## Search found 116 matches

Thu Mar 12, 2020 3:07 pm
Forum: First Order Reactions
Topic: equation derivations
Replies: 9
Views: 166

### Re: equation derivations

I know that on a previous test they were asked to derive Van't Hoff's equation! But it is always useful to understand derivations so you know how to apply the equation.
Thu Mar 12, 2020 3:03 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: salt bridge
Replies: 11
Views: 99

### Re: salt bridge

I remember seeing somewhere that certain salts are not ideal for salt bridges... does anyone have an idea of what salts these include?
Thu Mar 12, 2020 9:23 am
Forum: *Enzyme Kinetics
Topic: How to distinguish the intermediates and catalysts?
Replies: 8
Views: 144

### Re: How to distinguish the intermediates and catalysts?

A catalyst is always regenerated!
Wed Mar 11, 2020 2:49 pm
Forum: Administrative Questions and Class Announcements
Topic: ENDGAME Review Session
Replies: 71
Views: 2972

### Re: ENDGAME Review Session

Thank you so much, Lyndon! Thank you for your dedication, patience, compassion, and hard work. I've been going to your workshops every week since 14A and I honestly could not have passed this class without you! Good luck in your future endeavors!
Wed Mar 11, 2020 2:40 pm
Forum: Method of Initial Rates (To Determine n and k)
Topic: intergrated rate law
Replies: 9
Views: 163

### Re: intergrated rate law

Even though both are given on the equation sheet I think it would be safe to know the derivations just in case anything is asked on the final.
Wed Mar 11, 2020 2:37 pm
Forum: Kinetics vs. Thermodynamics Controlling a Reaction
Topic: kinetics
Replies: 9
Views: 166

### Re: kinetics

The reaction will only happen if a catalyst is added and therefore the activation energy is lowered so the reaction can proceed
Wed Mar 11, 2020 2:33 pm
Forum: Balancing Redox Reactions
Topic: Ecell values
Replies: 12
Views: 229

### Re: Ecell values

The higher Ecell value is usually reduced!
Wed Mar 11, 2020 2:24 pm
Forum: Arrhenius Equation, Activation Energies, Catalysts
Topic: Difference between catalyst and intermediate
Replies: 9
Views: 129

### Re: Difference between catalyst and intermediate

A catalyst is always regenerated! So if you see it on the reactants and products side then it is a catalyst!
Wed Mar 11, 2020 2:22 pm
Forum: Administrative Questions and Class Announcements
Topic: review session packets
Replies: 4
Views: 101

### Re: review session packets

Yes! I believe they said answers will still be posted on chemistry community.
Wed Mar 11, 2020 2:22 pm
Forum: Zero Order Reactions
Topic: straight line to fit data
Replies: 5
Views: 95

### Re: straight line to fit data

Depending on the order of the reaction, the straight line (whether it is a positive or negative slope and the graph axis labels itself) will tell you the order of the reaction.
Wed Mar 11, 2020 2:21 pm
Forum: Second Order Reactions
Topic: units
Replies: 5
Views: 349

### Re: units

You can always solve for the units by knowing the rate reaction equation (rate=k[A]^2) and solving for k!
Wed Mar 11, 2020 2:12 pm
Forum: Administrative Questions and Class Announcements
Topic: Earthquake FINAL REVIEW SESSION
Replies: 11
Views: 492

### Re: Earthquake FINAL REVIEW SESSION

This is such a good idea and thank you for organizing this!
Wed Mar 11, 2020 2:08 pm
Forum: Arrhenius Equation, Activation Energies, Catalysts
Topic: same equation?
Replies: 5
Views: 87

### Re: same equation?

They are the exact same equations just the very last equation has been raised to the e.
Tue Mar 10, 2020 7:31 pm
Forum: Zero Order Reactions
Topic: Graphs
Replies: 4
Views: 54

### Re: Graphs

In addition, the y-intercept is the initial concentration!
Sun Feb 23, 2020 10:19 pm
Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
Topic: Nernst Equation
Replies: 4
Views: 52

### Re: Nernst Equation

You use the Nernst equation to quantitatively determine the direction of the electron transfer under non-standard conditions. We use it when there's a dependence of cell potential on concentration.
Sun Feb 23, 2020 4:02 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: 5.J.11b)
Replies: 1
Views: 107

