## Search found 65 matches

Sat Mar 16, 2019 11:14 pm
Forum: Arrhenius Equation, Activation Energies, Catalysts
Topic: Arrhenius equation
Replies: 2
Views: 316

### Re: Arrhenius equation

I don't think they are related. Delta H is a state function that just refers the the final and initial enthalpy values. The activation energy in the Arrhenius equation has to do with the pathway of the reaction.
Sat Mar 16, 2019 11:08 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Porous Disk vs Salt Bridge
Replies: 3
Views: 285

### Re: Porous Disk vs Salt Bridge

Well I would imagine it to be that way because a porous disk is one layer thats touching both solutions while the salt bridge has two sides that touch only their respective part of the cell.
Sat Mar 16, 2019 11:06 pm
Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
Topic: Nerst Equation
Replies: 10
Views: 467

### Re: Nerst Equation

The nerst equation is on the equation sheet given.
Sun Mar 10, 2019 5:01 pm
Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
Topic: question 5 on Test 2
Replies: 2
Views: 150

### Re: question 5 on Test 2

You would use the Van't Hoff equation, ln(K2/K1)=-(deltaH/R)*((1/T2)-(1/T1))to find the Kw of water at 10 C. convert 25 c and 10 c to kelvin and then plug in the given values to find K2. The sqaure root of K2 would be the concentration of H+ and taking the negative log would give u the ph of water a...
Sun Mar 10, 2019 4:56 pm
Forum: Reaction Mechanisms, Reaction Profiles
Topic: Slowest step
Replies: 4
Views: 196

### Re: Slowest step

In reactions the fast steps occur at such a high rate that overall they contribute almost nothing to the total time of the reaction. Although they do contribute a little we just approximate the rate to be just the slow step only. A way to think about this is if the slow step took a year and the fast...
Sun Mar 10, 2019 4:46 pm
Forum: Second Order Reactions
Topic: pseudo first order rxns
Replies: 3
Views: 123

### Re: pseudo first order rxns

You use pseudo rate laws are used when all reactant concentrations change. When all reactant concentrations are changing it is difficult to study the rate of the reaction. So in order to study it we assume one reactant concentration is small and the others are so much larger that the concentration d...
Sun Mar 03, 2019 8:42 pm
Forum: General Rate Laws
Replies: 3
Views: 178

The syllabus says that this class is not curved.
Sun Mar 03, 2019 8:31 pm
Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
Topic: Standard cell potential
Replies: 3
Views: 172

### Re: Standard cell potential

n is the number of electrons being lost and gain so you would need to write the balanced half reactions to determine n.
Sun Mar 03, 2019 8:00 pm
Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
Topic: Melting of ice
Replies: 9
Views: 381

### Re: Melting of ice

Delta G is less than 0.
Sun Feb 24, 2019 2:40 pm
Forum: Balancing Redox Reactions
Topic: Which Equation to Flip?
Replies: 9
Views: 478

### Re: Which Equation to Flip?

The E cell is the reduction potential plus the oxidation potential but the tables give only the reduction potentials. To get the oxidation potential you flip the reduction potential. Since the anode is being oxidized you flip that value since the given potential of the anode is the reduction potenti...
Sun Feb 24, 2019 2:37 pm
Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
Topic: Spontaneity in Cells
Replies: 2
Views: 112

### Re: Spontaneity in Cells

If the standard cell potential is positive it is spontaneous.
Sun Feb 24, 2019 2:36 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Salt Bridge
Replies: 1
Views: 80

### Re: Salt Bridge

its basically a tube filled with liquid or gel that has negative and positive ions like Na+ or Cl-. There are membranes at each end that only allow the ions to diffuse. When the galvanic cell is operating the solution on the side of the cathode will build up a negative charge as the metal ions will ...
Sun Feb 17, 2019 10:34 pm
Forum: Student Social/Study Group
Topic: Test
Replies: 17
Views: 653

### Re: Test

Gibbs free energy and electrochemistry
Sun Feb 17, 2019 5:26 pm
Forum: Concepts & Calculations Using Second Law of Thermodynamics
Topic: Enthalpy
Replies: 4
Views: 337

### Re: Enthalpy

Entropy=enthalpy/temperature so since temperature is in the denominator the higher the temperature is the less entropy will be.
Sun Feb 17, 2019 5:24 pm
Forum: Calculating Work of Expansion
Topic: work
Replies: 2
Views: 107

