## Search found 90 matches

Sun Mar 17, 2019 8:44 am
Forum: Administrative Questions and Class Announcements
Topic: LYNDON'S PORK RAMEN REVIEW
Replies: 37
Views: 3526

### Re: LYNDON'S PORK RAMEN REVIEW

For question 14 part (c). What information is needed to determine the order of each step?
Sat Mar 16, 2019 10:17 pm
Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
Topic: 7th 6.65
Replies: 2
Views: 273

### Re: 7th 6.65

I used $E=-\frac{RT}{NF}lnQ=-\frac{8.314\times 298.15}{1\times 96485}ln\frac{10^{-14}}{10^{-7}}\approx 0.414$. I thought Q is between 10^-7 and 10^7, but the answer seems to imply that instead it should be between 10^-14 and 10^14.
Wed Mar 13, 2019 9:14 pm
Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
Topic: 7th 6.65
Replies: 2
Views: 273

### 7th 6.65

Can anyone tell me how to arrive at this answer?
Mon Mar 11, 2019 7:09 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: reducing power and oxidizing power
Replies: 2
Views: 189

### Re: reducing power and oxidizing power

The more positive the reduction potential, the stronger the oxidizing power and the weaker the reducing power. Just think reduction potential as measuring a compound's tendency to be reduced. A more positive reduction potential means that itself is more easily reduced than oxidized.
Mon Mar 11, 2019 7:06 pm
Forum: Reaction Mechanisms, Reaction Profiles
Topic: Frequency factor A
Replies: 7
Views: 288

### Re: Frequency factor A

In the book, A is just called the pre-exponential factor. I think it will become clearer in the next lecture as we get into collision theory. Then you see what constants are included in A.
Mon Mar 11, 2019 6:45 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Anode positive or negative in galvanic cell
Replies: 1
Views: 101

### Re: Anode positive or negative in galvanic cell

First, a galvanic cell is not connected to a battery. A galvanic cell is a cell that generates electricity through a spontaneous chemical reaction. A cell that is connected to a battery is an electrolytic cell. An electrolytic cell uses energy from the battery to drive reactions. Then to answer your...
Tue Mar 05, 2019 3:57 pm
Forum: General Rate Laws
Topic: how to calculate reaction rates
Replies: 2
Views: 139

### Re: how to calculate reaction rates

Use any formula from rate law, integrated rate law, and half-life. Taking a look at the examples in the textbook is pretty helpful.
Tue Mar 05, 2019 3:47 pm
Forum: First Order Reactions
Topic: Rate constant and half life
Replies: 3
Views: 157

### Re: Rate constant and half life

Because $t_{1/2}=(ln2)/k$ for first-order reactions.
Tue Mar 05, 2019 3:44 pm
Forum: First Order Reactions
Replies: 3
Views: 95

Because it has a constant half-life. All first-order reactions have constant half-lives.
Tue Feb 26, 2019 7:55 pm
Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
Topic: Cell potential
Replies: 2
Views: 114

### Re: Cell potential

Can you specify what you mean by changing the "stoichiometric coefficient of one reactant changes"? Will the equation still be balanced if you change only one reactant's coefficient?
Mon Feb 25, 2019 2:29 pm
Forum: Van't Hoff Equation
Topic: Derivation
Replies: 3
Views: 350

### Re: Derivation

From the 7th ed textbook page 433.
Mon Feb 25, 2019 2:24 pm
Forum: Balancing Redox Reactions
Topic: 7th edition 6L.7, Adams, Disc 1A
Replies: 2
Views: 155

### Re: 7th edition 6L.7, Adams, Disc 1A

For the same question, how is the right-half cell set up with three solids?
Fri Feb 22, 2019 11:31 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Reactants As Electrodes
Replies: 1
Views: 80

### Reactants As Electrodes

In some half-cells the solid reactant can be used as the electrode, such as zinc in Zn/$Zn^{+2}$. How do I know which solid reactants can be used as electrodes and which ones cannot?
Fri Feb 22, 2019 10:47 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Porous Disk
Replies: 1
Views: 95

### Porous Disk

I have two questions about porous disks. 1. When a porous disk is used, why do electrons flow through electrodes instead of through the solution to the other half-cell? 2. When a porous disk is used, are the reactants mixed? If they are, why don't they react directly without donating electrons to an...
Thu Feb 21, 2019 2:48 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Standard Cell Potential
Replies: 2
Views: 146

