Search found 68 matches

Sun Jan 24, 2021 11:32 am
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: Heat released/ gained
Replies: 17
Views: 157

Re: Heat released/ gained

Think about it as when you break a bond, you need energy to break it. When you form a bond, the atoms are now more stable, releasing the extra energy.
Sun Jan 24, 2021 11:29 am
Forum: Phase Changes & Related Calculations
Topic: Determining Stronger Acids
Replies: 18
Views: 50

Re: Determining Stronger Acids

Small pKa is stronger acid. Think about it like the pH scale, lower pH means more H3O which means stronger acid.
Sun Jan 24, 2021 11:27 am
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: enthalpy units
Replies: 3
Views: 14

Re: enthalpy units

I think its kJ/mol^-1. (someone correct me if I'm wrong)
Sun Jan 24, 2021 11:26 am
Forum: Phase Changes & Related Calculations
Topic: Steam causing severe burns
Replies: 19
Views: 68

Re: Steam causing severe burns

The steam will cool down significantly before it reaches your face, so it wouldn't be hot enough to cause severe burns
Sun Jan 24, 2021 11:15 am
Forum: Phase Changes & Related Calculations
Topic: No Heat Change
Replies: 13
Views: 34

Re: No Heat Change

The energy being put into the system can be increasing, ie increasing the heat on a stove to boil water. That extra energy is going to break water bonds faster, but it is not going to increase the temperature of the water.
Sun Jan 17, 2021 12:00 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: When is it safe to approximate?
Replies: 3
Views: 19

Re: When is it safe to approximate?

That's what I assumed, but in the problem, Kb was 6.605x10^-5, and the concentrations of the OH- and the BH+ was 1.09x10^-5. I couldn't solve that without approximating. If you plug that in, you will get a [B] that's less than the concentration of [OH-].
Sun Jan 17, 2021 11:58 am
Forum: Ideal Gases
Topic: Q and K relationship
Replies: 22
Views: 92

Re: Q and K relationship

I just think of K as a baseline, and everything else that is not K is Q. If Q is bigger than K, it will favor reactants, and if Q is less than K, it will favor products.
Sun Jan 17, 2021 11:56 am
Forum: Ideal Gases
Topic: Gas for equilibrium equation
Replies: 8
Views: 31

Re: Gas for equilibrium equation

C stands for concentration and p stands for partial pressure
Sun Jan 17, 2021 11:54 am
Forum: Ideal Gases
Topic: Kc vs. Kp
Replies: 14
Views: 41

Re: Kc vs. Kp

Kp is calculated the same way as kc.
Sun Jan 17, 2021 11:53 am
Forum: Equilibrium Constants & Calculating Concentrations
Topic: When is it safe to approximate?
Replies: 3
Views: 19

When is it safe to approximate?

On Sapling question #5 WK2, I saw that kb was 10^-5 so I tried approximating, but it ended up not working. I needed to include to the -x on the base in order to get the right answer. When is it ok to approximate and when is it not? I thought that when kb or ka was less than 10^-3, it was ok.
Sun Jan 10, 2021 5:07 pm
Forum: Ideal Gases
Topic: partial pressures
Replies: 14
Views: 63

partial pressures

What do partial pressures really mean? Why can they be converted to concentrations? I'm just not quite understanding what the term means.
Sun Jan 10, 2021 5:05 pm
Forum: Ideal Gases
Topic: Non-Ideal gases?
Replies: 26
Views: 123

Re: Non-Ideal gases?

So do non-ideal gases not appear in biological systems?
Sun Jan 10, 2021 4:59 pm
Forum: Non-Equilibrium Conditions & The Reaction Quotient
Topic: Water
Replies: 28
Views: 95

Re: Water

H20 is only included when it is not a solvent and changes significantly when the reaction occurs.
Sun Jan 10, 2021 4:57 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Units
Replies: 27
Views: 97

Re: Units

Bars and atm are very close. But bars is officially the SI unit.
Sun Jan 10, 2021 4:55 pm
Forum: Ideal Gases
Topic: value of R
Replies: 24
Views: 77

Re: value of R

You use the value of R that cancels out the other units.
Tue Dec 15, 2020 11:15 am
Forum: Naming
Topic: Ligand use -ate
Replies: 18
Views: 108

Re: Ligand use -ate

When the entire coordination compound (the stuff inside the square brackets) is negatively charged.
Tue Dec 15, 2020 11:15 am
Forum: Conjugate Acids & Bases
Topic: Sapling 14
Replies: 6
Views: 73

Re: Sapling 14

It would be neutral!
Tue Dec 15, 2020 11:09 am
Forum: Identifying Acidic & Basic Salts
Topic: What is a Salt?
Replies: 9
Views: 68

Re: What is a Salt?

