Search found 102 matches

by J Medina 2I
Sat Mar 14, 2020 8:42 pm
Forum: Arrhenius Equation, Activation Energies, Catalysts
Topic: Arrhenius equation and activation energies
Replies: 2
Views: 72

Re: Arrhenius equation and activation energies

Yes, if given all other information, the Arrhenius equation can be used to find the activation energy, Ea. I think exponential could be referring to when both sides are raised to the power of e which cancels the ln on the left and then raises the right side to the power of e.
by J Medina 2I
Sat Mar 14, 2020 8:37 pm
Forum: Balancing Redox Reactions
Topic: Test 2 Return
Replies: 20
Views: 403

Re: Test 2 Return

I think it depends on your individual TA
by J Medina 2I
Sat Mar 14, 2020 7:55 pm
Forum: General Rate Laws
Topic: Kr Units for Different Order Reactions
Replies: 3
Views: 107

Kr Units for Different Order Reactions

What units is Kr in a first order, 2nd order, and 0 order reaction?
by J Medina 2I
Sat Mar 14, 2020 11:11 am
Forum: Arrhenius Equation, Activation Energies, Catalysts
Topic: Arrhenius Equation
Replies: 3
Views: 160

Arrhenius Equation

What is ln [A] in the Arrhenius equation, ln kr = ln A - (Ea/RT)
by J Medina 2I
Fri Mar 13, 2020 2:36 pm
Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
Topic: Calculating lnQ in Nernst Equation
Replies: 2
Views: 50

Calculating lnQ in Nernst Equation

In the Nernst Equation, E = Eo -(RT/nF)ln Q , for Q specifically, do we put the anode concentration at the top or the bottom? And why?
by J Medina 2I
Wed Mar 11, 2020 9:10 pm
Forum: General Rate Laws
Topic: 7A.3A Reaction Concentration
Replies: 3
Views: 47

7A.3A Reaction Concentration

I'm confused on the following question and was wondering if someone could provide a mental walkthrough of how they got the answer. (The answer is given by the textbook: (a) Second order in NO, first order in O2 ) "When the NO concentration is doubled, the rate of the reaction 2NO (g) + O2 (g) -...
by J Medina 2I
Sun Mar 08, 2020 11:59 pm
Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
Topic: n in NFE
Replies: 19
Views: 255

Re: n in NFE

n is the number of electrons transferred which cannot be determined until your redox half-reactions are balanced. These half-reactions should have the same number of electrons transferred on opposite sides.
by J Medina 2I
Sun Mar 08, 2020 11:57 pm
Forum: Reaction Mechanisms, Reaction Profiles
Topic: Exothermic vs. Endothermic
Replies: 14
Views: 157

Re: Exothermic vs. Endothermic

With reaction profiles to get delta H you have to subtract the end of the graph (products) by the beginning of the graph (reactants). So you have to remember that EXOTHERMIC reactions release energy into their surroundings meaning there is a loss of energy from the system ( meaning delta H = - ). So...
by J Medina 2I
Sun Mar 08, 2020 11:49 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: galvanic vs electrolytic
Replies: 12
Views: 125

Re: galvanic vs electrolytic

When Galvanic cells are brought up it helps me to immediately think of batteries to help me remember that Galvanic cells convert chemical energy into electrical energy.
by J Medina 2I
Sun Mar 08, 2020 11:47 pm
Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
Topic: Concentration Cell
Replies: 7
Views: 103

Re: Concentration Cell

If a concentration cell has the same concentration on the anode and cathode then the reaction is at equilibrium and there is no net transfer of electrons in either direction. If this happens in a battery it means that the battery is dead.
by J Medina 2I
Sun Mar 08, 2020 11:45 pm
Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
Topic: G=-nFe
Replies: 7
Views: 130

Re: G=-nFe

n is the number of electrons transferred and can be seen in the half reactions when balanced. Since your redox half reactions are balanced, the number of electrons given off should be the same for both half-reactions.
by J Medina 2I
Sun Mar 08, 2020 11:42 pm
Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
Topic: Calculating ln Q
Replies: 20
Views: 269

