## Search found 77 matches

Fri Mar 16, 2018 8:37 pm
Forum: Arrhenius Equation, Activation Energies, Catalysts
Topic: Negative activation energy?
Replies: 2
Views: 188

### Re: Negative activation energy?

Activation energy can be negative if the rate decreases as temperature rises (not common). However, I do not believe we have had a problem with this case, so I personally would double check that answer if I got it.
Tue Mar 13, 2018 12:48 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: 371

### Re: 9.23

I attached the Lewis structure pictures and Sahaj Gill is right.
Tue Mar 13, 2018 12:20 pm
Forum: Reaction Mechanisms, Reaction Profiles
Topic: Pseudo First Order?
Replies: 1
Views: 147

### Re: Pseudo First Order?

I believe it could be a fair concept to test on. As for problems, 15.30 explicitly asks about pseudo first order, but 15.29 and 15.37 contain related concepts.
Tue Mar 13, 2018 11:10 am
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: Specific Heat Capacity vs. deltaHfus and deltaHvap
Replies: 2
Views: 338

### Re: Specific Heat Capacity vs. deltaHfus and deltaHvap

The specific heat capacity is the amount of energy it takes to raise a certain unit of mass a certain unit of temperature. Usually this unit of mass is grams and the unit of temperature is Celsius or Kelvin. For example 1 calorie is the amount of energy it takes to raise the temperature by one degre...
Fri Mar 09, 2018 7:18 pm
Forum: Balancing Redox Reactions
Topic: Oxidation Number
Replies: 4
Views: 233

### Re: Oxidation Number

The oxidation number of elements will usually add up to the overall charge of the ion. For example, in MnO4 with a charge of 1-, the oxidation numbers of the atoms must add up to -1. Oxygen will be -2 in most cases, and since there are 4 oxygen atoms, Mn would have an oxidation number of +7. +7 +4(-...
Fri Mar 09, 2018 7:06 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: The Daniell Cell [ENDORSED]
Replies: 1
Views: 159

### Re: The Daniell Cell[ENDORSED]

As electrons leave the anode to the cathode, the anode part becomes positively charged while the cathode part becomes negatively charged. The porous barrier allows for ions usually sulfate to move from the cathode to the anode part, thus keeping the parts relatively neutral so the reaction can proce...
Fri Mar 09, 2018 12:28 pm
Forum: Reaction Mechanisms, Reaction Profiles
Topic: Effect of Activation Energy on a Reaction [ENDORSED]
Replies: 2
Views: 158

### Re: Effect of Activation Energy on a Reaction[ENDORSED]

Temperature cannot change the activation energy, but it does allow the collision frequency of the molecules to increase, meaning the reaction has an easier time crossing the activation energy barrier with an increase in temperature.
Fri Mar 09, 2018 11:26 am
Forum: Second Order Reactions
Topic: Units of k for orders above 2nd
Replies: 6
Views: 478

### Re: Units of k for orders above 2nd

Yes, for example, the k for a 10th order reaction would be M^(-9) * s^(-1).
Fri Mar 02, 2018 12:19 pm
Forum: Arrhenius Equation, Activation Energies, Catalysts
Topic: Arrhenius Reaction
Replies: 6
Views: 354

### Re: Arrhenius Reaction

I do not believe we have.
Fri Mar 02, 2018 12:15 pm
Forum: General Rate Laws
Topic: Calculating Rate vs. Unique Average Rate
Replies: 2
Views: 172

### Re: Calculating Rate vs. Unique Average Rate

I believe the problem should specify since they are different.
Fri Mar 02, 2018 10:23 am
Forum: Administrative Questions and Class Announcements
Topic: Kinetics Test (#3)
Replies: 2
Views: 197

### Re: Kinetics Test (#3)

Since the test is from 15.1 to 15.6, I'm assuming the last point will be:
Know how to determine the order of a reaction, its rate law, and its rate constant for reactions with more than one reactant.
Fri Mar 02, 2018 10:19 am
Forum: *Complex Reaction Coordinate Diagrams
Topic: Unique Rate. [ENDORSED]
Replies: 4
Views: 1419

### Re: Unique Rate.[ENDORSED]

A unique rate is the rate of a substances consumption or formation divided by the stoichiometric coefficient of that substance. This number will be the same for every substance in the reaction.
Fri Feb 23, 2018 12:35 pm
Forum: Arrhenius Equation, Activation Energies, Catalysts
Topic: Textbook Problem
Replies: 2
Views: 166

