Search found 56 matches

by julia_lok_2K
Sat Mar 16, 2019 11:22 pm
Forum: Arrhenius Equation, Activation Energies, Catalysts
Topic: Ea
Replies: 1
Views: 169

Re: Ea

Equations involving Ea are: lnk=-(Ea/RT) + lnA, or k=Ae^(-Ea/RT). You get Ea from the slope of the line (-Ea/R) on the graph plotting 1/T vs lnk.
by julia_lok_2K
Sat Mar 16, 2019 11:14 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: standard cell potential and free energy
Replies: 3
Views: 190

standard cell potential and free energy

If standard cell potential is an intensive property, does that mean standard Gibbs free energy is also intensive for a reaction?
by julia_lok_2K
Wed Mar 13, 2019 12:33 am
Forum: Reaction Mechanisms, Reaction Profiles
Topic: molecularity
Replies: 2
Views: 53

Re: molecularity

It would be bimolecular because two molecules of O3 are involved.
by julia_lok_2K
Wed Mar 13, 2019 12:29 am
Forum: First Order Reactions
Topic: finding the concentration of a reactant
Replies: 1
Views: 43

Re: finding the concentration of a reactant

You can find the number of moles of the reactant used up in the reaction from the final concentration of the product by using the stoichiometry coefficients. You then subtract that value from the initial concentration of the reactant to get the final concentration.

Hope this helps!
by julia_lok_2K
Sat Mar 09, 2019 11:51 pm
Forum: First Order Reactions
Topic: 15.19c (6th ed)
Replies: 2
Views: 46

Re: 15.19c (6th ed)

So it's standard for the units to be in mol/L and not in mmol/L? I thought it didn't matter, as long as you were consistent with your units.
by julia_lok_2K
Sat Mar 09, 2019 11:47 pm
Forum: First Order Reactions
Topic: Homework #37 6th edition part b
Replies: 1
Views: 33

Re: Homework #37 6th edition part b

Yes, you would. To make things simple, you can assume that the concentration of SO2Cl2 is 100 M, so the final concentration would be 10 M, thus ln(10). Therefore, with this same principle, if SO2Cl2 concentration were to decrease to 20% its original concentration, you would use ln(20). Generally, I ...
by julia_lok_2K
Sat Mar 09, 2019 11:39 pm
Forum: Zero Order Reactions
Topic: Half-life
Replies: 6
Views: 90

Re: Half-life

A half life is the time it takes for a substance to fall/decay/be consumed to half its original concentration. Half lives do not depend on the concentration, i.e. the half life of a substance remains the same at any stage in the reaction. We use the t1/2=0.693/k equation to relate half life to the r...
by julia_lok_2K
Sat Mar 09, 2019 9:40 pm
Forum: First Order Reactions
Topic: 15.19c (6th ed)
Replies: 2
Views: 46

15.19c (6th ed)

For the rate constant, I keep getting 2.85 instead of 2.85 * 10^14. I don't understand how they got the exponent. Do I have to convert mmol to mol, or do I have to use data from experiment 4, like how the solution manual did it? Am I just making a dumb mistake??
by julia_lok_2K
Thu Mar 07, 2019 12:33 am
Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
Topic: Ka vs K
Replies: 1
Views: 50

Re: Ka vs K

Because K= Ka*Kb, so you need to square K to get only Ka.
by julia_lok_2K
Thu Mar 07, 2019 12:30 am
Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
Topic: 14.93a (6th ed)
Replies: 1
Views: 39

14.93a (6th ed)

Why does the electrode with the higher concentration of the species undergoes reduction and not the electrode with the lower concentration?
by julia_lok_2K
Thu Mar 07, 2019 12:27 am
Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
Topic: 6th edition, 14.35
Replies: 1
Views: 41

Re: 6th edition, 14.35

The equation from the solutions manual is a simplified version of the original formula, the 0.02568 is what you get when you combine all the constants in the original formula. You can directly plug the numbers into the original formula. I'm a bit confused by exactly what units you're referring to, b...
by julia_lok_2K
Tue Feb 26, 2019 4:31 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: List of Cell Potentials
Replies: 1
Views: 28