### Re: Standard Cell Potential

When it's above 0, it means that the flow of electron from the left half-cell to the right half-cell is spontaneous. That is, oxidation in the left half-cell and reduction in the right half-cell.
Thu Feb 21, 2019 2:43 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Inert Electrodes
Replies: 2
Views: 104

### Re: Inert Electrodes

I think platinum is often used as an inert electrode because it does not react with the reactants in the cell. They are only responsible for conduction of current. An example is a hydrogen half-cell with uses platinum as the electrode.
Thu Feb 21, 2019 8:55 am
Forum: Gibbs Free Energy Concepts and Calculations
Topic: Gibbs Free Energy Meaning
Replies: 6
Views: 282

### Re: Gibbs Free Energy Meaning

G=H-TS. Gibbs free energy is the energy available to do work. It's less than the energy of a system because not all of the energy can be used to do work.
Tue Feb 12, 2019 10:26 pm
Forum: Calculating Work of Expansion
Topic: Uses of different formulas
Replies: 3
Views: 177

### Re: Uses of different formulas

If the external pressure is constant, it's irreversible expansion.
Sun Feb 10, 2019 10:18 pm
Forum: Calculating Work of Expansion
Topic: Reversible Expansion
Replies: 3
Views: 131

### Re: Reversible Expansion

It depends on the system at hand. If the system is isolated, heat cannot come into the reversible expansion and replace the additional energy loss, so the first law of thermodynamics tells us that in the case that both systems (reversible and irreversible) are isolated, the irreversible one would i...
Sun Feb 10, 2019 10:11 pm
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: Contribution of Motion to Internal Energy
Replies: 1
Views: 198

### Contribution of Motion to Internal Energy

Have trouble getting the right answer of Self-test 4B.3A on the 7th ed book. "Estimate the contribution of motion to the molar internal energy of water vapor at 25 Celcius degrees." Why is it not 3.72 kJ.Mol^-1?
Sun Feb 10, 2019 9:21 pm
Forum: Calculating Work of Expansion
Topic: Reversible Work and Maximum Work
Replies: 5
Views: 159

### Re: Reversible Work and Maximum Work

The expansion for a reversible system is done infinitely slowly and less heat is released to the surroundings resulting in more work done. You can better understand this process by viewing the pressure volume graphs for the two types of systems. The area under the curves shows you the work done by ...
Sun Feb 10, 2019 9:17 pm
Forum: Calculating Work of Expansion
Topic: Reversible Expansion
Replies: 3
Views: 131

### Reversible Expansion

I understand mathematically and graphically why a reversible expansion does more work, but does gas undergoing irreversible expansion ends up with more internal energy because it does less work?
Tue Feb 05, 2019 4:57 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: heat capacity
Replies: 2
Views: 111

### Re: heat capacity

I think they are the same, except the enthalpy ones are often in J per mol while specific heat capacity can be in J per mole or J per gram. The value of the enthalpy ones can also change when you change the stoichiometry of the reaction of vaporization/sublimation.
Tue Feb 05, 2019 4:18 pm
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: ΔH and ΔU
Replies: 6
Views: 234

### Re: ΔH and ΔU

And if concentration is concerned, it would be 1M.
Tue Feb 05, 2019 4:14 pm
Forum: Concepts & Calculations Using Second Law of Thermodynamics
Topic: Microstate
Replies: 7
Views: 322

### Re: Microstate

According to Boltzmann’s equation S=k*ln(W), where W is the degeneracy, what I understand to be the number of possible microstates of the same energy level, more the number of microstates with the same energy level higher the entropy value.
Tue Feb 05, 2019 4:09 pm
Forum: Calculating Work of Expansion
Topic: Work on Phases of Matter
Replies: 2
Views: 140

### Re: Work on Phases of Matter

I think any system changes energy when work is done on it.
Mon Jan 28, 2019 4:59 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: Delta H
Replies: 4
Views: 166

### Re: Delta H

An increase in T means that the surroundings have taken up some energy given out by the reaction. If a reaction system gives off energy then its own energy content has decreased, hence a decrease in enthalpy (H).
Mon Jan 28, 2019 4:55 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: Surface area and heat capacity [ENDORSED]
Replies: 2
Views: 131

### Re: Surface area and heat capacity[ENDORSED]

I think a large surface area allows a quicker rise in temperature instead of a larger one. Which means the magnitude of the increase in temperature would still be the same when two objects of different surface areas are given the same amount of thermal energy.
Mon Jan 28, 2019 4:49 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: Neutralization reactions
Replies: 6
Views: 198

