## Search found 109 matches

Mon Mar 09, 2020 7:54 am
Forum: Reaction Mechanisms, Reaction Profiles
Topic: Ways to Approach Reaction Mechanisms
Replies: 3
Views: 25

### Re: Ways to Approach Reaction Mechanisms

I think he was just explaining how there were multiple ways to approach seeing whether certain reaction mechanisms are valid.However, we don't have to know them except for the preequilibrium approach.
Mon Mar 09, 2020 7:52 am
Forum: General Rate Laws
Topic: 7A.1
Replies: 3
Views: 35

### Re: 7A.1

Yes, it just has to do with stoichiometric coefficients.For part a for example, the rate of consumption of N2 is 1/3 times the rate of consumption of H2 because H2 is consumed three times as much as N2.
Mon Mar 09, 2020 7:50 am
Forum: Method of Initial Rates (To Determine n and k)
Topic: differential rate law to integrated rate law
Replies: 3
Views: 35

### Re: differential rate law to integrated rate law

Integrated rate laws allow you to consider how time relates to the reaction. As opposed to only knowing initial time/concentration, the integrated rate law lets you know what is going on in the reaction at any point in time.
Mon Mar 09, 2020 7:48 am
Forum: Reaction Mechanisms, Reaction Profiles
Topic: Homework 7C11
Replies: 2
Views: 13

### Re: Homework 7C11

rates would be equal to the rate constant multiplied by the reactant concentrations to the power of what order they are (whether they are zeroeth, first, or second order). At equilibrium, the rates of forward and reverse reactions are equal, but the rate constants don't have to be equal.
Mon Mar 09, 2020 7:46 am
Forum: First Order Reactions
Topic: Homework 7B.7
Replies: 1
Views: 22

### Re: Homework 7B.7

For natural logs, when you make something a negative, you flip the fraction. This is why, instead of dividing by -k, you can first divide by - first, which would make the natural log fraction 1/0.15. Then, you can also divide by k, which would give you t.
Mon Mar 02, 2020 7:56 am
Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
Topic: equilibrium constant from standard potentials
Replies: 1
Views: 24

### Re: equilibrium constant from standard potentials

You have the equations delta Go= -nFEo, and delta G0 = -RTlnK (at equilibrium). You could calculate the equilibrium constant from standard potential by setting these two equations equal to each other.
Mon Mar 02, 2020 7:54 am
Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
Topic: Voltage Signs for Oxidation Reactions
Replies: 2
Views: 23

### Re: Voltage Signs for Oxidation Reactions

When calculating the cell potential, you could reverse the voltage sign of the oxidation reaction.
Mon Mar 02, 2020 7:53 am
Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
Topic: gibbs free energy vs cell standard potential
Replies: 3
Views: 33

### Re: gibbs free energy vs cell standard potential

Gibbs free energy is related to cell potential by the equation G = -nfE. When you rearrange this equation, you can also get E = -G/nf. When you multiply a chemical reaction by a factor, G is also changed by that factor. However, n is also changed by that factor (since it is the electrons in the bala...
Mon Mar 02, 2020 7:50 am
Forum: Method of Initial Rates (To Determine n and k)
Topic: factors that affect k
Replies: 8
Views: 182

### Re: factors that affect k

K also correlates to cell potential too. If the cell potential is large and positive, then delta G would be a large negative. Since delta G is also equal to -RTlnK, K would also be a large number.
Mon Mar 02, 2020 7:48 am
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: 6L.3
Replies: 2
Views: 20

### Re: 6L.3

I think the note is because the cell potential is negative. When the cell potential is negative, deltaG (free energy) is positive. This means it would be non spontaneous in the forward reaction, but spontaneous in the reverse reaction.
Mon Mar 02, 2020 7:46 am
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: 6M.5
Replies: 2
Views: 25

### Re: 6M.5

The electrons in the half reaction would go on the left side of the reaction because you want to make sure the charges on both sides are balanced. Since Hg2 2+ has a charge on 2+, adding 2 electrons to that side would make the net charge 0, which is what 2Hg on the right side is.
Mon Feb 24, 2020 8:10 am
Forum: Van't Hoff Equation
Topic: Van't Hoff Equation
Replies: 3
Views: 69

### Re: Van't Hoff Equation

The Van't Hoff Equation is used to calculate K at different temperatures. In finding the K, you would assume that the delta S and delta H are not significant.
Mon Feb 24, 2020 8:07 am
Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
Topic: Gibs free energy
Replies: 3
Views: 52

### Re: Gibs free energy

n stands for the moles of electrons transferred in the equation. One example you could use is the reaction where Zn is oxidized to Zn2+ and Cu2+ is reduced to Cu. Since each reactant is oxidized/reduced by 2, the n would be 2.
Mon Feb 24, 2020 8:04 am
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Convention for cell diagrams
Replies: 3
Views: 41