Re: Calculating ln Q

Q is the the concentration of the products divided by the concentration of the reactants. It is used in the Nernst equation as a replacement for K when a reaction is not at equilibrium.
by J Medina 2I
Tue Mar 03, 2020 10:55 pm
Forum: Balancing Redox Reactions
Topic: Acidic and Basic Redox Reactions
Replies: 9
Views: 80

Acidic and Basic Redox Reactions

Will we usually be told if the redox reaction we're asked to balance is either acidic or basic?
by J Medina 2I
Sun Mar 01, 2020 11:44 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Going from pKa to pH
Replies: 10
Views: 179

Re: Going from pKa to pH

Maybe you meant that when pKa = 10^-7 that the pH = 7, which would be true.
by J Medina 2I
Sun Mar 01, 2020 11:40 pm
Forum: Kinetics vs. Thermodynamics Controlling a Reaction
Topic: Kinetics in Test 2?
Replies: 13
Views: 153

Re: Kinetics in Test 2?

No, the test will only cover material from page 2 of Outline 4: Thermodynamics and all of Outline 5: Electrochemistry.
by J Medina 2I
Sun Mar 01, 2020 11:35 pm
Forum: Balancing Redox Reactions
Topic: half rxn or ionization
Replies: 3
Views: 59

Re: half rxn or ionization

I think half reactions do not give the state of the reactants and products, like (aq), (s), or (g).
by J Medina 2I
Sun Mar 01, 2020 11:34 pm
Forum: Balancing Redox Reactions
Topic: Acidic and Basic Reactions
Replies: 9
Views: 110

Re: Acidic and Basic Reactions

H+ is used for balancing hydrogen atoms in acidic solutions and OH- is used to balance hydrogen in basic solutions. H2O is used to balance oxygen for both types of reactions.
by J Medina 2I
Mon Feb 24, 2020 1:00 am
Forum: Balancing Redox Reactions
Topic: Balancing Redox Reactions
Replies: 7
Views: 63

Re: Balancing Redox Reactions

What are basic conditions?
by J Medina 2I
Mon Feb 24, 2020 12:58 am
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Oxidation versus reduction
Replies: 9
Views: 99

Re: Oxidation versus reduction

Conventionally it is shown flowing left from right where the left is the anion (anode) and the right is the cation (cathode).
by J Medina 2I
Mon Feb 24, 2020 12:56 am
Forum: Balancing Redox Reactions
Topic: Determining direction of flow
Replies: 15
Views: 228

Re: Determining direction of flow

Eesha Sohail 1D wrote:If the direction is reversed, does G become positive? And what is this reverse case named, if the normal is a battery?


I think batteries are Galvanic cells and happen when G is negative. When G is positive the reaction becomes nonspontaneous and is called an electrolytic cell.
by J Medina 2I
Mon Feb 24, 2020 12:49 am
Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
Topic: Nernst Equation usage
Replies: 6
Views: 61

Re: Nernst Equation usage

The Nernst Equation relates cell potential to the concentration of what is being reduced and oxidized in their aqueous solutions.
by J Medina 2I
Mon Feb 24, 2020 12:31 am
Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
Topic: STP
Replies: 13
Views: 191

Re: STP

STP means Standard Temperature and Pressure which is 273 K and 1 atm.
by J Medina 2I
Sun Feb 16, 2020 5:31 pm
Forum: Calculating Work of Expansion
Topic: work = 0
Replies: 14
Views: 276

Re: work = 0

Pressure inside a vacuum is zero so when using the equation w = - P ex * delta V, the work done by a system is also equal to zero.
by J Medina 2I
Tue Feb 11, 2020 11:46 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Calculating Enthalpy with Atoms, Linear Molecules, and Nonlinear Molecules.
Replies: 2
Views: 32

Calculating Enthalpy with Atoms, Linear Molecules, and Nonlinear Molecules.

What are some examples of monatomic gases where we will have to calculate enthalpy with Cv,m as 3/2 R? Will most calculations for with Cv,m use the values associated with Linear molecules (5/2 R) and Nonlinear molecules (3 R)?
by J Medina 2I
Sun Feb 09, 2020 8:44 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: Volume decrease
Replies: 7
Views: 100

Re: Volume decrease

PranaviKolla2B wrote:Can someone explain what it means when the reaction shifts one way or another?

