## Search found 62 matches

Sat Mar 16, 2019 8:47 pm
Forum: Concepts & Calculations Using Second Law of Thermodynamics
Topic: Delta S?
Replies: 2
Views: 344

### Re: Delta S?

Irreversible situations are always in isolated containers. This means delta S of surroundings equals delta S of system so total delta S is 0.
Sat Mar 16, 2019 8:46 pm
Forum: General Rate Laws
Topic: coefficient of product
Replies: 1
Views: 274

### Re: coefficient of product

You can directly use the coefficients of a balanced reaction for the rate law of an intermediate equation.
Sat Mar 16, 2019 8:45 pm
Forum: Student Social/Study Group
Topic: Lyndon's Review Question 7 clarification
Replies: 2
Views: 378

### Re: Lyndon's Review Question 7 clarification

delta G = delta G (eq 1) - delta G (eq 2)

You are subtracting the delta Gs from each other, but also be very aware of the negative signs from -nFE.
In total it should be:

-nFE(total) = -nFE(eq1) + nFE(eq2)

You will get 1.26 V
Sat Mar 16, 2019 8:42 pm
Forum: Kinetics vs. Thermodynamics Controlling a Reaction
Topic: THERMO with KINETICS
Replies: 1
Views: 277

### Re: THERMO with KINETICS

I would say the graph of different steps of equations that have intermediates is a good concept to test us on both. There is kinetics in terms of speed of reaction and also thermo with Gibbs free energy.
Sat Mar 16, 2019 8:39 pm
Forum: Arrhenius Equation, Activation Energies, Catalysts
Topic: Activation Energy
Replies: 3
Views: 111

### Re: Activation Energy

It is not inverse. Activation energy is a part of the negative exponent. But, this means that a higher activation energy is related to a lower rate, just not directly.
Sat Mar 16, 2019 11:42 am
Forum: Bronsted Acids & Bases
Topic: pH and pOH
Replies: 1
Views: 363

### Re: pH and pOH

Bronsted acids and bases participate in the conjugate seesaw, meaning a weak acid and base either gains or loses a H+ to become the conjugate acid/base. This results in an OH- or H30+ ion being created. These directly contribute to the pH.
Sat Mar 16, 2019 11:40 am
Forum: General Rate Laws
Topic: exponential decay
Replies: 2
Views: 289

### Re: exponential decay

Rate laws are usually directly dependent on the amount of reactants, so if the reactants are lower, the rate law will be lower.
Sat Mar 16, 2019 11:37 am
Forum: Calculating Work of Expansion
Topic: expansion work question
Replies: 1
Views: 300

### Re: expansion work question

If there is said to be no change in volume, then no expansion work has been done. If you are given moles and temperature, you can calculate work from -nRT. If that is positive and you are not in an isolated system, expansion work has been done.
Sat Mar 16, 2019 11:35 am
Forum: *Enzyme Kinetics
Topic: graphing intermediates
Replies: 2
Views: 262

### Re: graphing intermediates

No graphing of catalysts is needed. The intermediates are essentially your product after your first reaction that are your reactants of your second reaction.
Sat Mar 16, 2019 11:34 am
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Phases Cell Diagram
Replies: 2
Views: 107

### Re: Phases Cell Diagram

It is always solid on the outside, then gases/liquids, then aqueous
Sat Mar 16, 2019 11:32 am
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Shifting K with changes in volume
Replies: 4
Views: 334

### Shifting K with changes in volume

So I know that the reaction will shift toward the side with less moles of gas if the volume is getting smaller/pressure is getting bigger. But what happens if the volume is getting bigger and the pressure is getting smaller? Will the reaction shift to the side with more moles of gas?
Sat Mar 16, 2019 11:31 am
Forum: Reaction Mechanisms, Reaction Profiles
Topic: Coefficients for the rate of reaction
Replies: 1
Views: 70

### Coefficients for the rate of reaction

Why is that you can use the coefficients from a reaction in the rate law for elementary reaction but not other types of reactions?
Fri Mar 15, 2019 9:41 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Electrolytic cell
Replies: 2
Views: 106

### Electrolytic cell

What kinds of problems do we have to be able to do with electrolytic cells? Or do we just have to know that they are the opposite of galvanic cells?
Fri Mar 15, 2019 5:49 pm
Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
Topic: Test 2 question 7b
Replies: 1
Views: 229