### Re: Convention for cell diagrams

I think that Dr. Lavelle was talking about how he usually likes to write the cell diagram by writing what species is getting reduced in order, and what species is getting oxidized in order. However, this is just how he likes to write it but it is not part of required notation.
Mon Feb 24, 2020 8:01 am
Forum: Concepts & Calculations Using Second Law of Thermodynamics
Topic: 4F.13
Replies: 2
Views: 84

### Re: 4F.13

The enthalpy is a state function, but it doesn't mean that it isn't dependent on amount there. A state function just means that the enthalpy value calculated from the reaction is independent of how the reaction got there.
Mon Feb 24, 2020 7:58 am
Forum: Administrative Questions and Class Announcements
Topic: Hw 8
Replies: 10
Views: 122

### Re: Hw 8

Hw 8 can probably be anything covered since the midterm, such as the second half of thermodynamics or the electrochemistry he talked about in class.
Mon Feb 17, 2020 8:42 am
Forum: Calculating Work of Expansion
Topic: Irreversible and Reversible problem
Replies: 4
Views: 108

### Re: Irreversible and Reversible problem

For irreversible and reversible problems, the work calculated would be different because work is a state function. For entropy change, entropy is a state function, and so the same equation can be used for calculating the irreversible and reversible entropy of the system.
Mon Feb 17, 2020 8:39 am
Forum: Van't Hoff Equation
Topic: Entropy in Van't Hoff Equation
Replies: 3
Views: 38

### Re: Entropy in Van't Hoff Equation

The entropy increases with temperature. In the Van't Hoff Equation though, you are using change of entropy and not entropy, and you are assuming that change of entropy is constant under temperature increase.
Mon Feb 17, 2020 8:35 am
Forum: Concepts & Calculations Using Second Law of Thermodynamics
Topic: Second Law Equation
Replies: 1
Views: 86

### Re: Second Law Equation

It is used to find the entropy of both and can be used for everything because entropy is a state function (so it doesn't matter how you get there, and thus how you calculate it). If you are finding entropy of the surroundings though under constant pressure, entropy of the surroundings would be oppos...
Mon Feb 17, 2020 8:33 am
Forum: Concepts & Calculations Using Second Law of Thermodynamics
Topic: entropy based on molecular name/structure
Replies: 2
Views: 107

### Re: entropy based on molecular name/structure

I think that in general, we just need to know the general entropy trend that entropy increases with the complexity of the molecule because it can occupy more positions. I'm not sure how in depth we would have to know though, such as if we need to know specific molecules by name.
Mon Feb 17, 2020 8:31 am
Forum: Entropy Changes Due to Changes in Volume and Temperature
Topic: Boltzmann Formula
Replies: 11
Views: 192

### Re: Boltzmann Formula

The number of orientations is the number of orientations where a molecule would be in a position with equal energy. W would be the number of positions to the power of however many molecules the question says.
Mon Feb 10, 2020 8:17 am
Forum: Polyprotic Acids & Bases
Topic: 6E.3 Ignoring second deprotonation
Replies: 1
Views: 149

### Re: 6E.3 Ignoring second deprotonation

You would ignore the second deprotonation if it is not significant, and doesn't really affect the pH overall. This usually happens when the second deprotonation has a K value super small, letting you know that not much H3O+ dissociates.
Mon Feb 10, 2020 8:14 am
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: delta U = 0
Replies: 2
Views: 28

### Re: delta U = 0

delta U is equal to 0 for an isolated system when it is isothermal and reversible.
Mon Feb 10, 2020 8:12 am
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: delta h rxn at different temperatures
Replies: 1
Views: 22

### Re: delta h rxn at different temperatures

I'll just use hypothetical temperatures of 50 degrees and 120 degrees. You would want to calculate the the delta h of the reaction using q=mcdeltaT, where delta T is the difference in temperature from 50 to 120 degrees. You would then want to use the delta H of the temperature they give you, such as...
Mon Feb 10, 2020 8:06 am
Forum: Calculating Standard Reaction Entropies (e.g. , Using Standard Molar Entropies)
Topic: Why is delta U = 0 for isothermal reactions?
Replies: 11
Views: 219

### Re: Why is delta U = 0 for isothermal reactions?

U would equal 0 because it is an isothermal reversible equation, as the internal energy of the system does not change overall.
Mon Feb 10, 2020 8:04 am
Forum: Entropy Changes Due to Changes in Volume and Temperature
Topic: delta s = q(rev)/T
Replies: 1
Views: 19

