## Search found 59 matches

Mon Jan 18, 2021 12:31 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Sapling #7 Week 2
Replies: 5
Views: 42

### Re: Sapling #7 Week 2

jeffrey van 2I wrote:Thanks, so just to confirm, I would just divide the value of Kw (1.0E-14) by the given Ka, right?

Yup this is correct in order to find Kb.
Mon Jan 18, 2021 12:24 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: textbook question 5.35
Replies: 2
Views: 18

### Re: textbook question 5.35

Which section is this question from? I can't find it.
Mon Jan 18, 2021 12:21 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: 6D13: calculating pH
Replies: 4
Views: 35

### Re: 6D13: calculating pH

I think you would need Ka and Kb values since most of the given compounds are weak acids and bases.
Mon Jan 18, 2021 12:17 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: finding conc. from Kc
Replies: 3
Views: 22

### Re: finding conc. from Kc

Only thing you missed was to balance the equation, put a 3 in front of HClO. Your final answer would then be missing a cube root.
Mon Jan 18, 2021 12:07 pm
Forum: Ideal Gases
Topic: Omitting solid/liquid
Replies: 13
Views: 41

### Re: Omitting solid/liquid

For liquids omit any solvents because it will be in excess so there would be no point tracking their molar concentration. Both solids and liquids are excluded because their effective concentrations will stay constant throughout the reaction.
Wed Jan 13, 2021 11:18 pm
Forum: Non-Equilibrium Conditions & The Reaction Quotient
Topic: Textbook Question 6B.3
Replies: 3
Views: 46

### Re: Textbook Question 6B.3

I don't know the full context of the question but just from reading what you typed, I'm guessing there's some confusion on sig figs: 0.025, 1.6, and 1.7 all have 2 sig figs. Make sure to include all non-zero digits left of the decimal in your sig fig count.

I hope this helped!
Wed Jan 13, 2021 11:13 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: Getting two positive x values when using quadratic
Replies: 43
Views: 157

### Re: Getting two positive x values when using quadratic

With two x values, there's always one value that just doesn't make sense with the numbers you have, like if the value is greater than your inital molar concentrations.
Wed Jan 13, 2021 11:11 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: Increase in Pressure
Replies: 15
Views: 43

### Re: Increase in Pressure

Pressure is associated with gasses, and something can only have a concentration if it is dissolved in a solvent.
Wed Jan 13, 2021 11:09 pm
Forum: Calculating pH or pOH for Strong & Weak Acids & Bases
Topic: Textbook practice problem 6B.11
Replies: 1
Views: 32

### Re: Textbook practice problem 6B.11

The pH of the diluted solution is given so set that equal to -log[H30+] and then solve for [H30+]. I got a value of 5.62 * 10^-14. Now you can use Kw = [H30+][OH-] = 10^-14, substitute and solve for [OH-] and that is the molar concentration of hydroxide ions of the diluted solution of 0.18M. Next, u...
Wed Jan 13, 2021 10:36 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Lecture Question
Replies: 9
Views: 62

### Re: Lecture Question

CH3COOH should be an acid.
Sat Dec 12, 2020 11:54 pm
Forum: Hybridization
Topic: Hybridization with coefficients
Replies: 3
Views: 37

### Re: Hybridization with coefficients

Look for the electronic geometry of a molecule which is basically counting how many areas of electron density. This number will tell you directly how many hybridized orbitals it is using. So 2 regions will use sp hybridized, 3 will use sp2, ..., 6 will use sp3d2.
Sat Dec 12, 2020 11:51 pm
Forum: Trends in The Periodic Table
Topic: O versus N Ionization Energy
Replies: 5
Views: 37

### Re: O versus N Ionization Energy

This is because oxygen has one more electron than a half-full orbital as in nitrogen with 3 of 6 p filled. So the energy needed to remove that outlier electron on oxygen will be lower despite the normal trend of ionization energy increasing down a period.
Sat Dec 12, 2020 11:46 pm
Forum: Bronsted Acids & Bases
Topic: Sapling #12
Replies: 6
Views: 41

