## Search found 62 matches

Tue Mar 12, 2019 11:31 pm
Forum: First Order Reactions
Topic: Homework question
Replies: 2
Views: 96

### Re: Homework question

This is because it is ln([A]0/[A]t) instead of ln([A]t/[A]0) which is when it would be -kt. This is just because of log rules so ln([A]t/[A]0)=-ln([A]0/[A]t) because coefficient of a log can be seen as the exponent inside the log function
Tue Mar 12, 2019 11:28 pm
Forum: First Order Reactions
Topic: Graphs
Replies: 2
Views: 143

### Re: Graphs

The linear graphs help to determine what order a reaction is. It is linear because the k is a constant and it is the slope.
Tue Mar 12, 2019 11:25 pm
Forum: Zero Order Reactions
Topic: Zero Order Reactions
Replies: 3
Views: 333

### Re: Zero Order Reactions

This can also be when there is a catalyst present or when there is an excess (so rate doesn't depend on concentration of reactant)
Thu Mar 07, 2019 12:04 am
Forum: Second Order Reactions
Topic: deciding which order
Replies: 2
Views: 150

### Re: deciding which order

It depends on what information you're given in the problem. If they give you initial concentrations and initial rate values often you are able to determine how concentration effects rate to find out that way. If they only give you time and initial concentration then you can use the linear plots to d...
Wed Mar 06, 2019 11:59 pm
Forum: Zero Order Reactions
Topic: Example of a zero order rxn
Replies: 4
Views: 201

### Re: Example of a zero order rxn

Examples of zero order reactions often have saturated enzymes that make the rate independent of reactant concentrations
Wed Mar 06, 2019 11:58 pm
Forum: General Rate Laws
Topic: Reaction Order
Replies: 4
Views: 196

### Re: Reaction Order

A general formula can be M^(1-p)*s^-1, where p is the overall order of the reaction.
Wed Feb 27, 2019 2:00 pm
Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
Topic: Melting/Spontaneous Processes
Replies: 3
Views: 158

### Re: Melting/Spontaneous Processes

A negative delta G value shows that a reaction is spontaneous. The forward reaction in this case is melting so if delta G is negative then that is favored.
Wed Feb 27, 2019 1:55 pm
Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
Topic: salt bridge
Replies: 4
Views: 235

### Re: salt bridge

Salt bridges allow for a circuit so that the cathode doesn't become too saturated with electrons and thus reject electrons. The salt bridge allows a transfer of electrons back to the anode so that the transfer of electrons is continuous.
Wed Feb 27, 2019 1:46 pm
Forum: Balancing Redox Reactions
Topic: Oxidized vs oxidizing agent
Replies: 6
Views: 183

### Re: Oxidized vs oxidizing agent

You can try to remember this like the oxidizing agent is the thing that does the oxidizing (accepting an electron) and in turn gets reduced. Basically just think of it as the action it is doing.
Wed Feb 20, 2019 10:50 pm
Forum: Balancing Redox Reactions
Topic: Adding Salt Bridge/Porous Disk to Reaction Beakers
Replies: 2
Views: 93

### Re: Adding Salt Bridge/Porous Disk to Reaction Beakers

If a solution becomes too negatively charged, it will repel electrons so the addition of a salt bridge or a porous disk is to allow flow of electrons back to the reducing agent so that the solutions remain neutral and can continue to transfer electrons. It essentially makes the flow of electrons int...
Wed Feb 20, 2019 10:47 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Porous disc explanation?
Replies: 6
Views: 205

### Re: Porous disc explanation?

The porous disk is between the two beakers and allows flow of electrons so that the solution that is reduced can still gain electrons and won't repel the electrons
Wed Feb 20, 2019 10:43 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: 6th edition 9.67
Replies: 3
Views: 170

### Re: 6th edition 9.67

We set deltaG equal to 0 because we need to determine at what temperature deltaG switches from positive to negative. Positive deltaG means it is not spontaneous and negative deltaG means it is spontaneous so we are looking for when deltaG=0 to find when it becomes spontaneous.
Tue Feb 12, 2019 5:25 pm
Forum: Entropy Changes Due to Changes in Volume and Temperature
Topic: Cp and Cv
Replies: 3
Views: 106

### Re: Cp and Cv

Cp is for when there is constant pressure whereas Cv is when there is constant volume. Hope this helps!
Tue Feb 12, 2019 5:18 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Ka value
Replies: 3
Views: 144

