Search found 63 matches

by Sjeffrey_1C
Sat Jan 25, 2020 9:00 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Energy of the reactants
Replies: 6
Views: 12

Re: Energy of the reactants

So in this case, visually the reaction's energy looks like this.
by Sjeffrey_1C
Sat Jan 25, 2020 8:58 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Standard enthalpy
Replies: 2
Views: 4

Re: Standard enthalpy

Because in a stable state, there isn't a release/absorption of energy during the reaction, or it is net 0.
by Sjeffrey_1C
Sat Jan 25, 2020 8:54 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Bond Enthalpy Method
Replies: 5
Views: 11

Re: Bond Enthalpy Method

PranaviKolla2B wrote:What is the most accurate way to calculate H?


I assume Hess's method is most accurate.
by Sjeffrey_1C
Sat Jan 25, 2020 8:52 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Bond Enthalpies and gas phases
Replies: 2
Views: 5

Re: Bond Enthalpies and gas phases

I don't think that is the case. I may be wrong, but I remember in lecture it being said that you can use bond enthalpies for liquids or solids but you need to add the enthalpy of the phase change, or something along those lines.
by Sjeffrey_1C
Sat Jan 25, 2020 8:48 pm
Forum: Phase Changes & Related Calculations
Topic: Entropy vs Enthalpy
Replies: 9
Views: 23

Re: Entropy vs Enthalpy

PranaviKolla2B wrote:What does each term relate to in the equation deltaG= deltaH-T*deltaS?


I believe delta G is gibbs free energy, Delta H is enthalpy, and delta S is entropy. T is temperature.
by Sjeffrey_1C
Sun Jan 19, 2020 10:53 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: ICE Table
Replies: 4
Views: 14

Re: ICE Table

You subtract or add x from the original concentration. X is either positive or negative depending on the direction of the reaction.
by Sjeffrey_1C
Sun Jan 19, 2020 10:51 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Approximations
Replies: 2
Views: 4

Re: Approximations

To be safe, I'd say just don't approximate on the test. But I'm not sure what you'd do in the case that you do.
by Sjeffrey_1C
Fri Jan 17, 2020 6:11 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: 5I.13 Equilibrium Composition
Replies: 2
Views: 29

5I.13 Equilibrium Composition

(a) in an experiment, 2.0 mmol Cl2 (g) was sealed in a reaction vessel of volume 2.0L and heated to 1000. K to study its dissociation into Cl atoms. Use info in table 5g.2 to calculate the equilibrium composition of the mixture. I keep getting the wrong answer. The table gives the k value to be 1.0 ...
by Sjeffrey_1C
Sun Jan 12, 2020 9:24 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Solids and Liquids
Replies: 6
Views: 21

Re: Solids and Liquids

Liquids and solids are essentially incompressible, unlike gas, which is compressible.
by Sjeffrey_1C
Sun Jan 12, 2020 9:23 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: What is this?
Replies: 23
Views: 128

Re: What is this?

It basically explains how a reaction will maintain stability.
by Sjeffrey_1C
Sun Jan 12, 2020 9:22 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: volume change with inert gas
Replies: 9
Views: 32

Re: volume change with inert gas

In class, he explained that if the pressure of a reaction vessel is increased by adding inert gas, then moles of reactant, product and volume are constant, so there's no change in [R] and [P].
by Sjeffrey_1C
Sun Jan 12, 2020 9:18 pm
Forum: Non-Equilibrium Conditions & The Reaction Quotient
Topic: Response of Equilibria to Change
Replies: 6
Views: 20

Re: Response of Equilibria to Change

He basically said that if volume decreases and there are more moles of gas on left, then the reaction shifts left, or if volume decreases and there are more moles of gas on the right, then the reaction shifts left. But this logic is incorrect.
by Sjeffrey_1C
Thu Jan 09, 2020 2:49 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: K and Q
Replies: 5
Views: 16

Re: K and Q

Additionally, if K and Q aren't equal, you know the equation is not in equilibrium. So If Q < K at some time during reaction, then [R] > [P] and the forward reaction is favored. If Q > K at some time during reaction, then [P] > [R] and the reverse reaction is favored.
by Sjeffrey_1C
Fri Dec 06, 2019 8:48 pm
Forum: Bronsted Acids & Bases
Topic: bronsted base and acid
Replies: 4
Views: 46

Re: bronsted base and acid

Lewis refers to eLectrons. Bronstead refers to protons. Bronstead acids or bases are always a Lewis acid or base (respectively). Aka a bronstead base is also a lewis base. But the vice-versa is not true. Ex. BF3 is a lewis acid (it accepts electrons) but is not a bronstead acid (doesn't have protons...
by Sjeffrey_1C
Fri Dec 06, 2019 8:47 pm
Forum: Shape, Structure, Coordination Number, Ligands
Topic: what is a ligand?
Replies: 7
Views: 39

Re: what is a ligand?