### Re: Textbook Problem

That negative sign changes to plus since pH is the -log[H+]. When they changed log[H+] to pH they had to multiply it by -1. Hope this makes sense!
Fri Feb 23, 2018 12:31 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Trends in Increasing Reducing Ability
Replies: 5
Views: 363

### Re: Trends in Increasing Reducing Ability

I believe you would use the equation where it the ion goes to neutral. So like In3+ to In instead of In3+ to In2+.
Fri Feb 23, 2018 12:26 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: 14.13d
Replies: 3
Views: 239

### Re: 14.13d

After multiplying the first reaction by 3 the Au on the left side of half reaction 2 will cancel out one of these on half reaction 1. If you are wondering why the electrons are on different sides for the reactions this is simply because Au is losing and gaining electrons. These are unique reactions ...
Fri Feb 23, 2018 12:20 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: 14.29 States of redox couples
Replies: 3
Views: 204

### Re: 14.29 States of redox couples

Also I am assuming standard temperature and pressure.
Fri Feb 23, 2018 12:19 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: 14.29 States of redox couples
Replies: 3
Views: 204

### Re: 14.29 States of redox couples

Items with a charge are usually aqueous, the metals are solid, while the diatomic molecules and O3 are gaseous. Basically, their location on the periodic table dictates their natural state if they are neutral.
Mon Feb 12, 2018 12:36 pm
Forum: Entropy Changes Due to Changes in Volume and Temperature
Topic: nR = PV/T (9.47) [ENDORSED]
Replies: 1
Views: 207

### Re: nR = PV/T (9.47)[ENDORSED]

Actually you did most of the calculation right. One thing though. When you did it, your units should be L*atm*K^(-1). One liter times atm equals 101.33 J so when you multiply your answer: 0.0379 by 101.33 you get around 3.84 just like the solution. Hope this helps!
Mon Feb 12, 2018 12:21 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: cis vs trans [ENDORSED]
Replies: 4
Views: 404

### Re: cis vs trans[ENDORSED]

I believe the more orientations a molecule has the more its entropy is. If a molecule did not have cis and trans versions it would have a lower entropy than a similar molecule that did.
Mon Feb 12, 2018 12:19 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: 9.25
Replies: 1
Views: 199

### Re: 9.25

I believe they are talking about if a bunch of SO2F2 molecules take a disordered arrangement as a whole. In a crystal structure, all the molecules are aligned perfectly so that they all look alike 3 dimensionally. This question asks if they are not all aligned the same way (like the fluorine atom on...
Mon Feb 12, 2018 12:14 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: 9.55, 9.57
Replies: 1
Views: 119

### Re: 9.55, 9.57

In 9.55 delta H (formation) equals delta H (reaction) since reactants for each equation you produce are in their standard states. These reactions have a total delta H of zero so subtracting the reactants like you did in 9.57 is not necessary.
Mon Feb 05, 2018 9:00 pm
Forum: Concepts & Calculations Using Second Law of Thermodynamics
Topic: Molar entropy value
Replies: 1
Views: 145

### Re: Molar entropy value

That molar entropy value you see is the actual entropy of that substance figuring in microstates and degeneracy and all that stuff. This can never be zero like enthalpy since all substances even ones in their natural states have entropy since the temperature never reaches 0 K. The standard entropy o...
Mon Feb 05, 2018 8:57 pm
Forum: Concepts & Calculations Using Second Law of Thermodynamics
Topic: Molar amount vs Pure Number in Reaction values
Replies: 1
Views: 169

### Re: Molar amount vs Pure Number in Reaction values

Basically for a delta H of a reaction, I would use the coefficients, whatever they may be. Even if all the numbers are doubled the delta h for the reaction would just get doubled and it would be the delta H for that reaction. If you are using J/mole divide the delta h reaction by the main product mo...
Mon Feb 05, 2018 8:51 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: HW 9.65
Replies: 1
Views: 134

### Re: HW 9.65

I believe SO2 entropy change is positive and since the equation for delta g is enthalpy - T(delta S), as T increases the value of delta g becomes more negative making it more stable.
Mon Feb 05, 2018 8:46 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: Stability
Replies: 1
Views: 82

### Re: Stability

Basically a negative delta G means its stable while a positive delta G means it is not. A positive delta G means that the formation reaction favors the reverse direction because of spontaneity so the product will degrade to its reactants most likely.
Thu Feb 01, 2018 5:06 pm
Forum: Concepts & Calculations Using Second Law of Thermodynamics
Topic: reversible vs irreversible
Replies: 3
Views: 271