### Re: delta s = q(rev)/T

There isn't one, but you can also use the one with a volume change. The reason the equations don't really matter is because entropy is a state function, whereas work isn't.
Mon Feb 03, 2020 8:38 am
Forum: Calculating Work of Expansion
Topic: Area under the curve
Replies: 3
Views: 37

### Re: Area under the curve

I think he showed us the curves to help us understand how the amount of work is equal to the area under the curve (since it was an integral). The curves showed that reversible expansions are able to do a greater amount of work than irreversible expansions.
Mon Feb 03, 2020 8:36 am
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Bond Enthalpies
Replies: 2
Views: 33

### Re: Bond Enthalpies

Usually you would be given bond enthalpies. Calculating the enthalpy change in general though is the bond enthalpies of the bonds broken (in reactants) - bond enthalpies of the bonds formed (in products).
Mon Feb 03, 2020 8:35 am
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: delta V
Replies: 4
Views: 45

### Re: delta V

I think it could also be when a gas is in a system that has constant volume, and so there can be no change in volume
Mon Feb 03, 2020 8:32 am
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: Cv vs Cp
Replies: 3
Views: 59

### Re: Cv vs Cp

Cv and Cp would change calculations when it relates to work. When a gas is under constant pressure, it can do work against that constant pressure and experience a change in volume. You can use the equation work = -Pex * delta V. For something that has constant volume, since the volume can't change, ...
Mon Feb 03, 2020 8:30 am
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: 4B.5
Replies: 3
Views: 43

### Re: 4B.5

Yes, you would want to convert the pressure from Torr first so that the units can match and cancel when you use the internal energy change equation.
Mon Jan 27, 2020 8:41 am
Forum: Equilibrium Constants & Calculating Concentrations
Topic: autoprotolysis
Replies: 7
Views: 81

### Re: autoprotolysis

Autoprotolysis is the reaction of 2 H2O --> OH - + H3O+. Like any reaction, you can write the K expression (products over reactants), and get Kw = [OH-][H3O+], since H2O is a liquid and so isn't counted in the K expression. Now , you can use the properties of logs, and do logKw = log[OH-] + log[H3O+...
Mon Jan 27, 2020 8:38 am
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Negative pH
Replies: 9
Views: 65

### Re: Negative pH

Usually the pH scale runs from 0 -14. However, it can sometimes have a negative pH if there is such a high concentration of hydronium ions that the pH of it becomes negative. I think these are called superacids.
Mon Jan 27, 2020 8:34 am
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Method 2 example
Replies: 3
Views: 27

### Re: Method 2 example

I think that the reason only some of the C-H bonds were shown to break or form was based on the lewis structure. When he drew CH2=CH2, most of the C-H bonds remained in the "same" place, and so there was no need to show the bond breaking or forming. However, the = definitely broke as the p...
Mon Jan 27, 2020 8:28 am
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: enthalpy/state properties
Replies: 4
Views: 47

### Re: enthalpy/state properties

The path is not relevant in enthalpy as you can still calculate delta H without knowing what happens in between as long as you know what happens in the initial and final state.
Mon Jan 27, 2020 8:26 am
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: Units for temperature?
Replies: 11
Views: 80

### Re: Units for temperature?

I think you would use K, although since q = mc(delta T) is the change in temperature, the change itself would be the same number whether you use celsius or K. For example, if something changed from 0 to 2 celsius (which is 273 to 275 K), the delta T would still be 2 no matter what you use.
Mon Jan 20, 2020 7:30 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: When to ignore the second (de)protonization?
Replies: 5
Views: 41

### Re: When to ignore the second (de)protonization?

I believe that they should give us the exact value of the Ka values, such as Ka1 = "" and Ka2 = "". Good luck on your test too!
Mon Jan 20, 2020 7:27 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Salt Solutions
Replies: 3
Views: 45

### Re: Salt Solutions

A salt is composed of a positively and negatively charged ion. It shouldn't be different from calculating other acid/base pH. Usually, one part of the salt will influence the pH - for example, in NaC2H3CO2, C2H3CO2 is negatively charged and will make for a basic solution. You would just do the ICE t...
Mon Jan 20, 2020 7:21 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: pH Examples
Replies: 3
Views: 66

### Re: pH Examples

I think that you would just want to know that CO2 when dissolved in water makes carbonic acid, which is H2CO3, which is responsible for all the environmental and biological examples listed in the outline below.
Mon Jan 20, 2020 7:16 pm
Forum: *Making Buffers & Calculating Buffer pH (Henderson-Hasselbalch Equation)
Topic: Test 1 material
Replies: 3
Views: 109