### Re: 5.J.11b)

I believe that because it is a Halogen, it's natural state is in X2 form (Cl2, F2, etc.) and therefore the reaction X2=2X is endothermic because it takes energy to pull the two atoms apart. Therefore we know the reaction will shift right towards the products when the temperature is increased.
Sun Feb 23, 2020 4:00 pm
Forum: Third Law of Thermodynamics (For a Unique Ground State (W=1): S -> 0 as T -> 0) and Calculations Using Boltzmann Equation for Entropy
Topic: 3rd law of thermodynamics
Replies: 3
Views: 128

### Re: 3rd law of thermodynamics

Yes, I believe the substance has to be in a solid state. It must be a perfect crystalline to have zero disorder and therefore have zero entropy.
Sun Feb 23, 2020 3:58 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: voltage
Replies: 8
Views: 98

### Re: voltage

Voltage is the amount of energy being produced by the electrodes. It is the potential difference between two electrodes.
Sun Feb 23, 2020 3:51 pm
Forum: Balancing Redox Reactions
Topic: Identifying Half Reactions
Replies: 4
Views: 90

### Re: Identifying Half Reactions

MnO4- is being reduced because when we calculate the oxidation of state of Mn in this compound it is +7 (do this knowing that O is -2, multiplying it by 4 and knowing that the entire molecule has a charge of -1). But in the products, Mn has a charge of +2. This shows that Mn has gained 5 electrons a...
Sun Feb 23, 2020 3:47 pm
Forum: Balancing Redox Reactions
Topic: spontaneous
Replies: 15
Views: 159

### Re: spontaneous

When the standard reduction potential is positive that means the reduction is spontaneous!
Sun Feb 23, 2020 3:45 pm
Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
Topic: how to get n in equation
Replies: 8
Views: 137

### Re: how to get n in equation

You look at how many electrons are being transferred!
Sat Feb 22, 2020 5:42 pm
Forum: Balancing Redox Reactions
Topic: Redox in Acidic/Basic Solutions
Replies: 3
Views: 62

### Redox in Acidic/Basic Solutions

What does it mean when a redox reaction takes place in an acidic or basic solution? How do you balance a redox reaction when it takes place in an acidic or basic solution?
Sat Feb 22, 2020 5:36 pm
Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
Topic: Nernst Equation and Le Chatelier's Principle
Replies: 3
Views: 124

### Re: Nernst Equation and Le Chatelier's Principle

Using Le Chatelier's principle which takes into account the increase in either products or reactants concentrations, the Ecell will either decrease or increase. If the concentrations of the reactants are increased, then Ecell will be greater than Estandard. If the concentrations of the products are ...
Wed Feb 19, 2020 9:50 pm
Forum: Administrative Questions and Class Announcements
Topic: Test 2 Material
Replies: 16
Views: 343

### Re: Test 2 Material

As Dr. Lavelle mentioned at the end of the lecture today, the test will cover the second page of the Thermodynamics outline and all of the Electrochemistry Outline. But the test will NOT include Chemical Kinetics.
Wed Feb 19, 2020 9:47 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Anode and Cathode position
Replies: 5
Views: 89

### Re: Anode and Cathode position

It is conventional to put the anode on the left and the cathode on the right. That being said it would be smart to double-check that this is true in a problem or on a test (if possible) by seeing which is being reduced and which is being oxidized.
Wed Feb 19, 2020 9:45 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Gibbs free energy
Replies: 9
Views: 203

### Re: Gibbs free energy

G* means that all the substances are in their standard states
Wed Feb 19, 2020 9:15 pm
Forum: Balancing Redox Reactions
Topic: Homework 6K.5 Part B
Replies: 1
Views: 29

### Re: Homework 6K.5 Part B

Br is both the oxidizing and reducing agent.
We balance it assuming using the fact that it is an aqueous solution so H2O.