A ligand forms a coordinate covalent bond with a transition metal cation, so I guess if CO did this it would be considered a ligand. A ligand is anything directly bound to the central atom.
by Sjeffrey_1C
Fri Dec 06, 2019 8:45 pm
Forum: Polyprotic Acids & Bases
Topic: bases
Replies: 2
Views: 31

Re: bases

In the case of H2SO4, these are the reactions that show this:

H2SO4 + H2O -> HSO4- + H3O+

HSO4- + H2O -> SO42- + H3O+

overall equation: H2SO4 + 2H2O -> SO42- + 2H30+
by Sjeffrey_1C
Fri Dec 06, 2019 8:42 pm
Forum: Naming
Topic: Naming Cont
Replies: 3
Views: 19

Re: Naming Cont

Also don't forget if a cation is present outside the brackets... like sodium in Na[Fe(Ox)2(OH2)2)]... name it first. Ex. Sodium diaquabisoxalato ferrate (III)
by Sjeffrey_1C
Fri Dec 06, 2019 8:38 pm
Forum: Properties & Structures of Inorganic & Organic Acids
Topic: Relative Acidity: e- withdrawing groups
Replies: 2
Views: 27

Re: Relative Acidity: e- withdrawing groups

An electron withdrawing group pulls electrons towards it from another source. It is a way of determining the relative strength of a conjugate base. E- with drawing groups delocalize a neg charge.

For example HClO or HBrO
by Sjeffrey_1C
Sun Dec 01, 2019 5:49 pm
Forum: Student Social/Study Group
Topic: final
Replies: 4
Views: 34

Re: final

I'm assuming information after Test #2 will be the most emphasized (since it's the only content we haven't been tested on), but I am not 100% sure. Maybe ask a TA during discussion.
by Sjeffrey_1C
Sun Dec 01, 2019 5:46 pm
Forum: Bronsted Acids & Bases
Topic: Strong/Weak Acid/Base
Replies: 2
Views: 14

Re: Strong/Weak Acid/Base

The strong acid I see most often is HCl!
by Sjeffrey_1C
Sun Dec 01, 2019 5:44 pm
Forum: Lewis Acids & Bases
Topic: 6.5 - how to identify which is the lewis acid and base?
Replies: 2
Views: 30

Re: 6.5 - how to identify which is the lewis acid and base?

If you draw the Lewis structures, look at which have lone pairs. This will give you an indication of which will donate electrons (lewis base) and which will accept electrons (lewis acid)!
by Sjeffrey_1C
Sun Dec 01, 2019 5:43 pm
Forum: General Science Questions
Topic: Memorization for Final
Replies: 2
Views: 24

Re: Memorization for Final

You definitely will have to know molecular geometry names and bond angles!
by Sjeffrey_1C
Sun Dec 01, 2019 5:36 pm
Forum: Conjugate Acids & Bases
Topic: NH3, acid or base?
Replies: 12
Views: 540

Re: NH3, acid or base?

A bronsted base accepts a proton and a bonsted donates a proton. Thus, NH3, in most reactions, is a bronsted base.
by Sjeffrey_1C
Fri Nov 15, 2019 3:12 pm
Forum: Polarisability of Anions, The Polarizing Power of Cations
Topic: Polarizing power vs polarizability
Replies: 5
Views: 42

Re: Polarizing power vs polarizability

Generally atoms with polarizing power have small atomic radii and are partial negative. Atoms that are polarizable have large atomic radii and are partial positive.
by Sjeffrey_1C
Fri Nov 15, 2019 3:10 pm
Forum: Dipole Moments
Topic: 3f.1
Replies: 3
Views: 27

Re: 3f.1

Also keep in mind that the dipole moment is a permanent dipole moment, meaning its polar.
by Sjeffrey_1C
Fri Nov 15, 2019 3:03 pm
Forum: Trends in The Periodic Table
Topic: Question
Replies: 17
Views: 145

