## Search found 54 matches

Sat Mar 17, 2018 5:57 pm
Forum: General Rate Laws
Topic: Rate Law where a concentration is to a negative power
Replies: 2
Views: 285

### Re: Rate Law where a concentration is to a negative power

The negative power brings the concentration of that species to the bottom of the rate so having more of it would lower the rate. So yeah it's much like an inhibitor.
Fri Mar 16, 2018 1:47 pm
Forum: Environment, Ozone, CFCs
Topic: Radical Chain Reactions
Replies: 1
Views: 537

### Re: Radical Chain Reactions

I dont think so, but if someone would confirm that would be good.
Tue Mar 13, 2018 1:32 pm
Forum: Balancing Redox Reactions
Topic: Winter 2013 final Q4
Replies: 9
Views: 513

### Re: Winter 2013 final Q4

n is the movement of electrons so if you do the oxidation and reduction half reactions you should find that n = 4. Also I think you can just look at the charge of iron going from 0 in the reactants to +4 in the products and determine that the iron is being oxidized and 4 electrons are leaving, but i...
Tue Mar 13, 2018 1:18 pm
Forum: Third Law of Thermodynamics (For a Unique Ground State (W=1): S -> 0 as T -> 0) and Calculations Using Boltzmann Equation for Entropy
Topic: 9.23
Replies: 4
Views: 322

### Re: 9.23

Just to segue off this post, there's molar mass, the positional disorder and what other factors that determine a compound's entropy? And which should we look at first if we were to rank them?
Tue Mar 13, 2018 1:15 pm
Forum: General Rate Laws
Topic: Distinguishing Different Types of Constants
Replies: 3
Views: 219

### Re: Distinguishing Different Types of Constants

As far as I know, yes the constant for the forward reaction, k, and the constant k used in the rate law are the same. And then for the others, the capital K is of course the concentration of products divided by concentration of reactants. And as you said, k' is the reverse rate law. So I guess the o...
Tue Mar 06, 2018 10:31 am
Forum: General Rate Laws
Topic: How the concentration of a reactant affects the rate of the reaction
Replies: 3
Views: 144

### Re: How the concentration of a reactant affects the rate of the reaction

More of the reactant means that the probability of collisions can occur more frequently which means the reaction is more likely to proceed faster.
Tue Mar 06, 2018 10:27 am
Forum: Arrhenius Equation, Activation Energies, Catalysts
Topic: Catalysts
Replies: 5
Views: 339

### Re: Catalysts

AS far as I know, lowering the activation energy of the reaction means the reaction has less of a barrier to overcome so the reaction would proceed faster.
Tue Mar 06, 2018 10:25 am
Forum: Zero Order Reactions
Topic: Slope From
Replies: 5
Views: 364

### Re: Slope From

As far as I know it just helps with identifying what the rate constant is.
Sat Mar 03, 2018 11:13 pm
Forum: General Rate Laws
Topic: writing rate law
Replies: 3
Views: 230

### Re: writing rate law

The slow elementary step is much like the concept of a limiting reactant from last quarter.
Sat Mar 03, 2018 11:10 pm
Forum: Kinetics vs. Thermodynamics Controlling a Reaction
Topic: Rate Constant Units
Replies: 9
Views: 596

### Re: Rate Constant Units

Know that zero order reactions are mol/(L*s) and then as you go up one order, multiply by L/mol each time.
Fri Mar 02, 2018 11:11 am
Forum: Zero Order Reactions
Topic: Units of k [ENDORSED]
Replies: 13
Views: 531

### Re: Units of k[ENDORSED]

Units of k start out at mol/(L*s) at the zero order and every time you go up one order you can multiply by L/mol to get the new units of k.
Thu Feb 22, 2018 10:32 pm
Forum: Balancing Redox Reactions
Topic: H+ or H3O+ [ENDORSED]
Replies: 3
Views: 248

### Re: H+ or H3O+[ENDORSED]

I'm pretty sure you're supposed to use H+ (at least thats what my TA said) but I guess as long as you balance both H and O atoms then you should be fine.
Thu Feb 22, 2018 10:30 pm
Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
Topic: anode vs cathode in non standard cell diagram
Replies: 5
Views: 288

### Re: anode vs cathode in non standard cell diagram

As far as I know, the anode is always on the left. I haven't seen it on the right - not yet at least.
Thu Feb 22, 2018 10:27 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Spontaneous Directions [ENDORSED]
Replies: 7
Views: 430