Its an ionic compound meaning its bounded by ionic bonds. A cation + and anion = salt
Fri Dec 11, 2020 9:34 am
Forum: Determining Molecular Shape (VSEPR)
Topic: AX3E2
Replies: 7
Views: 62

Re: AX3E2

Thank you! It makes a lot of sense now.
Thu Dec 10, 2020 1:19 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: AX3E2
Replies: 7
Views: 62

AX3E2

Why is it that with 5 regions of election density and two lone pairs, the shape is t shaped instead of trigonal planar. I'm imagining a molecule with lone pairs on the top and bottom, and three atoms bounded to the central atom on its equator (is that the right word?). Instead, in t shaped, the lone...
Sun Dec 06, 2020 2:48 pm
Forum: Coordinate Covalent Bonds
Topic: Coordinate Covalent Bonds and Covalent Bonds
Replies: 7
Views: 70

Re: Coordinate Covalent Bonds and Covalent Bonds

A coordinate covalent bond needs to have one species donate both electrons. A normal covalent bond is just when two species each have one electron and they share both.
Sun Dec 06, 2020 2:43 pm
Forum: Bronsted Acids & Bases
Topic: bronsted vs. lewis acid
Replies: 10
Views: 75

Re: bronsted vs. lewis acid

I think this post is very useful: viewtopic.php?t=38472
Sun Dec 06, 2020 2:39 pm
Forum: Calculating pH or pOH for Strong & Weak Acids & Bases
Topic: Does pH indicate strength of an acid?
Replies: 26
Views: 146

Re: Does pH indicate strength of an acid?

Yes. The lower the pH, the more higher the concentration of [H30+] which means it's a stronger acid.
Sun Dec 06, 2020 2:36 pm
Forum: Properties & Structures of Inorganic & Organic Acids
Topic: pH Chart
Replies: 16
Views: 112

Re: pH Chart

I think it might be a good idea to know some of the items on the chart, but we probably won't be tested on what is the pH of vinegar.
Sun Dec 06, 2020 2:33 pm
Forum: Amphoteric Compounds
Topic: Amphoteric
Replies: 11
Views: 207

Re: Amphoteric

An amphoteric compound has both acidic and basic character, meaning it can react as an acid and base. An amphiprotic compound can be a proton donor and proton acceptor. Just think of the "pro" in protic and know it means proton acceptor or donor.
Sun Nov 29, 2020 2:39 pm
Forum: Hybridization
Topic: Sapling #20
Replies: 4
Views: 22

Re: Sapling #20

Thank you for explaining :)
Sun Nov 29, 2020 2:38 pm
Forum: Coordinate Covalent Bonds
Topic: Hydrogen bonds
Replies: 19
Views: 125

Re: Hydrogen bonds

It's the difference in electronegativity. The difference between C and H aren't great enough to cause hydrogen bonding.
Sun Nov 29, 2020 2:36 pm
Forum: Polarisability of Anions, The Polarizing Power of Cations
Topic: Sapling Q.20
Replies: 7
Views: 53

Re: Sapling Q.20

Oh. I thought it was polar because it had a charge. Does this not make the entire molecule polar?
Sun Nov 29, 2020 2:35 pm
Forum: Electronegativity
Topic: polar vs nonpolar
Replies: 19
Views: 86

Re: polar vs nonpolar

The difference has to be between 0.5 and 1.6
Sun Nov 29, 2020 2:34 pm
Forum: Coordinate Covalent Bonds
Topic: Hydrogen bonding
Replies: 15
Views: 112

Re: Hydrogen bonding

Hydrogen bonding is not a intermolecular force, it is an intramolecular force which means it happens between molecules.
Sun Nov 29, 2020 2:32 pm
Forum: Hybridization
Topic: Sapling #20
Replies: 4
Views: 22