### Test 1 material

Do we have to know how to calculate buffers and titrations for test 1?
Mon Jan 20, 2020 7:12 pm
Forum: Ideal Gases
Topic: Equilibrium Constant
Replies: 7
Views: 67

### Re: Equilibrium Constant

If a K is that small (less than 10^-3), then at equilibrium, there will be way more reactants than products, indicating only a small amount of product was formed before the reaction reached equilibrium. This is because the reactant state has greater stability, so the reactants will want to stay reac...
Mon Jan 20, 2020 7:10 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: K
Replies: 5
Views: 59

### Re: K

Changing the temperature would change the K. This is because if a reaction is exothermic, then increasing temp will cause the reaction to shift towards the reactants, so K would be smaller. The opposite would be true for endothermic reactions, where an increase in temp would result in an increase in...
Mon Jan 20, 2020 7:08 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: When to ignore the second (de)protonization?
Replies: 5
Views: 41

### Re: When to ignore the second (de)protonization?

I think that you would ignore it if the second deprotonization or third (etc.) does not affect the pH of the solution. In the textbook, it says that for most polyphonic acid, the 2nd or more Ka is so small that pH of the solution isn't really affected. However, for H2SO4, this is an exception where ...
Mon Jan 13, 2020 8:56 am
Forum: Administrative Questions and Class Announcements
Topic: Test One Content
Replies: 6
Views: 105

### Re: Test One Content

I think it would be equilibrium and acid/base, and will probably cover up to what we do Friday
Mon Jan 13, 2020 8:54 am
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Example 5I.3 (page 556 on pdf)
Replies: 3
Views: 26

### Re: Example 5I.3 (page 556 on pdf)

I believe the solutions used an approximation for this, and so took off the -2x and -x so that calculating would be easier. This is because x is believed to be so small (less than 5%) that it wouldn't really matter if you included the -2x/-x or not.
Mon Jan 13, 2020 8:48 am
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: Change in Pressure
Replies: 6
Views: 34

### Change in Pressure

How does a reaction shift when the pressure of a system is decreased?
Mon Jan 13, 2020 8:46 am
Forum: Non-Equilibrium Conditions & The Reaction Quotient
Topic: Q=K
Replies: 14
Views: 131

### Re: Q=K

Q can be calculated at any point during the reaction, whether the reaction is at equilibrium or not. As such, the value of Q could indicate that a reaction is not yet at equilibrium (such as Q<K or Q>K) or that it is at equilibrium (Q=K).
Mon Jan 13, 2020 8:44 am
Forum: Equilibrium Constants & Calculating Concentrations
Topic: intermediate values of K
Replies: 3
Views: 21

### Re: intermediate values of K

if K is between 10 ^-3 and 10^3, the reaction is neither strongly favoring the products or the reactants. If K is greater than 10^3, it strongly favors products, and if K is less than 10^-3, the reaction strongly favors reactants.
Mon Jan 13, 2020 8:43 am
Forum: Equilibrium Constants & Calculating Concentrations
Topic: ICE
Replies: 3
Views: 25

### Re: ICE

Basically, the ICE table is a way to calculate the predicted quantitative values of a reaction at equilibrium. You would start by balancing the reaction first, and then in the first row (I), writing down the initial concentration or partial pressures of the reactants and products. You would then exp...
Mon Jan 06, 2020 5:01 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Reactant Quotient vs Equilibrium Constant
Replies: 3
Views: 58

### Re: Reactant Quotient vs Equilibrium Constant

The rules for calculating both the reaction and equilibrium constant would be the same. You would calculate the equilibrium constant when the reaction is at equilibrium and calculate the reaction quotient at any other point of the reaction.
Mon Jan 06, 2020 4:58 pm
Forum: Ideal Gases
Topic: ICE Table Variables
Replies: 6
Views: 94

### Re: ICE Table Variables

You also would not have to use variables if any part of your equation includes species that are not in aqueous or gas states. Since a pure solid or liquid would be the same, you would only use variables when determining changes in aqueous/gas reactants and products.
Mon Jan 06, 2020 4:53 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: The Significance of K
Replies: 5
Views: 52

### Re: The Significance of K

You would use Kc when you are given molarity/concentrations of the reactants and products. If you are given partial pressure values, you can use Kp.
Mon Jan 06, 2020 3:56 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Post Assessment Problem 18
Replies: 2
Views: 59

### Re: Post Assessment Problem 18

To find the equilibrium constant here, you would want to use the partial pressures given. The K would be equal to the partial pressures of the product over the reactant. After balancing the equation, you would find K by multiplying the partial pressures of N2 and H2 (with H2 raised to the 3rd) over ...
Mon Jan 06, 2020 3:53 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Question 5H.3
Replies: 3
Views: 59