### Re: work

Yes, we use W=-pdeltav when the process is irreversible and pressure can be constant in that case. We use W=-nRTln(V2/V1) when the process is reversible and that's when pressure and volume can both not be constant. In a irreversible process if the pressure is not constant and volume is constant no w...
Sun Feb 10, 2019 5:34 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: degeneracy
Replies: 2
Views: 107

### Re: degeneracy

Degeneracy is how different particles can be in different positions but have the same energy levels. To calculate W you take the number of possible positions or orientations available and raise it the power of the number of particles. so if you had 4 particles that could be in 2 different positions ...
Sun Feb 10, 2019 5:15 pm
Forum: Phase Changes & Related Calculations
Topic: Change In Internal Energy
Replies: 1
Views: 93

### Re: Change In Internal Energy

If the temperature doesn't change then the internal energy can't change. Delta U would be equal to 0 in an isothermal system.
Sun Feb 10, 2019 4:18 pm
Forum: Calculating Work of Expansion
Topic: Work on System vs Surrondings
Replies: 3
Views: 142

### Re: Work on System vs Surrondings

If work is done on the system then the surrounding is putting energy into the system. The system would be gaining energy and the surroundings would be losing energy. If the system is doing work then energy is being put into the surroundings. The system would be losing energy and the surroundings wou...
Sun Feb 03, 2019 9:49 pm
Forum: Thermodynamic Systems (Open, Closed, Isolated)
Topic: Work Formula
Replies: 5
Views: 225

### Re: Work Formula

You can think of D in PxAxD as height. Area times height would give you the amount of volume that has changed. so AxD would give you delta V
Sun Feb 03, 2019 9:28 pm
Forum: Thermodynamic Systems (Open, Closed, Isolated)
Topic: Midterm [ENDORSED]
Replies: 49
Views: 2008

### Re: Midterm[ENDORSED]

The review sessions held by TAs and UAs are very helpful. Doing all the homework assigned is also another good way to prepare.
Sun Feb 03, 2019 9:13 pm
Forum: Calculating Work of Expansion
Topic: Heat Capacity vs. Specific Heat Capacity
Replies: 3
Views: 154

### Re: Heat Capacity vs. Specific Heat Capacity

The heat capacity is how much energy is required to raise the temperate of on object by one degree Celsius. The heat capacity will only pertain to that specific object that it is referring to. The specific heat capacity is the amount of energy to raise a material's temperature by 1 degree Celsius pe...
Sun Jan 27, 2019 11:43 pm
Forum: Non-Equilibrium Conditions & The Reaction Quotient
Topic: Units of Kp
Replies: 9
Views: 1109

### Re: Units of Kp

The units would be any units that measure pressure like atmospheres.
Sun Jan 27, 2019 11:42 pm
Forum: Phase Changes & Related Calculations
Topic: Delta Hº versus delta H
Replies: 7
Views: 689

### Re: Delta Hº versus delta H

Delta H is just the difference between the final and initial values of H. Delta Hº is the value of the difference between the final and initial values of H when the products and reactions are at standard conditions.
Sun Jan 27, 2019 11:38 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: Injecting noble gasses
Replies: 7
Views: 281

### Re: Injecting noble gasses

It does not affect the direction in which the reaction will proceed in because since the volume is constant the concentrations of reactants and products will be the same. Concentration is mols/volume and adding an inert gas will not affect volume.
Sat Jan 19, 2019 6:11 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: Delta H
Replies: 2
Views: 185

### Re: Delta H

Delta H is the change in enthalpy of a system. When Delta H is positive that means the heat is going into the system and so what that means is that heat is required to create the product and so the reaction is endothermic. When delta H is negative that means that heat is leaving the system so heat i...
Sat Jan 19, 2019 6:02 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: Pressure
Replies: 4
Views: 217

### Re: Pressure

If there are an equal number of mols on both sides of the equation changing pressure will have no effect on the reaction.
Sat Jan 19, 2019 5:54 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Determining when k is small or big
Replies: 2
Views: 85

### Re: Determining when k is small or big

When K is equal to 1 that means there is equal concentration of products and reactants. If K is larger than 1 that means the concentration of products is higher than the concentration of reactants so products are favored. If K is less than 1 that means the concentration of reactants is higher than t...
Sun Jan 13, 2019 11:53 am
Forum: Ideal Gases
Topic: When to Use PV=nRT
Replies: 8
Views: 503