### Re: Neutralization reactions

I think it's always exothermic because the only change in bonds is the formation of water molecules. Since the other ions are dissolved in water, they don't have a change in bonds.
Sat Jan 26, 2019 10:56 pm
Forum: Phase Changes & Related Calculations
Topic: Phase Changes and Temperature
Replies: 3
Views: 104

### Re: Phase Changes and Temperature

Heat energy is used to break intermolecular bonds, so kinetic energy stays constant.
Fri Jan 25, 2019 3:42 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: bond enthalpies
Replies: 5
Views: 208

### Re: bond enthalpies

Yes, because breaking a bond is always endothermic.
Fri Jan 25, 2019 3:37 pm
Forum: Calculating pH or pOH for Strong & Weak Acids & Bases
Topic: Strength and Weakness
Replies: 12
Views: 494

### Re: Strength and Weakness

If possible, you can compare their X-H bond strength to see which one is more likely to lose protons. That would be the stronger acid.
Fri Jan 25, 2019 3:34 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: What not to count
Replies: 9
Views: 358

### Re: What not to count

Do you mean what not to include in equilibrium constant formula? If so then you should just disregard anything in solid and liquid state.
Mon Jan 21, 2019 9:17 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Ka1 Ka2
Replies: 3
Views: 157

### Re: Ka1 Ka2

Ka2 would always be smaller than Ka1 because it's harder to lose a proton from an already positively charged molecule.
Mon Jan 21, 2019 9:15 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: how to determine if something is an acid or base
Replies: 4
Views: 139

### Re: how to determine if something is an acid or base

A base tends to take on a proton, so having an OH group does not make it a base. You can try to memorize the names and formulae of common acids and bases. They are listed somewhere in the Fundamentals part of the book if you are using the 7th edition.
Mon Jan 21, 2019 9:08 pm
Forum: Administrative Questions and Class Announcements
Replies: 179
Views: 12629

Don't we need the volume to solve question 5 on worksheet 1?
Mon Jan 21, 2019 8:40 pm
Forum: Administrative Questions and Class Announcements
Replies: 179
Views: 12629

lindsey_ammann_4E wrote:
Meigan Wu 2E wrote:On Worksheet 2, why is the concentration of CO3 the same as Ka2 for problem 4b?

^ I have the same question

Because some approximation was used. You can look at the example on page 488 on the 7th edition textbook.
Tue Jan 15, 2019 8:52 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Hydrofluoric Acid
Replies: 3
Views: 141

### Hydrofluoric Acid

Is hydrofluoric acid a strong acid?
Tue Jan 15, 2019 5:20 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: 11.43 6th edition
Replies: 4
Views: 166

### Re: 11.43 6th edition

Do you know the volume? I think an ICE box can be used for partial pressure.
Tue Jan 15, 2019 5:13 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Temperature
Replies: 3
Views: 98

### Re: Temperature

I think we should always use Kelvin unless you are just using the temperature difference.
Tue Jan 15, 2019 5:11 pm
Forum: Equilibrium Constants & Calculating Concentrations
Replies: 3
Views: 146

You can multiply the equilibrium constants of the two reactions to get that of the third reaction.
Fri Jan 11, 2019 6:23 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: 6th Edition 11.115
Replies: 1
Views: 83

### Re: 6th Edition 11.115

Yes, we should only consider the number of moles of gases on each side in case of a change in pressure.
Fri Jan 11, 2019 6:19 pm
Forum: Ideal Gases
Topic: Definition of Ideal Gases?
Replies: 3
Views: 129

### Definition of Ideal Gases?

What defines ideal gases?
Fri Jan 11, 2019 6:14 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Kp vs Kc
Replies: 6
Views: 210

### Re: Kp vs Kc

In a reaction that only involves gases, Kp is much more useful than Kc.
Wed Dec 05, 2018 7:26 pm
Forum: Lewis Acids & Bases
Topic: Identifying Lewis Acids and Bases
Replies: 3
Views: 362

### Identifying Lewis Acids and Bases

Question 6.5 in 7th edition asks that, in the reaction between hydrogen peroxide H2O2 and sulfur trioxide SO3 to form H2SO5, which reactant is Lewis acid and which is base. Can anyone explain why SO2 is the acid and H2O2 the base?
Wed Dec 05, 2018 6:35 pm
Forum: Polyprotic Acids & Bases
Topic: Defintion
Replies: 11
Views: 626