### Re: Question 5H.3

For this question, you could use the K values of 2 different equations, one that includes BrCl and another that has H2 in the equation. You can then find the overall K value of the equation in question by multiplying the K of the first equation with the K of the second equation.
Mon Dec 02, 2019 7:07 am
Forum: Biological Examples
Topic: How Cisplatin Works?
Replies: 2
Views: 52

### How Cisplatin Works?

In class, Dr. Lavelle talked about how cisplatin works as a chemotherapy drug while translation does not. Why is this, and could someone explain how cisplatin interacts with DNA?
Mon Dec 02, 2019 7:04 am
Forum: Polyprotic Acids & Bases
Topic: Polyprotic acids and bases
Replies: 2
Views: 135

### Re: Polyprotic acids and bases

Another common example would be H3PO4. In polyprotic acids, the first Ka, which measures the strength of the acid when it donates its first proton, is usually the strongest. The subsequent Kas, which measure the strength of the acid as it donates its second (or third) proton is weaker because it is ...
Mon Dec 02, 2019 7:00 am
Forum: Naming
Topic: Coordination compounds latin names
Replies: 2
Views: 26

### Re: Coordination compounds latin names

You would use a Latin name for Fe. When writing the coordination compound name, you would write ferrum (or ferrate) instead of iron.
Mon Dec 02, 2019 6:59 am
Forum: Naming
Topic: 9C.5
Replies: 2
Views: 31

### Re: 9C.5

You would also want to look at the single and double bonds in the molecule too since single bonds (sigma) allow for rotation but double bonds (with pi bonds) do not. Sometimes, even though there is a lone pair on an atom, it cannot be a binding site because the double bond does not allow the atom to...
Mon Dec 02, 2019 6:57 am
Forum: Identifying Acidic & Basic Salts
Topic: 6C. 21
Replies: 2
Views: 31

### Re: 6C. 21

For both, you would want to look at the difference in electronegativities. The one with a greater difference in electronegativity would make the O-H bond weaker by pulling electron density away, making the acid with the greater electronegativity difference stronger. For example, in the first one, th...
Mon Nov 25, 2019 9:09 am
Forum: Naming
Topic: Coordination shape
Replies: 3
Views: 46

### Coordination shape

In class, it was mentioned how a coordination number of 4 could mean that the molecule is either tetrahedral or square planar complex. How can you determine when a coordination sphere is a tetrahedral complex or square planar complex?
Mon Nov 25, 2019 9:07 am
Forum: *Molecular Orbital Theory Applied To Transition Metals
Topic: Ligands
Replies: 5
Views: 163

### Re: Ligands

For example, a metal atom with four ligands attached would have a coordination number of 4. An atom with six ligands attached would have a coordination number of 6.
Mon Nov 25, 2019 9:03 am
Forum: Shape, Structure, Coordination Number, Ligands
Topic: Shape
Replies: 2
Views: 45

### Re: Shape

A complex would be tetrahedral if it has four regions of electron density and none of them are lone pairs. A shape would be sure planar if there are six regions of electron density but only four atoms around the central atom (since two of the electron densities are lone pairs).
Mon Nov 25, 2019 8:56 am
Forum: Hybridization
Topic: Sigma and Pi Bonds
Replies: 5
Views: 49

### Re: Sigma and Pi Bonds

Sigma bonds also allow for rotation. Pi bonds do not allow for rotations. Pi bonds are also broken first and are weaker because the side-to-side overlap does not allow for as much overlap as the end-to-end overlap found in sigma bonds.
Mon Nov 25, 2019 8:54 am
Forum: Administrative Questions and Class Announcements
Topic: Points
Replies: 11
Views: 166

### Re: Points

I think you can check how many posts you've done under quick links and then "your posts." I believe each week is five points.
Mon Nov 25, 2019 8:53 am
Forum: Shape, Structure, Coordination Number, Ligands
Topic: brackets
Replies: 13
Views: 145

### Re: brackets

Brackets are used when writing the formula for the coordination sphere, which includes the metal atom and the ligands attached to it.
Mon Nov 18, 2019 8:34 am
Forum: Determining Molecular Shape (VSEPR)
Topic: Determining polarity 2E 25 pt d
Replies: 3
Views: 47

### Re: Determining polarity 2E 25 pt d

Yes, AX2, AX3, AX4, AX5, and AX6 are non polar if there are no electron pairs and if X is all the same.
Mon Nov 18, 2019 8:31 am
Forum: Determining Molecular Shape (VSEPR)
Topic: lone pair shape
Replies: 3
Views: 56