A reaction shifts left when reactants are being produced at a higher rate than products and a reaction that shifts right means that products are being formed at a higher rate than the reactants.
by J Medina 2I
Sun Feb 09, 2020 8:41 pm
Forum: Thermodynamic Definitions (isochoric/isometric, isothermal, isobaric)
Topic: Isothermal and Reversible
Replies: 6
Views: 44

Re: Isothermal and Reversible

So does irreversible just refer to anything that is not at constant temperature, or is there a more specific definition?
by J Medina 2I
Sun Feb 09, 2020 8:39 pm
Forum: Non-Equilibrium Conditions & The Reaction Quotient
Topic: ICE BOX
Replies: 27
Views: 269

Re: ICE BOX

If you exclude the x and want to double check afterwards to see if the approximation is accurate, then you can calculate the protonation percentage, or deprotonation percentage depending on the question, and if it is below 5% then the approximation is correct.
by J Medina 2I
Sun Feb 09, 2020 8:17 pm
Forum: Administrative Questions and Class Announcements
Topic: Midterm Content
Replies: 6
Views: 82

Re: Midterm Content

I think so, Lavelle mentioned that everything on the first page of the Thermodynamics Outline, which I think is also the first two rows of problems.
by J Medina 2I
Sun Feb 09, 2020 8:14 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Finding concentration of H30 and OH from Kw
Replies: 2
Views: 78

Re: Finding concentration of H30 and OH from Kw

I would guess that you take the square root of the Kw value given since we are dealing with water.
by J Medina 2I
Sun Feb 02, 2020 6:34 pm
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: extensive property
Replies: 12
Views: 158

Re: extensive property

An example of an extensive property is Heat Capacity because it tells you the amount of heat required to raise the temperature of an object by 1 degree celsius but it does not tell you how much of that object is present, so the information provided is not useful for other calculations.
by J Medina 2I
Sun Feb 02, 2020 6:30 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: Heat Capacity 4C.3
Replies: 3
Views: 45

Re: Heat Capacity 4C.3

For this problem you would not be able to find the heat capacity of Kr gas because the final volume is not given to us, but I am also confused on determining which equation to use for this.
by J Medina 2I
Sun Feb 02, 2020 6:19 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Ka approximation
Replies: 6
Views: 53

Re: Ka approximation

You could probably check by including the -x and then using the Quadratic Formula and then comparing this value to the value you got when you ignored the -x.
by J Medina 2I
Sun Feb 02, 2020 6:09 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: Test 1 Pressure
Replies: 5
Views: 58

Re: Test 1 Pressure

If more pressure is exerted, then the reaction will shift to the side with less moles. I like to think of the reaction as being squeezed and to adapt, the reaction overflows onto the side that is less cramped up because there is more space there.
by J Medina 2I
Sun Feb 02, 2020 5:17 pm
Forum: Phase Changes & Related Calculations
Topic: Relevance of Phase Changes
Replies: 9
Views: 79

Re: Relevance of Phase Changes

If you are calculating the change in enthalpy of a substance and that substance changes phases then it is important to add the energy required by the phase change in order to get an accurate calculation for ΔH.
by J Medina 2I
Sun Jan 26, 2020 7:44 pm
Forum: Phase Changes & Related Calculations
Topic: Delta H
Replies: 3
Views: 26

Re: Delta H

For the methods discussed in lecture on Friday, we will need to be given multiple ΔH's so that we can add or subtract them to find out the value of the ΔH we don't know.
by J Medina 2I
Sun Jan 26, 2020 7:38 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Standard States
Replies: 2
Views: 18

Re: Standard States

The standard state is the substance's phase (solid, liquid,gas) at 25 degrees Celsius and at 1 atm of pressure.
by J Medina 2I
Sun Jan 26, 2020 7:26 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: Pressure vs. Volume
Replies: 6
Views: 81

