## Search found 48 matches

Mon Mar 04, 2019 4:24 pm
Forum: Kinetics vs. Thermodynamics Controlling a Reaction
Topic: Reaction order
Replies: 4
Views: 140

### Re: Reaction order

The overall order of a reaction comes from the addition of the two exponents "n" and "m" which for single step reactions are equal to the stoichiometric coefficients of the reactants
Mon Mar 04, 2019 4:20 pm
Forum: General Rate Laws
Topic: units of rates and rate constants
Replies: 4
Views: 191

### Re: units of rates and rate constants

For 0 order reactions, the units for k are M/s, for 1st order reactions, the units for k are 1/s, and for 2nd order reactions the units for k are 1/M*s. With M being molarity or concentration
Mon Mar 04, 2019 4:17 pm
Forum: General Rate Laws
Topic: What is a Unique Rate of Reaction? HW #3, 6th Edition
Replies: 1
Views: 121

### Re: What is a Unique Rate of Reaction? HW #3, 6th Edition

I think the unique rate of reaction is in the form:
-1/a * dA/dt = 1/b * dB/dt = 1/c * dC/dt for an equation like aA --> bB + cC
Mon Feb 25, 2019 5:28 pm
Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
Topic: n value
Replies: 11
Views: 256

### Re: n value

n isn't just moles and probably isn't given in the problem. n is moles of electrons transferred once you balance the redox half reactions
Mon Feb 25, 2019 5:26 pm
Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
Topic: Problem 6L.1
Replies: 4
Views: 246

### Re: Problem 6L.1

Once you do what those people mentioned, I believe the balanced reaction comes out to 2 e-. So n = 2
Mon Feb 25, 2019 4:33 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: Gibbs Free Energy [ENDORSED]
Replies: 1
Views: 99

### Gibbs Free Energy[ENDORSED]

Under what conditions do ΔG and ΔG° = 0 respectively?
Tue Feb 19, 2019 4:42 pm
Forum: Entropy Changes Due to Changes in Volume and Temperature
Topic: Pressure Equation
Replies: 7
Views: 452

### Re: Pressure Equation

This equation is exactly the same if it were (v2/v1) since from the ideal gas law pv=nRT, you know that pressure and volume are inversely proportional. it just depends what the problem gives you
Tue Feb 19, 2019 4:38 pm
Forum: Thermodynamic Definitions (isochoric/isometric, isothermal, isobaric)
Topic: Reversible vs irreversible
Replies: 6
Views: 465

### Re: Reversible vs irreversible

Lavelle said that reversible reactions are pretty much entirely theoretical, since it's pretty much not possible for all heat to be converted to work with nothing being lost to the surroundings. Most reactions are irreversible, especially biological reactions.
Tue Feb 19, 2019 4:35 pm
Forum: Calculating Work of Expansion
Topic: irreversible and reversible
Replies: 5
Views: 414

### Re: irreversible and reversible

Yes, reversible reactions are actually just theoretical, since it would mean that all energy in the form of heat can be transferred to work, with nothing being lost to the surroundings, which is almost never possible. Lavelle said almost every reaction is irreversible, especially biological applicat...
Thu Feb 14, 2019 5:08 pm
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: 3/2R vs 5/2R
Replies: 8
Views: 390

### Re: 3/2R vs 5/2R

Agreed. You know which one to use in the context of the problem, so it's important to identify what is being held constant in the given problem
Thu Feb 14, 2019 5:06 pm
Forum: Entropy Changes Due to Changes in Volume and Temperature
Topic: adding entropy
Replies: 5
Views: 242

### Re: adding entropy

If there is a change in volume and in temperature, you split the problem up into two steps, first using the deltaS equation with V2/v1 and then using the equation with T2/T1. These two deltaS values added together are equal to the deltaS of the whole system
Thu Feb 14, 2019 5:03 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: Delta G
Replies: 2
Views: 115

### Delta G

How can you tell if increasing temperature will increase or decrease the stability of a molecule?
Tue Feb 05, 2019 5:12 pm
Forum: Calculating Work of Expansion
Topic: irreversible and reversible
Replies: 5
Views: 414

### irreversible and reversible

So for an irreversible reaction where pressure is constant, the equation is w = -PΔV and for a reversible reaction where pressure is constantly becoming smaller, the equation is w = -nRTln(v2/v1). Is this right?