### Re: reversible vs irreversible

I can explain part of your question. Basically work is being done in a reversible process but not for an irreversible process. When work is being done, q(surr) exists therefore entropy change of the surroundings does too. This will usually equal the entropy change of the system making total entropy ...
Thu Feb 01, 2018 5:02 pm
Forum: Entropy Changes Due to Changes in Volume and Temperature
Topic: 9.47 B
Replies: 2
Views: 163

### Re: 9.47 B

For a reversible path, work is done, so there is a q(surr) this means entropy change for the surroundings is not 0. In fact it is the exact opposite of the entropy change in the system so they cancel out and make total entropy change equal to 0. for the irreversible process no work is being done, q(...
Thu Feb 01, 2018 4:55 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: Energy calculation precision
Replies: 2
Views: 145

### Re: Energy calculation precision

There is actually a fourth equation too which derives delta g from a standard state cell potential: delta G= (-)moles of electrons*faraday's constant*cell potential. Depending on what information is given will tell you which equation to use. The accuracy of them depends on how accurate and precise t...
Thu Feb 01, 2018 4:47 pm
Forum: Concepts & Calculations Using Second Law of Thermodynamics
Topic: Entropy as a Probability
Replies: 1
Views: 108

### Re: Entropy as a Probability

Yes, from what I've learned so far, you have a good idea of what entropy is. Entropy is the degree of randomness or disorder rather than disorder or randomness itself. So the more microstates, the more the potential for a higher entropy.
Wed Jan 24, 2018 7:48 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: deltaH Units
Replies: 5
Views: 322

### Re: deltaH Units

An example would be the delta H of a reaction is in kJ. However delta H formation could be written in kJ/mole of the product if we divide the original number by the molar coefficient of the product. The kJ/mole is specific for a substance and if you know the amount of moles of the substance you can ...
Wed Jan 24, 2018 7:44 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: Heat Released
Replies: 3
Views: 141

### Re: Heat Released

Thanks guys!
Wed Jan 24, 2018 7:42 pm
Forum: Thermodynamic Systems (Open, Closed, Isolated)
Topic: Car Engine [ENDORSED]
Replies: 4
Views: 330

### Re: Car Engine[ENDORSED]

The engine requires gasoline and oxygen which are matter. It also dissipates heat. Since both matter and energy can enter/leave the system, it is considered open.
Wed Jan 24, 2018 7:40 pm
Forum: Calculating Work of Expansion
Topic: Reversible expansion and work in a vacuum
Replies: 2
Views: 183

### Re: Reversible expansion and work in a vacuum

I believe the piston had a string with mass attached to it on the outside of the chamber. Not fully sure, but I would recommend looking at the picture in your notes again.
Wed Jan 24, 2018 11:32 am
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: Heat Released
Replies: 3
Views: 141

### Heat Released

I know that if heat is released, q is negative. If the question asks for how much heat was released to we still put the negative sign on the number of Joules or calories?
Fri Jan 19, 2018 3:09 pm
Forum: Phase Changes & Related Calculations
Topic: 8.47
Replies: 3
Views: 151

### Re: 8.47

Actually delta u equals q + w, so delta u = delta h +pv. I think you are confusing it with the equation delta h = delta u -pv which is a derivation of the first one.
Wed Jan 17, 2018 10:17 am
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: Celsius vs Kelvin with heat capacities [ENDORSED]
Replies: 3
Views: 344

### Re: Celsius vs Kelvin with heat capacities[ENDORSED]

Usually in the equation, they are using delta T and since both Celsius and Kelvin have the same unit interval, final temp minus initial temp would be the same.
Wed Jan 17, 2018 10:15 am
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: Specific Heat capacity
Replies: 2
Views: 159

### Re: Specific Heat capacity

Normally the calorimeter is not included in the equations and is assumed that it does not loose heat, but it could be in certain cases. However each of the heat constants have units attached to them. If you are using q=mCdeltaT, make sure the c you choose has mass, energy, and a unit of temperature ...
Wed Jan 17, 2018 10:07 am
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: Heat Transfer at Constant Volume/Pressure
Replies: 4
Views: 179

### Re: Heat Transfer at Constant Volume/Pressure

I believe you are correct. At a constant pressure, Delta H = Delta U - PV and when both pressure and volume are constant, Delta H = Delta U.
Fri Jan 12, 2018 8:26 am
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: State function vs non state function
Replies: 2
Views: 2362