### Re: lone pair shape

You would also want to take from the equatorial position and not the axial position because a lone pair in the equatorial position results in the molecule having lower energy. Lower energy is what most molecules strive for too.
Mon Nov 18, 2019 8:26 am
Forum: Hybridization
Topic: 2F.15
Replies: 2
Views: 34

### Re: 2F.15

In an sp3 hybrid, there is around 25% s character since there is one part s and three parts p. For sp2, there is about 33% character. Since the bond angle for sp2, which has greater s character, is a bigger angle than sp3, you could expect the bond angle to increase as the s character of the hybrids...
Mon Nov 18, 2019 8:24 am
Forum: Interionic and Intermolecular Forces (Ion-Ion, Ion-Dipole, Dipole-Dipole, Dipole-Induced Dipole, Dispersion/Induced Dipole-Induced Dipole/London Forces, Hydrogen Bonding)
Topic: 1/r^6
Replies: 3
Views: 63

### Re: 1/r^6

I believe that this equation shows the the strength of the interaction is dependent on the distance between molecules. For 1/r^6, it means that the strength of the interactions drops quite quickly as the distance between the molecules become greater. Not sure if we'll need to know this for the test
Mon Nov 18, 2019 8:22 am
Forum: Interionic and Intermolecular Forces (Ion-Ion, Ion-Dipole, Dipole-Dipole, Dipole-Induced Dipole, Dispersion/Induced Dipole-Induced Dipole/London Forces, Hydrogen Bonding)
Topic: Polarizability
Replies: 2
Views: 33

### Re: Polarizability

The size of the atom is usually related to polarizability, and greater polarizability usually makes interactions stronger since London dispersion forces would increase. As the size of the atom gets bigger, usually there are more electrons. Since there are more electrons, the nucleus doesn't have as ...
Mon Nov 18, 2019 8:17 am
Forum: Sigma & Pi Bonds
Topic: Sigma and Pi Bonds
Replies: 8
Views: 111

### Re: Sigma and Pi Bonds

Sigma and pi bonds are also relevant as part of the valence bond theory, which takes into account the wave nature orbitals. It is also significant because it helps understand the concept of hybridization.
Tue Nov 12, 2019 9:18 am
Forum: Dipole Moments
Topic: Textbook question 3F.1
Replies: 5
Views: 73

### Re: Textbook question 3F.1

I think it helps to draw the lewis structures of these molecules to see if they are polar or non polar. Generally, if the net dipole moments cancel out and the molecule is non polar, it would have London dispersion forces (induced dipole-induced dipole). If it is polar, then I believe dipole dipole ...
Tue Nov 12, 2019 9:13 am
Forum: Dipole Moments
Topic: 3F.11
Replies: 3
Views: 47

### Re: 3F.11

Hydrogen bonds form when there is a lone pair on the N, O, and F atom. This can be seen in HNO2 too and makes the intermolecular forces between the molecules strong.
Tue Nov 12, 2019 9:09 am
Forum: Determining Molecular Shape (VSEPR)
Topic: Determining Bond Angle
Replies: 1
Views: 21

### Re: Determining Bond Angle

For some molecules, drawing the structure and arranging them according to the VSEPR model could help determine bond angle. For example, if a molecule is linear, then the bond angle will be 180 degrees. If a molecule is trigonal planar, the bond angle will be 120 degrees and if it is tetrahedral, the...
Tue Nov 12, 2019 9:03 am
Forum: Dipole Moments
Topic: 3F.5
Replies: 6
Views: 88

### Re: 3F.5

To find which has a higher melting point, you would want to find out what types of IMFs each molecule or compound has, and determine which compound has the stronger IMF. For example, in a) HCl is a covalently bonded molecule while NaCl is an ionic compound. NaCl will have a higher melting point beca...
Tue Nov 12, 2019 8:58 am
Forum: Dipole Moments
Topic: 3F.3
Replies: 5
Views: 88

### Re: 3F.3

In these types of questions, it could be helpful to first draw the Lewis structures. CCl4 and CH4 are symmetric and are non polar structures overall since the net moments cancel out; they will have London dispersion forces. CH3Cl, CH2Cl2, and CHCl3 will also have dipole dipole interactions, so those...
Mon Nov 04, 2019 8:06 am
Forum: Electron Configurations for Multi-Electron Atoms
Topic: aufbau principle
Replies: 4
Views: 93

### Re: aufbau principle

The Aufbau principle is the building up principle that combines both Pauli Exclusion principle and Hunds rule. Pauli Exclusion principle states that there can be a max of two electrons per orbital and that the two electrons must be spin paired. Hunds rule states that the electrons should be placed o...
Mon Nov 04, 2019 8:01 am
Forum: Quantum Numbers and The H-Atom
Topic: n, l ,ml, ms
Replies: 13
Views: 515