### Re: Spontaneous Directions[ENDORSED]

If the standard potential is positive (it'll make delta G negative bc of delta G = -nFE) so it'll be spontaneous.
Fri Feb 16, 2018 12:18 am
Forum: Concepts & Calculations Using Second Law of Thermodynamics
Topic: s vs. delta s
Replies: 7
Views: 374

### Re: s vs. delta s

Just to add on, the S in the residual entropy is like the minimum energy of the molecule - it's the entropy that the molecule has without anything being done to it. That's about the only time we use S instead of delta S.
Fri Feb 16, 2018 12:15 am
Forum: Balancing Redox Reactions
Topic: Splitting Redox Reactions
Replies: 3
Views: 225

### Re: Splitting Redox Reactions

The spectator ions get cancelled out anyway when you go from the ionic reaction to the net ionic reaction, I think. I don't think we need to know that for the test, but they cancel out anyway and don't matter.
Fri Feb 16, 2018 12:10 am
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Cell Diagrams
Replies: 3
Views: 152

### Re: Cell Diagrams

My TA was telling us that when we do the cell diagrams, the anode goes on the left and then the cathode on the right by convention.
Thu Feb 08, 2018 7:59 pm
Forum: Calculating Standard Reaction Entropies (e.g. , Using Standard Molar Entropies)
Topic: 9.33
Replies: 2
Views: 172

### Re: 9.33

I think that it would - at least that's what I did when I was doing this problem. Gas to liquid means less movement of molecules so that explanation should suffice.
Thu Feb 08, 2018 7:57 pm
Forum: Entropy Changes Due to Changes in Volume and Temperature
Topic: Heat Capacity when cooling
Replies: 1
Views: 117

### Re: Heat Capacity when cooling

I'm pretty sure you're just supposed to use the C value that corresponds to the phase of the reactant. So if it's a liquid, use the regular C value at 4.184, or if its solid then use that one and the same with vapor.
Thu Feb 08, 2018 7:54 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: 11.81
Replies: 2
Views: 162

### Re: 11.81

I'm pretty sure you can just look at the K value changing and come to a conclusion based off that. I don't really know how to solve this mathematically, so using K sufficed for me.
Sat Feb 03, 2018 12:01 pm
Forum: Entropy Changes Due to Changes in Volume and Temperature
Topic: Exergonic [ENDORSED]
Replies: 5
Views: 232

### Re: Exergonic[ENDORSED]

Oddly enough, water going from liquid to solid can also be exergonic given that the delta H being negative outweighs the fact that the entropy is decreasing.
Sat Feb 03, 2018 11:56 am
Forum: Calculating Standard Reaction Entropies (e.g. , Using Standard Molar Entropies)
Topic: How to tell what happens to entropy by seeing a reaction?
Replies: 6
Views: 352

### Re: How to tell what happens to entropy by seeing a reaction?

Generally speaking, the entropy for gas > liquid > solid.
Sat Feb 03, 2018 11:54 am
Forum: Concepts & Calculations Using Second Law of Thermodynamics
Topic: 9.35 [ENDORSED]
Replies: 5
Views: 248

### Re: 9.35[ENDORSED]

To put it another way, since b and c are bound they will have less disorder than the molecules that aren't so the entropy would be lower for those than say compared to the molecules that aren't bound to one another.
Thu Jan 25, 2018 11:50 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: Superheating
Replies: 3
Views: 220

### Re: Superheating

That wasn't mentioned in class nor was it mentioned in discussion so I'd imagine that you don't need to worry about superheating.
Thu Jan 25, 2018 11:46 pm
Forum: Calculating Standard Reaction Entropies (e.g. , Using Standard Molar Entropies)
Topic: Homework 8.57
Replies: 2
Views: 211

### Re: Homework 8.57

It seems like the product and reactant enthalpies are negative. And if we're doing products minus reactants the reactants are now a positive value (-products - (-reactants) is the same as reactants - products). Hope that helps
Wed Jan 24, 2018 11:48 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Exercise 8.39
Replies: 2
Views: 98

### Re: Exercise 8.39

That's the amount of energy it takes for water to change phases
Sun Jan 21, 2018 9:09 pm
Forum: Calculating Work of Expansion
Topic: Reversible and Irreversible Reactions
Replies: 2
Views: 176

### Re: Reversible and Irreversible Reactions

Reversible processes are incredibly slow whereas irreversible processes are done quickly and inefficiently. If there was all the time in the world where our car engine could turn 100% of the fuel it was given into the energy that's needed to drive the car then it would be reversible and it would tak...
Thu Jan 18, 2018 10:09 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Q. 8.65
Replies: 2
Views: 96

