## Search found 68 matches

Sun Mar 17, 2019 10:13 am
Forum: Method of Initial Rates (To Determine n and k)
Topic: Types of Molecularity
Replies: 4
Views: 890

### Re: Types of Molecularity

The three types are unimolecular, bimolecular, and termolecular. It depends on how many reactants there are in the rate law.
Sun Mar 17, 2019 10:09 am
Forum: Arrhenius Equation, Activation Energies, Catalysts
Topic: Catalysts and pathways
Replies: 2
Views: 295

### Re: Catalysts and pathways

You can essentially use the vant Hoff equation but this time plug in Ea instead of delta H. Solving that out should allow you to solve for any variable involved.
Sun Mar 17, 2019 10:08 am
Forum: Zero Order Reactions
Topic: Zero order reaction
Replies: 8
Views: 428

### Re: Zero order reaction

You can tell if the concentration doesn’t affect the rate at all. Also the k will be a negative slope.
Thu Mar 07, 2019 5:34 pm
Forum: Zero Order Reactions
Topic: how do we tell if a reaction is zero order?
Replies: 5
Views: 202

### Re: how do we tell if a reaction is zero order?

You can tell if it is a zero order reaction by seeing whether the reaction rate is dependent on the concentration. If it is independent, the reaction is zero order.
Thu Mar 07, 2019 5:32 pm
Forum: General Rate Laws
Topic: Order of a Reaction
Replies: 3
Views: 147

### Order of a Reaction

Why would a reaction involving [A][B] creating some product [P] not necessarily be a second order reaction even though two different molecules must collide for the reaction to occur? Is a reaction only second order if the concentration of the reactants are raised to the power of 2?
Thu Mar 07, 2019 5:27 pm
Forum: Second Order Reactions
Topic: Rounding Reaction Orders
Replies: 4
Views: 142

### Re: Rounding Reaction Orders

When reaction orders are not whole numbers, its most likely due to experimental errors and therefore we just round them.
Thu Feb 28, 2019 6:16 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: cathode vs anode
Replies: 4
Views: 188

### Re: cathode vs anode

The Ecell must be positive, and so you use the Ecathode -Eanode equation to determine which reaction is the cathode and anode by looking at the values you get when you put the E of one reaction in the cathode place and the other in the anode place. If the value is positive, the place you have the E ...
Thu Feb 28, 2019 6:13 pm
Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
Topic: Finding n for the equation ΔG⁰=-nFE⁰
Replies: 8
Views: 285

### Re: Finding n for the equation ΔG⁰=-nFE⁰

Once you balance the reduction and oxidation reactions to add them together, you will get the same number of electrons being transferred on either side. The number in front of the e- (or the coefficient) is the n value.
Thu Feb 28, 2019 6:12 pm
Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
Topic: Element's potentials
Replies: 5
Views: 228

### Element's potentials

What makes an element be able to have a stranger reducing ability? A stronger oxidizing ability?
Sun Feb 24, 2019 4:25 pm
Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
Topic: n value
Replies: 11
Views: 250

### Re: n value

n is just the amount of moles present, so the problem will give you that information or a way to calculate it.
Sun Feb 24, 2019 4:19 pm
Forum: Balancing Redox Reactions
Topic: platinum
Replies: 7
Views: 189

### Re: platinum

Platinum doesn't affect the reaction at all, so it should not need to be included.
Sun Feb 24, 2019 4:17 pm
Forum: Balancing Redox Reactions
Topic: Which Equation to Flip?
Replies: 9
Views: 480

### Re: Which Equation to Flip?

The reaction that is being oxidized will always be the reaction that needs to have its equation, and therefore the E cell potential value, flipped.
Fri Feb 15, 2019 5:16 pm
Forum: Thermodynamic Systems (Open, Closed, Isolated)
Topic: Internal energy (U) of an isolated system
Replies: 17
Views: 978

### Re: Internal energy (U) of an isolated system

An isolated system will never exchange energy regardless of how much time passes.
Fri Feb 15, 2019 5:15 pm
Forum: Calculating Work of Expansion
Topic: S=0
Replies: 12
Views: 669