3Br2 + 6OH- --> 5Br- + BrO3- + 3H2O
Wed Feb 19, 2020 9:00 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Replies: 6
Views: 112

The absence of the flow of electrons or charge between the anode and cathode can also be solved by using a salt bridge!
Tue Feb 18, 2020 1:31 am
Forum: Balancing Redox Reactions
Topic: Reduction vs. oxidation
Replies: 29
Views: 351

### Re: Reduction vs. oxidation

One thing my high school teacher taught me to remember oxidation/reduction is L.E.O (loses electrons oxidation) the lion goes G.E.R (gaining electrons reduction)! Hope this helps make memorization easier :)
Thu Feb 06, 2020 12:43 am
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: Textbook question 4A.13
Replies: 5
Views: 62

### Re: Textbook question 4A.13

Qreaction=-Qcalorimeter and so that is why the answer is negative 1.19kJ!
Sun Feb 02, 2020 5:57 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Variables
Replies: 3
Views: 53

### Re: Variables

As someone else said I think it would be a good thing to familiarize yourself with the Constants and Equations sheet that's on Dr. Lavelle's website and it is likely that you will be able to deduce what each variable is!
Sun Feb 02, 2020 5:09 pm
Forum: Phase Changes & Related Calculations
Topic: Liquid/Steam
Replies: 3
Views: 40

### Liquid/Steam

Can someone explain to me why steam causes worse burns than boiling water? I know he went over it in great detail during lecture but I want to be sure that I have the concepts solidified.
Sun Feb 02, 2020 4:59 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: Calorimeter
Replies: 5
Views: 80

### Re: Calorimeter

A bomb calorimeter is completely sealed and insulated, making it an isolated system. It maintains a constant volume.
A constant pressure calorimeter gives enthalpy values.
Sun Feb 02, 2020 4:55 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Enthalpy units
Replies: 5
Views: 74

### Re: Enthalpy units

It should be in terms of Joules whether that is J or kJ. It can also be in J/mol or kJ/mol depending on the context.
Sun Feb 02, 2020 4:54 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: thermochemistry equations
Replies: 5
Views: 67

### Re: thermochemistry equations

Make sure to familiarize yourself with the Constants and Equations sheet on Dr. Lavelle's website, therefore, you know what you should and shouldn't memorize!
Sun Jan 26, 2020 8:10 pm
Forum: Phase Changes & Related Calculations
Topic: Standard State
Replies: 1
Views: 34

### Re: Standard State

Typically a substance is in its standard state when a gas is at 1 atm and 1M. For a pure liquid or sold it is most stable at 1 atm and a temperature of interest or about 25C.
Sun Jan 26, 2020 8:08 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Method 2
Replies: 4
Views: 42

### Re: Method 2

In Method 2 you use each individual bond enthalpies to calculate delta H. Using the Lewis structures you look at which bonds are broken in the reactants and which bonds are formed in the products. The bonds broken are positive enthalpies and bonds formed are negative. Then you add the enthalpies of ...
Sun Jan 26, 2020 8:05 pm
Forum: Phase Changes & Related Calculations
Topic: Phase Changes
Replies: 7
Views: 96

### Re: Phase Changes

If the substance is not in the most stable/standard phases then you must use the total of the enthalpy of the phase change and the bond enthalpy when calculating.
Sun Jan 26, 2020 8:02 pm
Forum: Phase Changes & Related Calculations
Topic: Focus 4 Homework Questions
Replies: 3
Views: 47

### Re: Focus 4 Homework Questions

Sun Jan 26, 2020 8:00 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: percent ionization
Replies: 5
Views: 55

### Re: percent ionization

The small percent ionization indicates the change in molar concentration or x is so small that it becomes negligible and this makes the approximation acceptable.
Sun Jan 19, 2020 7:50 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Stoichiometric coefficients for pH/pOH
Replies: 3
Views: 45

### Re: Stoichiometric coefficients for pH/pOH

No, you do not need to raise it to the stoichiometric coefficients because when you take the pOH you are taking the -log of the concentration of OH- ions, not the ratio of them.
Sun Jan 19, 2020 7:43 pm
Forum: Non-Equilibrium Conditions & The Reaction Quotient
Topic: Shift Of Reaction
Replies: 4
Views: 94

### Re: Shift Of Reaction

It means that the reaction has to shift towards the reactants or products in order to achieve the same ratio and the same K value.
Sun Jan 19, 2020 7:42 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: 5%
Replies: 4
Views: 42