List of Cell Potentials

Will we be given a list of reduction potentials for the test?
by julia_lok_2K
Sat Feb 23, 2019 8:30 pm
Forum: Balancing Redox Reactions
Topic: 14.5b (6th ed)
Replies: 1
Views: 42

14.5b (6th ed)

Since there is only one reactant in the reaction, would Br2 be involved in both half reactions? Would Br2 also act as both the oxidizing and reducing agent?
by julia_lok_2K
Sat Feb 23, 2019 8:26 pm
Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
Topic: Standard Potentials and Equilibrium Constants
Replies: 2
Views: 44

Re: Standard Potentials and Equilibrium Constants

I don't think so, since it wasn't covered in lecture. Looking at the material covered in his lectures, it seems like the test covers only up to Section 14.6 (6th edition).
by julia_lok_2K
Sat Feb 23, 2019 8:23 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: inert conductor in cell diagrams
Replies: 3
Views: 65

Re: inert conductor in cell diagrams

You add the inert conductor when the reactants or products don't involve a conducting solid.
by julia_lok_2K
Tue Feb 12, 2019 9:28 pm
Forum: Phase Changes & Related Calculations
Topic: Steam vs Boiling Water
Replies: 8
Views: 292

Re: Steam vs Boiling Water

It's because the steam has more heat energy than boiling water, i.e. higher enthalpy.
by julia_lok_2K
Tue Feb 12, 2019 3:04 pm
Forum: Thermodynamic Systems (Open, Closed, Isolated)
Topic: Internal energy (U) of an isolated system
Replies: 17
Views: 426

Re: Internal energy (U) of an isolated system

There wouldn't be any change after time passes because it's isolated--it won't be able to exchange energy or matter with its surroundings.
by julia_lok_2K
Tue Feb 12, 2019 2:31 pm
Forum: Phase Changes & Related Calculations
Topic: joules conversion factor
Replies: 7
Views: 275

Re: joules conversion factor

I don't think you have to. On the constants and equations sheet, they give the conversion between atm and kPa, which is essentially the same conversion between atm L and joules.
by julia_lok_2K
Tue Feb 05, 2019 3:04 pm
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: Self-Test 8.4B
Replies: 1
Views: 40

Re: Self-Test 8.4B

It's correct. I guess for this problem you would disregard mass because it's asking for heat capacity and not specific heat capacity.
by julia_lok_2K
Tue Feb 05, 2019 2:51 pm
Forum: Calculating Work of Expansion
Topic: Reversible and Irreversible Reactions
Replies: 2
Views: 50

Reversible and Irreversible Reactions

Why does a change carried out in reversible reactions always does more work than a change carried out in irreversible reactions?
by julia_lok_2K
Wed Jan 23, 2019 10:45 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: 12.81b (6th edition)
Replies: 1
Views: 41

12.81b (6th edition)

In the solution manual, it says that Ka2 can be ignored. But Ka2 is larger than Ka1/1000, so wouldn't you have to do another ICE table using Ka2?
by julia_lok_2K
Wed Jan 23, 2019 10:42 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: 11.89 (6th edition)
Replies: 1
Views: 43

11.89 (6th edition)

I don't really understand how the coefficient for compound A is 2. I assumed that since C has twice the pressure of B, the coefficient for C would be 2 and for B, 1. But A isn't twice the pressure of either B or C, so why is the coefficient 2 as well?
by julia_lok_2K
Wed Jan 23, 2019 10:31 pm
Forum: Polyprotic Acids & Bases
Topic: Ignoring Deprotonations
Replies: 1
Views: 194

Re: Ignoring Deprotonations

In the textbook, it says that if Ka2 is less than Ka1/1000, then you can ignore the second deprotonation.

