## Search found 104 matches

Sat Mar 14, 2020 5:41 pm
Forum: Ideal Gases
Topic: 5% Rule
Replies: 6
Views: 152

### Re: 5% Rule

You put the concentration you got from approximated the concentrations in the equilibrium values (from an ICE table) over the original concentration that's given and if it is less than 5% the approximation is sound, then if not then you have to use the quadratic formula to find the values.
Sat Mar 14, 2020 5:35 pm
Forum: General Rate Laws
Topic: Initial Rate
Replies: 5
Views: 98

### Re: Initial Rate

They should give something that remains constant because that is the method being employed.
Sat Mar 14, 2020 5:46 am
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: 5.57
Replies: 2
Views: 105

### 5.57

How can we find [NO] if the concentration of [NO2] is not given to us? Since it is included in the k equation and we are given every other value.
Wed Mar 11, 2020 4:51 pm
Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
Topic: Enaught in Concentration Cells
Replies: 4
Views: 99

### Enaught in Concentration Cells

If the Enaught is always zero in a concentration cell, then will the Gibbs free energy also be zero?
Wed Mar 11, 2020 3:54 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Change in Ecell
Replies: 5
Views: 76

### Change in Ecell

Will Ecell increase if the size of the anode metal is increased? Does the metal have anything to do with it? And will Ecell increase if a substance is added to the cathode side?
Sun Mar 08, 2020 10:26 pm
Forum: Arrhenius Equation, Activation Energies, Catalysts
Topic: Equations
Replies: 2
Views: 27

### Re: Equations

Yes! You would use the log properties to rearrange it depending on what you want to solve for.
Sun Mar 08, 2020 10:19 pm
Forum: General Rate Laws
Topic: 7A.9
Replies: 5
Views: 65

### Re: 7A.9

First, convert the grams of N2O5 to mols and divide by the liters to get the molarity. You should get 0.0426M and then you just multiply it by the rate to get the second order reaction.
Sat Mar 07, 2020 10:57 am
Forum: Reaction Mechanisms, Reaction Profiles
Topic: Arrhenius Equation
Replies: 6
Views: 77

### Re: Arrhenius Equation

You would use it to find the equilibrium constant, k.
Wed Mar 04, 2020 4:49 pm
Forum: General Rate Laws
Topic: Independent Rates (7A.15)
Replies: 2
Views: 68

### Independent Rates (7A.15)

The solution for problem 7A.15 states that experiment [C] is independent of the rate. The problem proceeds to disregard the elements of reaction C as a valid comparison to find the rate, why is this?
Mon Mar 02, 2020 9:51 pm
Forum: Balancing Redox Reactions
Topic: 6L.5 (part d)
Replies: 2
Views: 72

### Re: 6L.5 (part d)

Does anyone know why we don't need an inert solid for the Au even though they are the same element?
Mon Mar 02, 2020 7:30 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: 6L.7 Part C
Replies: 1
Views: 38

### 6L.7 Part C

I understand why we put the solid Ni onto the cathode side of the cell diagram, but am still a little confused as to why the OH- is not on the cathode side even though it is in the half reaction.
Mon Mar 02, 2020 4:11 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: 6L.7a cell diagram
Replies: 2
Views: 57

### Re: 6L.7a cell diagram

How do we know that Ag is both the oxidizing and reducing agent? Doesn't Br go from Br-(oxidation of -1) to AgBr (which has an oxidation of 0)?
Sun Mar 01, 2020 11:55 pm
Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
Topic: 6O.3
Replies: 2
Views: 44

### 6O.3

I am a little confused what the question is asking. It asks whether or not the metal ion or water will be reduced at the cathode or not? Doesn't everything get reduced at the cathode?
Sun Mar 01, 2020 11:12 pm
Forum: Balancing Redox Reactions
Topic: 6K.3 Part D
Replies: 5
Views: 114

### Re: 6K.3 Part D

So how does the charge of cl go from 0 to -1, don't both the cl2 have an oxidation number of 0?
Tue Feb 25, 2020 2:07 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: 6L.1
Replies: 2
Views: 58

### 6L.1

For part b of the problem it shows an already balanced redox reaction. I'm having trouble finding n for it because I don't know exactly how the charges for hydrogen and water would work.
Sun Feb 23, 2020 11:38 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Salt Bridges
Replies: 3
Views: 71