### Re: Defintion

when it can donate or accept more than one proton
Wed Dec 05, 2018 6:31 pm
Forum: Lewis Acids & Bases
Topic: Weak Acids and Bases 12.51
Replies: 2
Views: 327

### Re: Weak Acids and Bases 12.51

Can anyone also explain question (d)? I know that HClO4 is a strong acid and H3PO4 is not, but why is H3PO4 weaker?
Tue Dec 04, 2018 11:09 am
Forum: Amphoteric Compounds
Topic: amphoteric substances
Replies: 3
Views: 173

### Re: amphoteric substances

Oxides formed by metalloids in the diagonal band are often amphoteric, such as barium oxides, aluminum oxides, gallium (Ga) oxides, tin (Sn) oxides, antimony (Sb) oxides and lead oxides.
Wed Nov 28, 2018 11:21 pm
Forum: Hybridization
Topic: Sulfur Trioxide Hybridization
Replies: 4
Views: 2600

### Re: Sulfur Trioxide Hybridization

I guess I wasn't clear enough about my question. I do understand the relationship between steric number and type of hybridization. What I am trying to ask is what (hybrid) orbitals is the sulfur atom using to form the three pi bonds. Normally pi bonds are formed by p orbitals, but in this case, only...
Wed Nov 28, 2018 11:10 pm
Forum: Hybridization
Topic: Sulfur Trioxide Hybridization
Replies: 4
Views: 2600

### Re: Sulfur Trioxide Hybridization

If you look at the Lewis structure of this molecule, a central S atom is bonded to 3 O atoms. Each S-O bond is a double bond, and S has no lone pairs. Thus, S has 3 regions of electron density (a double bond counts as a single region of electron density, and there are 3 of them, hence 3 regions of ...
Wed Nov 28, 2018 9:31 pm
Forum: Hybridization
Topic: Sulfur Trioxide Hybridization
Replies: 4
Views: 2600

### Sulfur Trioxide Hybridization

Why is SO3 sp2 hybridized? If two of the three p orbitals are used in hybridization, how are the three pi bonds formed with only one unhybridized p orbital left? Can d orbitals form pi bonds with p orbitals?
Wed Nov 28, 2018 7:37 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: N2O Lewis Structure
Replies: 2
Views: 183

### Re: N2O Lewis Structure

I think the less electronegative one should be in the middle because they more readily share electrons.
Wed Nov 28, 2018 2:39 pm
Forum: Shape, Structure, Coordination Number, Ligands
Topic: TM charge
Replies: 4
Views: 204

### Re: TM charge

Yes, the chlorine ions are bound to the metal. The metal forms ionic bonds with chlorine ions and coordinate covalent bonds with ligands. You can consider this as adding a few ligands to an ionic compound.
Wed Nov 28, 2018 2:31 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Seesaw Bond Angles
Replies: 6
Views: 10161

### Re: Seesaw Bond Angles

the shape should look like this
Wed Nov 28, 2018 2:27 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: ClO2+
Replies: 7
Views: 555

### Re: ClO2+

Shouldn't the molecule be linear? If the chlorine atom has two lone pairs and two bonding pairs. if there are two lone pairs and two bonding pairs it should be bent. I know it sounds weird bc the two bonding and lone "cancel" each other out but if you think about it, we all know the shape...
Tue Nov 13, 2018 8:27 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: ClO2+
Replies: 7
Views: 555

### Re: ClO2+

Shouldn't the molecule be linear? If the chlorine atom has two lone pairs and two bonding pairs.
Tue Nov 13, 2018 8:24 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Difference between molecular shape & shape
Replies: 2
Views: 125

### Re: Difference between molecular shape & shape

I think they are the same. We always consider lone pairs when determining the shape of a molecule, even if we kind of ignore them when naming the shape. So an angular molecule is never trigonal planar whether we are talking about "shape" or "molecular shape".
Tue Nov 13, 2018 8:14 pm
Forum: Dipole Moments
Topic: Determining Intermolecular Forces
Replies: 5
Views: 313

### Re: Determining Intermolecular Forces

Try to determine whether the molecule is ionic, polar covalent, or non-polar covalent. Ionic compounds have ion-ion interaction. Polar molecules have polar-polar or hydrogen bonding. And, I think, all three have London dispersion forces.
Sat Nov 10, 2018 4:19 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: VSEPR?
Replies: 9
Views: 377

