nov 29, 2020 10:52 pm
Forum: Hybridization
Topic: Single Bonds and Sigma Bonds
Replies: 23
Views: 108

Re: Single Bonds and Sigma Bonds

Single bonds are only composed of Sigma bonds, however they also exist in double and triple bonds
Tue Nov 24, 2020 9:54 pm
Forum: Octet Exceptions
Topic: Phosphate
Replies: 7
Views: 37

Re: Phosphate

Phosphate is in the 3p orbital, so it has access to the 3d orbital of electrons, so it can fill that shell to compensate.
Tue Nov 24, 2020 9:49 pm
Forum: Formal Charge and Oxidation Numbers
Topic: oxidation numbers and resonance
Replies: 3
Views: 28

Re: oxidation numbers and resonance

Oxidation numbers are hypothetical values, so using formal charge for specific resonance structures is probably better.
Tue Nov 24, 2020 9:33 pm
Forum: Electronegativity
Topic: How to memorize
Replies: 6
Views: 67

Re: How to memorize

A general rule to also remember could be that going down the table decreases more than going towards the left. Hope this helps!
Tue Nov 24, 2020 9:29 pm
Forum: Ionic & Covalent Bonds
Topic: Stronger Melting Point
Replies: 9
Views: 68

Re: Stronger Melting Point

Ionic bonds are the highest energy bonds that we know of in this class up until now, so it would have a higher melting point.
Tue Nov 24, 2020 9:27 pm
Forum: Ionic & Covalent Bonds
Topic: Textbook Question 1A.13
Replies: 4
Views: 41

Re: Textbook Question 1A.13

The parentheses on the NH2 denote that the 2 hydrogens are only bonded to the N, which is bonded to the first C, which is denoted by how COOH is after the NH2
Sun Nov 15, 2020 5:58 pm
Forum: Octet Exceptions
Topic: Octet Rule Exceptions
Replies: 20
Views: 169

Re: Octet Rule Exceptions

If somebody could help me make a list of all of the exceptions for this midterm, that would help a lot. Right now I have the first four elements, elements past period 3 can exceed, and group 13 only need 6. Thanks!
Sun Nov 15, 2020 5:31 pm
Forum: Ionic & Covalent Bonds
Replies: 7
Views: 48

AlyssaMaynard1C wrote:Will we be able to look at a chart on the midterm for the electronegativity and other descriptions?

I'm pretty sure electronegativity will be given but all the other trends are probably just comparisons
Sun Nov 15, 2020 5:29 pm
Forum: Ionic & Covalent Bonds
Topic: Electronegativity
Replies: 18
Views: 104

Re: Electronegativity

I would suggest learning and memorizing the trends given, and also the fact that electronegativity differences between 0.4 and 1.7 are polar bonds. They should be given on the test. Hope this helps!
Sun Nov 15, 2020 5:26 pm
Forum: Ionic & Covalent Bonds
Topic: Sulfate
Replies: 8
Views: 28

Re: Sulfate

Any element past the 3rd period of the periodic table is able to have an expanded octet of electrons due to having access to more values of l.
Sun Nov 15, 2020 5:21 pm
Forum: Ionic & Covalent Bonds
Topic: What do delta positive and delta negative refer to?
Replies: 3
Views: 28

Re: What do delta positive and delta negative refer to?

The negative sign in this unit usually means the subject has an attractive force. This would mean that the part of the atom that has the highest electronegativity would have a delta negative. Hope this helped!
Sun Nov 08, 2020 10:16 pm
Forum: Electronegativity
Topic: Noble Gases
Replies: 40
Views: 1711

Re: Noble Gases

Noble Gases are exceptions from the rules because they are out of the running so to speak for gaining/losing electrons
Sun Nov 08, 2020 10:15 pm
Forum: Ionic & Covalent Bonds
Topic: Electron Affinity
Replies: 8
Views: 63