### Re: Sapling #12

I think more oxygens means the strength of the bond to hydrogen will decrease because of more resonance, basically more electron delocalization away from the hydrogen because more electronegative atoms are present.
Fri Dec 04, 2020 8:24 pm
Forum: Shape, Structure, Coordination Number, Ligands
Topic: Sapling Homework 9 Problem 2
Replies: 10
Views: 109

### Re: Sapling Homework 9 Problem 2

If an attached ligand is monodentate then count 1 towards the coordination number for each, and for bidentates count 2 towards the coordination number of the central atom, etc. Hope this helped!
Fri Dec 04, 2020 8:20 pm
Forum: Shape, Structure, Coordination Number, Ligands
Topic: Coordination Numbers
Replies: 8
Views: 55

### Re: Coordination Numbers

The coordination number of a central atom refers to the number of atoms, ions, or molecules bonded to it, while the steric number is the number of bonds and lone pairs.
Fri Dec 04, 2020 8:15 pm
Forum: Shape, Structure, Coordination Number, Ligands
Topic: Textbook Question 9C:5
Replies: 2
Views: 16

### Re: Textbook Question 9C:5

To figure out if a ligand is polydentate, look at the molecular structure and look if there are atoms like carbon between the donor atoms. Spacing is the key factor.
Fri Dec 04, 2020 8:02 pm
Forum: Shape, Structure, Coordination Number, Ligands
Topic: Oxidation Number
Replies: 6
Views: 59

### Re: Oxidation Number

Yes you're correct for accounting for both the ligands inside and outside of the coordination sphere.
Fri Dec 04, 2020 7:58 pm
Forum: Formal Charge and Oxidation Numbers
Topic: Sapling HW 9 Problem #6
Replies: 3
Views: 49

### Re: Sapling HW 9 Problem #6

Yup for oxidative number, we take into account the atoms and ions inside and outside of the coordination sphere.
Sun Nov 29, 2020 1:28 pm
Forum: Hybridization
Topic: delocalized pi bonds
Replies: 15
Views: 70

### Re: delocalized pi bonds

If you can imagine the Lewis structure in your head from the molecular formula, then you can check for resonance and as a result delocalized pi bonds. I would recommend just drawing out the different structures just to be safe though and more practice.
Sun Nov 29, 2020 1:25 pm
Forum: Shape, Structure, Coordination Number, Ligands
Topic: formation of coordination compounds
Replies: 3
Views: 47

### Re: formation of coordination compounds

It probably has to do with the relative stability of the different ligands and their bonding. I'm assuming water is less stable than some of the compounds you listed when bonded with a metal ion.
Sun Nov 29, 2020 1:14 pm
Forum: Shape, Structure, Coordination Number, Ligands
Replies: 2
Views: 25

There exists tetradentates, pentadentates, and octadentates. I'm guessing there is a cap to how many atoms a ligand can bind to, but I'm not sure on that exact number.
Sun Nov 29, 2020 1:08 pm
Forum: Resonance Structures
Topic: Sapling #17
Replies: 4
Views: 29

### Re: Sapling #17

The 3 possible structures of C3H4 include one ring structure and two linear structures. Since all three of these have different atom connectivities, we cannot say they are resonance structures of each other.
Sun Nov 29, 2020 12:56 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Sapling week 8 #18
Replies: 2
Views: 61

### Re: Sapling week 8 #18

The carbons on the end have 3 regions of electron density which means that they have 3 sp2 orbitals and 1 p orbital. The carbons in the middle, whose amount is determined by x only has 2 regions of electron density which means they have 2 sp hybrid orbitals and 2 p orbitals. This means that in H2CC...
Sat Nov 28, 2020 3:19 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Sapling week 8 #18
Replies: 2
Views: 61

### Sapling week 8 #18

Could someone explain the rule of when x is even or odd in H2C(C)xCH2 that determines if the terminal hydrogens lie in the same plane? More specifically why exactly does this happen? I know from the answer that odd number of carbon atoms will result in pi bonds that are perpendicular and an even num...
Sun Nov 22, 2020 5:09 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: different shapes given in notes
Replies: 4
Views: 39