Re: Pressure vs. Volume

A change in volume will also directly affect the pressure of a system. A decrease in volume will lead to a higher pressure and an increase in volume will lead to lower pressure. Thinking of the equation PV=nRT is helpful since it shows how pressure and volume are inversely proportional.
by J Medina 2I
Sat Jan 25, 2020 6:44 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Excluding H2O from Ka and Kb
Replies: 5
Views: 53

Excluding H2O from Ka and Kb

I know we don't include H2O (l) in caluclations for Kb and Ka but why is that?
by J Medina 2I
Sat Jan 25, 2020 6:18 pm
Forum: Phase Changes & Related Calculations
Topic: Endothermic and Exothermic
Replies: 13
Views: 99

Re: Endothermic and Exothermic

If you have trouble deciding whether a reaction is endothermic or exothermic based on direction of heat flow, I find it helpful to think of the melting of ice as an example. Ice melting into liquid water is an ENDOTHERMIC reaction. The ice's surrounding has to be warm in order for liquid water to be...
by J Medina 2I
Sun Jan 19, 2020 7:00 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Titration
Replies: 3
Views: 33

Re: Titration

I think he just mentioned how the information we are learning will be helpful if we take Chem 14Bl where we will be doing titrations, but no I don't think we'll be tested on them.
by J Medina 2I
Sun Jan 19, 2020 6:48 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Buffer
Replies: 6
Views: 44

Re: Buffer

When making a buffer, you want to choose weak acids or weak bases since strong acids or bases will make the solution's pH too extreme. The reason for this is that weak acids and bases do not fully dissociate.
by J Medina 2I
Sun Jan 19, 2020 6:46 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: pH vs. pOH
Replies: 13
Views: 163

Re: pH vs. pOH

Sometimes certain problems will make it easier to calculate pH, and if the pOH is being asked then you can take the pH (-log(H3O+)) and subtract that value from 14 (since pH + pOH + 14).
by J Medina 2I
Sun Jan 19, 2020 6:43 pm
Forum: Calculating pH or pOH for Strong & Weak Acids & Bases
Topic: Approximation
Replies: 6
Views: 127

Re: Approximation

Does it have to do with using significant figures? Like when we round our answer to a significant figure, the difference in our answer that a -X would have provided does not even make a difference in our final rounded answer?
by J Medina 2I
Sun Jan 19, 2020 6:28 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: Endo vs. Exothermic
Replies: 5
Views: 44

Re: Endo vs. Exothermic

If you're looking at a graph, an endothermic reaction will be drawn so that the ending of the graph is higher than the beginning. This means that the products of the reaction will have greater energy than the reactants. And for an exothermic reaction graph, the ending of the graph will be lower than...
by J Medina 2I
Sun Jan 12, 2020 11:50 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Homogenous Equilibrium
Replies: 13
Views: 96

Re: Homogenous Equilibrium

Is there a different way we should approach a problem where we have to calculate the equilibrium constant if the given chemical reaction is heterogeneous and not homogeneous.
by J Medina 2I
Sun Jan 12, 2020 11:31 pm
Forum: Ideal Gases
Topic: K and Units
Replies: 7
Views: 50

Re: K and Units

The units cancel out (concentration/concentration), making K unitless.
by J Medina 2I
Sun Jan 12, 2020 11:29 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Types of Equilibrium Constants
Replies: 7
Views: 56

Re: Types of Equilibrium Constants

005384106 wrote:In what instances would the state of a molecule be important? (gaseous, aqueous, solid, or liquid)


Solids and liquids are excluded from calculating K. But, a gaseous reaction indicated using Kp and an aqueous reaction indicates using Kc.
by J Medina 2I
Sun Jan 12, 2020 10:37 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Comparing K
Replies: 9
Views: 78

Re: Comparing K

I don't think K can equal 0. If K were to equal 0, then that means there would be no product, meaning a reaction isn't taking place.
by J Medina 2I
Sun Jan 12, 2020 10:29 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Q
Replies: 10
Views: 114

Re: Q

You could calculate Q and if it matches K, then the reaction is at equilibrium.
by J Medina 2I
Sun Dec 08, 2019 1:07 am
Forum: Identifying Acidic & Basic Salts
Topic: homework question 6D.11
Replies: 2
Views: 122