### Re: Salt Bridges

Hey Roomie! Since there is a flow of electrons, the salt bridge is used to balance the charges in the solution :)
Sat Feb 22, 2020 9:16 pm
Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
Topic: 6L.1
Replies: 4
Views: 46

### Re: 6L.1

They are the same number, it's just another way to write is so the numbers seem smaller.
Sat Feb 22, 2020 9:09 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Determining if a cell reaction is spontaneuous
Replies: 5
Views: 54

### Re: Determining if a cell reaction is spontaneuous

I believe that if the reaction potential is positive then the reaction is spontaneous. They are related by deltaG = -nFE where E is the cell potential. If it is positive then delta G must be negative so it's spontaneous.
Sat Feb 22, 2020 8:57 pm
Forum: Balancing Redox Reactions
Topic: Oxidizing Agents (6K.5)
Replies: 2
Views: 54

### Oxidizing Agents (6K.5)

For problem 6k.5 part a I don't see an oxidizing agent, since it doesn't look like the oxygen is being reduced. If oxygen is on its own are the redox numbers still 0 or are the values -2?
Mon Feb 17, 2020 11:38 pm
Forum: Balancing Redox Reactions
Topic: Oxidizing and Reducing Agents
Replies: 3
Views: 58

### Oxidizing and Reducing Agents

Can something be both an oxidizing and reducing agent? If so, how is that possible and would we make two separate half reactions?
Sun Feb 16, 2020 7:35 pm
Forum: Balancing Redox Reactions
Topic: Oxygen and Hydrogen
Replies: 4
Views: 49

### Re: Oxygen and Hydrogen

It is not always the case, but they typically do not change. A special case is in a peroxide the charge on oxygen is -1 instead.
Sun Feb 16, 2020 7:33 pm
Forum: Balancing Redox Reactions
Topic: Charge of permanganate
Replies: 5
Views: 93

### Re: Charge of permanganate

Yes, since it has a charge of -1 that is the total charge you want to get at the end. Since oxygen has a -2 charge and there are 4 that makes it minus 8 so in order to get a net of -1 the remaining element would have a charge of +7.
Sun Feb 16, 2020 7:20 pm
Forum: Balancing Redox Reactions
Topic: Determining charge
Replies: 5
Views: 65

### Re: Determining charge

You would use the periodic table patterns and trends. Metals which are on the left of the periodic table will be a positively charged ion depending on the column (column 1 = +1 charge) and will go up to the fourth column. Non-metals, which are on the right of the periodic table, starting the fifth c...
Wed Feb 12, 2020 12:13 am
Forum: Entropy Changes Due to Changes in Volume and Temperature
Topic: Delta S Universe
Replies: 1
Views: 26

### Delta S Universe

When do we know that the delta S of the universe is equal to 0. In the solutions manual it says that a reversible process has delta S=0
Sun Feb 09, 2020 8:03 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: 4D.3
Replies: 1
Views: 20

### Re: 4D.3

in order to find q of the reaction, we must find q of the calorimeter, and since q of the reaction equals -q of the calorimeter, the final answer will be negative.
Sun Feb 09, 2020 7:19 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: 4D.21
Replies: 3
Views: 31

### Re: 4D.21

I'm getting -138.13 so it might just be a calculation error!
Mon Feb 03, 2020 7:21 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: Question 4C.11
Replies: 4
Views: 78

### Re: Question 4C.11

Use Table 4C.1 to find the enthalpy of fusion of water. Convert 80.0 grams of ice to moles and multiply by the enthalpy of fusion to get the heat needed to melt the ice. Then, use 80.0 g in the equation q= mCΔT to find the heat needed to raise the temperature from 0 to 25 degrees C. Do you know why...
Mon Feb 03, 2020 6:46 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: Expansion Work on a Piston
Replies: 1
Views: 18

### Expansion Work on a Piston

For expansion on a piston, the formula is work = -p*deltaV, but how do these units become joules?
Sun Feb 02, 2020 9:01 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Forming bonds
Replies: 8
Views: 69

### Re: Forming bonds

Bond formation is exothermic because when two molecules are joined together it is increasing stability, and the system is losing energy that gets released.
Sun Feb 02, 2020 6:32 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: Heat Capacity 4C.3
Replies: 3
Views: 45