### Re: different shapes given in notes

The only shapes we will have to know will be the ones directly covered in lecture! He won't test us on material that he hasn't discussed.
Sun Nov 22, 2020 5:07 pm
Forum: Administrative Questions and Class Announcements
Topic: Thanksgiving
Replies: 26
Views: 171

### Re: Thanksgiving

We probably will since the lectures are prerecorded, but only Lavelle can confirm this!
Sun Nov 22, 2020 5:05 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Sapling Week 7-8 #1
Replies: 8
Views: 28

### Re: Sapling Week 7-8 #1

This sulfite ion in VSEPR model notation is AX3E, so the molecular geometry will be trigonal pyramidal.
Sun Nov 22, 2020 4:59 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: book problem 2E.5
Replies: 3
Views: 30

### Re: book problem 2E.5

An ion by definition will have lost or gained electrons, so this can result in a change of the number of electron densities, therefore ions tend to be angular shaped. For OClO there are 3 regions of electron so the electron domain geometry will be trigonal planar, but since only 2 of the 3 positions...
Sat Nov 14, 2020 4:48 pm
Forum: Student Social/Study Group
Topic: Drawing Lewis Structures
Replies: 4
Views: 32

### Re: Drawing Lewis Structures

We will probably be given a couple of choices of Lewis structures and then asked what is the correct one. Since it's on CCLE, there won't be a drawing feature I'm guessing.
Sat Nov 14, 2020 4:30 pm
Forum: Electron Configurations for Multi-Electron Atoms
Replies: 2
Views: 11

Palladium is more stable if it completes its d-orbital as opposed to filling the s-orbital and leaving 2 empty electrons in the d-orbital.
Sat Nov 14, 2020 4:22 pm
Forum: Trends in The Periodic Table
Topic: Diagonal Relationships
Replies: 3
Views: 20

### Re: Diagonal Relationships

Lavelle never mentioned diagonal relationships in lecture, so I don't think so. Focus on horizontal and vertical trends. :)
Sat Nov 14, 2020 4:18 pm
Forum: Dipole Moments
Topic: Sapling number 17
Replies: 4
Views: 38

### Re: Sapling number 17

Yes, you're right, electron repulsion from the lone pair pushes the other fluorine bonds which contribute to molecular shape which in turn makes an overall molecule polar or nonpolar. Hope this helped.
Sat Nov 14, 2020 4:11 pm
Forum: Lewis Structures
Topic: Outline 3 Sheet Question
Replies: 3
Views: 27

### Re: Outline 3 Sheet Question

Organic molecules have carbon-hydrogen bonds and these are made by biological systems, inorganic molecules don't have these bonds. Line structures is referring to the rings and lines formed by carbon chains.
Sat Nov 14, 2020 4:04 pm
Forum: Dipole Moments
Topic: Boiling/Melting Points
Replies: 15
Views: 112

### Re: Boiling/Melting Points

I think one factor to focus on for determining boiling points is examining how strong the force of attractions that are present and how many there are between the atoms in a molecule. For example, more Van der Waals forces results in more energy needed to melt or boil a compound and thus increases t...
Sat Nov 14, 2020 3:53 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Midterm #2
Replies: 14
Views: 102

### Re: Midterm #2

Midterm 2 covers all material after MT1 to the end of Outline 3 (Chemical Bonds)
Sat Nov 07, 2020 2:53 pm
Forum: Lewis Structures
Topic: Atom in the middle of a lewis structure
Replies: 7
Views: 40

### Re: Atom in the middle of a lewis structure

The less energy that is needed for an atom to lose an electron, the greater the number of bonds that atom can participate in. Hope this helped :)
Sat Nov 07, 2020 2:49 pm
Forum: Trends in The Periodic Table
Topic: Atomic radius when changing sub- shells
Replies: 4
Views: 19