Also, where does the equation ΔU = 3/2nRΔT come from?
Tue Feb 05, 2019 5:09 pm
Forum: Thermodynamic Systems (Open, Closed, Isolated)
Topic: isolated systems
Replies: 2
Views: 109

### Re: isolated systems

An isolated system cannot exchange energy or matter with the surroundings, which pretty much means that pressure can't change, so yes, an isolated system would have constant volume
Tue Feb 05, 2019 4:58 pm
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: U clarifications
Replies: 3
Views: 162

### U clarifications

How does the equation ΔU = q + w change when ΔP is 0 and ΔV is 0 respectively?
Mon Jan 28, 2019 12:20 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Bond Enthalpies of Diatomic Molecules
Replies: 2
Views: 100

### Re: Bond Enthalpies of Diatomic Molecules

Since diatomic molecules are the most stable form of those elements, those elements pretty much only occur in that state, so the bond enthalpies are known an accurate. Bonds between other elements, like Carbon for example, can be found in multiple different molecules. Therefore the enthalpies of the...
Mon Jan 28, 2019 12:16 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Why Enthalpy Changes Are Additive
Replies: 2
Views: 91

### Re: Why Enthalpy Changes Are Additive

A state function is something that doesn't depend on the path taken to get to a certain state, but only depends on the initial and final states. Another state function is volume. For example, if a bucket first had 5 L of water, then someone added 3 L and then took away 6 L, you end up with 2 L, and ...
Mon Jan 28, 2019 12:12 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Clarification on Calculation Methods
Replies: 1
Views: 91

### Re: Clarification on Calculation Methods

The first method is Hess's Law, which you use when you know the deltaH of two different reactions and are able to combine them to find the deltaH of the new reaction. The second method uses bond enthalpies, since in chemical reactions, bonds in reactants and broken and bonds in products are formed. ...
Thu Jan 24, 2019 5:01 pm
Forum: Phase Changes & Related Calculations
Topic: Endothermic or Exothermic
Replies: 20
Views: 864

### Re: Endothermic or Exothermic

Solid --> Liquid --> Gas is endothermic (surroundings get warmer)
Gas --> Liquid --> Solid is exothermic (surroundings get cooler)
Thu Jan 24, 2019 4:54 pm
Forum: Phase Changes & Related Calculations
Topic: Why steam causes severe burns
Replies: 9
Views: 543

### Re: Why steam causes severe burns

How I understood this idea is that when water comes into contact with skin, it is already in liquid form and does not change state, therefore it's temperature decreases, releasing energy. When steam comes into contact with the skin, it does change state, from gas to liquid. During this condensation ...
Tue Jan 22, 2019 11:01 am
Forum: Ideal Gases
Topic: ICE table
Replies: 5
Views: 409

### Re: ICE table

K values of gas phase reactants and products can be solved as either Kp or Kc, depending on what is given. However, k values for aqueous reactants and products can only be written in Kc.
Tue Jan 22, 2019 10:57 am
Forum: Equilibrium Constants & Calculating Concentrations
Topic: when to ignore the second ionization constant
Replies: 3
Views: 190

### Re: when to ignore the second ionization constant

On one problem regarding H2SO4, I was confused about the same thing, since the textbook just said Ka1 was "strong" and didn't actually have a value. In this case I used Ka2 which was given, however I think that if Ka2 is significantly less than Ka1, then you're just supposed to use Ka1
Tue Jan 22, 2019 10:55 am
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: 5% rule
Replies: 12
Views: 349