Hope this helps!
by julia_lok_2K
Wed Jan 23, 2019 10:30 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: buffers
Replies: 1
Views: 56

Re: buffers

A buffer is a solution that undergoes only slight changes in pH when acids and/or bases are added. I think that you just have to know how to solve problems involving buffers, like the last problem that Professor Lavelle went over during lecture last Friday.
by julia_lok_2K
Sat Jan 12, 2019 7:26 pm
Forum: Non-Equilibrium Conditions & The Reaction Quotient
Topic: Phases and Reaction Quotient (HW)
Replies: 3
Views: 75

Re: Phases and Reaction Quotient (HW)

It's because the concentrations of solids and liquids do not change during the reactions, so it is kind of pointless to consider solids and liquids for equilibrium.
by julia_lok_2K
Sat Jan 12, 2019 4:24 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: "quick" way to solve changes in pressure
Replies: 3
Views: 58

Re: "quick" way to solve changes in pressure

Based on the balanced reaction, if the volume decreases and there are more moles of gas on the left, the reaction will shift to the right. If there are more moles of gas on the right, the reaction will then shift to the left. This happens because the side with more moles of gas would have a larger p...
by julia_lok_2K
Sat Jan 12, 2019 12:21 am
Forum: Equilibrium Constants & Calculating Concentrations
Topic: ice table
Replies: 4
Views: 55

Re: ice table

You would put x because you don't know the change in concentration for each molecule. Since the initial concentrations of the products are 0, the system would shift to the right, i.e. make more products, in order to achieve equilibrium, thus you put +x. Conversely, you would know that the concentrat...
by julia_lok_2K
Sun Dec 09, 2018 9:00 am
Forum: Sigma & Pi Bonds
Topic: orbitals
Replies: 1
Views: 214

Re: orbitals

The principle quantum number is 5, so the possible l values are 0,1,2,3,4. The total possible ml values for each subshell, therefore, would be 1, 3, 5, 7, and 9, respectively, adding up to a total of 25 orbitals. However, since it involves the g subshell, I don't think you need to know this informat...
by julia_lok_2K
Sun Dec 09, 2018 8:46 am
Forum: Shape, Structure, Coordination Number, Ligands
Topic: Abbreviations
Replies: 1
Views: 205

Re: Abbreviations

I would be safe and just memorize the formulas. You can refer to the "Naming Coordination Compounds" worksheet on the website to help you know which ligands to memorize.
by julia_lok_2K
Sun Dec 09, 2018 8:44 am
Forum: General Science Questions
Topic: Equations Given on the Final
Replies: 2
Views: 252

Re: Equations Given on the Final

I'm not sure if it will be the same from previous tests since he makes slight changes to the curriculum every quarter, but he probably will use the same one that is posted on the website.
by julia_lok_2K
Sun Dec 09, 2018 8:37 am
Forum: Trends in The Periodic Table
Topic: 2nd Ionization Energy
Replies: 2
Views: 190

Re: 2nd Ionization Energy

Since we didn't have any homework problems on it but still went over it in lecture, we will probably be tested on at least the concept of second ionization energy.
by julia_lok_2K
Sun Dec 09, 2018 8:34 am
Forum: Naming
Topic: Churro Review- 28
Replies: 1
Views: 85

Re: Churro Review- 28

Cl and CN would be first by alphabetical order.
by julia_lok_2K
Sat Dec 08, 2018 1:06 pm
Forum: Shape, Structure, Coordination Number, Ligands
Topic: Polydentate
Replies: 11
Views: 268

Re: Polydentate

Would carbonato also be considered a polydentate then?
by julia_lok_2K
Mon Dec 03, 2018 10:39 pm
Forum: Calculating pH or pOH for Strong & Weak Acids & Bases
Topic: Ka calculations
Replies: 2
Views: 61

Re: Ka calculations

If you look at Ka = ([A-][H+])/[AH], a higher Ka value denotes higher concentrations of [A-] and [H+], which means the acid has become more ionized/dissociated. Therefore, a higher Ka value makes a stronger acid.
by julia_lok_2K
Mon Dec 03, 2018 10:25 pm
Forum: Shape, Structure, Coordination Number, Ligands
Topic: Water as a Monodentate
Replies: 1
Views: 60

Water as a Monodentate

Why is water a monodentate, even though it has 2 lone pairs of electrons? Wouldn't water also possibly be a bidentate?
by julia_lok_2K
Mon Dec 03, 2018 10:16 pm
Forum: Conjugate Acids & Bases
Topic: Ligands?
Replies: 1
Views: 49

Re: Ligands?