### Re: When to Use PV=nRT

You use PV=nRT when the problem gives you have to convert between partial pressure and concentration. If a problem gave you concentrations and made you solve for Kp then you would rearrange the equation into P=(V/n)RT. Since V/n represents concentration you would then just plug in the concentration ...
Sun Jan 13, 2019 11:38 am
Forum: Ideal Gases
Topic: K and Q rules
Replies: 3
Views: 161

### Re: K and Q rules

You can memorize the rules but I think it is also good to understand why the rules are the way they are. If you think of K and Q as ratios and know that Q will be moving towards being equal to K then it's not necessary to memorize the rules. If Q is smaller than K its because the denominator (reacta...
Sun Jan 13, 2019 11:33 am
Forum: Equilibrium Constants & Calculating Concentrations
Topic: solids & liquids
Replies: 5
Views: 170

### Re: solids & liquids

It's not that solids and liquids don't have a concentration it's just that they remain constant throughout the reaction so there would be no point in including them since it would not change the value of Q or K.
Sun Dec 09, 2018 2:15 am
Forum: Lewis Acids & Bases
Topic: Acids and Bases affecting the pH
Replies: 1
Views: 249

### Re: Acids and Bases affecting the pH

A strong acid dissociates completely so it would result in more H+ ions in the solution meaning a lower pH. A weak acid will not dissociate completely. Some of the acid will remain while some will dissociate into H+ and the conjugate base. Therefore not as much H+ will be present in the solution so ...
Sun Dec 09, 2018 2:11 am
Forum: Naming
Topic: Oxidation Number
Replies: 4
Views: 323

### Re: Oxidation Number

You would need to first see what the overall charge of the molecule is. Then add up the negative charges in the complex compound by looking at the ligands and adding up each individual charge. The charge of the metal would be the positive charge that is needed to add to the negative charges of the l...
Fri Dec 07, 2018 8:34 pm
Forum: Shape, Structure, Coordination Number, Ligands
Topic: Polydentate ligands
Replies: 2
Views: 135

### Re: Polydentate ligands

A ligand is polydentate when it has multiple atoms that can donate a lone pair and become a ligand. Bidentate is still polydentate. Anything that forms more than one bond is polydentate.
Fri Dec 07, 2018 5:51 pm
Forum: Bond Lengths & Energies
Topic: Double bond lengths
Replies: 2
Views: 333

### Double bond lengths

Why is the double bond between Oxygen and Carbon stronger than the double bond between Carbon and Carbon and the double bond between Carbon and Nitrogen?
Sun Dec 02, 2018 8:27 pm
Forum: Amphoteric Compounds
Topic: Amphoteric Compounds
Replies: 5
Views: 246

### Re: Amphoteric Compounds

If the amphoteric compound is reacting with an acid it's a base. If it's reacting with a base it's an acid.
Sun Dec 02, 2018 3:13 pm
Forum: Bronsted Acids & Bases
Topic: Water with Acids and Bases
Replies: 3
Views: 175

### Re: Water with Acids and Bases

Water is an acid when it reacts with a base and it is a base when it reacts with an acid. I don't think water affects whether the acid or base it reacts with completely dissociates or not.
Sun Dec 02, 2018 3:10 pm
Forum: Amphoteric Compounds
Topic: Amphoteric Compounds
Replies: 5
Views: 246

### Re: Amphoteric Compounds

I think we just have to memorize which ones on the periodic table would be amphoteric. I guess another way to see is if in the reaction, if you know that one reactant is definitely always a acid or base, the other reactant would be amphoteric.
Sun Dec 02, 2018 3:06 pm
Forum: Shape, Structure, Coordination Number, Ligands
Topic: Oxidation State
Replies: 2
Views: 84

### Re: Oxidation State

First you should look at the overall charge. From there you should identify components of the compound where you know what charge it is. For example you know that elements in group 1 and 2 would have a charge of +1 nad +2 respectively, and elements in group 16 and 17 would have -2 and -1. Then look ...
Sun Nov 25, 2018 7:07 pm
Forum: Properties of Light
Topic: Speed of light
Replies: 13
Views: 3198

### Re: Speed of light

I've been using the speed of light as 3.0 x 10^8 and I've had no problems with getting the correct answers on the tests and midterms.
Sun Nov 25, 2018 7:01 pm
Forum: Octet Exceptions
Topic: How do we know if an element can have an expanded octet?
Replies: 3
Views: 458