Sapling #20

I drew As to have 3 single bonds and 1 double bond. The question asked what is the hybridization of the As atom. I thought it was sp^3 d because it had 5 bonds if you count the double bond as two. The answer according to sapling was sp^3. Can someone explain this?
Sun Nov 22, 2020 9:01 pm
Forum: Trends in The Periodic Table
Topic: Ionic Character
Replies: 11
Views: 93

Re: Ionic Character

The larger the difference between electronegativity, the more ionic the bond will be. The less, the more covalent.
Sun Nov 22, 2020 9:00 pm
Forum: Hybridization
Topic: Double bonds structures
Replies: 5
Views: 69

Re: Double bonds structures

[quote="Nicole Bruno Dis 1B"]If these atoms are essentially locked into position in the presence of pi double (or triple) bonds, then would they even have resonance structures??

Usually in resonance structures, their bonds are a mix between the different structures.
Sun Nov 22, 2020 3:57 pm
Forum: Dipole Moments
Topic: Trans-dichloroethene
Replies: 5
Views: 17

Re: Trans-dichloroethene

Lol I don't know why I had CH4 in my head. Ok it makes sense now. Thank you
Sun Nov 22, 2020 3:49 pm
Forum: Dipole Moments
Topic: Trans-dichloroethene
Replies: 5
Views: 17

Re: Trans-dichloroethene

But they're not pointing in opposite directions? Using this generic picture of CH4, which is the same shape(I think), putting the chlorines on there wouldn't make them equal and opposite. https://lh5.googleusercontent.com/-mlkw7FMInLg/TXPZehEru-I/AAAAAAAAAA4/pmIkpGaxXpo/s1600/CH4.jpg . Do the hydrog...
Sun Nov 22, 2020 3:40 pm
Forum: Dipole Moments
Topic: Trans-dichloroethene
Replies: 5
Views: 17

Trans-dichloroethene

In the lecture on Friday, trans-dichloroethene was mentioned as a non-polar molecule because of the vectors of the dipole moments being equal and opposite. I don't quite get how it is equal and opposite. I thought the vectors are pointing towards the chlorines and thus be more negative in different ...
Mon Nov 16, 2020 9:27 am
Forum: Polarisability of Anions, The Polarizing Power of Cations
Topic: dipole moments
Replies: 10
Views: 54

Re: dipole moments

A negative dipole is the more electronegative element because they pull harder on the electrons compared to the other atom.
Mon Nov 16, 2020 9:19 am
Forum: Bond Lengths & Energies
Topic: Bond Length
Replies: 5
Views: 44

Re: Bond Length

Usually I just choose whichever one the actual bond length is closer to. Although I'm not sure if that's correct. What do you guys do?
Mon Nov 16, 2020 9:17 am
Forum: Dipole Moments
Topic: Which interactions are intermolecular?
Replies: 7
Views: 58

Re: Which interactions are intermolecular?

I think about like this: inter- between and intra- within
Mon Nov 16, 2020 9:16 am
Forum: Electronegativity
Topic: determining electronegativity
Replies: 31
Views: 253

Re: determining electronegativity

Top right corner (F) should be the most electronegative. As you move left or down, the electronegativity decreases
Mon Nov 16, 2020 9:14 am
Forum: Formal Charge and Oxidation Numbers
Topic: Oxidation Number
Replies: 8
Views: 90

Re: Oxidation Number

What are some of the exceptions to oxidation numbers?
Sun Nov 08, 2020 4:13 pm
Forum: Formal Charge and Oxidation Numbers
Topic: Oxidation number?
Replies: 8
Views: 77

Re: Oxidation number?

I remember learning oxidations in high school, but I'm confused reading other posts about them. Are they just the number of electrons an atom gains/loses frequently?
Sun Nov 08, 2020 4:10 pm
Forum: Lewis Structures
Topic: Lone Pairs Question
Replies: 22
Views: 119

Re: Lone Pairs Question

Lone pairs are valance electrons that are not participating in any bond nor sharing.
Sun Nov 08, 2020 4:07 pm
Forum: Octet Exceptions
Topic: selenium
Replies: 6
Views: 40

Re: selenium

Selenium is in the same group as sulfur which in lecture was an example of an expanded octet (SO4^2-)
Sun Nov 08, 2020 4:03 pm
Forum: Resonance Structures
Topic: Valence Electrons [ENDORSED]
Replies: 43
Views: 326