### Re: Ka value

Really strong acids that dissociate completely do not have a Ka value. However we classify really weak acids with a Ka value of less than 10^(-3)
Tue Feb 12, 2019 5:15 pm
Forum: Thermodynamic Definitions (isochoric/isometric, isothermal, isobaric)
Topic: Reversible Reactions
Replies: 8
Views: 613

### Re: Reversible Reactions

I believe all reversible reactions are isothermal but all isothermal reactions may not be reversible
Wed Feb 06, 2019 9:37 pm
Forum: Calculating Work of Expansion
Topic: Integral Expression for Work
Replies: 4
Views: 192

### Re: Integral Expression for Work

You only need to know it to understand the derivation of the 2nd law of thermodynamics. The actual equations used do not include the integral.
Wed Feb 06, 2019 9:33 pm
Forum: Thermodynamic Definitions (isochoric/isometric, isothermal, isobaric)
Topic: Reversible Processes
Replies: 4
Views: 196

### Reversible Processes

Can someone explain how you know when it is reversible vs irreversible?
Wed Feb 06, 2019 9:31 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: 6th Edition Hw #8.3 Delta V
Replies: 1
Views: 109

### Re: 6th Edition Hw #8.3 Delta V

This is because you are finding the change in volume and the container is a cylinder. The pump being depressed is the depth you need to calculate changed volume and the equation gives you the diameter so you can find the area of the face of the cylinder.
Mon Jan 28, 2019 7:08 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Energy vs. Enthalpy
Replies: 2
Views: 94

### Re: Energy vs. Enthalpy

Enthalpy is the change in heat from the two stages of a reaction. The energy required for the reaction to take place is generally greater than the enthalpy, even for endothermic reactions.
Mon Jan 28, 2019 6:54 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Standard Enthalpies
Replies: 2
Views: 119

### Re: Standard Enthalpies

I beleive standard enthalpy is just when a pure element is under standard conditions of pressure and temperature, so it would just the phase of the element when it is under 1 atm and at 25 degrees C
Mon Jan 28, 2019 6:48 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Method 3
Replies: 2
Views: 114

### Re: Method 3

I think this relates to the strength of the bonds. So when CO2 is formed, it releases more heat because two double bonds are stronger than four single bonds like in CH4.
Wed Jan 23, 2019 11:00 pm
Forum: Non-Equilibrium Conditions & The Reaction Quotient
Replies: 2
Views: 89

### Re: Question about problem 6D.15(b)

Why does H2O attach to the aluminum when H2O is uncharged?
Wed Jan 23, 2019 10:55 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: Strong Acids and Bases
Replies: 3
Views: 170

### Re: Strong Acids and Bases

In the textbook the only polyprotic strong acid listed is sulfuric acid which dissociates completely.
Sun Jan 20, 2019 10:19 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: 5% rule
Replies: 12
Views: 404

### Re: 5% rule

This is when approximating x while using the ICE table. For instance, if the equation becomes (x^2)/(.10-x)=K then you can approximate it to (x^2)/.10=K so you have to do easier calculations.
Tue Jan 15, 2019 8:29 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: 5J.11 Part b
Replies: 2
Views: 83

### 5J.11 Part b

The question is does a temperature increase shift equilibria towards products or reactants for X2<-->2X?
Why is X2-->2X endothermic? Isn't it a catabolic reaction and therefore exothermic?
Tue Jan 15, 2019 11:54 am
Forum: Non-Equilibrium Conditions & The Reaction Quotient
Topic: Equilibrium in relation to K and Q
Replies: 5
Views: 186

### Re: Equilibrium in relation to K and Q

Solving for Q is the same as solving for K in regards to setting up the problem. The only difference is that K is when the reaction is at equilibrium whereas Q is at any arbitrary stage in the reaction.
Tue Jan 15, 2019 11:51 am
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Replies: 3
Views: 289

### Re: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions

Homogenous vs heterogenous reactions just refers to the phases of the reactants and the products. So if all the reactants and products are the same phase then it will be a homogenous reaction. Hope this helps!
Tue Jan 15, 2019 11:49 am
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: Le Chatelier's Principle
Replies: 7
Views: 152

### Re: Le Chatelier's Principle

Le Chatelier's principle essentially says that a reaction in equilibrium will adjust to minimize the stress of changing factors ie pressure or concentration. For example when more reactants are added to a reaction, the reaction will in turn produce more products to limit the stress.
Wed Jan 09, 2019 5:13 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Bar vs. atm
Replies: 4
Views: 93

### Re: Bar vs. atm

1 bar = 0.987 atm, but both are just units of pressure. Hope this helps!
Wed Jan 09, 2019 5:04 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: finding K Value
Replies: 3
Views: 69