Re: Electron Affinity

Electron affinity measures how inclined an atom is to take on another electron
Sun Nov 08, 2020 10:14 pm
Forum: Ionic & Covalent Bonds
Replies: 38
Views: 220

More protons equals more positive charge to attract electrons
Sun Nov 08, 2020 10:13 pm
Forum: Ionic & Covalent Bonds
Topic: Sapling Question #3
Replies: 6
Views: 60

Re: Sapling Question #3

Any element past period 3 of the periodic table can form more bonds than accounted for by the octet rule as dictated by its d orbital having the capacity to take in more electrons
Sun Nov 08, 2020 10:12 pm
Forum: Formal Charge and Oxidation Numbers
Topic: Formal charges and stability
Replies: 5
Views: 58

Re: Formal charges and stability

I think any charge that sums up to +2 should be counted the same in any configuration just based on the fact that it has charge as opposed to being neutral.
Sun Nov 01, 2020 6:22 pm
Forum: Properties of Light
Topic: Do we need to know the ranges of waves on the electromagnetic spectrum?
Replies: 7
Views: 56

Re: Do we need to know the ranges of waves on the electromagnetic spectrum?

I think we only need to know ranges for prominent ones like visible and UV. Hope this helps!
Sun Nov 01, 2020 6:08 pm
Forum: Photoelectric Effect
Topic: Lyman Series
Replies: 30
Views: 199

Re: Lyman Series

Adding on to other answers, the Balmer series would be n=2 and the Paschen series would be n=3. Hope this helps!
Sun Nov 01, 2020 6:01 pm
Forum: Properties of Light
Topic: spectral lines
Replies: 6
Views: 48

Re: spectral lines

It would depend on the direction relative to which the electron moved up and down the energy levels.
Sun Nov 01, 2020 5:39 pm
Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
Topic: Week 2,3,4 Sapling HW
Replies: 5
Views: 72

Re: Week 2,3,4 Sapling HW

I haven't seen chem community in a while, sorry about that! To answer your question if you still need it, I used a different variable of the Rydberg equation that uses a different R constant. So if you wanted to do the question using the equation that he gives us you would have to find out the frequ...
Sun Nov 01, 2020 5:32 pm
Forum: Ionic & Covalent Bonds
Topic: hydrogen
Replies: 19
Views: 231

Re: hydrogen

Hydrogen bonds are only able to be established on those 3 elements due to how electronegative they are relative to Hydrogen
Sun Oct 25, 2020 6:17 pm
Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
Topic: Rydberg Equation and Negative Signs
Replies: 11
Views: 87

Re: Rydberg Equation and Negative Signs

Usually, the question will ask for something related to the magnitude of energy that was released. However, when you use the Rydberg Constant, you will usually be solving for the energy released by one single electron, so relatively, the energy will be negative. Hope this helps!
Sun Oct 25, 2020 6:15 pm
Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
Topic: When n= infinity, the energy required = 0
Replies: 4
Views: 45

Re: When n= infinity, the energy required = 0

Because when the denominator is infinity, the entire fraction equates to zero, since it is an infinitesimally small fraction. Hope this helps!
Sun Oct 25, 2020 6:14 pm
Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
Topic: Atomic Spectra Post Module Assessment #28
Replies: 1
Views: 42

Re: Atomic Spectra Post Module Assessment #28

It would be D. The question states that there are 1,650,763.73 wavelengths in one meter, so in order to find the length of one wavelength, you have to divide 1 meter by 1,650,763.73, in order to get the wavelength, 6.058*10^-7. From there you can use E=h(c/wavelength) in order to find the energy req...
Sun Oct 25, 2020 6:10 pm
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: Electrostatic potential energy
Replies: 2
Views: 26

Re: Electrostatic potential energy

Whereas electrostatic potential energy is the energy between two charges, quantized energy of an electron is only exclusively dealing with one electron. Hope this helps!
Sun Oct 25, 2020 6:07 pm
Forum: Properties of Light
Topic: Balmer or Lyman Series
Replies: 9
Views: 50

Re: Balmer or Lyman Series

Rather than the starting point, the Balmer and Lyman series denote the endings of an energy change. The Balmer series consists of visible light, ending in n=2, and the Lyman series consists of UV light, ending in n=1. Each lower energy level (Ex. n=2 to n=1 as opposed to n=3 to n=2), has a higher en...
Sun Oct 25, 2020 6:04 pm
Forum: SI Units, Unit Conversions
Topic: Can someone explain Avogrado's #?
Replies: 8
Views: 91

Re: Can someone explain Avogrado's #?