### Re: 5%

The 5% rule applies to when you use the ICE table. If K is less than 10^-3, then you can assume that X is so small that it will not make a difference. For example if you have K=X^2/(0.3-X), then you can change it to X^2/0.3 because the X in the denominator becomes negligible. The 5% rule is if you f...
Sun Jan 19, 2020 7:00 pm
Forum: Calculating pH or pOH for Strong & Weak Acids & Bases
Topic: Molar concentration of acids & bases
Replies: 8
Views: 176

### Re: Molar concentration of acids & bases

If it asks for molar concentrations I believe it is asking for mol/L. pH or pOH will be asked for specifically.
Sun Jan 19, 2020 6:55 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: Strong Acids/Bases vs. Weak Acids/Bases
Replies: 9
Views: 65

### Re: Strong Acids/Bases vs. Weak Acids/Bases

In discussion, my TA mentioned these as strong acids and bases! I think they would be helpful to memorize so that you know which acids or bases completely dissociate.
Strong Acids: HCl, HNO3, H2SO4, HBr, HI, HClO4
Strong Bases: LiOH, NaOH, KOH, Ca(OH)2, Ba(OH)2, Sr(OH)2
Sun Jan 19, 2020 6:51 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: 5% rule
Replies: 3
Views: 46

### Re: 5% rule

The 5% percent rule is used to check if our "X is small" approximation is valid or not. We check to see if the X we solve for is less than 5% of the initial concentration. If it IS less than 5% then the approximation is valid.
Sun Jan 19, 2020 6:48 pm
Forum: Non-Equilibrium Conditions & The Reaction Quotient
Topic: ICE Tables
Replies: 13
Views: 109

### Re: ICE Tables

H2O is often not included because it is a liquid, or solvent in the solution. Therefore, it is not included in the K expression or in the ICE table.
Sun Jan 19, 2020 6:45 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Homework problem 5.I.15
Replies: 4
Views: 102

### Re: Homework problem 5.I.15

I don't think ICE tables are necessary to get full credit on tests as long as you get the right answer. Although I would suggest using one because there's possible partial credit.
Sun Jan 19, 2020 6:42 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: 5.I.23
Replies: 3
Views: 56

### Re: 5.I.23

You still need to include the H2O in the equilibrium expression. You can only disregard it if it is a solid or liquid!
Sun Jan 19, 2020 6:40 pm
Forum: Non-Equilibrium Conditions & The Reaction Quotient
Topic: 5I.19
Replies: 1
Views: 46

### Re: 5I.19

Since we know that 60% of the H2 reacted, then at equilibrium we can use the fact that there will be 40% left when solving for the equilibrium concentrations. Therefore, when we use the ICE table, we can set the change in H2 (0.133-x) equal to the equilibrium value of H2 (0.4 x 0.133) and solve for X!
Sun Jan 19, 2020 6:37 pm
Forum: Calculating pH or pOH for Strong & Weak Acids & Bases
Topic: 5I.29
Replies: 1
Views: 72

### Re: 5I.29

Using the reaction given, set up an ICE table. You should get a Kp equation that looks like x^2/(0.22-2x)^2 and set this equal to the Kp given. Because the equilibrium constant is small, we can assume that X is negligible compared to 0.22, therefore we can ignore it in the denominator. We end up hav...
Wed Jan 15, 2020 10:28 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: K units
Replies: 10
Views: 131

### Re: K units

For the purpose of this class, K is unitless. But in higher classes, it refers to the "activity" of the reactants and products.
Sat Dec 07, 2019 5:21 pm
Forum: Heisenberg Indeterminacy (Uncertainty) Equation
Topic: Uncertainty in Position
Replies: 1
Views: 129

### Re: Uncertainty in Position

Yes! The diameter is the uncertainty in position.
Sat Dec 07, 2019 5:18 pm
Forum: Biological Examples
Topic: Polydentate
Replies: 3
Views: 49

### Re: Polydentate

Polydentate is referring to anything that can bind in two or more places. I would describe EDTA as a hexadentate to be more specific!
Fri Dec 06, 2019 4:23 pm
Forum: Bronsted Acids & Bases
Topic: J.13 B
Replies: 1
Views: 44

### Re: J.13 B

Yes, CH3COOH is the acid and CH3NH2 is the base!
Fri Dec 06, 2019 4:19 pm
Forum: Sigma & Pi Bonds
Topic: hybridization and sigma and pi bonds
Replies: 1
Views: 127