### Re: S=0

S is equal to zero in a perfect crystal when the temperature is 0K.
Fri Feb 15, 2019 5:14 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: Equation based on equilibrium
Replies: 5
Views: 180

### Re: Equation based on equilibrium

You would use the equation with the K when the reaction is at equilibrium. Meanwhile, use the equation with the Q at any time.
Fri Feb 08, 2019 9:05 pm
Forum: Concepts & Calculations Using Second Law of Thermodynamics
Topic: Determining Spontaneity of a Reaction
Replies: 4
Views: 215

### Re: Determining Spontaneity of a Reaction

We use Gibbs Free energy to determine spontaneity. Gibbs free energy is determined using entropy and enthalpy, and if the value of Gibbs free energy is negative, than the reaction is spontaneous. Therefore, entropy and enthalpy help to determine whether a reaction is spontaneous.
Fri Feb 08, 2019 8:59 pm
Forum: Thermodynamic Systems (Open, Closed, Isolated)
Topic: w=-PdeltaV
Replies: 6
Views: 214

### Re: w=-PdeltaV

The first equation is used in the case of a reversible expansion, meanwhile the second equation is used in the case of an irreversible expansion.
Fri Feb 08, 2019 8:56 pm
Forum: Phase Changes & Related Calculations
Topic: Negative work
Replies: 11
Views: 369

### Re: Negative work

Yes, negative work is done when a system does work on its surroundings.
Thu Jan 31, 2019 9:01 pm
Forum: Phase Changes & Related Calculations
Topic: finding heat
Replies: 3
Views: 172

### Re: finding heat

Latent heat is used in the case where a phase change is occurring while specific heat is defined as the amount of heat required to raise either a mol or a gram of something by 1 degree C.
Thu Jan 31, 2019 8:57 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Bonds and energy release
Replies: 2
Views: 151

### Bonds and energy release

Why is it that when a bond is formed it uses energy and when it is broken it releases energy?
Thu Jan 31, 2019 8:54 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Enthalpy Symbol
Replies: 5
Views: 255

### Re: Enthalpy Symbol

The naught symbolizes that all the standard conditions are being met.
Thu Jan 24, 2019 11:14 am
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Test 1
Replies: 8
Views: 351

### Re: Test 1

If the Ka value is greater than 10^3 you know it is a strong acid and if it is less than 10^-3 than you know it is a weak acid. However, it is just good to know the list of strong acids so I recommend learning them at some point.
Thu Jan 24, 2019 11:12 am
Forum: Ideal Gases
Topic: The Difference between Q and Kc [ENDORSED]
Replies: 18
Views: 1772

### Re: The Difference between Q and Kc[ENDORSED]

Q and K are both calculated in the same way. However, they are different in that Q can be calculated at any time during the reaction, while K is the value only at equilibrium. Therefore you can use Q in comparison to K to determine which way a reaction is "shifted" towards. If Q is less th...
Thu Jan 24, 2019 11:09 am
Forum: Phase Changes & Related Calculations
Topic: Water heating curve
Replies: 7
Views: 264

### Re: Water heating curve

The heat being added during a phase change solely contributes to breaking apart molecules instead of to increasing the temperature of the system.
Wed Jan 16, 2019 9:46 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: ICE
Replies: 5
Views: 196

### Re: ICE

X is the variable you use to represent the unknown concentration of something. -X and +X therefore then represent the change in concentration of a reactant.
Wed Jan 16, 2019 9:45 pm
Forum: Non-Equilibrium Conditions & The Reaction Quotient
Topic: Weak Acids and Bases
Replies: 6
Views: 242

### Re: Weak Acids and Bases

What Lavelle was talking about is that if you have a very small amount of a weak acid the pH of the mixture remains at 7. This is because adding something like 10^-9 to 10^-7, which you have to do because the H30+ mixture starts off at 10^-7, would give you a number that would remain at 10^-7. There...
Wed Jan 16, 2019 9:41 pm
Forum: Non-Equilibrium Conditions & The Reaction Quotient
Topic: Percentage Ionization
Replies: 3
Views: 163

### Re: Percentage Ionization

Yes because % ionization relates to the amount of acid that reacts with water to form H30+.
Fri Jan 11, 2019 3:39 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Kp
Replies: 9
Views: 296