### Re: Test 2 question 7b

Since this releases heat, it seems like it is a spontaneous reaction.
Fri Mar 15, 2019 5:44 pm
Forum: Balancing Redox Reactions
Topic: Test 2
Replies: 5
Views: 169

### Re: Test 2

Reducing ability is the ability for a molecule to reduce another molecule and oxidize itself. When ranking these molecules, the ones that will oxidize the strongest are the ones with the lowest standard reduction potential.
Fri Mar 15, 2019 5:41 pm
Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
Topic: Test 2 question 7b
Replies: 1
Views: 229

### Test 2 question 7b

The dissolving of a salt in water which causes the release of a small amount of heat.

Is this spontaneous, non spontaneous, or at equilibrium?
Fri Mar 15, 2019 5:07 pm
Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
Topic: Test 2 help!
Replies: 3
Views: 180

### Re: Test 2 help!

I used the van't Hoff equation to get the equilibrium constant at 40 degrees Celsius, but how do I use this to find pH?
Fri Mar 15, 2019 3:54 pm
Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
Topic: Test 2 help!
Replies: 3
Views: 180

### Test 2 help!

Could someone help me out with an explanation for #5? This is the question that asks for an analysis of whether the pH of a water solution is acidic or basic?
Fri Mar 15, 2019 3:30 pm
Forum: Non-Equilibrium Conditions & The Reaction Quotient
Topic: Increasing volume
Replies: 5
Views: 346

### Increasing volume

So I know if you decrease volume, K will shift to increase whichever side has less moles of gas. But, if volume increases, will K shift to increase whichever side has more moles of gas? or will K not change at all?
Thu Mar 07, 2019 11:06 pm
Forum: Zero Order Reactions
Topic: definitions
Replies: 2
Views: 117

### definitions

Can someone define zero, first, second order reactions? I thought it had to do with how many components are coming together, but that wouldn't make sense for a zero order rxn.
Thu Mar 07, 2019 9:51 pm
Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
Topic: Electrodes in a concentration cell
Replies: 1
Views: 124

### Re: Electrodes in a concentration cell

Nope. The Ecell value is intensive, meaning it isn't determined by the volume of the reactants or products.
Thu Feb 28, 2019 11:18 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Standard Conditions
Replies: 1
Views: 85

### Re: Standard Conditions

The standard conditions relate to being at equilibrium for E and a balanced equation for n.
Thu Feb 28, 2019 11:17 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Finding n for Galvanic Cell Equations
Replies: 2
Views: 118

### Re: Finding n for Galvanic Cell Equations

Exactly. It is the amount of electrons transferred.
Thu Feb 28, 2019 11:17 pm
Forum: Balancing Redox Reactions
Topic: Short hand notation
Replies: 8
Views: 293

### Re: Short hand notation

A salt bridge is a tube that is enclosed and allows for transfer of the salt ion from cathode to anode.
Thu Feb 28, 2019 11:16 pm
Forum: Balancing Redox Reactions
Replies: 13
Views: 508

### Re: Adding H+ and H2O

You can do both. Both are needed to balance reactions.
Thu Feb 28, 2019 11:13 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: H+ in cell diagrams
Replies: 5
Views: 249

### Re: H+ in cell diagrams

The only things that we add into cell diagrams are the solid and the salt ions. I don't think H+ is ever supposed to be in cell diagrams.
Tue Feb 12, 2019 5:22 pm
Forum: Phase Changes & Related Calculations
Topic: Negative and Positive values of delta H and w
Replies: 6
Views: 1096

### Negative and Positive values of delta H and w

Can someone explain the transfer of energy that happens when both delta H and w are negative and positive? I know the when work is positive, energy is going into the system. This means that some sort of pressure is condensing the system or the volume is getting smaller. When delta H is negative, is ...
Thu Jan 10, 2019 11:14 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Q vs K
Replies: 5
Views: 200

### Re: Q vs K

Q and K and calculated the same exact way: concentration of products over concentration of reactants. However, Q calculates the status of a reaction when it is not in equilibrium; the purpose is to understand what direction the reaction is currently moving in.
Thu Jan 10, 2019 11:07 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Clarification from lecture 1 - Jan 7th
Replies: 2
Views: 76