### Re: finding K Value

Stoichiometric coefficients are used as the exponent when calculating the equilibrium constant. So if it was 2CO2 then it will be [CO2]^2 in when finding K.
Tue Dec 04, 2018 8:14 pm
Forum: Conjugate Acids & Bases
Topic: Determining Conjugate Acid
Replies: 5
Views: 467

### Re: Determining Conjugate Acid

Conjugate acids and bases deal with the Bronsted definition of acids and bases so it is proton (H+) transfer
Tue Dec 04, 2018 8:12 pm
Forum: Identifying Acidic & Basic Salts
Topic: Identifying the Different Types of Acidic and Bases
Replies: 2
Views: 67

### Re: Identifying the Different Types of Acidic and Bases

These are the only definitions of acids and bases that Lavelle has taught. Just remember that Bronsted deals with protons while Lewis deals with electrons! Hope this helps
Tue Dec 04, 2018 7:48 pm
Forum: Properties & Structures of Inorganic & Organic Acids
Topic: Fundamentals J7
Replies: 5
Views: 300

### Re: Fundamentals J7

For Part A, water is produced as OH- is taken from KOH and an H atom is taken from CH3COOH, thus leaving CH3CO2K as the salt produced
Tue Dec 04, 2018 7:31 pm
Forum: Naming
Topic: 9C.5 7th Edition
Replies: 2
Views: 154

### Re: 9C.5 7th Edition

If you are unfamiliar with a ligand you can draw a Lewis structure to help you determine the number of lone pairs
Mon Nov 26, 2018 3:32 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Determining Shape
Replies: 4
Views: 208

### Re: Determining Shape

The arrangement is just based on number of regions of electron density whereas the shape includes if the regions are lone pair vs bonds
Mon Nov 26, 2018 3:28 pm
Forum: Hybridization
Topic: Lone pair
Replies: 4
Views: 199

### Re: Lone pair

I think hybridization depends on the number of regions of electron density, not the sigma or pi bonds, so it would be sp3
Mon Nov 26, 2018 3:26 pm
Forum: Hybridization
Topic: 2F.7
Replies: 1
Views: 96

### Re: 2F.7

The question asks for the hybrid orbitals so you need to determine the regions of electron density. Tthe d-orbital is incorporated when there are too many regions of electron density for sp3
Tue Nov 20, 2018 1:34 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Memorization
Replies: 4
Views: 187

### Re: Memorization

You will have to memorize the names of the molecular geometry but you can figure out the regions of electron density from the Lewis structure. Hope this helps!
Tue Nov 20, 2018 1:29 pm
Forum: Hybridization
Topic: d Orbital
Replies: 6
Views: 195

### Re: d Orbital

Lavelle said we wouldn't need to draw them but it is probably recommended that you know the shapes
Tue Nov 20, 2018 1:27 pm
Forum: Hybridization
Topic: Molecular Shape & Hybridization
Replies: 4
Views: 178

### Re: Molecular Shape & Hybridization

Yes because hybridization depends on the number of regions of electron density
Wed Nov 14, 2018 7:43 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Homework for Week 7
Replies: 2
Views: 90

### Re: Homework for Week 7

My TA has mentioned that you do not necessarily have to do homework in the current sections as long as they are recent and applicable to what we're learning now. Hope that helps!
Wed Nov 14, 2018 7:40 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: H20
Replies: 3
Views: 230

### Re: H20

The electron geometry is tetrahedral whereas the molecular geometry is bent. This is because oxygen has two lone pairs and two covalent bonds.
Wed Nov 14, 2018 7:38 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Bond Angles
Replies: 8
Views: 628

### Re: Bond Angles

I believe that for certain molecular shapes you will know the angles ie trigonal planar is 120 degree angles, but for the case of molecules with lone pair electrons those you will have to give a range because there is no way to calculate the actual bond angle just by looking at VSEPR. Hope that helps!
Mon Nov 05, 2018 3:19 pm
Forum: Resonance Structures
Topic: Bond Lengths
Replies: 7
Views: 441

### Re: Bond Lengths

The bond lengths are equal despite that double and single bonds have different lengths. Somehow the actual bond length will fall between the length of single or double if those are the only bonds present.
Mon Nov 05, 2018 3:16 pm
Forum: Formal Charge and Oxidation Numbers
Topic: Ideal lewis structure with Formal Charge
Replies: 4
Views: 2129

### Re: Ideal lewis structure with Formal Charge

Does only the net formal charge matter? Or do you also have to account for each atom as well?
Mon Nov 05, 2018 3:15 pm
Forum: Octet Exceptions
Topic: Octet exceptions
Replies: 8
Views: 485