### Re: hybridization and sigma and pi bonds

The triple bond between C and N has one sigma bond and two pi bonds.
The sigma bond is written as sigma(Chybridization,Nhybridization)
Then you will have two pi bonds are written as pi(C2p,N2p)
Fri Dec 06, 2019 4:13 pm
Forum: Calculating pH or pOH for Strong & Weak Acids & Bases
Topic: Calculating KA
Replies: 1
Views: 34

### Re: Calculating KA

For 14A we will not have to calculate the Ka for weak acids. We will learn that in 14B. I would know how to calculate the pKa of a weak acid when given Ka though assuming that it is given to us.
Sun Dec 01, 2019 7:32 pm
Forum: Dipole Moments
Topic: dipole moments
Replies: 6
Views: 162

### Re: dipole moments

Yes, polar molecules possess a permanent dipole moment.
Sun Dec 01, 2019 7:30 pm
Forum: Naming
Topic: Naming Order
Replies: 5
Views: 90

### Re: Naming Order

(Greek Prefix) Ligand names in alphabetical order, Transition Metal Cation Name (Roman Numeral). If there are anions, then add it to the end. If there is water then add (Greek Prefix) Hydrate.
Sun Dec 01, 2019 7:27 pm
Forum: *Molecular Orbital Theory (Bond Order, Diamagnetism, Paramagnetism)
Topic: Diamagnetism and Paramagnetism
Replies: 2
Views: 117

### Re: Diamagnetism and Paramagnetism

A paramagnetic electron is an unpaired electron. An atom is considered paramagnetic if even one orbital has a net spin. Diamagnetic electrons are whenever two electrons are paired together in an orbital, or their total spin is 0. Also, diamagnetic atoms/compounds (and atoms) have paired electrons an...
Sun Dec 01, 2019 7:25 pm
Forum: Shape, Structure, Coordination Number, Ligands
Topic: Random Example
Replies: 1
Views: 37

### Re: Random Example

Since this is a coordination compound the lewis structure would have the transition metal in the middle and the ligands in bonded to it, all in square brackets.
Sun Dec 01, 2019 7:24 pm
Forum: *Crystal Field Theory
Topic: Crystal Field Theory
Replies: 3
Views: 288

### Re: Crystal Field Theory

Crystal field theory (CFT) is a bonding model that explains many important properties of transition-metal complexes, including their colors, magnetism, structures, stability, and reactivity. It qualitatively describes the strength of the metal-ligand bonds in transition-metal complexes. Based on the...
Sun Dec 01, 2019 7:17 pm
Forum: Naming
Topic: 9C.1
Replies: 1
Views: 51

### Re: 9C.1

To figure out the charge of the metal you can look at the ligands and overall charge of the complex. Since there are 6 CN- and the overall charge is 4-, that means the charge of Fe is 2+. To name the compound, you should write out the name for it by beginning with each ligand, in alphabetical order,...
Sun Nov 24, 2019 6:12 pm
Forum: Hybridization
Topic: Strength of sigma vs pi bonds
Replies: 6
Views: 59

### Re: Strength of sigma vs pi bonds

A sigma bond is stronger. Sigma bonds result from the head-on overlap of the orbitals of the two atoms, which has more area of overlap than pi bonds which result from the parallel overlap of orbitals. That is why sigma bonds are stronger.
Sun Nov 24, 2019 6:11 pm
Forum: *Molecular Orbital Theory (Bond Order, Diamagnetism, Paramagnetism)
Topic: diamagnetism
Replies: 5
Views: 153

### Re: diamagnetism

Any time two electrons share the same orbital, their spin quantum numbers have to be different. Whenever two electrons are paired together in an orbital, or their total spin is 0, they are diamagnetic electrons.
Sun Nov 24, 2019 6:10 pm
Forum: *Molecular Orbital Theory (Bond Order, Diamagnetism, Paramagnetism)
Topic: paramagnetism
Replies: 6
Views: 195

### Re: paramagnetism

A paramagnetic electron is an unpaired electron. An atom is considered paramagnetic if even one orbital has a net spin.
Sun Nov 24, 2019 6:06 pm
Forum: *Molecular Orbital Theory (Bond Order, Diamagnetism, Paramagnetism)
Topic: Reactivity of pi bonds
Replies: 2
Views: 119