Avogadro's number is just the amount of OBJECTS in a mole of x. So if I were to say that there is 1 mol of carrots in Billy's garden, then there'd be 6.0221*10^23 carrots in his garden. Hope this helps!
Sun Oct 18, 2020 4:02 pm
Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
Topic: Rydberg's Constant
Replies: 2
Views: 12

Re: Rydberg's Constant

Thanks for the clear explanation, I understand now!
Sun Oct 18, 2020 3:46 pm
Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
Topic: Rydberg's Constant
Replies: 2
Views: 12

Rydberg's Constant

On Dr. Lavelle's lectures, he uses 3.29*10^15, but when I use it in the Rydberg equation it's 1.07*10^7, could anyone explain the difference to me? Thanks!
Sun Oct 18, 2020 3:45 pm
Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
Topic: Week 2,3,4 Sapling HW
Replies: 5
Views: 72

Re: Week 2,3,4 Sapling HW

For this question, you first have to look at the given wavelength, which is 6.563 *10^-7 m (converted from nanometers). Matching this with the numbers given on the EM spectrum tells us that this light is on the wavelength of visible light, which fits in the Balmer series, which means that the light ...
Sat Oct 17, 2020 6:38 pm
Forum: Properties of Electrons
Topic: Bound electron v. Free electron
Replies: 5
Views: 47

Re: Bound electron v. Free electron

I like to think of it this way: the electrons at lower energy levels have lower energy because they're essentially being held still due to being closer to the nucleus. Hope this helps!
Wed Oct 07, 2020 5:57 pm
Forum: Significant Figures
Topic: Sig Fig usage on exams
Replies: 11
Views: 109

Re: Sig Fig usage on exams

As people have stated above, I use the sig figs presented in the problem and only round at the end. If there are multiple numbers with different amounts of sig figs in the problem, then I just round to 4 decimal points. Hopefully Dr. Lavelle will mention this in lecture soon.
Wed Oct 07, 2020 5:48 pm
Forum: Balancing Chemical Reactions
Topic: Fractions
Replies: 34
Views: 566

Re: Fractions

I think in one of the modules Prof. Lavelle specifically states that you need to simplify out fraction stoichiometric ratios. Hope this helps!
Wed Oct 07, 2020 5:44 pm
Forum: SI Units, Unit Conversions
Topic: Formula Units
Replies: 8
Views: 68

Re: Formula Units

The textbook states that Avogadro's CONSTANT is a pure number with no units, while Avogadro's NUMBER can have any unit pertaining to objects. Hope this helps!
Wed Oct 07, 2020 5:41 pm
Forum: Empirical & Molecular Formulas
Topic: Outline 1 Question L39
Replies: 3
Views: 33

Re: Outline 1 Question L39

Given: 1.5g Sn 26.45g Crucible Mass 28.35g Mass of Crucible + Product From here, you can calculate the mass of Oxygen, 28.35g (total) - 26.45g (crucible) = 1.9g product 1.9g product - 1.5g Sn = .4g O Use this .4g O in order to find out the moles of O .4g O/16.11g O/mol = .025 Use given 1.5g Sn in or...
Tue Oct 06, 2020 4:36 pm
Forum: Limiting Reactant Calculations
Topic: Sapling #10 Step by Step
Replies: 6
Views: 64

Re: Sapling #10 Step by Step

As VSU_2G stated above, you would only be using a molar mass conversion of 2 butanone, or C4H8O, which is roughly 72 g/mol, hopefully this helps!