### Re: Clarification from lecture 1 - Jan 7th

All values for the reactants and products will be the same. However, if you are just finding the equilibrium constant of the inverse, you know that the numerator and denominator of the reaction will be flipped. So, you can simply take the inverse of the equilibrium for the forward reaction.
Thu Jan 10, 2019 10:46 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: 5H3 from 7th edition
Replies: 2
Views: 64

### 5H3 from 7th edition

The problem asks you to the find the equilibrium constant of a reaction from a separate table in the book. 2BrCl + H2 --> Br2 + 2HCl can be broken down into 2BrCl --> Br2 + Cl2 AND H2 + Cl2 --> 2HCl and the equilibrium constants for both of these reactions can be found in the table. However, the ans...
Fri Dec 07, 2018 11:08 pm
Forum: Coordinate Covalent Bonds
Topic: Chelates
Replies: 4
Views: 404

### Re: Chelates

Chelates are basically complexes that have ligands that form a ring of atoms around the transition metal ion. When ligands bond at more than one tie, they are likely to form a chelate.
Fri Dec 07, 2018 11:07 pm
Forum: Polarisability of Anions, The Polarizing Power of Cations
Topic: Difference Between Polarizability and Polarizing Power
Replies: 3
Views: 632

### Re: Difference Between Polarizability and Polarizing Power

Polarizability is how easy it is to move or pull an atom's cloud of electrons. Polarizing power is how good an atom is at pulling on bonded electrons. These two concepts are directly opposite. Atoms with high polarizability are bigger and have a greater negative charge, while atoms that have a highe...
Fri Dec 07, 2018 11:05 pm
Forum: Biological Examples
Topic: What should we know for the final?
Replies: 9
Views: 551

### Re: What should we know for the final?

I definitely think we should know cisplatin! It is the well known chemotherapy drug that forms coordination compounds with DNA to stop cell division. The two chlorides are on one side and can bond with the guanines in two separate locations to effectively stop uncontrolled division.
Fri Dec 07, 2018 11:01 pm
Forum: Polarisability of Anions, The Polarizing Power of Cations
Topic: Least to Most Polarizable/Polarizing Power
Replies: 3
Views: 669

### Re: Least to Most Polarizable/Polarizing Power

Both size and charge need to be taken into account when organizing atoms. The charge density, which is a measure of the charge in terms of the volume that the atom takes up, is used to compare atoms to each other (not solely charge or solely size). s2- is smaller and should be more difficult to pola...
Fri Dec 07, 2018 10:55 pm
Forum: Hybridization
Topic: Sigma and pi bonds
Replies: 5
Views: 195

### Re: Sigma and pi bonds

We need to know the hybridization of the bonds. This means we must be able to find the hybridization of the neighboring atoms and represent the bond with both of them.
Fri Dec 07, 2018 10:54 pm
Forum: Sigma & Pi Bonds
Topic: Rotation
Replies: 5
Views: 442

### Re: Rotation

This relates directly to labeling molecules as bidentate. My TA gave an example of two aspects of a molecule connected by a double bond versus a single bond. The single bond could spin any way it wanted to, so rotating one aspect of the molecule 180 degrees put the two nitrogen atoms right next to e...
Fri Dec 07, 2018 10:44 pm
Forum: Hybridization
Topic: Hybridizaiton
Replies: 1
Views: 128

### Re: Hybridizaiton

Hybridization isn't necessarily lowering the energy to allow an atom to form more bonds. Instead, it is establishing that all electrons have an equal likelihood of forming an equal bond with another atom. For carbon, this does seem to look like you are forming more bonds as you move from 2 unpaired ...
Fri Dec 07, 2018 10:42 pm
Forum: Heisenberg Indeterminacy (Uncertainty) Equation
Topic: Final Exam
Replies: 1
Views: 287

### Re: Final Exam

All the equations we learned related to the quantum world will be given to us on the test, so memorization is not needed. The equations such as E=hv and c = wavelength(v) deal specifically with photons. De Broglie's equation, wavelength = h/p and kinetic energy E=(1/2)mv^2 are for any particle that ...
Fri Dec 07, 2018 1:45 pm
Forum: Lewis Acids & Bases
Topic: Bronsted vs Lewis
Replies: 4
Views: 150