### Re: Reactivity of pi bonds

Sigma bonds result from the head-on overlap of the orbitals of the two atoms, which has more area of overlap than pi bonds which result from the parallel overlap of orbitals. That is why sigma bonds are stronger.
Sun Nov 24, 2019 1:54 pm
Forum: Biological Examples
Topic: Heme complex
Replies: 8
Views: 163

### Re: Heme complex

A heme complex forms when an iron ion binds to the porphyrin ligand. The porphyrin ligand is a tetradentate ring structure, meaning the fact that there are four nitrogens facing inward that can can form coordination complexes with the iron. When this complex binds with another protein they make up m...
Sun Nov 24, 2019 1:48 pm
Forum: Hybridization
Topic: sp3 hybridization
Replies: 1
Views: 60

### Re: sp3 hybridization

The characteristic tetravalence of carbon is due to the small promotion energy of a carbon atom. This energy is small because a 2s-electron is transferred from an orbital that it shares with another electron to an empty 2p-orbital. Although the promoted electron enters an orbital of higher energy, i...
Sun Nov 17, 2019 8:08 pm
Forum: Determining Molecular Shape (VSEPR)
Replies: 5
Views: 80

The VESPR theory applies to radicals, and they can be counted as electron densities. For example, in CH3 you have 7 total electrons it's going to be a trigonal planar you're going to have the Carbon as the central atom that is bonded to 3 H's and then you have one electron (unpaired lone pair) on th...
Sun Nov 17, 2019 8:00 pm
Forum: Hybridization
Topic: VSEPR Models
Replies: 1
Views: 34

### Re: VSEPR Models

The VSEPR model is used to determine the molecular geometry and the electron-group geometry. The Lewis structure helps us identify the bond pairs and the lone pairs.
Sun Nov 17, 2019 2:55 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: 2E.1
Replies: 1
Views: 37

### Re: 2E.1

The one with the bond angle as 120 degrees must have lone pairs. The one that is 180 degrees may have lone pairs.
Sun Nov 17, 2019 1:14 pm
Forum: Bond Lengths & Energies
Topic: Polarizability
Replies: 4
Views: 92

### Re: Polarizability

Typically, cations will have less polarizability because there are less electrons and therefore the effective nuclear charge on the electrons are stronger and pulled in closer to the nucleus. Therefore, it is harder to "distort" the electron cloud making it less polarizable. The opposite i...
Sun Nov 17, 2019 1:13 pm
Forum: Interionic and Intermolecular Forces (Ion-Ion, Ion-Dipole, Dipole-Dipole, Dipole-Induced Dipole, Dispersion/Induced Dipole-Induced Dipole/London Forces, Hydrogen Bonding)
Topic: Hydrogen Bonds
Replies: 3
Views: 65

### Re: Hydrogen Bonds

Yes, hydrogen bonds are the strongest IMF. The δ+ hydrogen is so strongly attracted to the lone pair on the other atom that it is almost as if you were beginning to form a covalent bond. It doesn't go that far, but the attraction is significantly stronger than an ordinary dipole-dipole interaction.
Sun Nov 17, 2019 1:09 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Lone Pair location
Replies: 3
Views: 52

### Re: Lone Pair location

In the see-saw shape the axial and equatorial positions are not chemically equivalent. If the lone pair is in the axial position, we have three LP–BP repulsions at 90°. If the lone pair is in the equatorial position, we have two 90° LP–BP repulsions at 90°. With fewer 90° LP–BP repulsions, we can pr...
Sun Nov 10, 2019 9:55 pm
Forum: Electronegativity
Topic: Electron affinity
Replies: 6
Views: 135

### Re: Electron affinity

Electronegativity is a measure of the tendency of an atom to attract a bonding pair of electrons. Electron affinity is defined as the change in energy (in kJ/mole) of a neutral atom (in the gaseous phase) when an electron is added to the atom to form a negative ion.
Sun Nov 10, 2019 1:52 pm
Forum: Electronegativity
Topic: Ionization energy of O vs N
Replies: 6
Views: 244

### Re: Ionization energy of O vs N

Since there are two electrons in the first orbital of the O sublevel, there is greater electronic repulsion in the 2p sublevel for O than N. Therefore, it is easier to remove an electron from the O than the N, and the ionization energy of O is lower than N. Also nitrogen has a lower ionization energ...
Sun Nov 10, 2019 1:50 pm
Forum: Dipole Moments
Topic: Dipole moments
Replies: 3
Views: 67