### Re: State function vs non state function

Basically, from what I know, a state function usually has final state - initial state (path has no impact) while a non state function will require the whole path or value in addition to its initial and final. So like friction, a non state function, includes the total distance traveled by a particle....
Fri Jan 12, 2018 8:18 am
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Enthalpy Change Signs
Replies: 5
Views: 374

### Re: Enthalpy Change Signs

Yes, reversing a reaction changes the sign of delta H.
Thu Jan 11, 2018 9:08 am
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Chapter 8
Replies: 6
Views: 297

### Re: Chapter 8

Personally, I believe your TA would accept any 7 homework problems from the listed HW problems for chapter 8 on the syllabus. So far I know for sure he has talked about the measurement of heat which is 8.5 and the enthalpy of physical change which is 8.11.
Thu Jan 11, 2018 9:01 am
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: standard enthalpiy of formation
Replies: 2
Views: 87

### Re: standard enthalpiy of formation

Overall, a standard enthalpy of formation is the change in enthalpy in the formation of 1 mole of the substance from the elements that make up the substance. For gases, we assume it follows the ideal gas law equation at 1 bar. For solutions, we assume 1 M and 1 bar.
Thu Jan 11, 2018 8:56 am
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: Celsius the same as Kelvin? [ENDORSED]
Replies: 9
Views: 2626

### Re: Celsius the same as Kelvin?[ENDORSED]

Yes, K and C have the same degree interval and to convert C to K you would add 273.15. In any equation I would recommend using K since that is SI. However in this case since the temp rises by 7.32 C; that means delta T is 7.32. If you converted to K and calculated delta T it would be the same since ...
Fri Dec 08, 2017 5:52 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: partial pressure
Replies: 1
Views: 173

### Re: partial pressure

Partial pressure of each gas is a factor when determining Kp. A higher or lower partial pressure of a gas participating in the reaction can either shift the reaction to the reactants or products.
Fri Dec 08, 2017 5:47 pm
Forum: Ideal Gases
Topic: Changes in Pressure
Replies: 1
Views: 257

### Re: Changes in Pressure

When changing the pressure through volume, concentration is inversely affected since concentration is n over V. Adding an inert gas changes the pressure but has no effect on volume therefore no effect on concentration.
Sat Dec 02, 2017 11:47 pm
Forum: Calculating pH or pOH for Strong & Weak Acids & Bases
Topic: HW: 12.49
Replies: 1
Views: 201

### Re: HW: 12.49

pKb is not a constant. It is the negative log(base 10) of the base dissociation constant(Kb). Also I hypobromite is more basic than Morphine.
Sat Dec 02, 2017 11:37 pm
Forum: Administrative Questions and Class Announcements
Topic: Link to Review Session Schedule? [ENDORSED]
Replies: 3
Views: 271

### Re: Link to Review Session Schedule?[ENDORSED]

I find it really funny when someone posts the answer while you’re typing it.
Sat Dec 02, 2017 11:36 pm
Forum: Administrative Questions and Class Announcements
Topic: Link to Review Session Schedule? [ENDORSED]
Replies: 3
Views: 271

### Re: Link to Review Session Schedule?[ENDORSED]

https://lavelle.chem.ucla.edu/wp-conten ... ns_14A.pdf

It’s in his 14A website with the link: Final Exam Review Sessions.
Sat Dec 02, 2017 11:33 pm
Forum: Shape, Structure, Coordination Number, Ligands
Topic: Drawing Coordination Compounds
Replies: 5
Views: 687

### Re: Drawing Coordination Compounds

I believe so only that the transition metal does not follow the octet rule.
Fri Dec 01, 2017 11:20 am
Forum: Lewis Acids & Bases
Topic: Strong acid+weak base
Replies: 2
Views: 248

### Re: Strong acid+weak base

The conjugate base of a strong acid placed in water is a week base. The conjugate acid of a strong base is a weak acid. I believe this should be true for both lewis and bronsted. Lewis definitions just include a wider array of acids and bases than bronsted.
Fri Dec 01, 2017 10:14 am
Forum: Determining Molecular Shape (VSEPR)
Topic: Do lone pairs affect polarization?
Replies: 1
Views: 213

### Re: Do lone pairs affect polarization?

Lone pairs definitely affect the polarity of a molecule. Unless they cancel out, the dipole will point to the atom with the most lone pairs.
Wed Nov 22, 2017 10:43 pm
Forum: Non-Equilibrium Conditions & The Reaction Quotient
Topic: Quadratic Formula [ENDORSED]
Replies: 1
Views: 132