Re: Question

Also keep in mind that although the trend is the same for both, ionization dips at oxygen (meaning oxygen is an exception to the trend) while electronegativity trend continues through oxygen.
by Sjeffrey_1C
Fri Nov 15, 2019 2:59 pm
Forum: Dipole Moments
Topic: IMFs
Replies: 2
Views: 25

Re: IMFs

Each IMF has defining characteristics. This image might help.
by Sjeffrey_1C
Fri Nov 15, 2019 2:55 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: polar/nonpolar
Replies: 2
Views: 13

Re: polar/nonpolar

Look at the charges. If there are partial positive or partial negative components, it's likely that dipole moments will occur.
by Sjeffrey_1C
Fri Nov 08, 2019 5:10 pm
Forum: Resonance Structures
Topic: Resonance Structures
Replies: 18
Views: 109

Re: Resonance Structures

Also resonance structures are used to determine the true most stable structure. So if multiple resonance structures contribute equally, the structure will be a hybrid of all the resonance structures. This is why sometimes if there's resonance, bond lengths will be between that of a single bond and a...
by Sjeffrey_1C
Fri Nov 08, 2019 5:07 pm
Forum: Student Social/Study Group
Topic: Class Grading
Replies: 36
Views: 496

Re: Class Grading

I think when he says there isn't a curve he means a bell curve, meaning there isn't a specific grade distribution he wants. But it does seem like he will be curving the class, or not using a standard grading scale. This way if the overall grades aren't very high, he will shift the cutoffs so that pe...
by Sjeffrey_1C
Fri Nov 08, 2019 5:04 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: Test 2
Replies: 6
Views: 46

Re: Test 2

Just to clarify so there's no confusion, someone above said next week but it is actually in 2 weeks! Its the week of the 18th - 22nd!
by Sjeffrey_1C
Fri Nov 08, 2019 5:00 pm
Forum: Electronegativity
Topic: Periodic Trend
Replies: 13
Views: 74

Re: Periodic Trend

Additionally, these are basically the same trends as electron affinity and ionization energy. (Although ionization energy does dip for oxygen)
by Sjeffrey_1C
Fri Nov 08, 2019 4:59 pm
Forum: Lewis Structures
Topic: Drawing Lewis Structures
Replies: 18
Views: 73

Re: Drawing Lewis Structures

The main goal is to minimize charges. So however you can get the charges to be lowest, while still adding up to the total charge and following octet rules etc. Placing larger charges on more electronegative elements is also important.
by Sjeffrey_1C
Wed Nov 06, 2019 8:46 am
Forum: SI Units, Unit Conversions
Topic: units for Equations Sheet
Replies: 2
Views: 40

units for Equations Sheet

Could someone give me a quick reminder of the units different things should be in for the constants and equations sheet? Like when to use nm vs m or kg vs g. Just for the most important equations! Thank you!
by Sjeffrey_1C
Wed Oct 30, 2019 9:55 pm
Forum: Ionic & Covalent Bonds
Topic: Format of midterm?
Replies: 12
Views: 68

Re: Format of midterm?

When it says questions come from hw and online, does this mean word for word or just similar format/topic?
by Sjeffrey_1C
Wed Oct 30, 2019 9:54 pm
Forum: Student Social/Study Group
Topic: Will different midterm review sessions cover the same material?
Replies: 8
Views: 62

Re: Will different midterm review sessions cover the same material?

Would someone mind posting the midterm review session times? I didn't write them down.
by Sjeffrey_1C
Wed Oct 30, 2019 9:50 pm
Forum: Lewis Structures
Topic: 4s and 3d
Replies: 4
Views: 57

Re: 4s and 3d

This confused me at first too. If writing the electron configuration for Ga itself you would first fill 4S before 3D, which made me believe that when Ga loses 3 electrons to become 3+, electrons would be removed from 3D since it was filled last. This though, is not the case. Electrons are removed fr...
by Sjeffrey_1C
Wed Oct 30, 2019 9:47 pm
Forum: Ionic & Covalent Bonds
Topic: 2A.21
Replies: 4
Views: 37

Re: 2A.21

You can tell that all of these have 0 unpaired electrons because the last orbitals are full in each case.
by Sjeffrey_1C
Wed Oct 30, 2019 9:45 pm
Forum: Lewis Structures
Topic: Drawing Lewis Structures
Replies: 4
Views: 24