### Re: VSEPR?

Lewis structure only considered valence electrons, while VSEPR also takes minimization of electron repulsion into account.
Thu Nov 08, 2018 9:17 am
Forum: Administrative Questions and Class Announcements
Topic: Test during Thanksgiving Week?
Replies: 2
Views: 160

### Re: Test during Thanksgiving Week?

The newest version of test schedule on the website says "Starting Tuesday November 27", though the version I downloaded earlier says November 20.
Thu Nov 08, 2018 9:08 am
Forum: Bond Lengths & Energies
Topic: Interaction Potential Energy equation
Replies: 2
Views: 141

### Re: Interaction Potential Energy equation

E_p∝−(α_1 α_2)/r^6
Mon Nov 05, 2018 9:23 am
Forum: Lewis Structures
Topic: ONF
Replies: 2
Views: 168

### Re: ONF

I think this is just an exception. Nitrogen is in the center because that gives the lowest formal charges of all three atoms.
Fri Nov 02, 2018 6:48 pm
Forum: Lewis Structures
Topic: valence electrons in d block
Replies: 1
Views: 113

### Re: valence electrons in d block

Valence electrons refer to the outermost electron shell, which also has the highest quantum number (n). So for d-block elements, I think we just need to show the 2 electrons in the outermost s orbital. Don't worry about the outermost d orbital because it's at a lower energy level, with a smaller qua...
Wed Oct 31, 2018 11:58 am
Forum: Formal Charge and Oxidation Numbers
Topic: Stable Condition
Replies: 8
Views: 1968

### Re: Stable Condition

I think a molecule is the most stable when the formal charge of each atom, instead of the whole molecule, is zero. In SO4 we can't organize electrons in the way that every atom has a formal charge of 0, and the SO4 with a 2- charge is the most stable one we can get which has a structure with least f...
Wed Oct 31, 2018 11:46 am
Forum: Formal Charge and Oxidation Numbers
Topic: Formal CHarge
Replies: 5
Views: 232

### Re: Formal CHarge

You'd have to check every single atom in the molecule because the molecule is the most stable when each atom in it has a formal charge of 0. You can calculate the formal charge of an atom using the formula [# of valence electrons] - [# of bonded electrons/2] - [# of non-bonding electrons]
Wed Oct 31, 2018 11:39 am
Forum: Trends in The Periodic Table
Topic: Electron Affinity equation/definition
Replies: 2
Views: 185

### Re: Electron Affinity equation/definition

So stronger the electron affinity, larger the value of Eea, because X would be fairly unstable with high energy right?
Sat Oct 27, 2018 3:07 pm
Forum: Heisenberg Indeterminacy (Uncertainty) Equation
Topic: Heisenberg- In relation to wavelength
Replies: 7
Views: 318

### Re: Heisenberg- In relation to wavelength

Because of λ=h/p, an increase in uncertainty of p increases the uncertainty of λ.
Wed Oct 24, 2018 8:40 pm
Forum: Administrative Questions and Class Announcements
Replies: 135
Views: 31273

Thank you so much Karen :)
Tue Oct 23, 2018 10:37 pm
Forum: DeBroglie Equation
Topic: deriving DeBroglie
Replies: 2
Views: 179

### Re: deriving DeBroglie

• for a photon: E=pc, E=hv
• ∴pc=hc/λ → λ=hp
Tue Oct 23, 2018 11:24 am
Forum: Heisenberg Indeterminacy (Uncertainty) Equation
Topic: Indeterminacy Equation use
Replies: 2
Views: 156

### Re: Indeterminacy Equation use

You need to divide deltaX by 2 to get the +/- value.
Mon Oct 22, 2018 9:49 am
Forum: Einstein Equation
Topic: 7th Edition Book, Section 1.A #9
Replies: 2
Views: 385

### Re: 7th Edition Book, Section 1.A #9

four events are mentioned in the question, you just need to infer the type of electromagnetic wave in each row using the wavelength you get, and then knowing the type of wave gives you the event
Mon Oct 22, 2018 9:45 am
Forum: *Particle in a Box
Topic: Test 2
Replies: 9
Views: 818

### Re: Test 2

yes
Mon Oct 22, 2018 9:44 am
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: 7th Edition Book, Section 1.D #23
Replies: 2
Views: 70

### Re: 7th Edition Book, Section 1.D #23

the 4 orbitals are 2s, 2px, 2py, and 2pz
Fri Oct 19, 2018 10:05 am
Forum: DeBroglie Equation
Topic: Energy=pc
Replies: 4
Views: 232