Ligands are atoms, ions, or molecules that are attached to a central metal atom in a coordinate compound. They typically have at least one lone pair of electrons to form a coordinate covalent bond with the central atom; thus the ligand acts as a Lewis base while the central atom acts as a Lewis acid...
by julia_lok_2K
Fri Nov 16, 2018 8:02 pm
Forum: Dipole Moments
Topic: Definition of a dipole
Replies: 2
Views: 83

Re: Definition of a dipole

Also, atoms with dipole moments typically result in a polar covalent bond, unless the atoms in a molecule are arranged in a way where the dipole moments cancel out, such as CCl4, in which case the molecule becomes nonpolar.
by julia_lok_2K
Fri Nov 16, 2018 9:16 am
Forum: Lewis Structures
Topic: Electron configuration
Replies: 3
Views: 86

Re: Electron configuration

You would first find the element with that ground state configuration, which would be As. Then, since you are looking for the ion of +1 charge, that means the ion lost an electron, so you would look at the element that is to the right of As, which is Se. Therefore, the answer is Se+.

Hope this helps!
by julia_lok_2K
Fri Nov 16, 2018 9:10 am
Forum: Determining Molecular Shape (VSEPR)
Topic: Sulfite Ion and its Bond Angle
Replies: 3
Views: 49

Re: Sulfite Ion and its Bond Angle

I think it's because instead of four bonding pairs in a tetrahedral, you have three bonding pairs and a lone pair of electrons in a trigonal pyramidal molecule. That lone pair of electrons wants to take up more space, thereby pushing down on the molecule. This causes the bond angle to be less than t...
by julia_lok_2K
Sat Nov 10, 2018 4:21 pm
Forum: Dipole Moments
Topic: VSPER
Replies: 8
Views: 152

Re: VSPER

VSEPR model explains how to draw the 3D shape of molecules. It stands for Valence Shell Electron Pairs Repel, which summarizes how to draw them--you want to draw the models in a way that will minimize electron repulsion. From the VSEPR model, you can determine the molecular shape and its name. I hop...
by julia_lok_2K
Sat Nov 10, 2018 4:18 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: VSEPR?
Replies: 9
Views: 197

Re: VSEPR?

Sorry for the typos, but I meant to say Valence Shell Electron Pairs Repel.
by julia_lok_2K
Sat Nov 10, 2018 4:17 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: VSEPR?
Replies: 9
Views: 197

Re: VSEPR?

It stands for Valence Electron Shell Pairs Reel--this name conceptualizes how to draw the 3D model of molecules. It denotes that you want to draw the model in a way that will minimize electron repulsion.

Hope this helps!
by julia_lok_2K
Fri Nov 02, 2018 9:36 am
Forum: Formal Charge and Oxidation Numbers
Topic: 6th edition: 3.23
Replies: 1
Views: 81

Re: 6th edition: 3.23

I think it complies with the octet rule, as in taking away electrons or adding more electrons until you get the previous or next noble gas configuration. So to find the minimum oxidation number, you take away electrons from the atom's outer shell until you reach the preceding noble gas. In this case...
by julia_lok_2K
Fri Nov 02, 2018 9:30 am
Forum: Lewis Structures
Topic: 6th Edition 3.65
Replies: 1
Views: 39

Re: 6th Edition 3.65

O is double bonded with Xe because that way, the formal charges for both will be zero, making the structure more stable. If O and Xe had a single bond, then O would have a formal charge of -1, and Xe would have a charge of +1, which is less favorable.

Hope this helps!
by julia_lok_2K
Fri Nov 02, 2018 9:27 am
Forum: Octet Exceptions
Topic: octet exceptions
Replies: 4
Views: 121

Re: octet exceptions

I don't think the textbook explains this exception, and I tried looking it up on other websites as well but they didn't really explain it either, and Lavelle didn't give a reason too. So my guess is that you only have to memorize this exception and won't have to explain this trend on the exam. Sorry...
by julia_lok_2K
Fri Oct 26, 2018 9:46 am
Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
Topic: atomic spectra Rydberg
Replies: 3
Views: 129