### Re: How do we know if an element can have an expanded octet?

The elements in the third period can have more than 8 electrons because those their atoms have the d orbital its just that it is empty. When they form bonds to have an expanded octet the surplus electrons fill the D orbital.
Sun Nov 25, 2018 6:57 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Electron Arrangement vs. Molecular Shape
Replies: 2
Views: 177

### Re: Electron Arrangement vs. Molecular Shape

To add on, the electron arrangement only considers the number of areas of electron density around the central atom. The actual molecule shape factors in the repulsion that results from lone pair electrons which results in shapes with angles other than 90, 120, and 180.
Sun Nov 18, 2018 7:33 pm
Forum: Student Social/Study Group
Topic: Turning in Homework (Thanksgiving Break)
Replies: 8
Views: 350

### Re: Turning in Homework (Thanksgiving Break)

My TA said we are able to turn in next week's homework with the homework that is due the following week after Thanksgiving Break.
Sun Nov 18, 2018 7:24 pm
Forum: Bond Lengths & Energies
Topic: Lengths of different types of bonds
Replies: 3
Views: 182

### Re: Lengths of different types of bonds

Single bonds are the longest, double bonds are shorter than single bonds, and triple bonds are the shortest in length.
Sun Nov 18, 2018 7:24 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Repulsion Strength
Replies: 2
Views: 114

### Re: Repulsion Strength

The different repulsion interactions are what gives molecules their shape. For example we can see how bond angles are greater between lone pairs and bonded pair electrons than between two bonded pair of electrons. This is because lone-bonded pair repulsion strength is greater than bonded-bonded pair...
Sun Nov 11, 2018 10:37 pm
Forum: Bond Lengths & Energies
Topic: Calculating Bond Length
Replies: 3
Views: 187

### Re: Calculating Bond Length

In the question the bond length of the single, double, and triple bonds will probably be given if they ask you to find the length of the bonds. With
that information, the bond length would be a value in-between the given lengths. To be safe, I just average the lengths of the bonds.
Sun Nov 11, 2018 10:25 pm
Forum: Ionic & Covalent Bonds
Topic: Hydrogen bond
Replies: 3
Views: 162

### Re: Hydrogen bond

So hydrogen bonds occur only between a hydrogen atom and a Nitrogen, Oxygen, or Fluorine atom since they are very electronegative.
Sun Nov 11, 2018 10:18 pm
Forum: Dipole Moments
Topic: Test
Replies: 15
Views: 467

### Re: Test

The next test will be given out starting november 27.
Sun Nov 11, 2018 10:15 pm
Forum: Formal Charge and Oxidation Numbers
Topic: Formal Charge
Replies: 12
Views: 690

### Re: Formal Charge

Last test I just drew the most stable form of the lewis structure. I wrote all the calculations. If they ask for resonance then I think you should draw the resonance structures.
Sun Nov 04, 2018 9:08 pm
Forum: Heisenberg Indeterminacy (Uncertainty) Equation
Topic: Heisenberg and Wavelength
Replies: 11
Views: 854

### Re: Heisenberg and Wavelength

This has to do with the equation wavelength=h/p. Since momentum is the denominator in that equation there is an inverse relationship between momentum and wavelength. Therefore if the uncertainty of the momentum increases then the uncertainty of wavelength decreases and vice versa.
Sun Nov 04, 2018 9:05 pm
Forum: *Shrodinger Equation
Topic: Midterm
Replies: 3
Views: 382

### Re: Midterm

We won't need to do calculations using that equation.
Sun Nov 04, 2018 9:04 pm
Forum: Formal Charge and Oxidation Numbers
Topic: Formal Charge on Central Atom
Replies: 9
Views: 397

### Re: Formal Charge on Central Atom

The center atom is the element with the lowest ionization energy so it would make sense for it to not have the negative charge. Since the atoms surrounding the center atom have higher ionization energy and electron affinity, they are more likely to carry the negative partial charge.
Sat Oct 27, 2018 5:28 pm
Forum: Student Social/Study Group
Topic: Studying
Replies: 7
Views: 400

### Re: Studying

An effective way for me to study is to reread my notes and complete all the problems assigned for homework. If you need extra help though, the step up programs and other peer learning sessions organized by Professor Lavelle are also helpful.
Sat Oct 27, 2018 5:13 pm
Forum: Heisenberg Indeterminacy (Uncertainty) Equation
Topic: Calculating Velocity
Replies: 4
Views: 211