### Re: 5% rule

If the K value is greater than 10^-3, that is when we cannot disregard x and have to solve using quadratic equation
Tue Jan 22, 2019 10:53 am
Forum: Equilibrium Constants & Calculating Concentrations
Topic: ICE chart
Replies: 2
Views: 103

### ICE chart

In an ice chart, are the values for change for reactants always negative and the products positive? Or does it depend on the direction the reaction will proceed?
Wed Jan 09, 2019 10:20 pm
Forum: Ideal Gases
Topic: Value of K
Replies: 6
Views: 214

### Re: Value of K

Typically a "small" value of K is < 10^-3 and a "large" value is > 10^3. Any K value in between is viewed as intermediate, in which neither reactants or products are favored.
Wed Jan 09, 2019 10:17 pm
Forum: Non-Equilibrium Conditions & The Reaction Quotient
Topic: "Shifting"
Replies: 15
Views: 1060

### "Shifting"

I remember learning about things that "shift" equilibrium in high school, but Dr. Lavelle said to avoid that word. Could someone explain to me what he means by equilibrium "sitting" to the left and not "shifting" to the left?
Wed Jan 09, 2019 10:14 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: ICE Table
Replies: 4
Views: 75

### Re: ICE Table

The initial concentration of products isn't always 0, though. Sometimes it will be given information in the problem. Usually if it's not given, we assume it's 0.
Sun Dec 09, 2018 9:16 am
Forum: *Shrodinger Equation
Topic: Calculations with Schrodinger [ENDORSED]
Replies: 1
Views: 3636

### Calculations with Schrodinger[ENDORSED]

We are still not expected to do any calculations with Schrodinger’s equation right?
Sun Dec 09, 2018 9:15 am
Forum: Polyprotic Acids & Bases
Topic: polyprotic acids and bases in equations
Replies: 3
Views: 381

### Re: polyprotic acids and bases in equations

When showing a polypeptide acid dissociating it should have both steps right? Or should we simplify into 1 step
Fri Dec 07, 2018 3:23 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Bent molecular geometry
Replies: 3
Views: 251

### Bent molecular geometry

Are both AX2E and AX2E2 bent shaped? Is there a difference?
Wed Dec 05, 2018 10:00 pm
Forum: Administrative Questions and Class Announcements
Topic: FINAL PRACTICE - Lyndon's Churro Review Session [ENDORSED]
Replies: 118
Views: 11209

### Re: FINAL PRACTICE - Lyndon's Churro Review Session[ENDORSED]

How do we know the shape of a coordination compound? Does it have to do with the number of bonded ligands?
Wed Dec 05, 2018 9:59 pm
Forum: Shape, Structure, Coordination Number, Ligands
Topic: Ligands
Replies: 4
Views: 239

### Re: Ligands

Does the number of ligands bonded to the central determine the shape of the coordination compound?
Wed Dec 05, 2018 9:57 pm
Forum: Hybridization
Topic: hybridization
Replies: 2
Views: 110

### hybridization

If something asks for the hybridization of a central atom, is sp3 (for example) enough? Do we need to include the 2sp3 if it happens to be in the second row of the periodic table?
Wed Dec 05, 2018 9:55 pm
Forum: Amphoteric Compounds
Topic: Definition
Replies: 6
Views: 244

### Re: Definition

Amphoteric simply means a compound that can act as either an acid or a base depending on the strength of the acid or base being added to it.
Mon Dec 03, 2018 1:30 pm
Forum: Amphoteric Compounds
Topic: Definition
Replies: 5
Views: 192

### Definition

Can someone define amphoteric for me?
Mon Dec 03, 2018 1:28 pm
Forum: Bronsted Acids & Bases
Topic: Bronsted v Lewis
Replies: 3
Views: 166