Re: Drawing Lewis Structures

Generally, if there is a singular of one element and multiple of another, the singular one will go in the middle. For example, CCl4, NF3, H2O, etc.
by Sjeffrey_1C
Sun Oct 27, 2019 8:24 pm
Forum: Ionic & Covalent Bonds
Topic: Videos
Replies: 2
Views: 31

Re: Videos

https://www.khanacademy.org/science/che ... structures This video is also helpful for drawing lewis diagrams!
by Sjeffrey_1C
Sun Oct 27, 2019 8:20 pm
Forum: Heisenberg Indeterminacy (Uncertainty) Equation
Topic: Questions with Heisenburg uncertainty principle
Replies: 2
Views: 18

Re: Questions with Heisenburg uncertainty principle

These are important because the more you know about the position (delta x) of an electron, the less you know about its momentum (delta p), and vice-versa. Thus, it's impossible to know both an electron's position and momentum.
by Sjeffrey_1C
Sun Oct 27, 2019 8:15 pm
Forum: Ionic & Covalent Bonds
Topic: Homework
Replies: 13
Views: 109

Re: Homework

As said, we can probably do some quantum problems. But since the past 3 weeks have been quantum, it might be good to move onto some new content in preparation.
by Sjeffrey_1C
Sun Oct 27, 2019 8:12 pm
Forum: Ionic & Covalent Bonds
Topic: Covalent Bonds
Replies: 14
Views: 75

Re: Covalent Bonds

I think only two non-metals. A non-metal and a metal would form an ionic bond. Two metals would form a metallic bond.
by Sjeffrey_1C
Sun Oct 27, 2019 7:59 pm
Forum: Resonance Structures
Topic: Octet
Replies: 13
Views: 84

Re: Octet

My TA mentioned that the 8th group is composed on octets. These are noble gases I believe.
by Sjeffrey_1C
Sun Oct 27, 2019 7:51 pm
Forum: Electron Configurations for Multi-Electron Atoms
Topic: 4f Subshell Clarification
Replies: 3
Views: 25

Re: 4f Subshell Clarification

I'm not sure about the order they fill. But yes, the 4f subshell can hold 14 electrons as it has 7 orbitals, and each can hold 2 electrons. (And each electron has to have an opposite spin bc of Pauli)
by Sjeffrey_1C
Sat Oct 19, 2019 9:29 pm
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: Shell, Subshell, Orbital Terminology
Replies: 8
Views: 90

Re: Shell, Subshell, Orbital Terminology

This is really important, thanks! I feel like most high school teachers didn't make those distinctions very clear, so it's easy to get confused.
by Sjeffrey_1C
Sat Oct 19, 2019 9:27 pm
Forum: *Shrodinger Equation
Topic: Wave functions
Replies: 9
Views: 66

Re: Wave functions

A wave function I believe gives you specific info regarding the wave's properties.
by Sjeffrey_1C
Sat Oct 19, 2019 9:26 pm
Forum: Properties of Light
Topic: Midterm Exam
Replies: 21
Views: 184

Re: Midterm Exam

On that note, does anyone know which topics will be covered which weeks? I expected to see weeks on the syllabus next to each new topic, but didn't notice anything like that.
by Sjeffrey_1C
Sat Oct 19, 2019 9:23 pm
Forum: *Black Body Radiation
Topic: General Question about this
Replies: 2
Views: 49

Re: General Question about this

I believe we went over it earlier last week but I might have just read about it in the textbook. It refers to something that can absorb all light frequencies.
by Sjeffrey_1C
Sat Oct 19, 2019 9:21 pm
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: determining types of orbitals (?)
Replies: 4
Views: 36

Re: determining types of orbitals (?)