### Bronsted vs Lewis

What's the main difference between Brontsted acids and bases and Lewis acids and bases? Why is AlCl3 a Lewis acid as opposed to a Bronsted acid?
Fri Dec 07, 2018 1:43 pm
Forum: General Science Questions
Topic: Determining states
Replies: 1
Views: 205

### Determining states

When writing out a full reaction of molecules, how do we know whether a molecule is a solid, liquid, gas, or aqueous? Are we just supposed to memorize the states of important molecules?
Mon Nov 26, 2018 10:21 pm
Forum: Bond Lengths & Energies
Topic: Bond Length
Replies: 2
Views: 106

### Re: Bond Length

Single bonds have the longest bond lengths. As it progresses to double and triple bonds, the bond lengths get shorter.
Mon Nov 26, 2018 9:27 pm
Forum: Hybridization
Topic: hybridization
Replies: 3
Views: 152

### Re: hybridization

Also, when an atom bonds, it realistically forms bonds that are equal in strength. Therefore, hybridization mixes together different orbital levels to create an entirely new orbital that equalizes all bonds.
Mon Nov 26, 2018 8:18 pm
Forum: Sigma & Pi Bonds
Topic: Homework 2F.3 7th Edition Part B
Replies: 1
Views: 100

### Re: Homework 2F.3 7th Edition Part B

The resonance structure of SO2 would also include a Lewis structure that only had one bond between S and an O. Resonance structure simply refers to another way of arranging the electrons in a way that fits them all in. The most stable structure would be the one with 2 double bonds because the formal...
Mon Nov 26, 2018 6:12 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: 2F3 part B (7th edition)
Replies: 1
Views: 40

### 2F3 part B (7th edition)

The problem asks about the amount of sigma and pi bonds in the molecule SO2. The answer key gives two answers (2 sigma, 2 pi OR 2 sigma, 1 pi depending on resonance structure). It seems like the problem is considering the resonance structures as one double bond between the S and an O and two double ...
Sun Nov 04, 2018 10:37 pm
Forum: Electron Configurations for Multi-Electron Atoms
Topic: Ionization Energies
Replies: 4
Views: 180

### Re: Ionization Energies

Yes. It gets progressively harder to remove electrons. We are getting closer to the positively charged nucleus that is pulling electrons towards it.
Sun Nov 04, 2018 10:07 pm
Forum: Resonance Structures
Topic: Resonance Structures
Replies: 3
Views: 194

### Re: Resonance Structures

I think so. If a problem asks for the Lewis structure, we should show all logical possibilities of it.
Sun Nov 04, 2018 10:01 pm
Forum: Lewis Structures
Topic: Expanded Octet Rule
Replies: 1
Views: 44

### Re: Expanded Octet Rule

If the atom includes d orbitals, it is 10. If the atom includes f orbitals, it is 14.
Sun Nov 04, 2018 10:01 pm
Forum: Ionic & Covalent Bonds
Topic: electronegativity difference
Replies: 4
Views: 217

### Re: electronegativity difference

If you look at a periodic table that includes electronegativity of atoms, you can calculate the electronegativity difference between the 2 bonding atoms and determine which molecule is more electronegative. C - 2.55 S - 2.58 O - 3.44 There is a greater difference between C and O, making CO2 more ele...
Sun Nov 04, 2018 9:55 pm
Forum: Formal Charge and Oxidation Numbers
Topic: Formal Charge and Lewis Structures
Replies: 5
Views: 248

### Re: Formal Charge and Lewis Structures

I don't think so. I'm guessing the question will explicitly ask for the formal charge if needed.
Sun Nov 04, 2018 9:47 pm
Forum: Photoelectric Effect
Topic: Work Function, Kinetic Energy
Replies: 2
Views: 351

### Re: Work Function, Kinetic Energy

Energy of photon - work function = kinetic energy

If you just need to find the kinetic energy and you have the velocity, plug in the mass of the electron (given value) and solve Ek = (1/2)mv^2.
Sun Nov 04, 2018 8:55 pm
Forum: Resonance Structures
Topic: Resonance with formal charge
Replies: 6
Views: 337

### Re: Resonance with formal charge

Yes. Resonance is simply different ways of drawing a molecule's structure in terms of double bonds. Formal charge is the most stable structure of all resonance structures.
Sun Nov 04, 2018 8:49 pm
Forum: Ionic & Covalent Bonds
Topic: Identifying ionic compounds
Replies: 1
Views: 111