### Re: Q. 8.65

This is a highly simplified version but: 1) go to appendix 2A and find the NO reaction and the enthalpy for it 2) using that reaction and the two reactions given, rearrange them so that things cancel out and all that's left on the product side is dinitrogen pentoxide. 3) Make sure you adjust the ent...
Thu Jan 18, 2018 10:02 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: Molar heat capacity
Replies: 3
Views: 185

### Re: Molar heat capacity

From what I know, specific heat is dependent on a unit mass to heat something up. So in terms of a gas, the volume and pressure are important because the smaller the volume, the less molecules of gas and when you heat it up, it would take more heat (thus a higher heat capacity).
Mon Jan 15, 2018 1:17 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: Intensive vs extensive property
Replies: 2
Views: 166

### Re: Intensive vs extensive property

An extensive property depends on the mass while intensive does not.
Fri Jan 12, 2018 8:42 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Standard Reaction Enthalpies
Replies: 1
Views: 102

### Re: Standard Reaction Enthalpies

For Hess's law they give us the enthalpy for each equation anyway so the compounds being in their standard states shouldnt matter (because from what I understand we would only need them in their standard states to get the correct enthalpy from the enthalpy table), but I'm not entirely sure. If anyon...
Wed Jan 10, 2018 5:39 pm
Forum: Phase Changes & Related Calculations
Topic: chapter 8
Replies: 6
Views: 331

### Re: chapter 8

I think so. I remember him saying something like that in class.
Fri Dec 08, 2017 12:25 pm
Forum: Calculating pH or pOH for Strong & Weak Acids & Bases
Topic: Strength of acids and bases
Replies: 3
Views: 179

### Re: Strength of acids and bases

Yes. If the element bonded to a Hydrogen atom is really electronegative then the electrons are largely attracted to that element instead of it being equally distributed so its more likely that the Hydrogen "falls off." That makes the compound more electronegative.
Sat Dec 02, 2017 4:15 pm
Forum: Amphoteric Compounds
Topic: 12.17 [ENDORSED]
Replies: 9
Views: 1033

### Re: 12.17[ENDORSED]

You can always try drawing out lewis structures and seeing if the compound can give, receive, or both give and receive lone pairs. If it can do both then its amphoteric. That's how I'd go about it - I dont really know of any other way.
Tue Nov 28, 2017 6:25 pm
Forum: Naming
Topic: dentates
Replies: 3
Views: 214

### Re: dentates

I look at the lone pairs on the atoms to see if it can bind to other atoms and then determine if its a mono, bi, tri,...poly-dentate.
Tue Nov 28, 2017 6:20 pm
Forum: Sigma & Pi Bonds
Topic: bonds relating to the internuclear axis
Replies: 1
Views: 198

### Re: bonds relating to the internuclear axis

I think the way you're thinking of it is fine. I actually think about it in more simpler terms; I just think that if you try to rotate two balls (representing atoms) when they're stuck together by 2 sticks, then the sticks are gonna break, the same way the pi bonds would break.
Fri Nov 24, 2017 12:40 am
Forum: Determining Molecular Shape (VSEPR)
Topic: Homework 4.41
Replies: 2
Views: 232

### Re: Homework 4.41

I'm pretty sure it would although it would only be slightly less and slightly more, respectively.
Tue Nov 21, 2017 8:14 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Ionization energy vs. Atomic radii
Replies: 1
Views: 151

### Re: Ionization energy vs. Atomic radii

I'm not sure about the first question, but the exception with ionization energy is that Oxygen has a lower ionization energy than Nitrogen because Oxygen has an extra electron in its first orbital that it would much rather remove whereas Nitrogen has nicely balanced 3 electrons.
Thu Nov 16, 2017 2:53 pm
Forum: Hybridization
Topic: Pi bonds
Replies: 4
Views: 283

### Re: Pi bonds

Yes (at least that's the way I understand it).
Thu Nov 16, 2017 2:51 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Lone Pairs
Replies: 5
Views: 378

### Re: Lone Pairs

It depends. For something like water, you'd put the lone pairs next to each other on top of oxygen to get that bent shape but for something like XeF4, then you'd be putting the lone pairs on opposite sides to get the right molecular geometry.
Wed Nov 08, 2017 9:45 pm
Forum: Octet Exceptions
Topic: Radical Placement [ENDORSED]
Replies: 3
Views: 339

### Re: Radical Placement[ENDORSED]

Just based off the periodic trends, we see that going down a group electronegativity decreases and chlorine is lower than oxygen. Also, since the chlorine atom is larger than the oxygen atom, it will be less electronegative because the electrons will be farther away from the pull of the nucleus. Oxy...
Wed Nov 08, 2017 9:40 pm
Forum: Lewis Structures
Topic: 3.95
Replies: 1
Views: 149