### Re: Kp

Kp and Kc are essentially the same. Kp is just used to specify that only gases are involved, and the p stands for partial pressure. Meanwhile Kc is in relation to equilibrium concentrations.
Fri Jan 11, 2019 3:36 pm
Forum: Student Social/Study Group
Topic: New to Lavelle
Replies: 32
Views: 3920

### Re: New to Lavelle

I had Lavelle last quarter and what helped me more than anything was the step up lectures and other discussions set up by TAs and UAs. You can go to them and get all your questions answered, or just go more in depth on a topic you are confused about.
Fri Jan 11, 2019 3:34 pm
Forum: Ideal Gases
Topic: Reaction Quotient
Replies: 5
Views: 222

### Re: Reaction Quotient

The problem should specify whether or not you have to use Kp or Kc by either telling you, or having units that demonstrate that you should use one or the other. You shouldn't have to guess.
Wed Dec 05, 2018 12:57 pm
Forum: Shape, Structure, Coordination Number, Ligands
Topic: Ligands
Replies: 7
Views: 222

### Re: Ligands

I'm confused about 17.33 (6th edition) on the homework which asks which ligands can be polydentate. Part B gives the molecule CO 3 2- . Why is the answer that it can bind through either one or two oxygen atoms? Why isn't the answer definite? Why can't it bind to all three oxygens? It can bind throu...
Wed Dec 05, 2018 12:52 pm
Forum: Lewis Acids & Bases
Topic: Difference between Bronsted and Lewis Acids
Replies: 2
Views: 5657

### Difference between Bronsted and Lewis Acids

Can an acid be both a Bronsted and a Lewis acid at the same time? If so, when are they not?
Wed Dec 05, 2018 12:48 pm
Forum: Naming
Topic: Polyatomic ions and naming
Replies: 7
Views: 212

### Polyatomic ions and naming

Do we have to memorize polyatomic ions and their charges in order to name a coordination compound that contains one?
Mon Nov 26, 2018 9:32 pm
Forum: Dipole Moments
Topic: Dipole Moments
Replies: 4
Views: 165

### Re: Dipole Moments

Yes, they relate to whether a molecule is polar. If the dipole moments are equal or point opposite directions, the molecule will be non polar. If they point towards similar directions (aren't opposite and canceling) then the molecule is polar.
Mon Nov 26, 2018 9:27 pm
Forum: Polarisability of Anions, The Polarizing Power of Cations
Topic: Polarizability
Replies: 5
Views: 176

### Re: Polarizability

Polarizability relates to atomic radius because the larger the radius, the easier it is to distort electrons because they are farther away from the nucleus. Therefore the larger the atom, the higher the polarizability.
Mon Nov 26, 2018 9:24 pm
Forum: Coordinate Covalent Bonds
Topic: Electronegativity
Replies: 12
Views: 938

### Re: Electronegativity

There is a trend that when ionization energy and electron affinity of an element are high, it will also have a high electronegativity. Because Fluorine has both a high e affinity and a high ionization energy, it has a high electronegativity.
Mon Nov 19, 2018 12:33 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Double bonds
Replies: 8
Views: 238

### Re: Double bonds

VSEPR doesn't take into account the number of bonds between atoms because it doesn't affect the shape of the structure.
Mon Nov 19, 2018 12:32 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Electron density of lone pairs
Replies: 3
Views: 99

### Re: Electron density of lone pairs

The don't contribute because the non-central atoms aren't bonded to multiple atoms. Therefore there isn't an 'angle' created by the repulsion like there is with the central atom.
Mon Nov 19, 2018 12:29 pm
Forum: Hybridization
Topic: Hybridization bonds
Replies: 2
Views: 40

### Hybridization bonds

I'm still confused on the topic of hybridization, can someone explain why when there is a single bond it is just a sigma bond but when there is a double bond it is a sigma and pi bond?
Wed Nov 14, 2018 9:04 pm
Forum: Bond Lengths & Energies
Topic: Bond Length
Replies: 9
Views: 394