### Re: n, l ,ml, ms

The magnetic spin of an electron can only be +1/2 or -1/2. This is because of the Pauli exclusion principle where there can only be two electrons per orbital, and that the electrons must be spin paired. So, one electron must go in an upwards spin (+1/2) and the other in a downwards spin (-1/2). As f...
Mon Nov 04, 2019 7:57 am
Forum: Lewis Structures
Topic: formal charge
Replies: 4
Views: 71

### Re: formal charge

Formal charge can also help you predict which structure is the lowest energy structure (and thus which structure contributes more to the hybrid) as the closer the formal charges are to 0 on the atoms gives you the lowest energy structure.
Mon Nov 04, 2019 7:54 am
Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
Topic: En=-hR/n^2
Replies: 1
Views: 39

### Re: En=-hR/n^2

You generally use this equation when dealing with atomic spectra problems, where calculating the energy difference (or wavelength and frequency) absorbed or emitted by an element that has gone from one energy level to another. For example, if you want to know the change in energy from the emitted ra...
Mon Nov 04, 2019 7:49 am
Forum: Einstein Equation
Topic: Module Question
Replies: 1
Views: 139

### Re: Module Question

This question is a photoelectric effect questions, and gives you the minimum frequency needed to eject an electron from the molybdenum metal surface. This means that any frequency lower than this will not eject any electrons and that with this particular frequency, there won't be any excess kinetic ...
Mon Nov 04, 2019 7:46 am
Forum: Quantum Numbers and The H-Atom
Topic: Quantum Numbers
Replies: 6
Views: 176

### Re: Quantum Numbers

The quantum number ms is the magnetic spin of the electron. In the Pauli Exclusion principle, it states that there can only be a maximum of two electrons per orbital, and that the two electron spins must be paired. That basically means that one electron will spin in an upwards direction and one in a...
Mon Oct 28, 2019 8:50 am
Forum: Photoelectric Effect
Topic: photoelectric effect book example
Replies: 2
Views: 44

### Re: photoelectric effect book example

hi! the mass of the electron, as well as the masses of neutrons/protons are on the constants and equations sheet that is on Dr. Lavelle's website. It should also be provided on the test!
Mon Oct 28, 2019 8:44 am
Forum: Electron Configurations for Multi-Electron Atoms
Topic: HW question 1D.11
Replies: 5
Views: 90

### Re: HW question 1D.11

As someone mentioned above, l= 0 is the s orbital, l=1 is p, l=2 is d, and l=3 is f. Because of that, the number of orbitals in subshells for s will be 1, p is 3, d is 5, and f is 7.
Mon Oct 28, 2019 8:40 am
Forum: Ionic & Covalent Bonds
Topic: 2A.11
Replies: 4
Views: 61

### Re: 2A.11

In order to find what metal with a 3+ state would have the ground state configuration, I find it helpful to first write what configuration the metal would have if it were not an ion. For the first one, for example, if the 3+ state is [Ar] 3d6, then the configuration for the unionized version would b...
Mon Oct 28, 2019 8:35 am
Forum: Lewis Structures
Topic: how to know which elements bonds to which?
Replies: 3
Views: 36

### Re: how to know which elements bonds to which?

In general, the central atom would be the one with the lower ionization energy. In class, Dr. Lavelle also mentioned that because H can only form one bond, it will never be the central atom.
Mon Oct 28, 2019 8:31 am
Forum: Resonance Structures
Topic: Lewis Structures for Resonance
Replies: 4
Views: 43

### Re: Lewis Structures for Resonance

Generally, the octet rule will be followed for lewis structures that have resonance. However, as someone mentioned above, some atoms can form more than four bonds because they are big enough and have the ability to fill the d orbitals. This only starts after the 3 p level though, and so some atoms i...
Mon Oct 28, 2019 8:29 am
Forum: Heisenberg Indeterminacy (Uncertainty) Equation
Topic: HW question 1B.25
Replies: 3
Views: 79

### Re: HW question 1B.25

Hi! So in this problem, you know that you should use the Heisenberg equation in order to find uncertainty of speed of the electron. Since Delta p * delta x = h/4pi, and delta p can be substituted by m * delta v (velocity), you can rearrange and solve for the minimum uncertainty in a particle's veloc...
Mon Oct 21, 2019 11:31 am
Forum: Heisenberg Indeterminacy (Uncertainty) Equation
Topic: What's the right equation?
Replies: 7
Views: 108

### Re: What's the right equation?

Both are the same equation. This is because the h is actually h bar and stands for h/2pi. 1/2 (h bar) would then be the same as the first equation as it is h/4pi.
Mon Oct 21, 2019 11:24 am
Forum: Electron Configurations for Multi-Electron Atoms
Topic: Electron Spin
Replies: 5
Views: 80