Re: homework question 6D.11

Why is part d neutral?

d) KBR

And is asking whether an aqueous solution of this will have a pH < 7 , pH > 7, or be neutral
by J Medina 2I
Sat Dec 07, 2019 10:45 pm
Forum: DeBroglie Equation
Topic: Identifying the need to use DeBroglie Equation
Replies: 3
Views: 150

Identifying the need to use DeBroglie Equation

What kind of things in a problem suggest that we use DeBroglie's equation?
by J Medina 2I
Sat Dec 07, 2019 9:11 pm
Forum: Calculating pH or pOH for Strong & Weak Acids & Bases
Topic: pH sig figs
Replies: 11
Views: 159

Re: pH sig figs

Does this work the other way around too? If we were given a H3O+ concentration of 1.56 x 10^-4 where there are 3 sig figs, would we have to write the pH as 3.807 or as 3.81 ?
by J Medina 2I
Sat Dec 07, 2019 7:41 pm
Forum: Calculating pH or pOH for Strong & Weak Acids & Bases
Topic: Negative pH
Replies: 5
Views: 101

Negative pH

What does it mean for pH to be negative?
by J Medina 2I
Sat Dec 07, 2019 12:19 pm
Forum: Naming
Topic: Abbreviations (oxalato)
Replies: 2
Views: 53

Abbreviations (oxalato)

When writing the formula for a coordination compound containing a ligand that can be abbreviated, such as sodium bisoxalato(diaqaua)ferrate(III) containing oxalato, are we able to also write the abbreviation in the formula. For example can this coordination compound be written as: Na[Fe(OH2)2(ox)2] ...
by J Medina 2I
Sun Dec 01, 2019 5:25 pm
Forum: Lewis Acids & Bases
Topic: acid v. base?
Replies: 16
Views: 234

Re: acid v. base?

Lewis bases are positively charged. Lewis acids are negatively charged and usually have a lone pair.
by J Medina 2I
Sun Dec 01, 2019 5:20 pm
Forum: Calculating pH or pOH for Strong & Weak Acids & Bases
Topic: pH scale
Replies: 12
Views: 137

Re: pH scale

Most solutions are in this range. Remember that pH is logarithmic so a pH of 15 would have a concentration of ions 10x greater than a solution with a pH of 14, which is not common.
by J Medina 2I
Sun Dec 01, 2019 5:13 pm
Forum: Naming
Topic: Naming for the final
Replies: 6
Views: 141

Re: Naming for the final

Neutral ligands have the same name except for a few. Water turns to "aqua," ammonia turns to "ammine," and CO turns to "carbonyl." Ligands that are anions end with o.
by J Medina 2I
Sun Dec 01, 2019 4:58 pm
Forum: Trends in The Periodic Table
Topic: Exceptions to Electroaffinity
Replies: 3
Views: 141

Re: Exceptions to Electroaffinity

I don't think we have been told of any exceptions in lecture so I think it's safe to assume that we wouldn't be asked any questions where knowledge of an exception would be needed to answer the question.
by J Medina 2I
Sun Dec 01, 2019 4:18 pm
Forum: Shape, Structure, Coordination Number, Ligands
Topic: Coordination Number
Replies: 6
Views: 67

Re: Coordination Number

However many ligands are attached to the central atom is what determines the coordination number. You can determine this by looking inside the brackets.
by J Medina 2I
Sun Dec 01, 2019 4:09 pm
Forum: Sigma & Pi Bonds
Topic: Drawing Sigma and Pi bonds
Replies: 7
Views: 123

Re: Drawing Sigma and Pi bonds

I think it's safest to label each bond individually with a "σ" on top of one line and a "π" on top of the other line.
by J Medina 2I
Sun Nov 24, 2019 5:07 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Seesaw
Replies: 23
Views: 244

Re: Seesaw

If a lone pair is present in a molecule, then it will affect the bond angles of the surrounding atoms since the repulsion force lone pairs is greater than bonded atoms.
by J Medina 2I
Sun Nov 24, 2019 4:46 pm
Forum: Resonance Structures
Topic: Resonance structures
Replies: 15
Views: 364

Re: Resonance structures

Patricia Cardenas wrote:Does anyone have advice on how to start drawing lewis structures/resonance structures?