### Re: Bond Length

To find the length of a resonance bond length you find the average of the length between the two bond lengths given. This is because in a resonance structure, no bonds are actually longer than others, it just appears that way when we draw them as a lewis structure.
Wed Nov 14, 2018 9:01 pm
Forum: Bond Lengths & Energies
Topic: Bond length question
Replies: 4
Views: 189

### Re: Bond length question

If there was a question on the test concerning bond lengths Lavelle would give us the length of them and then probably ask a question concerning the strength of them in comparison to each other.
Wed Nov 14, 2018 8:59 pm
Forum: Dipole Moments
Topic: How do you draw dipole moments
Replies: 6
Views: 194

### Re: How do you draw dipole moments

You draw an arrow pointing towards the most electronegative atom in the molecule.
Mon Nov 05, 2018 10:32 pm
Forum: Octet Exceptions
Topic: Copper
Replies: 10
Views: 358

### Re: Copper

It is more stable when the 3d orbital is full, which it is when it is at 3d10.
Mon Nov 05, 2018 10:29 pm
Forum: Ionic & Covalent Bonds
Topic: Ionization Energies
Replies: 13
Views: 445

### Re: Ionization Energies

Yes helium would have the highest ionization energy.
Mon Nov 05, 2018 10:26 pm
Forum: Resonance Structures
Replies: 11
Views: 740

A radical is when there is an electron that is unpaired (meaning it would be one dot by itself on the lewis structure instead of 2 next to each other).
Mon Nov 05, 2018 10:24 pm
Forum: Octet Exceptions
Topic: Octet exceptions
Replies: 8
Views: 438

### Re: Octet exceptions

Elements in period three can, but don't always have to, have an expanded octet. Usually just P, Cl, and S will in that period.
Mon Oct 29, 2018 7:36 pm
Forum: Resonance Structures
Topic: Bond lengths
Replies: 6
Views: 133

### Re: Bond lengths

We will not have to find these bond lengths. In lecture, he used the lengths to show that the more bonds, the shorter the length of the bonds. Therefore a single bond will have a shorter length than a double bond. Also, he used it to show how in resonance structures the true length of the bonds are ...
Mon Oct 29, 2018 7:33 pm
Forum: Ionic & Covalent Bonds
Topic: Formal Charges
Replies: 3
Views: 131

### Re: Formal Charges

Yes, when adding the individual charges of elements together they should equal the overall formal charge. This is a good way to check and make sure the work you have done in calculating the individual charges was correct.
Mon Oct 29, 2018 7:32 pm
Forum: Ionic & Covalent Bonds
Topic: Octet Rule Guideline
Replies: 3
Views: 138

### Re: Octet Rule Guideline

It is essentially saying that the number of valence electrons determine the number of covalent bonds an element can make. If an element has two valence electrons they can form two bonds.
Mon Oct 22, 2018 12:49 pm
Forum: Properties of Electrons
Topic: Wave Properties
Replies: 4
Views: 168

### Re: Wave Properties

Yes, all objects have wavelike properties. However, the bigger the object, the harder it is to be able to detect the wavelength.
Mon Oct 22, 2018 12:47 pm
Forum: Properties of Light
Topic: Visible Light
Replies: 5
Views: 155

### Re: Visible Light

It is between 400nm-700nm.
Mon Oct 22, 2018 12:45 pm
Forum: Properties of Light
Topic: SI Units
Replies: 6
Views: 260

### Re: SI Units

I would suggest learning all of them that you can (they will also be useful on further tests). But also make sure you know not only nm but pm as well because that often comes up in the practice problems.
Mon Oct 22, 2018 12:43 pm
Forum: Properties of Light
Topic: TEST 2
Replies: 7
Views: 375

### Re: TEST 2

They will be given to us on the formula sheet so don't worry.
Sun Oct 21, 2018 10:39 pm
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: Labeling Electron Orbitals
Replies: 5
Views: 245

### Re: Labeling Electron Orbitals

N is the shell. Based on n, l can be any number up to n-1. If 1=0 it is an s-orbital, if l=1 it is a p orbital, if l=2 it is a d-orbital, and if l=3 it is an f-orbital. Then, the MI can be l...l-1...to negative l. The last number, or the spin, is just either -1/2 of +1/2.
Sun Oct 21, 2018 10:36 pm
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: Quantum Number Ml
Replies: 2
Views: 92