### Re: Electron Spin

The last quantum number, the electron spin, only has two types of spin . It's notated by +1/2 and -1/2. There should only be two types as the Pauli Exclusion Principle states that there should only be 2 electrons per orbital, and that if there are 2 electrons, the spins should be paired up (one up a...
Mon Oct 21, 2019 11:20 am
Forum: DeBroglie Equation
Topic: 1B. 19
Replies: 4
Views: 66

### Re: 1B. 19

Yes, you could use the De Broglie equation, where the wavelength is equal to Planck's constant divided by momentum (which is mass times velocity).Since h is a constant and m is nearly the same, the only thing that could be variable is the velocity. However, in this problem, it states that the proton...
Mon Oct 21, 2019 11:16 am
Forum: Properties of Light
Topic: calculating frequency of light
Replies: 4
Views: 97

### Re: calculating frequency of light

Yes, since it says lowest frequency possible, we can assume that the KE is 0. We could then use the equation where the energy of the incident light is equal to the work function plus the KE (which is 0). You could then work backwards to find the energy of the light since you know what the work funct...
Mon Oct 21, 2019 11:13 am
Forum: Photoelectric Effect
Topic: KE energy & intensity
Replies: 5
Views: 68

### Re: KE energy & intensity

The kinetic energy is related to the frequency of the incoming light because the frequency of the incoming light, by the equation E = hv, can be used to find the incident light's energy. This energy, by the conservation of energy, is equal to the work function (the energy needed to eject an electron...
Mon Oct 21, 2019 11:10 am
Forum: *Shrodinger Equation
Topic: Calculating the probability of finding an electron at a certain location
Replies: 5
Views: 227

### Re: Calculating the probability of finding an electron at a certain location

Hi, 1D4 talks about the probability of finding electrons depending on the shapes of the orbitals. In this class, we would be discussing the orbitals s, p, and d. As far as the probability of finding an electron goes, s orbitals are said to be spherically symmetrical, meaning that the probability is ...
Mon Oct 14, 2019 9:11 pm
Forum: Einstein Equation
Topic: Homework Problem B.5
Replies: 2
Views: 57

### Re: Homework Problem B.5

KeV is a unit of energy. It is equivalent to 1000 eV because of the prefix kilo. From there, you can convert this unit to another energy unit - Joules by using the constants and equations sheet. 1 eV is equivalent to 1.6022*10^-19 J, so you can then use stoichiometry to convert KeV to Joules. After ...
Mon Oct 14, 2019 9:06 pm
Forum: *Shrodinger Equation
Topic: probability vs probability density
Replies: 3
Views: 167

### Re: probability vs probability density

The probability density, symbolized by psi squared, is the probability that something will be found in a space divided by region volume. For example, if psi squared is 0, then there is a probability of 0 that the electron will be found in that space in that region's volume. Probability has no unit b...
Mon Oct 14, 2019 8:57 pm
Forum: Heisenberg Indeterminacy (Uncertainty) Equation
Topic: Heisenberg indeterminacy equation
Replies: 2
Views: 49

### Re: Heisenberg indeterminacy equation

These two expressions are actually the same. This is because the h/2 is not h, but h bar. H bar is equal to h/2pi. Thus, this would make it the same as h/4pi because 1/2hbar = 1/2(h/2pi) = h/4pi. Hope this helps a bit
Mon Oct 14, 2019 8:54 pm
Forum: Electron Configurations for Multi-Electron Atoms
Replies: 2
Views: 34

In addition, the radius of a cation is usually smaller than its regular atom. The radius of an anion is larger than what the neutral atom would normally be because of the increased electron repulsion effects (since anions have more electrons). For atomic radius, the atomic radius increases as you go...
Mon Oct 14, 2019 8:50 pm
Forum: Ionic & Covalent Bonds
Topic: Bonds
Replies: 4
Views: 156

### Re: Bonds

Hi, usually a metal and a nonmetal together will form an ionic bond. In an ionic bond, an electron is basically donated.Metals are usually atoms, or elements found in group 1 or 2 of the periodic table. Covalent bonds generally consist of two nonmetals together.In a covalent bond, the electron is us...
Mon Oct 07, 2019 9:44 pm
Forum: Limiting Reactant Calculations
Topic: Percent yield
Replies: 3
Views: 63

### Re: Percent yield

The theoretical yield actually doesn't have to depend on information on percent or actual yield. Theoretical yield just means the maximum yield that a product can be based on a chemical equation. So, the theoretical yield is can purely be based on calculations, stoichiometry, and molar ratios from t...