The first step would be to identify the least electronegative atom because this one will typically be the central atom.
by J Medina 2I
Sun Nov 24, 2019 4:43 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Bent Shape
Replies: 31
Views: 840

Re: Bent Shape

Yea if the formula is AX2E then the angles are similar to a trigonal planar molecule (<120) but if the formula is AX2E2 then the bond angles are similar to a tetrahedral molecule (<109.5)
by J Medina 2I
Sun Nov 24, 2019 4:39 pm
Forum: Biological Examples
Topic: cisplatin
Replies: 6
Views: 103

Re: cisplatin

I think Lavelle mentioned in lecture that cisplatin not only stops cell division of cancer cells but stops division for all cells
by J Medina 2I
Sun Nov 24, 2019 4:31 pm
Forum: Shape, Structure, Coordination Number, Ligands
Topic: square planar vs tetrahedral
Replies: 5
Views: 75

Re: square planar vs tetrahedral

Square planar has 6 electron dense regions but two of those are lone pairs, making the formula AX4E2 whereas tetrahedral only has 4 electron dense regions, all of which are bonds to another atom, making the formula AX4. The two lone pairs in a square planar molecule repulse the 4 bonds to form a squ...
by J Medina 2I
Sun Nov 17, 2019 11:04 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Lone vs. Bonding Pair
Replies: 6
Views: 99

Re: Lone vs. Bonding Pair

Lone pairs take up more space making the rest of the bonds move away in order to lower repulsion.
by J Medina 2I
Sun Nov 17, 2019 10:49 pm
Forum: *Molecular Orbital Theory (Bond Order, Diamagnetism, Paramagnetism)
Topic: Vsepr Rules
Replies: 2
Views: 72

Re: Vsepr Rules

If you're talking about the rules stated in the textbook, Rule 2 is telling us that multiple bonds (double bonds, triple bonds) count as only a single region of high electron density. The same way a single bond is counted as one. And the same way a lone pair counts as one. Adding up all the electron...
by J Medina 2I
Sun Nov 17, 2019 10:33 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: SF4
Replies: 3
Views: 35

Re: SF4

Lone pairs and bonds need to be placed where they will cause the least amount of repulsion. Considering lone-pairs have a stronger amount of repulsion than bonds do, their placement is prioritized in terms of where it will cause the least amount of repulsion. In the see-saw example shown in class th...
by J Medina 2I
Sun Nov 17, 2019 10:23 pm
Forum: Lewis Structures
Topic: Why can Xenon break the octet rule?
Replies: 8
Views: 631

Re: Why can Xenon break the octet rule?

Xenon has d-orbitals, allowing it to store more electrons in its valence shell than atoms without any d-orbitals, like those that are at or come before 4s^2 .
by J Medina 2I
Sun Nov 17, 2019 10:13 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: bond angles
Replies: 8
Views: 92

Re: bond angles

Lone pairs have the strongest repulsion strength because lone pairs are less restrained than a bonding pair would be so it takes up more space making the rest of the atoms move away to lower the repulsion acting upon them.
by J Medina 2I
Sun Nov 10, 2019 11:35 pm
Forum: Bond Lengths & Energies
Topic: Rankings
Replies: 2
Views: 40

Re: Rankings

Hydrogen bonds are the strongest intermolecular force
by J Medina 2I
Sun Nov 10, 2019 11:34 pm
Forum: Trends in The Periodic Table
Topic: Atomic Radius
Replies: 30
Views: 346

Re: Atomic Radius

Atomic radius increases going left across and down groups of the periodic table. Having higher atomic numbers means having more protons that pull the electrons closer to the nucleus, decreasing the atomic radius as you move right across the periodic table.
by J Medina 2I
Sun Nov 10, 2019 11:07 pm
Forum: Coordinate Covalent Bonds
Topic: Coordinate Covalent Bond
Replies: 3
Views: 83