### Re: Dipole moments

Yes, dipole moments is referring to the fact that one atom is more electronegative. The larger the difference in electronegativity, the larger the dipole moment. It is conventional to draw a dipole moment arrow from positive to negative.
Sun Nov 10, 2019 1:39 pm
Forum: Formal Charge and Oxidation Numbers
Topic: Formal Charge Equation?
Replies: 12
Views: 128

### Re: Formal Charge Equation?

305416361 wrote:
Victoria Otuya 4F wrote:I learned an easier way to remember the formal charge equation: valence electron -(dots + line).

does this count "dots" as pairs of dots or individual ones?

Count each dot as one electron each.
Sun Nov 10, 2019 1:25 pm
Forum: Dipole Moments
Topic: Boiling Point
Replies: 11
Views: 163

### Re: Boiling Point

Professor Lavelle uses boiling points to indicate which dipole interactions are stronger because the stronger the interactions between molecules, the more energy/heat required to separate them from each other, which raises the boiling point of the molecule.
Sun Nov 10, 2019 1:17 pm
Forum: Bond Lengths & Energies
Topic: polarizability
Replies: 9
Views: 98

### Re: polarizability

When polarizability of molecules increases, it takes more energy to break the stronger bonds between molecules resulting higher melting and boiling points.
Sun Nov 03, 2019 11:19 pm
Forum: Quantum Numbers and The H-Atom
Topic: magnetic quantum number
Replies: 5
Views: 71

### Re: magnetic quantum number

The magnetic quantum number tells you how many orbitals there are in a subshell and it tells you the orientation of the orbital.
Sun Nov 03, 2019 11:17 pm
Forum: Heisenberg Indeterminacy (Uncertainty) Equation
Topic: +- vs Uncertainty
Replies: 3
Views: 164

### Re: +- vs Uncertainty

Use 0.5 for the uncertainty!
Sun Nov 03, 2019 12:41 am
Forum: Heisenberg Indeterminacy (Uncertainty) Equation
Topic: Which equations can be used for what topics
Replies: 2
Views: 52

### Re: Which equations can be used for what topics

You can use c=(lambda)(nu) for electromagnetic radiation, or light.
You can use lambda=h/p or lambda=h/mv for electrons because they have mass.
Sun Nov 03, 2019 12:35 am
Forum: Electronegativity
Topic: Ionization energy and electronegativity
Replies: 8
Views: 119

### Re: Ionization energy and electronegativity

Electronegativity is a measurement of a neutral atom's likelihood of gaining an electron.
Ionization energy is the minimum energy required to remove a valence electron.
Both of these have the trend of increasing going towards the right and increasing going up the periodic table.
Sun Nov 03, 2019 12:32 am
Forum: Electron Configurations for Multi-Electron Atoms
Topic: Electron configurations of ions
Replies: 4
Views: 116

### Re: Electron configurations of ions

I think it is important to write the ground state first so that we can see which orbital has the highest energy so we can easily see where to remove or add electrons. It may not be totally necessary though, more just useful.
Sun Nov 03, 2019 12:30 am
Forum: Properties of Light
Topic: Equations
Replies: 4
Views: 84

### Re: Equations

I'm assuming they will be given to us because Dr. Lavelle's Constants and Equations sheet on his site has all three of these equations on it!
Sun Oct 27, 2019 10:17 pm
Forum: Ionic & Covalent Bonds
Topic: Ionization Energy Unit
Replies: 6
Views: 69

### Re: Ionization Energy Unit

kJ/mol!
Sun Oct 27, 2019 10:16 pm
Forum: Trends in The Periodic Table
Topic: Cations vs Parent atoms
Replies: 4
Views: 52

### Re: Cations vs Parent atoms

Cations are smaller than their parent ions because cations lose electrons and when an atom loses electrons, the positively charged nucleus pulls the electrons more closely making it smaller.
Sat Oct 26, 2019 11:39 pm
Forum: Electron Configurations for Multi-Electron Atoms
Topic: Pauli Exclusion Principle
Replies: 3
Views: 41