### Re: Octet exceptions

Why can they have expanded shells?
Tue Oct 30, 2018 6:44 pm
Forum: Resonance Structures
Topic: Determining Bond Length
Replies: 2
Views: 146

### Determining Bond Length

How do you determine the average bond length when there are not just single bonds? When we did the problem in class, there was one bond 1.2 Angstrom and two 1.4 Angstrom but the actual length was 1.24 Angstrom. How do you find the actual bond length from those numbers?
Tue Oct 30, 2018 6:40 pm
Forum: Lewis Structures
Topic: 7th Edition 2.B.9
Replies: 5
Views: 114

### Re: 7th Edition 2.B.9

For ionic compounds, how do you know which elements will become cations and which will be anions?
Tue Oct 30, 2018 6:34 pm
Forum: Lewis Structures
Topic: Drawing Lewis Structures
Replies: 14
Views: 741

### Re: Drawing Lewis Structures

Lewis structures are meant to represent where the electrons are and how the molecule is bonded, not an accurate visual representation
Tue Oct 23, 2018 12:25 pm
Forum: Heisenberg Indeterminacy (Uncertainty) Equation
Topic: Value of Delta X
Replies: 9
Views: 554

### Re: Value of Delta X

Yesterday at office hours the TA said delta X should be in meters
Tue Oct 23, 2018 11:49 am
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: 7th edition 1D.25
Replies: 3
Views: 84

### Re: 7th edition 1D.25

2d cannot exist because the principle quantum number is 2 and the magnetic quantum number must be at least less than the quantum number so it can either be 1 or 0, but not 2
Tue Oct 23, 2018 11:46 am
Forum: DeBroglie Equation
Topic: Rest Mass
Replies: 7
Views: 385

### Re: Rest Mass

De Broglie's equation is only applicable to things that have rest mass
Tue Oct 23, 2018 11:42 am
Forum: *Shrodinger Equation
Topic: Schrodinger's Equation
Replies: 6
Views: 766

### Re: Schrodinger's Equation

You should also know that it changes a probability into an observable value
Tue Oct 16, 2018 8:43 pm
Forum: Properties of Light
Topic: Week 3 HW
Replies: 5
Views: 308

### Re: Week 3 HW

My TA just said to do hw problems that are relevant to what we're learning so as long as they aren't super old problems then you can do them too
Tue Oct 16, 2018 7:14 pm
Forum: Properties of Light
Topic: 7th Edition 1A.3
Replies: 4
Views: 110

### Re: 7th Edition 1A.3

For b, wavelength and frequency are inversely related so they cannot both decrease at the same time due to c=lambda*nu
Tue Oct 16, 2018 6:32 pm
Forum: Significant Figures
Topic: knowing how many sig figs to use
Replies: 17
Views: 1030

### Re: knowing how many sig figs to use

What does it mean when there is a period after a number but no decimals after the period? For example, 50. g of something. Is that still 2 sigfigs?
Mon Oct 08, 2018 8:59 pm
Forum: Accuracy, Precision, Mole, Other Definitions
Replies: 7
Views: 642

Avogadro's constant can be used as the number of particles per mole of a substance
Mon Oct 08, 2018 8:55 pm
Forum: Molarity, Solutions, Dilutions
Topic: Changing Units
Replies: 10
Views: 497

### Re: Changing Units

I think in class he said you should convert to L when using a formula that uses L and then you can choose to convert again at the end of the problem depending on what the question is asking for.
Mon Oct 08, 2018 8:53 pm
Forum: Balancing Chemical Reactions
Topic: States of Matter
Replies: 11
Views: 485

### Re: States of Matter

My TA said that you should always include states of matter when writing out an equation
Mon Oct 01, 2018 2:45 pm
Forum: Empirical & Molecular Formulas
Topic: Multiple Ratio Possibility?
Replies: 4
Views: 204

### Re: Multiple Ratio Possibility?

Is there a tip on how to find integers when you get a ratio that isn't whole numbers?
Mon Oct 01, 2018 2:41 pm
Forum: Limiting Reactant Calculations
Topic: Limiting reagents
Replies: 12
Views: 367

### Re: Limiting reagents

Is it possible that two reagents get used up at the same time so that an equation can have two limiting reactants?
Mon Oct 01, 2018 2:35 pm
Forum: Significant Figures
Topic: Significant Figures [ENDORSED]
Replies: 6
Views: 244

### Re: Significant Figures[ENDORSED]

Are you supposed to keep sigfigs the entire time while doing conversions or do you round to sigfigs only at the end of the problem?