Re: Coordinate Covalent Bond

A coordinate covalent bond is when one atom is responsible for giving off a lone pair that contributes to making the bond with another atom without the second atom having to sacrifice one of their own electrons to create the bond.
by J Medina 2I
Sun Nov 10, 2019 10:47 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Writing e- Configurations
Replies: 15
Views: 217

Re: Writing e- Configurations

I think the question would specify if you had to use a specific notation.
by J Medina 2I
Sun Nov 10, 2019 10:45 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: Interaction Strength
Replies: 4
Views: 40

Re: Interaction Strength

This is why rod-shaped molecules will generally have higher melting points. A lot more dipole interactions have to be broken.
by J Medina 2I
Sun Nov 03, 2019 10:52 pm
Forum: Resonance Structures
Topic: Octet
Replies: 13
Views: 260

Re: Octet

Hydrogen and Helium fill up a duplet (2 valence electrons). Other exceptions include atoms in the d-block since they have 5 orbitals allowing them to hold more than 8 outer electrons.
by J Medina 2I
Sun Nov 03, 2019 10:34 pm
Forum: Lewis Structures
Topic: Lone Pairs
Replies: 12
Views: 135

Re: Lone Pairs

It's easy to think of it as any valence electrons that aren't touching (being shared by) any other atoms in the lewis structure
by J Medina 2I
Sun Nov 03, 2019 10:28 pm
Forum: Electronegativity
Topic: electronegativity trend
Replies: 9
Views: 98

Re: electronegativity trend

Electronegativity decreases down a column because the atom gets larger and the electron gets farther away from the pull of the positively charged nucleus. Ionization is related to this since this weaker pull allows less energy to be needed to remove an electron from an atom.
by J Medina 2I
Sun Nov 03, 2019 10:09 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Writing e- Configurations
Replies: 15
Views: 217

Re: Writing e- Configurations

I think you can assume you're able to write the shorthand notation unless told directly by the question to write the entire configuration out.
by J Medina 2I
Sun Nov 03, 2019 9:59 pm
Forum: Bond Lengths & Energies
Topic: Does bond length have any effects?
Replies: 5
Views: 46

Re: Does bond length have any effects?

Bond length does have effects. Shorter bonds (such as triple bonds) will require more energy to break apart because the shared electrons are closer to the positively charged nuclei and thus have a stronger pull on these electrons.
by J Medina 2I
Sun Oct 27, 2019 8:11 pm
Forum: Lewis Structures
Topic: Lone Pairs
Replies: 12
Views: 135

Re: Lone Pairs

In a Lewis structure they're the two dots on the sides.
by J Medina 2I
Sun Oct 27, 2019 8:09 pm
Forum: Trends in The Periodic Table
Topic: Central Atom
Replies: 13
Views: 152

Re: Central Atom

Atom ionization energy levels generally follow a trend of decreasing as you move left across and down the periodic table.
by J Medina 2I
Sun Oct 27, 2019 7:58 pm
Forum: Resonance Structures
Topic: Octet
Replies: 13
Views: 260

Re: Octet

I think in lecture Lavelle mentioned that H, He, Li, and Be are exceptions to the octet rule.
by J Medina 2I
Sun Oct 27, 2019 7:56 pm
Forum: Bond Lengths & Energies
Topic: Single bond vs double bond
Replies: 14
Views: 305

Re: Single bond vs double bond

These numbers are the length of each bond. The double bonds are shorter because there is a stronger pull there which makes it tighter.
by J Medina 2I
Tue Oct 22, 2019 9:02 am
Forum: Trends in The Periodic Table
Topic: Periodic Table trends
Replies: 11
Views: 450

Re: Periodic Table trends

The biggest difference is their shape and their ability to hold e-. The s-orbital can only hold 2 e-. The p-orbital can only only 6 e-. The d-orbital can only hold 10 e-. The f-block can hold 14 e-. In the ground state of an atom, the electrons must fill up all spots in lower energy levels before m...
by J Medina 2I
Sun Oct 20, 2019 11:36 pm
Forum: *Black Body Radiation
Topic: Black Body Radiation
Replies: 12
Views: 325