### Quadratic Formula[ENDORSED]

Sometimes when using an ice table and plugging x back in, we must solve a quadratic formula. If K is small enough can we say x is negligible? If so, how small can K be so that x is negligible?
Wed Nov 22, 2017 10:36 pm
Forum: Naming
Topic: Naming the metal
Replies: 4
Views: 286

### Re: Naming the metal

I believe it depends if the metal is alone, has a charge, or is part of a larger compound. Metals with no charge are written just as their name appears on the periodic table. Metals with a charge are the same however the charge is written in parentheses. Metals part of compounds must have charges an...
Tue Nov 21, 2017 1:28 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Aqueous and Gaseous Phases
Replies: 3
Views: 240

### Aqueous and Gaseous Phases

If a chemical reaction has both aqueous and gaseous substances, how would you determine K if given the concentrations? Would you use Kp or Kc? Also if using Kc, are gases included? Dr. Lavelle said only solid and liquids were excluded in the calculation.
Fri Nov 17, 2017 9:03 pm
Forum: Shape, Structure, Coordination Number, Ligands
Topic: Number of Ligands
Replies: 1
Views: 133

### Number of Ligands

Does someone know the range of how many ligands a transition metal can receive? I know the common one is 6 but how higher and lower can they go?
Fri Nov 17, 2017 9:00 pm
Forum: Hybridization
Topic: 4.45
Replies: 2
Views: 1695

### Re: 4.45

Well first I would draw the lewis structure, then count the regions of electron density for C and O since hybridization can explain their bonds. That number (3) corresponds with the sp2 hybrid orbital. The bond angle is determined by vsepr. The structure is a trigonal planar which results in 120 deg...
Fri Nov 17, 2017 11:19 am
Forum: Determining Molecular Shape (VSEPR)
Topic: Hybridization of VSEPR Models
Replies: 2
Views: 186

### Re: Hybridization of VSEPR Models

In fact, the number of regions of electron density (number of lone pairs (count two as a pair) and bonds (single, double, triple all count as one)) will always be able to tell the hybridization configuration.
Fri Nov 17, 2017 11:13 am
Forum: Shape, Structure, Coordination Number, Ligands
Topic: TM Cations
Replies: 2
Views: 232

### Re: TM Cations

It does not always have to be six, however that is a very common configuration for a coordination complex.
Tue Nov 07, 2017 11:42 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Central Atom
Replies: 4
Views: 339

### Re: Central Atom

Usually the least electronegative atom is the central atom.
Tue Nov 07, 2017 11:40 pm
Forum: Octet Exceptions
Topic: Radical Rules
Replies: 1
Views: 193

### Re: Radical Rules

Radicals are in chapter 3, so a question regarding them on the midterm is possible. Radicals occur usually when there is an electron that is not part of a lone pair. An easy way to tell is if the compound has an odd number of outer electrons (the ones that go on the Lewis structure). To be sure you ...
Tue Nov 07, 2017 11:36 pm
Forum: Lewis Structures
Topic: Where to place lone pairs
Replies: 2
Views: 214

### Re: Where to place lone pairs

I’m assuming you mean in Lewis structures. Usually I just try to space them out. If there is one line pair, I just place it on the opposite side of the bond.
Thu Nov 02, 2017 1:12 pm
Forum: Electron Configurations for Multi-Electron Atoms
Topic: d orbital or s orbital first?
Replies: 5
Views: 401

### Re: d orbital or s orbital first?

A d orbital with a lower n value will always go before an s orbital of a higher n value. For example, Titanium would be 3d^2 4s^2
Thu Nov 02, 2017 1:08 pm
Forum: Electron Configurations for Multi-Electron Atoms
Topic: Orbitals
Replies: 1
Views: 127

### Orbitals

In the p-orbital, for instance, does the l value from first to last go from -l to +l or +l to -l?
Thu Nov 02, 2017 1:05 pm
Forum: Electron Configurations for Multi-Electron Atoms
Topic: Drawing the configuration
Replies: 4
Views: 268

### Drawing the configuration

When filling up orbitals does it matter if you start with spin downs or spin ups?
Wed Oct 25, 2017 11:04 pm
Forum: Electron Configurations for Multi-Electron Atoms
Topic: Valence Electrons (2.55)
Replies: 2
Views: 178

### Re: Valence Electrons (2.55)

Basically, the (n-1) is used for the d orbital since it is always one level lower in each configuration.
Wed Oct 25, 2017 11:01 pm
Forum: Lewis Structures
Topic: Lewis Dot Structure Example
Replies: 3
Views: 192