### Re: Atomic radius when changing sub- shells

Yup, atomic radius increases due to the extra shell of electrons.
Sat Nov 07, 2020 2:48 pm
Forum: Octet Exceptions
Topic: Group 13
Replies: 3
Views: 41

### Re: Group 13

I believe that all group 13 elements are electron deficient and act like Lewis acids. Not entirely sure on the second question but I think electron deficient just means the atom doesn't have enough electrons to fill an octet, but compounds with boron and aluminum are exceptions to the octet rule.
Sat Nov 07, 2020 2:39 pm
Forum: Lewis Structures
Topic: Which atom to add positive/negative charge?
Replies: 6
Views: 50

### Re: Which atom to add positive/negative charge?

Nonmetals will typically gain electrons and metals will typically lose electrons. If an ion gains e- it will have a negative charge and if it loses e- it will have a positive charge. Hope this helps!
Mon Nov 02, 2020 3:21 pm
Forum: SI Units, Unit Conversions
Topic: Using a Calculator
Replies: 10
Views: 86

### Re: Using a Calculator

Pressing 2nd then comma is also a shortcut for *10^ this helps save a lot of time for me.
Sun Nov 01, 2020 10:40 pm
Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
Topic: Sapling #8 week2-4
Replies: 5
Views: 37

### Re: Sapling #8 week2-4

I second what Hannah says! Make sure you put an extra pair of parentheses in the denominator when using your calculator.
Sun Nov 01, 2020 10:37 pm
Forum: Trends in The Periodic Table
Topic: sapling #23
Replies: 6
Views: 21

### Re: sapling #23

Convert the given wavelength of light to energy using E=hc/lambda, then concert joules to eV with the conversion factor above has stated. After finding the difference in eV convert from eV/atom to kJ/mol!
Sun Nov 01, 2020 10:29 pm
Forum: DeBroglie Equation
Topic: When to use de Broglie and what numbers to use
Replies: 8
Views: 55

### Re: When to use de Broglie and what numbers to use

Rydberg formula is used to calculate the wavelength of spectral lines, while de Broglie describes the wavelength of any particle. There are 3 different numbers I believe when using Rydberg and the last one not mentioned was 2.178 x 10^-18 J for energy calculations. Look for what the question calls f...
Sun Nov 01, 2020 10:23 pm
Forum: *Shrodinger Equation
Topic: Schrodinger Equation
Replies: 5
Views: 61

### Re: Schrodinger Equation

I feel that the actual math operations behind Shrodinger's equation are well beyond the scope of a general chem class. I think we should focus on the conceptual idea behind what the equation stands for including that electrons can be described by a wave function which then describes electron orbitals.
Sun Nov 01, 2020 10:19 pm
Forum: Trends in The Periodic Table
Topic: Noble Gas Electron Affinity
Replies: 6
Views: 45

### Re: Noble Gas Electron Affinity

I'm not entirely sure, but I feel in Chem there are rarely absolutes as most things are viewed in comparison to one another. I know it is possible for a noble gas to receive an electron, just very very unlikely, so we can't say zero affinity.
Sun Nov 01, 2020 10:15 pm
Forum: Photoelectric Effect
Topic: Sapling HW (Max Wavelength of Radiation)
Replies: 5
Views: 57

### Re: Sapling HW (Max Wavelength of Radiation)

Since you are finding the wavelength of the threshold energy needed to eject electrons, then you can disregard kinetic energy.

Set work function equal to h*frequency to find frequency.

Next, use c=lambda*frequency to solve for wavelength.