Re: Black Body Radiation

A black body is a material that absorbs all radiation. No object is a true black body, it is more of an idea in the same way frictionless surfaces are used in physics problems.
by J Medina 2I
Sun Oct 20, 2019 11:25 pm
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: Nodal Planes
Replies: 3
Views: 67

Re: Nodal Planes

Orbitals are probability density functions and nodal planes are where there is a 0 percent likelihood of finding an electron.
by J Medina 2I
Sun Oct 20, 2019 8:29 pm
Forum: Properties of Light
Topic: Unit for Wavelength
Replies: 34
Views: 437

Re: Unit for Wavelength

Wavelengths are measured in meters since it is a distance. It is common to see them measured in nanometers which is 1x10^-9 of a meter.
by J Medina 2I
Sun Oct 20, 2019 8:07 pm
Forum: Properties of Light
Topic: What are the units of hertz
Replies: 41
Views: 528

Re: What are the units of hertz

s^-1

refers to cycles per second
by J Medina 2I
Sun Oct 20, 2019 8:02 pm
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: Advice for studying
Replies: 92
Views: 1951

Re: Advice for studying

I found it helpful to read the chapters covered in lecture and going through all the example problems given. I also write question marks in my notes during lecture to remind myself what seemed confusing at the time so I can study it later.
by J Medina 2I
Sun Oct 13, 2019 11:19 pm
Forum: Properties of Light
Topic: Energy Equation
Replies: 3
Views: 37

Re: Energy Equation

It's Planck's Constant. If you multiply it with frequency (v) you get the energy of the photon.
by J Medina 2I
Sun Oct 13, 2019 10:39 pm
Forum: Significant Figures
Topic: sig figs and periodic tables
Replies: 11
Views: 408

Re: sig figs and periodic tables

If we use the rounded version of the atomic mass (let's say to the hundredths) and correctly use significant figures, would our answer be wrong if the answer we get is right according to the rounded calculations we made?
by J Medina 2I
Sun Oct 13, 2019 10:31 pm
Forum: Photoelectric Effect
Topic: Intensity vs. Length of Waves
Replies: 4
Views: 63

Re: Intensity vs. Length of Waves

Shorter wavelengths imply higher frequency (v), means more crowded bumps and higher energy for removing electrons
by J Medina 2I
Sun Oct 13, 2019 9:59 pm
Forum: Properties of Light
Topic: Wavelength
Replies: 4
Views: 55

Re: Wavelength

I think you can use the Mass of electron given in the constants sheet and plug that into the 1/2mv^2 equation which will give you the kinetic energy of the electron. Then you use c=(lambda)v to get the wavelength.
by J Medina 2I
Sun Oct 13, 2019 9:32 pm
Forum: SI Units, Unit Conversions
Topic: Angstrom
Replies: 16
Views: 474

Re: Angstrom

It's also important to remember that the Angstrom is not an SI unit
by J Medina 2I
Fri Oct 04, 2019 1:29 am
Forum: SI Units, Unit Conversions
Topic: scientific notation
Replies: 7
Views: 81

Re: scientific notation

I think it'd be a good idea to leave an answer in scientific notation if the answer in normal form would be an ambiguous number of significant figures. For example if you want to show 1000 with 3 significant figures just write 1.00 x 10^3
by J Medina 2I
Fri Oct 04, 2019 1:21 am
Forum: SI Units, Unit Conversions
Topic: Sig Fig Rules
Replies: 7
Views: 119

Re: Sig Fig Rules

No the rules are different. For adding and subtracting when dealing with decimals you can only include the decimal value that was closest to the decimal. For example if we had to add 522.7 + 49.44 = 572.14, we would have to round down so that the answer is 572.1 But for multiply or dividing you can ...
by J Medina 2I
Fri Oct 04, 2019 1:00 am
Forum: Empirical & Molecular Formulas
Topic: Homework Question F.9
Replies: 6
Views: 101

Re: Homework Question F.9

Yes, you would assume that your sample is 100 g, but to convert to moles, you actually have to divide by the molar mass of each element as found on the periodic table (so 12.01 g/mol for C). You don't need to divide 63.15 by 100 because if you assume the sample is 100 g, then 63.15% of 100 would ju...

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