Re: atomic spectra Rydberg

Honestly I never remember which one to use, but how I think of it is whichever order will get you a positive value. And if it's asking for energy of an electron going from a higher level to a lower level, I just get the positive value first then stick the negative sign in front of it, or say "t...
by julia_lok_2K
Fri Oct 26, 2018 9:41 am
Forum: Electron Configurations for Multi-Electron Atoms
Topic: Homework 2.43e
Replies: 3
Views: 120

Homework 2.43e

I know there's the exception for electron configurations where if the d orbital is almost half full or almost full, one of the electrons from the outermost s orbital will go to that d orbital to make it half full or full. I know that Cr, Cu, and Ag are exceptions, so wouldn't tungsten also be an exc...
by julia_lok_2K
Fri Oct 26, 2018 9:31 am
Forum: *Shrodinger Equation
Topic: Schrodinger and quantum numbers
Replies: 3
Views: 304

Re: Schrodinger and quantum numbers

One of the UAs said that all you have to know is that the solutions you get from Schrodinger's equation are the quantum numbers. And an orbital is a wave function that relates those quantum numbers, specifically n, l, and ml, i.e. denotes the locations of electrons.

Hopefully this helps!
by julia_lok_2K
Fri Oct 26, 2018 9:27 am
Forum: Trends in The Periodic Table
Topic: Trends in the Periodic Table
Replies: 2
Views: 107

Re: Trends in the Periodic Table

So far, we have learned about the trends for atomic size, ionization energy, and electron affinity. 1. Atomic size: atomic radii increase as you go down a group because additional shells are farther from the nucleus atomic radii decrease as you go across a period because while more electrons are add...
by julia_lok_2K
Wed Oct 17, 2018 11:47 pm
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: Orbitals
Replies: 3
Views: 53

Re: Orbitals

I think a nodule plane is the area where the electron probability density is zero.

I don't know if I answered your question well, but I hope this helps!
by julia_lok_2K
Wed Oct 17, 2018 10:39 pm
Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
Topic: Atomic Spectra
Replies: 4
Views: 85

Re: Atomic Spectra

I think this is because a smaller amount of energy is emitted when an electron goes from n=4 to n=2 compared to going from n=5 to n=1 since the energy difference is smaller. This energy can be represented by E=hv, from which the equation E=(ch)/wavelength, or wavelength=(ch)/E, can be derived. From ...
by julia_lok_2K
Thu Oct 11, 2018 10:23 am
Forum: Balancing Chemical Reactions
Topic: Test 1
Replies: 6
Views: 213

Re: Test 1

I would definitely show work on the test. In addition to getting partial points, it also decreases your chances of making minor mistakes instead of doing the work in your head.
by julia_lok_2K
Thu Oct 11, 2018 10:21 am
Forum: Limiting Reactant Calculations
Topic: Test 1
Replies: 8
Views: 519

Re: Test 1

I agree, homework problems definitely help with solidifying your understanding of the concepts that will appear on the test. In fact, I think that the quiz was easier than the homework, so if you did all the homework then you should be fine. And it's definitely possible to finish earlier--some peopl...
by julia_lok_2K
Thu Oct 04, 2018 11:10 pm
Forum: Limiting Reactant Calculations
Topic: Aqueous Products in Limiting Reactant Problems
Replies: 3
Views: 63

Re: Aqueous Products in Limiting Reactant Problems

I suppose so. Can you give a problem as an example?
by julia_lok_2K
Thu Oct 04, 2018 11:52 am
Forum: Accuracy, Precision, Mole, Other Definitions
Topic: Problem F.7
Replies: 4
Views: 104

Re: HW Problem F.7

I didn't see this in the list of homework problems? Anyway, how I did it was that since they give you the mass percent of M, you can figure out the mass percent of O by subtracting 88.8 from 100 to get 11.2. You can then set this number out of 100g to get 11.2 g, then find the number of moles of O, ...
by julia_lok_2K
Thu Oct 04, 2018 11:27 am
Forum: Accuracy, Precision, Mole, Other Definitions
Topic: Question E29 c.
Replies: 3
Views: 80

Re: Question E29 c.

So you know how many moles of copper(II) chloride tetrahydrate you have. You multiply that number by the molar ratio of water and the molecule to get the number of moles of water. In this case, since there are 4 molecules of water in in one molecule of copper(II) chloride tetrahydrate, you would mul...

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