Hope this helps :)
Sun Nov 01, 2020 10:08 pm
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Replies: 6
Views: 56

I think the most important concept to understand is the basic trends of ionization energy and atomic radius as you move down a period or group.
Sun Nov 01, 2020 10:06 pm
Forum: Administrative Questions and Class Announcements
Topic: Participation Points [ENDORSED]
Replies: 62
Views: 1014

### Re: Participation Points[ENDORSED]

Could someone clarify if we do 5 posts per week in terms of the participation points or a total of 50 at the end of the quarter?
Sun Nov 01, 2020 10:03 pm
Forum: Quantum Numbers and The H-Atom
Topic: Ionization Energy Trend
Replies: 6
Views: 54

### Re: Ionization Energy Trend

I believe ionization energy increases as you move up a group because the valence electrons are getting closer and closer to the nucleus, thus needing more energy to counteract the attraction of electrons with the nucleus. Basically, less shielding effect.
Sun Oct 25, 2020 8:12 pm
Forum: Accuracy, Precision, Mole, Other Definitions
Topic: E.23 Part A and C
Replies: 4
Views: 61

### Re: E.23 Part A and C

This isn't a mass percent problem, it only consists of dimensional analysis. So, for part A the process of solving the question would be: 3.00g CaBr2 x (1 mole CaBr2 / 199.197g) x (1 mole Ca2+ / 1 mole CaBr2) You would repeat the same steps for part C, just make sure to convert kg to g first. Hopef...
Sun Oct 25, 2020 4:51 pm
Forum: Accuracy, Precision, Mole, Other Definitions
Topic: E.23 Part A and C
Replies: 4
Views: 61

### E.23 Part A and C

The question asked to calculate the moles of: a) Ca2+ ions in 3.00 g of CaBr2 c) F- ions in 25.2 kg of UF6 I seem to be getting the calculations involving ions wrong. Is there something I possible could be not considering and could someone walk through these questions? I'm finding the molar mass of ...
Sat Oct 24, 2020 6:51 pm
Forum: *Shrodinger Equation
Topic: Sapling week 2/3
Replies: 12
Views: 148

### Re: Sapling week 2/3

You can find the molar mass of a Helium atom on the periodic table: 4.002 g/mol. Since we are using Joules with Planck's constant, convert grams to kilograms, so 4.002 x 10^-3 kg. And make sure to multiply by Avogadro's number so 6.002 x 10^23 He atoms/mol in this question so that you get the value ...
Sat Oct 24, 2020 6:33 pm
Forum: Properties of Light
Topic: Constants
Replies: 21
Views: 106

### Re: Constants

Got it thanks everyone! ^^
Sat Oct 24, 2020 3:58 pm
Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
Topic: Sapling #11
Replies: 2
Views: 49

### Re: Sapling #11

First, make sure you convert the given wavelength to meters so it would be 486.1 x 10^-9 m. Use v=c/lambda to convert to frequency. Plug frequency and n1=2 into Rydberg Equation to find n2. You should get n2=4.
Sat Oct 24, 2020 12:00 pm
Forum: Properties of Light
Topic: Constants
Replies: 21
Views: 106

### Constants

How many decimals are we expected to use for constants like the speed of light and Planck's constant for the midterm?
Sun Oct 18, 2020 10:05 pm
Forum: Photoelectric Effect
Topic: Questions from Discussion
Replies: 2
Views: 30

### Re: Questions from Discussion

After calculating the work function by subtracting max KE from energy of the photon, you should then divide total energy by the work function. The answer should be the max number of electrons ejected!
Sun Oct 18, 2020 9:53 pm
Forum: Student Social/Study Group
Topic: How are you studying?
Replies: 203
Views: 1287

### Re: How are you studying?

For me, the most important aspect of studying is being an active questioner and try to think of every aspect of a question and bring them up during discussions or this forum. Still working on trying to find the right balance of textbook questions that works for me.
Thu Oct 15, 2020 9:27 pm
Forum: Photoelectric Effect
Topic: Error in Lec #6?
Replies: 3
Views: 41

### Re: Error in Lec #6?

Ah I see I wasn't paying attention to the decimal. Thank you!
Thu Oct 15, 2020 12:06 pm
Forum: Photoelectric Effect
Topic: Error in Lec #6?
Replies: 3
Views: 41

### Error in Lec #6?

I could be wrong but when the prof was calculating the wavelengths if the first example wouldn't the answer be 551 x 10^-7 instead of 551 x 10^-9?