### Re: Bronsted v Lewis

The difference between bronsted and lewis acids is basically if you're focusing on H+ ions or electrons. Bronsted acids donate hydrogen ions and bronsted bases accept hydrogen ions where as lewis acids accept a lone pair while lewis bases donate lone pair.
Mon Dec 03, 2018 1:22 pm
Forum: Naming
Topic: Water as a ligand
Replies: 4
Views: 91

### Re: Water as a ligand

So it depends on which atom (O or H) is bonding to the central transition metal?
Mon Dec 03, 2018 1:20 pm
Forum: Naming
Topic: Order of Ligand Naming
Replies: 6
Views: 208

### Re: Order of Ligand Naming

Thank you!
Sat Dec 01, 2018 4:27 pm
Forum: Naming
Topic: Water as a ligand
Replies: 4
Views: 91

### Water as a ligand

When should the ligand of water be written as OH2 versus H20?
Sat Dec 01, 2018 4:26 pm
Forum: Naming
Topic: Order of Ligand Naming
Replies: 6
Views: 208

### Order of Ligand Naming

Is there a rule for which ligand should be named first?
Mon Nov 12, 2018 1:42 pm
Forum: Dipole Moments
Topic: Dipole Moments [ENDORSED]
Replies: 10
Views: 440

### Re: Dipole Moments[ENDORSED]

A dipole moment occurs when one atom in a molecule (or one side of a molecule) is more electronegative than the other, meaning that it attracts electrons. This attraction causes a net negative charge on one end of the molecule and consequently a positive charge on the other end. This polarity within...
Mon Nov 12, 2018 1:38 pm
Forum: Dipole Moments
Topic: Test
Replies: 15
Views: 480

### Re: Test

I agree I think the next test will be mainly covering chemical bonds and molecular shape and structure.
Mon Nov 12, 2018 1:34 pm
Forum: Bond Lengths & Energies
Topic: High Boiling Points and Bond Strengths [ENDORSED]
Replies: 4
Views: 238

### Re: High Boiling Points and Bond Strengths[ENDORSED]

Do higher melting points work in the same way? Stronger bonds means higher melting point?
Sun Nov 04, 2018 9:09 pm
Forum: Administrative Questions and Class Announcements
Topic: MIDTERM PRACTICE - Garlic Bread Review Session [ENDORSED]
Replies: 121
Views: 6888

### Re: MIDTERM PRACTICE - Garlic Bread Review Session[ENDORSED]

I don't understand why in order of increasing ionization energy, it goes C O N F. I thought it would be C N O F. Anyone know why?
Sun Nov 04, 2018 8:29 pm
Forum: Heisenberg Indeterminacy (Uncertainty) Equation
Topic: Uncertainty concept
Replies: 1
Views: 130

### Uncertainty concept

I am struggling to conceptualize the idea of using diameter as a delta X value... can someone explain how the diameter of something, for example an alveoli sac, is also equal to the uncertainty in position of something within that diameter?
Sun Nov 04, 2018 8:27 pm
Forum: Properties of Light
Topic: calculating wavelength
Replies: 10
Views: 576

### Re: calculating wavelength

The De Broglie equation can be used for any object that has rest mass, because it was found that just as light as both wave and particle properties, electrons also have both. So, the De Broglie equation is usually used to when the object's wavelength we are told to find has mass. If we are doing pr...
Sun Nov 04, 2018 8:23 pm
Forum: Properties of Light
Topic: Quantum Test
Replies: 11
Views: 587

### Re: Quantum Test

Something that helps me a lot is to remember that when solving for wavelength, wavelength = hc/E is used when looking at photons, whereas the De Broglie wavelength equation, wavelength = h/p is used when looking at particles that have mass.
Tue Oct 16, 2018 11:50 pm
Forum: Properties of Light
Topic: calculating wavelength
Replies: 10
Views: 576

### calculating wavelength

Since we know two equations involving wavelength, (c = (wavelength)(frequency) and wavelength = h/p) I was wondering when to use which equation. Does it just depend on the information given? Or are there certain times when you have to use the De Broglie wavelength versus the speed of light equation?

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