Also during lecture, he provided some specific things you just need to know regarding orbitals. I'd recommend going through those and making sure you know those as they might help.
by Sjeffrey_1C
Wed Oct 16, 2019 8:04 pm
Forum: DeBroglie Equation
Topic: Textbook Question 1B21
Replies: 3
Views: 34

Re: Textbook Question 1B21

I had a similar issue where I kept getting an answer that was slightly off. Make sure you check all your conversions. For the mass, make sure you convert to grams, and then kg... you should get .145745kg. For the velocity, you need to convert miles to meters and hours to seconds. Remember that 1 met...
by Sjeffrey_1C
Sun Oct 13, 2019 12:59 pm
Forum: DeBroglie Equation
Topic: De Broglie Equation Clarification
Replies: 4
Views: 44

Re: De Broglie Equation Clarification

To add on, the concepts mentioned above are that in constructive interference, the amplitudes of the two waves summate (add together). In destructive interference, the amplitude's of the two waves cancel each other out.
by Sjeffrey_1C
Sun Oct 13, 2019 12:56 pm
Forum: Properties of Light
Topic: wavelike properties
Replies: 6
Views: 37

Re: wavelike properties

As others explained, electrons have wave-like properties, which are explained in the textbook, as well as particle properties. This concept as a whole is know as wave-particle duality, meaning electrons cannot be explained as merely a wave, or merely a particle, but as a combination of the two.
by Sjeffrey_1C
Sun Oct 13, 2019 12:52 pm
Forum: Significant Figures
Topic: Sig Figs at the Beginning or End
Replies: 14
Views: 154

Re: Sig Figs at the Beginning or End

As said above, you shouldn't convert to sig figs till the end so storing in your calculator as you go is very helpful. You can generally assign values to a letter so you can call it back later. For example, on the TI-30X, once you have a value you click "STO" and select a a letter to assig...
by Sjeffrey_1C
Sun Oct 13, 2019 12:48 pm
Forum: SI Units, Unit Conversions
Topic: Unit conversion
Replies: 15
Views: 193

Re: Unit conversion

Angstroms are equal to 10^−10 meter. Using this, you can convert angstroms to other units using 1meter/10^10 angstrom or vice versa. So if you covert angstroms to meters, you can easily convert meters to other units.
by Sjeffrey_1C
Wed Oct 09, 2019 4:38 pm
Forum: Balancing Chemical Reactions
Topic: HW Problem H7
Replies: 4
Views: 93

Re: HW Problem H7

I just realized you use the element's position on the periodic table to figure it out. Totally forgot about that. Thanks though!
by Sjeffrey_1C
Wed Oct 09, 2019 2:53 pm
Forum: Balancing Chemical Reactions
Topic: HW Problem H7
Replies: 4
Views: 93

HW Problem H7

Problem H7 asks us to balance the chemical equation for "calcium metal reacts with water to produce hydrogen gas and aqueous calcium hydroxide"? I don't remember anything about writing chemical formulas from highschool chem. Obviously we know basic formulas off the top of our heads like H2...
by Sjeffrey_1C
Wed Oct 02, 2019 6:16 pm
Forum: Empirical & Molecular Formulas
Topic: HW 1 Problem F.9
Replies: 7
Views: 145

Re: HW 1 Problem F.9

The answer provided in the textbook is the empirical formula. Though I assume since it wasn't specified, any sort of ratio would suffice. I just included both the decimal values I got from my calculations, as well as the empirical formula.
by Sjeffrey_1C
Wed Oct 02, 2019 6:13 pm
Forum: Empirical & Molecular Formulas
Topic: Homework E.15 Solutions
Replies: 4
Views: 252

Re: Homework E.15 Solutions

Is it assumed we know that the M in M(OH)2 is a sulfide? Or was there some way to determine this?
by Sjeffrey_1C
Wed Oct 02, 2019 6:11 pm
Forum: SI Units, Unit Conversions
Topic: rounding of the elements. [ENDORSED]
Replies: 6
Views: 66

Re: rounding of the elements. [ENDORSED]

To add, all periodic tables round to different decimal positions. Therefore, it ca't be expected that everyone gets the exact same answers unless there is one singular periodic table we were told to use. This isn't the case though, right?
by Sjeffrey_1C
Wed Oct 02, 2019 6:08 pm
Forum: Empirical & Molecular Formulas
Topic: HW E17 part C
Replies: 5
Views: 56

Re: HW E17 part C

Your logic is correct! It isn't even necessary to do any calculations for part c. Since the number of atoms of both are the same, the number of moles of each must also be the same.
by Sjeffrey_1C
Wed Oct 02, 2019 6:04 pm
Forum: Empirical & Molecular Formulas
Topic: HW problem F9
Replies: 8
Views: 83

Re: HW problem F9

I answered with both the ratio I got by converting the percents to grams, then dividing by the g/mol to get the moles of each, then dividing each value by the lowest mole value (1.972), as well as a ratio in full numbers (empirical formula).

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