### Re: Energy=pc

I'm confused, when is mass squared in 1/2 pc? Isn't that for electrons, 1/2 pc=1/2 mv*c=1/2 mv*v?
Thu Oct 18, 2018 7:55 pm
Forum: Properties of Light
Topic: Do I have to memorize the spectrum?
Replies: 20
Views: 754

### Re: Do I have to memorize the spectrum?

No, you don't.
Thu Oct 18, 2018 2:56 pm
Forum: DeBroglie Equation
Topic: Energy=pc
Replies: 4
Views: 232

### Energy=pc

KE=1/2 mv^2, but why is Energy=pc true instead of Energy=1/2 pc?
Thu Oct 18, 2018 2:30 pm
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: Nodes/ Nodals
Replies: 2
Views: 85

### Re: Nodes/ Nodals

What's a nodal 0?
Mon Oct 15, 2018 12:29 pm
Forum: DeBroglie Equation
Topic: Mass of electrons
Replies: 4
Views: 213

### Re: Mass of electrons

Because other units are based on kg, like joule(J) for energy and watt(W) for power. Joule is ‎kg⋅m2⋅s−2, and watt is ‎kg⋅m2⋅s−3. Using kg saves us from changing unit of mass during calculation.
Mon Oct 15, 2018 12:23 pm
Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
Replies: 4
Views: 161

The energy is still positive. It's just a convention to set the energy of free electrons as 0, which makes electrons in atoms have negative values when the formula you mentioned is applied.
Sun Oct 14, 2018 2:03 pm
Forum: Significant Figures
Topic: When to round the answers to significant figures
Replies: 11
Views: 709

### When to round the answers to significant figures

Do we round the answer in every step of the calculation, or do we just round the final answer to the number of significant figures? Because when I round the answer in every step, my final answers are often different from those given by the textbook.
Sun Oct 14, 2018 1:14 pm
Forum: Properties of Electrons
Topic: Photoelectric Experiment
Replies: 9
Views: 215

### Re: Photoelectric Experiment

maybe the larger number of photons means more energy in total
Wed Oct 10, 2018 10:25 pm
Forum: SI Units, Unit Conversions
Topic: State of the molecules
Replies: 4
Views: 250

### Re: State of the molecules

My TA also said that we don't need to worry about states for now
Tue Oct 09, 2018 8:48 pm
Forum: Administrative Questions and Class Announcements
Replies: 2
Views: 180

Josephine Chan 1B wrote:Im not sure about 14b but for 14a, dr lavelle sent an email out about the class website with the password. So try checking the emails you got from the class email.

Thanks a lot!
Tue Oct 09, 2018 8:33 pm
Forum: Administrative Questions and Class Announcements
Replies: 2
Views: 180

Does anyone know the password to the 14B class website?
Tue Oct 09, 2018 8:05 pm
Forum: SI Units, Unit Conversions
Topic: Conversions
Replies: 2
Views: 157

### Re: Conversions

tonnes?
Tue Oct 09, 2018 7:47 pm
Forum: Balancing Chemical Reactions
Topic: Percent Yield
Replies: 5
Views: 269

### Re: Percent Yield

I think so. Percent yield is in some questions in Fundamentals.
Tue Oct 02, 2018 1:04 pm
Forum: Significant Figures
Topic: Mass Percent Composition
Replies: 4
Views: 462

### Re: Mass Percent Composition

Should use significant figures instead of decimal places because finding the mass percent composition uses division. The number of significant figures in your answer should be the same as that of the value with the least significant figures that you use in the calculation.
Tue Oct 02, 2018 12:58 pm
Forum: Empirical & Molecular Formulas
Topic: Empirical Formula Calculations
Replies: 2
Views: 162

### Re: Empirical Formula Calculations

You can round the number. When calculating the empirical formula you often get numbers that are really close to whole numbers like 3.997 or 2.003. But if you get something like 6.667, consider multiplying it by a factor that gets you close to a whole number, like 3 in this case.
Tue Oct 02, 2018 12:45 pm
Forum: Administrative Questions and Class Announcements
Topic: 'extra credit' in Sapling Learning
Replies: 7
Views: 672

### Re: 'extra credit' in Sapling Learning

hey, where did you find the quizzes, on the class website?
Sun Sep 30, 2018 3:03 pm
Forum: SI Units, Unit Conversions
Topic: How does grading for discussion posts work?
Replies: 80
Views: 3792

### Re: How does grading for discussion posts work?

Does anyone know when the grading for discussion posts starts, week 1?