### Re: Quantum Number Ml

Yes you would need to list them all, and don't forget 0.
Sun Oct 21, 2018 10:35 pm
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: Test Question
Replies: 8
Views: 270

### Re: Test Question

It is useful to conceptually understand the shapes of the orbitals however for the test itself you will not need to draw them.
Sun Oct 21, 2018 10:34 pm
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: Quantum numbers
Replies: 5
Views: 196

### Re: Quantum numbers

Yes, the answer would be 4f. You know this because n is always the first number, and in this case n=4. Then, looking at l=3 we know it has an f-orbital. Therefore it would be 4f.
Mon Oct 15, 2018 9:16 pm
Forum: Heisenberg Indeterminacy (Uncertainty) Equation
Topic: What the equation is used for
Replies: 5
Views: 168

### What the equation is used for

I am still slightly confused what the Heisenberg equation is used for. In class we used it to show that an atomic model was incorrect because the atom's diameter was too small. What other applications can this equation have?
Mon Oct 15, 2018 9:11 pm
Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
Topic: Test Question
Replies: 3
Views: 182

### Re: Test Question

They should be given to us on the sheet with all of the constants but it is always good to ask your TA just to double check.
Mon Oct 15, 2018 9:08 pm
Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
Topic: Rydberg Equation
Replies: 4
Views: 155

### Rydberg Equation

So I know that we aren't taught the Rydberg Equation in class but should we still learn it ourselves? Are we allowed to use it on tests?
Thu Oct 11, 2018 10:15 am
Forum: Empirical & Molecular Formulas
Topic: when to multiply empirical formula [ENDORSED]
Replies: 9
Views: 1423

### Re: when to multiply empirical formula[ENDORSED]

Always multiply by the smallest number possible to get a whole number. In this case it sounds like you would multiply by 2 so that the 3.5 would turn into 7, a whole number.
Thu Oct 11, 2018 10:13 am
Forum: Empirical & Molecular Formulas
Topic: Naming Compounds on Test?
Replies: 5
Views: 297

### Re: Naming Compounds on Test?

From what I've heard, we will be taught how to do that later on and so we shouldn't have to on the first test. However, I cannot promise anything.
Thu Oct 11, 2018 10:11 am
Forum: Molarity, Solutions, Dilutions
Topic: Finding the volume of stock solution to dilute
Replies: 13
Views: 738

### Re: Finding the volume of stock solution to dilute

Like everyone else said, it isn't necessarily required. However, if you ever want to use that volume to find molarity or moles, you would need to convert it into L, so I would say that it is usually best to do so at the beginning of a problem regardless.
Thu Oct 11, 2018 10:09 am
Forum: Balancing Chemical Reactions
Topic: Test 1
Replies: 6
Views: 2595

### Re: Test 1

I would always show my work on a test just to be safe. It also helps show whoever is grading it your thought process, and some teachers even give out partial credit if your work shows you just made a minor error instead of a conceptual one.
Wed Oct 03, 2018 10:52 pm
Forum: Limiting Reactant Calculations
Topic: Percent yield
Replies: 10
Views: 589

### Re: Percent yield

Almost always, the actual yield will be given to you. You then will usually have to calculate the theoretical yield and divide the actual yield by the theoretical yield to get the percent yield.
Wed Oct 03, 2018 10:42 pm
Forum: Empirical & Molecular Formulas
Topic: Formula Mass and Molar Mass
Replies: 2
Views: 280

### Re: Formula Mass and Molar Mass

Formula mass is when you add together the molar mass of every element in the formula.
Wed Oct 03, 2018 10:40 pm
Forum: SI Units, Unit Conversions
Topic: Homework Questions [ENDORSED]
Replies: 14
Views: 524

### Re: Homework Questions[ENDORSED]

We can choose any 7 questions we want. However, I recommend choosing ones on subjects that you feel you need the most practice on.
Wed Oct 03, 2018 10:36 pm
Forum: Balancing Chemical Reactions
Topic: Order of balancing an equation
Replies: 8
Views: 312

### Order of balancing an equation

How do you know which element to start balancing first?