### Re: 3.95

The carbon is the central atom (as given) and the CH2's come off the sides of carbon with each C atom having 2 Hydrogens attached to it. There are 24 valence electrons total so I started out by simply drawing it out with single bonds and then I made the central Carbon and another random carbon a dou...
Mon Oct 30, 2017 11:18 pm
Forum: Electron Configurations for Multi-Electron Atoms
Topic: 2.63
Replies: 2
Views: 208

### Re: 2.63

A cool trick to knowing these trends by the way is only knowing the atomic radius one (which decreases across the table and increases down a group) and everything else is just the opposite of that.
Mon Oct 30, 2017 11:13 pm
Forum: Trends in The Periodic Table
Topic: Chapter 2, #93
Replies: 3
Views: 235

### Re: Chapter 2, #93

Isn't it the other way around? Cl becomes the larger circle because it gains an electron and it's greater than its ground state because of that gained electron whereas Na loses that electron to Cl and becomes the smaller circle.
Mon Oct 23, 2017 9:58 pm
Forum: Electron Configurations for Multi-Electron Atoms
Topic: Confusion on e- Notes
Replies: 2
Views: 198

### Re: Confusion on e- Notes

Yes that's exactly what that means. It's called the noble gas configuration if we we're being fancy and it's really a short hand way of writing the noble gas configuration up to the noble gas (in this case argon) instead the whole 1s2, 2s2, 2p6..and so on.
Mon Oct 23, 2017 9:55 pm
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: p-orbitals
Replies: 3
Views: 235

### Re: p-orbitals

I don't think you'd have to do that unless it would better help you personally understand that the p sublevel has 3 orbitals (and therefore 6 electrons max).
Wed Oct 18, 2017 11:23 pm
Forum: Photoelectric Effect
Topic: Ionization in energy levels
Replies: 4
Views: 293

### Re: Ionization in energy levels

Ionization energy is the energy to remove an electron, so I'm pretty sure that the energy to ionize an electron would be the energy that would remove it.
Wed Oct 18, 2017 12:25 am
Forum: Photoelectric Effect
Topic: Energy of Photon [ENDORSED]
Replies: 9
Views: 1909

### Re: Energy of Photon[ENDORSED]

From what I know (and if someone would confirm) if the energy of the photon equals the amount of energy to eject the electron then that electron is ejected with a 0 kinetic energy.
Wed Oct 18, 2017 12:21 am
Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
Topic: Homework #1.11
Replies: 2
Views: 218

### Re: Homework #1.11

I think this refers to the fact that for lyman series, for example, the energy levels are jump up from n=1 to the other energy levels or they all come down from other energy levels to n=1. Same applies to balmer and paschen except for n=2 and n=3, respectively. Also it could mean the fact that lyman...
Thu Oct 12, 2017 11:08 pm
Forum: Properties of Light
Topic: 1.15
Replies: 4
Views: 265

### Re: 1.15

Yes from what I was told today in my discussion, you can assume that n1 is 1 if it's not given to you.
Thu Oct 12, 2017 10:42 pm
Forum: Properties of Light
Topic: Photons and Photoelectric effect
Replies: 3
Views: 212

### Re: Photons and Photoelectric effect

Oh I thought they didn't. Okay cool
Thu Oct 12, 2017 10:48 am
Forum: Properties of Light
Topic: Photons and Photoelectric effect
Replies: 3
Views: 212

### Photons and Photoelectric effect

Conservation of momentum and conservation of energy imply that when a photon hits an electron on the surface of a metal with enough energy to eject it, the electron would conserve both the energy of momentum; however, if a photon has no mass - by which mv (momentum) and .5mv^2 (kinetic energy) equal...
Fri Oct 06, 2017 1:40 pm
Forum: General Science Questions
Topic: Covalent Bonds
Replies: 3
Views: 530

### Re: Covalent Bonds

I would think that the attraction between the nuclei of the atoms and the electrons of the other atom are stronger than the repulsion between the two nuclei of those atoms and that holds covalently bonded atoms together.
Fri Oct 06, 2017 1:33 pm
Forum: Empirical & Molecular Formulas
Topic: Getting molecular formula from molecule name [ENDORSED]
Replies: 3
Views: 323

### Re: Getting molecular formula from molecule name[ENDORSED]

My TA was telling us that we'd probably need to know how to name molecules after the first test. We may go over it in class, but I'm unsure as to when. I guess the sooner you start learning them, the better off you'll be for the next test.

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