Re: Valence Electrons[ENDORSED]

Cutting out the d block, the first group (column) has 1 VE and the second group has 2VE, then hopping over to the p-block, the column with Boron has 3VE and so on until the noble gases which have 8.
Sun Nov 08, 2020 3:59 pm
Forum: Properties of Electrons
Topic: Electron Spin
Replies: 7
Views: 82

Re: Electron Spin

So just to clarify, this angular momentum is what causes it to differentiate themselves in experiments? Also, what would be the difference between the up and down spin?
Sun Nov 01, 2020 5:15 pm
Forum: Ionic & Covalent Bonds
Topic: hydrogen
Replies: 19
Views: 241

Re: hydrogen

N, O, and F are super electronegative because they have minimal shielding (due to having less electrons) and they are really close to their octet. Hydrogen, having only one proton, can't hold onto its single electron as well, so the N, O , and F essentially hog them.
Sun Nov 01, 2020 5:12 pm
Forum: Octet Exceptions
Topic: Reasoning for Octet Exception
Replies: 19
Views: 456

Re: Reasoning for Octet Exception

Are expanded octets more unstable than regular octets?
Sun Nov 01, 2020 5:09 pm
Forum: Ionic & Covalent Bonds
Topic: Octet Rule Lecture 12
Replies: 7
Views: 44

Re: Octet Rule Lecture 12

How do you know whether an atom has to gain electrons to fill its shell to become stable, or lose enough electrons to drop to the lower shell to be most stable? Usually elements that are closer to 8 electrons (5+) gain electrons whereas elements that have less (3-) lose electrons because it would t...
Sun Nov 01, 2020 5:05 pm
Forum: Lewis Structures
Topic: Carbon and triple bonds
Replies: 7
Views: 53

Re: Carbon and triple bonds

From this wikipedia article, https://en.wikipedia.org/wiki/Quadruple_bond, There seems to be a quadruple bond between Re - Re. It states that quadruple bonds usually form with d-block elements.
Sun Nov 01, 2020 5:00 pm
Forum: Ionic & Covalent Bonds
Topic: Covalent Bonds
Replies: 9
Views: 76

Re: Covalent Bonds

So which one is it? Is ionic or covalent stronger? There are differing answers here.
Sat Oct 24, 2020 10:30 pm
Forum: DeBroglie Equation
Topic: Advice for Correct Units for Midterm
Replies: 8
Views: 81

Re: Advice for Correct Units for Midterm

Thank you so much for the PSA! I make so many mistakes because I work to fast and skip units.
Sat Oct 24, 2020 10:27 pm
Forum: Quantum Numbers and The H-Atom
Topic: Stern and Gerlach Experiment
Replies: 1
Views: 29

Stern and Gerlach Experiment

In the Stern and Gerlach Experiment, I don't really understand how the electron's "spin" makes it go different directions. Is there a way I can visualize spin better?
Sat Oct 24, 2020 10:22 pm
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: s and p Orbitals
Replies: 4
Views: 59

Re: s and p Orbitals

To add on to the post above, shielding is when electrons closer to the nucleus partially blocks the attraction between the positive nucleus and the negative electrons from the electrons further away.
Sat Oct 24, 2020 10:14 pm
Forum: *Particle in a Box
Topic: Midterm 1
Replies: 16
Views: 258

Re: Midterm 1

I wonder if some of the orbital stuff we were getting into is going to be on the midterm.
Sat Oct 24, 2020 10:11 pm
Forum: Heisenberg Indeterminacy (Uncertainty) Equation
Topic: Uncertainty equation with ±
Replies: 10
Views: 57

Re: Uncertainty equation with ±

You multiply by two because it will take into account the range of values.
Sun Oct 18, 2020 4:49 pm
Forum: Administrative Questions and Class Announcements
Topic: More modules
Replies: 3
Views: 29

Re: More modules

Even just videos would be fine.
Sun Oct 18, 2020 7:40 am
Forum: Properties of Electrons
Topic: 1b 15
Replies: 1
Views: 14