### Re: Lewis Dot Structure Example

Actually he drew the Lewis dot structures for salts like KF. The only difference was that he used square brackets to differentiate the individual charges of the ions. So, I believe you could do the same for ammonium sulfate (there would be two ammonium ions since it has a plus one charge while sulfa...
Wed Oct 25, 2017 10:50 pm
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: Xenon noble gas [ENDORSED]
Replies: 1
Views: 209

### Xenon noble gas[ENDORSED]

Even though Xe is a noble gas why does it form molecules? And how would one do the Lewis dot structures for these molecules?
Tue Oct 17, 2017 3:47 pm
Forum: Properties of Light
Topic: Light travels as a "wave"
Replies: 5
Views: 385

### Re: Light travels as a "wave"

I think this picture that was shown in the lecture illustrates a light wave pretty well.
Tue Oct 17, 2017 3:42 pm
Forum: Heisenberg Indeterminacy (Uncertainty) Equation
Topic: What does Heisenberg Indeterminacy indicate with respect to the “randomness” of the electrons that are near nucleus
Replies: 3
Views: 499

### Re: What does Heisenberg Indeterminacy indicate with respect to the “randomness” of the electrons that are near nucleus

I really got a better understanding of this from Dr. Lavelle’s diagram. Normally for a large object we can use light beams to detect its position and velocity. However the same process will not work for an electron since the photons hitting the electron will cause the electron to take an unpredictab...
Tue Oct 17, 2017 3:32 pm
Forum: Trends in The Periodic Table
Topic: List of all trends?
Replies: 5
Views: 599

### Re: List of all trends?

For atomic size, it increases as you go down the columns but decreases as you go from left to right on the rows. Ionization energy follows the exact opposite trend. Metallic characteristics increase going left and down but decrease when going right and up.
Tue Oct 17, 2017 3:23 pm
Forum: Photoelectric Effect
Topic: Number of Photons
Replies: 4
Views: 288

### Re: Number of Photons

Another way to think of more photons is a higher amplitude. The wavelength determines whether the beam of light can eject an electron. Amplitude and wavelength can change independently from one another.
Wed Oct 11, 2017 10:26 pm
Forum: Properties of Light
Topic: Velocity [ENDORSED]
Replies: 13
Views: 959

### Re: Velocity[ENDORSED]

In this case it's very similar. Velocity is just speed with direction. Sometimes a negative sign will denote a leftward direction and a positive will denote a rightward direction, but nowhere is this set in stone. As long as the reference point is kept constant throughout the experiment, there shoul...
Wed Oct 11, 2017 10:21 pm
Forum: Properties of Light
Topic: Calculating the wavelength of light [ENDORSED]
Replies: 5
Views: 440

### Re: Calculating the wavelength of light[ENDORSED]

This equation is just a combination of the equations: E=hv and c= λv. When asked for the wavelength and given the energy or asked for the energy and given the wavelength, this equation is just quicker than using the two equations above.
Wed Oct 11, 2017 10:17 pm
Forum: Empirical & Molecular Formulas
Topic: Empirical Coefficients [ENDORSED]
Replies: 12
Views: 1493

### Re: Empirical Coefficients[ENDORSED]

Thanks guys.
Wed Oct 04, 2017 11:11 pm
Forum: Empirical & Molecular Formulas
Topic: Empirical Coefficients [ENDORSED]
Replies: 12
Views: 1493

### Empirical Coefficients[ENDORSED]

Sometimes when I solve for the empirical formula I get moles like 3.1 or 2.9. Looking at the answers, I found out that rounds to 3. After what decimal digit (3.15 or 3.2) should I multiply all the moles by a constant to get better whole numbers?
Wed Oct 04, 2017 11:01 pm
Forum: Accuracy, Precision, Mole, Other Definitions
Topic: Amount of a stubstance
Replies: 2
Views: 230

### Re: Amount of a stubstance

If the question asks for an amount in grams, then, using your example, O2 would have twice the amount of grams than O. If asking for moles, then it does not matter. However, in most questions oxygen means oxygen gas and that is O2 which has a molar mass of around 32g per mole.
Wed Oct 04, 2017 10:51 pm
Forum: SI Units, Unit Conversions
Topic: Sig Figs
Replies: 12
Views: 1221

### Re: Sig Figs

Hi Michelle,

Leading zeros are not significant digits so 0.020 would only have 2 sig figs. The 2 and the 0 after it are significant digits.

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