### Re: Identifying ionic compounds

Usually bonds between metals and non-metals are ionic and bonds between non-metals and non-metals are covalent. When looking at bonding between molecules, however, I think we just have to be aware of the common ionic molecules. NH^4 always has a positive charge and OH- always has a negative charge.
Sun Nov 04, 2018 8:47 pm
Forum: Properties of Electrons
Topic: Frequency of an electron equation
Replies: 2
Views: 341

### Re: Frequency of an electron equation

De Broglie's equation is used with things that have mass (i.e. electrons). The photoelectric effect includes three components. E=hv is used ONLY for photons/light. The threshold equation is the energy needed to eject an electron and that is usually a given value. The kinetic energy of the electron i...
Sun Nov 04, 2018 8:40 pm
Forum: Photoelectric Effect
Topic: Test 2 #4 neon lamp light emitted
Replies: 1
Views: 159

### Re: Test 2 #4 neon lamp light emitted

Convert kilojoules to joules. Use E/h = v. The answer should be 5.45 x 10^14 Hz.
Sun Nov 04, 2018 8:37 pm
Forum: Heisenberg Indeterminacy (Uncertainty) Equation
Topic: Uncertainty concept
Replies: 1
Views: 126

### Re: Uncertainty concept

When diameter of a region is referred to in a Heisenberg uncertainty principle problem, the question is usually asking whether the electron is within that region (alveoli sac in this question). If the delta x is larger than the diameter of the region, we know that the electron is not confined to tha...
Sun Nov 04, 2018 8:36 pm
Forum: Formal Charge and Oxidation Numbers
Topic: Formal charges in charged molecules
Replies: 5
Views: 128

### Re: Formal charges in charged molecules

There is no difference in process. You still draw all the resonance Lewis structures and use the F = valence - (non bonding electrons - (bonding electrons/2)) equation.
Sun Nov 04, 2018 8:06 pm
Forum: Lewis Structures
Topic: Double bonds vs. lone pairs
Replies: 5
Views: 452

### Re: Double bonds vs. lone pairs

Before even calculating formal charge, we have to find a structure that contains all 20 valence electrons. Carbon is in the middle because it has 4 potential bonding sites. We know the both hydrogens have to bond to carbon with a single bond because hydrogens can only have two electrons in their val...
Sun Nov 04, 2018 8:01 pm
Forum: *Shrodinger Equation
Topic: Midterm
Replies: 3
Views: 382

### Re: Midterm

I don't think so. I think we just need to conceptually understand it, but we do not need to ever apply the equation.
Sun Nov 04, 2018 8:00 pm
Forum: Polarisability of Anions, The Polarizing Power of Cations
Topic: Electron Configuration
Replies: 4
Views: 127

### Re: Electron Configuration

The electron configuration of nickel is [Ar]3d^8 4s^2. When you take away 3 electrons to make it Ni3+, you take 2 electrons off of the 4s orbital (highest energy state) and one electron off the 3p orbital. This is not to be confused with considering Ni3+ to be Mn. The electron configuration of Mn is...
Sun Nov 04, 2018 7:13 pm
Forum: Properties of Light
Topic: Quantum Test
Replies: 11
Views: 584

### Re: Quantum Test

Since the equations are all provided for us, I think we just have to understand when to use them. E = hν, c = λν, and, therefore, E = hc/λ, are only used for calculations relating to light/photons. De Broglie's equation, λ = h/mv, is mostly used for particles that have mass, but it can also be appli...
Sun Nov 04, 2018 6:56 pm
Forum: Properties of Light
Topic: 3b on Quantum Test
Replies: 2
Views: 175

### Re: 3b on Quantum Test

The speed does not change as intensity increases. Since photons have particle properties, they can only eject one electron at a time. Increasing intensity will only increase the amount of electrons ejected.
Sun Nov 04, 2018 6:38 pm
Forum: Empirical & Molecular Formulas
Topic: Limiting Reactants
Replies: 3
Views: 414

### Re: Limiting Reactants

Either product can be used to understand which reactant is limiting. The moles and of product are always proportional to each other, and they both rely on the same limiting reactant to determine how much is produced.