### Re: Pauli Exclusion Principle

The spins of two electrons are said to be paired if one is ↑ and the other ↓. Paired spins are denoted ↑↓, and electrons with paired spins have spin magnetic quantum numbers of opposite signs. No two electrons in an atom can have the same set of four quantum numbers.
Sat Oct 26, 2019 2:16 pm
Forum: Ionic & Covalent Bonds
Replies: 4
Views: 149

Atomic size decreases from left to right across a period of elements. This is because protons are being added to the nucleus making it more positively charged as well as the fact that electrons are added to the same shell. This creates greater nuclear attraction and therefore the electrons are pulle...
Sat Oct 26, 2019 2:10 pm
Forum: Electron Configurations for Multi-Electron Atoms
Topic: Special elements
Replies: 2
Views: 27

### Re: Special elements

The two main exceptions are Chromium ([Ar]3d^5 4s^1) and Copper ([Ar] 3d^10 4s^1)

These are exceptions to the general rule because a completely full or half full d sub-level is more stable than a partially filled d sub-level.
Sat Oct 26, 2019 1:43 pm
Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
Topic: Energy Level transition in hydrogen atom
Replies: 2
Views: 53

### Re: Energy Level transition in hydrogen atom

Frequency = -R [(1/n*2) - (1/N*2)]
in which "n" is the initial energy level, and "N" is the final energy level and we are supposed to solve for "n"

1.14x10^14 = -3.29x10^15 [(1/n^2) - (1/4^2)]

Solving for n, I ended up with n=6!
Sat Oct 26, 2019 1:34 pm
Forum: Ionic & Covalent Bonds
Topic: Cation
Replies: 23
Views: 507

### Re: Cation

As others have said, a cation loses electrons and anions gain electrons. Therefore, cations have a positive charge and anions have a negative charge.

My high school teacher told us to think that a cat has "paws" so therefore CATions are "pawsitive"
Sun Oct 20, 2019 9:51 pm
Forum: Electron Configurations for Multi-Electron Atoms
Topic: Electron Configuration Rules
Replies: 3
Views: 35

### Re: Electron Configuration Rules

A completely full or half full d sub-level is more stable than a partially filled d sub-level, so an electron from the 4s orbital is excited and rises to a 3d orbital. It is easier for them to remove a 4s electron and bring it to the 3d subshell, which will give them a half-filled or completely fill...
Sun Oct 20, 2019 9:50 pm
Forum: Trends in The Periodic Table
Replies: 7
Views: 145

You can calculate it using the distance between two nuclei of touching identical atoms, but as far as trends for atomic radius,
The size of an atom will decrease as you move from left to the right of a period.
The radius of atoms increases as you go down a certain group.
Sun Oct 20, 2019 9:46 pm
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: Ground State
Replies: 5
Views: 89

### Re: Ground State

In a ground-state atom, all electrons are in the lowest possible energy levels.
Sun Oct 20, 2019 9:45 pm
Forum: Quantum Numbers and The H-Atom
Topic: Balmer and Lyman Series
Replies: 6
Views: 458

### Re: Balmer and Lyman Series

They both apply to the Hydrogen atom. Emission or absorption processes in hydrogen give rise to series, which are sequences of lines corresponding to atomic transitions, each ending or beginning with the same atomic state in hydrogen. For the Lyman series, which corresponds to UV light, the electron...
Sun Oct 20, 2019 9:39 pm
Forum: Photoelectric Effect
Topic: 1B.3
Replies: 3
Views: 72

### Re: 1B.3

In the photoelectric experiment, a certain light was used to attempt to eject an electron from a metal. The experiment showed that if the light were a wave, then simply increasing the intensity would increase energy. But, increasing the intensity of the light did not result in ejection. Scientists t...
Sun Oct 20, 2019 8:43 pm
Forum: Einstein Equation
Topic: 1B.9 help
Replies: 4
Views: 74

### Re: 1B.9 help

You need to convert nm to m then use the equation: E=hc/lambda. E = [(6.626 x 10^-34 Js)(3.0 x 10^8 m/s)]/(420 x 10^-9 m) = 4.7 x 10^-19 J Doing this gives us how much energy in Joules each photon has. Then multiply 32 W by 2, so 64 J are generated in 2.0 seconds. Use the answer we found above to ge...