### Re: Calculating Velocity

When you calculate for velocity using the Heisenberg Indeterminancy Equation, you are solving for the uncertainty in velocity not the velocity itself. Therefore the values can be very large or very small. The value you get just indicates how large the margin of error is for the actual velocity. If y...
Sat Oct 27, 2018 5:09 pm
Forum: DeBroglie Equation
Topic: Kg vs Grams
Replies: 6
Views: 428

### Re: Kg vs Grams

We deal with Kg in DeBroglie's equation because in that equation we are dealing with momentum. Momentum is measured in kg*ms/s. We use kg in equations that deal with momentum, energy (Joules), etc. because those values are measured with kg in it. For example the units of joules is kg⋅m^2/s^2.
Sun Oct 21, 2018 6:57 pm
Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
Topic: Deriving Rydberg's Equation
Replies: 2
Views: 120

### Re: Deriving Rydberg's Equation

Sinve E=hv we can rearrange it into E/h=v. Then we substitute E/h for v in rydberg’s equation and multiply by h on both sides to isolate E.
Sun Oct 21, 2018 6:49 pm
Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
Topic: Rydberg's Equation
Replies: 1
Views: 142

### Rydberg's Equation

Why in the equation ΔE=Rhc((1/nf^2)−(1/ni^2)) is nf always the smaller of the two energy levels?
Sun Oct 21, 2018 6:23 pm
Forum: Properties of Light
Topic: Intensity vs energy
Replies: 6
Views: 294

### Re: Intensity vs energy

Intensity is the amount of photons while the energy of the light described as E=hv is the amount of energy per individual photon.
Sun Oct 21, 2018 6:17 pm
Forum: DeBroglie Equation
Topic: Rest Mass
Replies: 7
Views: 344

### Re: Rest Mass

Rest mass is the mass of the object when it has no momentum. Since photons are never at 0 momentum, light is something that has no rest mass. De Broglie’s equation can be used to transition between dealing with particle properties and wave properties.
Tue Oct 16, 2018 7:46 pm
Forum: Properties of Light
Topic: Photons of light
Replies: 5
Views: 6279

### Re: Photons of light

I get how you got E from the wavelength, but why do you need to divide 64 by the answer? (I also understand where the 64 came from) Is it to get the photons isolated from the J?? So 64 is the total amount of energy there is and since the E calculated from wavelength tells you the amount of energy p...
Tue Oct 16, 2018 7:30 pm
Forum: DeBroglie Equation
Topic: Formulas
Replies: 5
Views: 255

### Re: Formulas

Formulas will be provided on the cover sheet of the test.
Mon Oct 15, 2018 3:27 pm
Forum: Properties of Light
Topic: Light Intensity
Replies: 4
Views: 287

### Re: Light Intensity

The energy of the photon must be equal to or greater than the energy required to remove an electron. Therefore, if the photon energy is greater, then the electron will be removed. However, due to conservation of energy there will be an excess of energy. The excess energy can be identified as the kin...
Tue Oct 09, 2018 11:32 pm
Forum: Limiting Reactant Calculations
Topic: HW M.7 B
Replies: 1
Views: 159

### HW M.7 B

When it asks what mass of boron can be produced when 125 kg of boron oxide is heated with 125 kg magnesium why is boron oxide supposed to be used to calculate the mass of boron produced instead of magnesium? I thought magnesium would be the limiting reactant in this situation.
Thu Oct 04, 2018 5:32 pm
Forum: Significant Figures
Topic: Molar Mass
Replies: 5
Views: 209

### Re: Molar Mass

I would use the most accurate value for molar mass in calculations and then round the final answer according to sig figs.
Thu Oct 04, 2018 5:30 pm
Forum: SI Units, Unit Conversions
Topic: HW E.9
Replies: 3
Views: 199

### HW E.9

Will we be expected to know how to write the formulas of any given compound for the upcoming test? In this case the problem asks to write the formula magnesium sulfate heptahydrate.
Wed Oct 03, 2018 4:21 pm
Forum: Significant Figures
Topic: Sig Figs
Replies: 3
Views: 134

### Re: Sig Figs

Yes, in my high school my teacher did not tolerate wrong sig figs. However, I don't think that no credit will be given at all. I think partial credit will be given.