1b 15

1B.15 The velocity of an electron that is emitted from a metallic surface by a photon is 3.6x 10^3 km/s-1 . (a) What is the wavelength of the ejected electron? (b) No electrons are emitted from the surface of the metal until the frequency of the radiation reaches 2.50x 10^16 Hz. How much energy is r...
Sat Oct 17, 2020 2:59 pm
Forum: Administrative Questions and Class Announcements
Topic: More modules
Replies: 3
Views: 29

More modules

I quite like the modules on the website and I was wondering if you can post extra videos of past lectures for the following weeks. Sometimes, I like to jump ahead because it takes my brain extra time to process things. These last two weeks have been easier because I had the chance to view the materi...
Sat Oct 17, 2020 2:48 pm
Forum: Properties of Light
Topic: Textbook Self Test 1b.3a
Replies: 3
Views: 28

Re: Textbook Self Test 1b.3a

You did the right first step by converting 3.63 eV to Joules. Next the question is asking for the longest wavelength of electromagnetic radiation that could eject electrons. Remember in the photoelectric effect, light hits the electrons and if the light has enough energy, the electron is ejected. If...
Sat Oct 17, 2020 2:36 pm
Forum: Properties of Light
Topic: 1B 5
Replies: 2
Views: 23

1B 5

There's a unit called keV here which I learned is a kiloelectronvolt. I'm wondering what this unit represents and if it's going to show up more and more.
Sat Oct 17, 2020 2:27 pm
Forum: Student Social/Study Group
Topic: How are you studying?
Replies: 203
Views: 1295

Re: How are you studying?

I see everyone mentioning step up sessions. What are those again? I might want to attend them if they help.
Tue Oct 13, 2020 7:09 pm
Forum: Properties of Light
Topic: Memorizing Wavelengths
Replies: 10
Views: 94

Re: Memorizing Wavelengths

I'm memorizing the names of each wavelength and what order they go in. If tests have something that mentions gamma or uv or infrared, you can have a general range of where your answer lies.
Sat Oct 10, 2020 3:11 pm
Forum: Empirical & Molecular Formulas
Topic: Naming conventions of certain covalently bonded molecules
Replies: 2
Views: 28

Naming conventions of certain covalently bonded molecules

I was working on a problem that mentioned boron oxide and from the name, I assumed the chemical formula was BO because there were no prefixes to guide me. A quick look up showed me that the chemical formula was in fact, B2O3. Wouldn't it be called diboron trioxide? Would the only way to determine th...
Thu Oct 08, 2020 9:58 am
Forum: Empirical & Molecular Formulas
Topic: Fundamentals F9
Replies: 2
Views: 62

Fundamentals F9

I was working on this problem F.9 Vanillin is found in vanilla extracted from Mexican orchids. A report on the analysis of vanillin listed the mass percentage composition as 63.15% C, 5.30% H, and 31.55% O. In what atom ratios are the atoms present in vanillin? I know the atom ratios, its 2.67:2.67:...
Thu Oct 08, 2020 9:43 am
Forum: SI Units, Unit Conversions
Topic: Dimensional Analysis
Replies: 4
Views: 64

Re: Dimensional Analysis

Usually you would have a problem like I have 5.00g of Chlorine and so how many moles of Cl do I have?
So,
5.00g Cl * 1 mol/35.45g Cl = 1.410 x 10^-1 moles of Cl.

If you have the molar mass of an element like Cl, 35.45g/mol, you already have your answer, 1 mol of Cl is equal to 35.45g of Cl.
Wed Oct 07, 2020 6:35 pm
Forum: SI Units, Unit Conversions
Topic: Rounding in Between Steps [ENDORSED]
Replies: 22
Views: 204

Re: Rounding in Between Steps[ENDORSED]

I don't think it makes sense to convert sums/differences to sig figs because it would lead to slight differences in the final answer. I'm not sure about Sapling, but some online learning programs have exact answers and sometimes sig figs can alter your answer just enough for it to be wrong. I sugges...
Wed Oct 07, 2020 9:41 am
Forum: Empirical & Molecular Formulas
Topic: Sapling HW 9
Replies: 21
Views: 225

Re: Sapling HW 9

@Aliya Roserie 3I I'm assuming you mean to ask do you need to submit the fundamental questions on the syllabus on Sapling and there doesn't seem to be a place on Sapling to submit them there. The questions on Sapling are different than the fundamental questions on the syllabus, but Lavelle did say t...

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