### Re: Heat Capacity 4C.3

I don't think you need to use the ideal gas equation. Heat capacity units are J/mol x K and they give you all of that information. The 1.00atm just shows that it is int he standard form.
Sun Feb 02, 2020 3:30 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: Question 4C.11
Replies: 4
Views: 78

### Question 4C.11

The problem is: how much heat is needed to convert 80.0 g of ice at 0.0 8C into liquid water at 20.0 8C? It says to use the table 4A.1 and 4A.C but I'm unsure of what information I need. The water is turning from solid to liquid, which is fusion. The enthalpy for the fusion of water is already given...
Tue Jan 28, 2020 2:51 pm
Forum: Phase Changes & Related Calculations
Topic: 4A.9
Replies: 4
Views: 30

### Re: 4A.9

How do you know the copper releases energy?
Tue Jan 28, 2020 2:49 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Delta U
Replies: 6
Views: 58

### Re: Delta U

Delta U stands for the change in internal energy of the system. Delta u = q (heat) + w(work). The units are in joules!
Tue Jan 28, 2020 2:44 pm
Forum: Phase Changes & Related Calculations
Topic: 4A.9
Replies: 4
Views: 30

### Re: 4A.9

Remember the property q(system) + q(surroundings) = 0, so this holds true for this problem as well but instead it's q(water) + q(copper) = 0. So we can deduce that q(water) = -q(copper). The copper decreased in temperature so the change in T will be negative, and that reveals that it is endothermic....
Tue Jan 28, 2020 2:24 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Replies: 5
Views: 52

I know for the k values when we added two equations together we would multiply the two k values, is it the same for the enthalpy values? What do we do when we need to reverse an equation or double it for enthalpy?
Mon Jan 27, 2020 5:15 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Units for enthalpy
Replies: 3
Views: 42

### Re: Units for enthalpy

qp(work at a constant temperature) does equal enthalpy. The units for a standard reaction enthalpy is kj/mol. q is typically just j or kj but i belive in order to get that you would just multiply by the number of moles in the system, but they are essentially the same value. Enthalpy, without being a...
Mon Jan 27, 2020 5:10 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: Calorimetry and Mass
Replies: 2
Views: 32

### Re: Calorimetry and Mass

Where are you seeing the absence of mass in the equation. Correct me if I'm wrong but I think that it always includes mass, the only thing different is the negative sign in front that means that it is exothermic. It will either include mass or moles in the equation.
Thu Jan 23, 2020 3:58 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: 5I.1
Replies: 1
Views: 27

### Re: 5I.1

Set up the equilibrium expression as k=[BrCl]^2/[Br2][Cl2] and set it to find [Br2] = 0.031*(.495/.145^2) to solve.
Thu Jan 23, 2020 3:46 pm
Forum: Calculating pH or pOH for Strong & Weak Acids & Bases
Topic: pKa vs pH
Replies: 4
Views: 115

### Re: pKa vs pH

pH shows the scale of acidity and how basic something is more so than the pKa. You can undo the pKA by raising it to 10^- and finding the Ka. By using an ice table you can find the pH using the equilibrium expression.
Thu Jan 23, 2020 3:38 pm
Forum: Non-Equilibrium Conditions & The Reaction Quotient
Topic: Endothermic Reaction.
Replies: 7
Views: 65

### Re: Endothermic Reaction.

Endothermic reactions require energy to proceed and temperature and adding heat acts as a reactant. This would have a positive delta H (enthalpy).
Thu Jan 23, 2020 3:17 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: 5G part c
Replies: 3
Views: 43

### Re: 5G part c

You could also explain it by writing out the equilibrium expression where it shows k = [products] / [reactants]. This is simply a ratio, so if reactants increase it would only drive the entire reaction to the right, thus creating more products since k needs to remain constant.
Thu Jan 23, 2020 2:52 pm
Forum: Non-Equilibrium Conditions & The Reaction Quotient
Topic: Strong/weak acids & bases
Replies: 14
Views: 219

### Re: Strong/weak acids & bases

You would just have to memorize the six strong acids H2SO4 Sulfuric Acid, HCl Hydrochloric Acid, HBr Hydrobromic Acid, HI Hydroiodic Acid, HNO3 Nitric Acid, HClO4 Perchloric Acid. Everything else is considered a weak acid. Strong bases have a group 1 or 2 metal attached to a hydroxide (OH-). Everyth...
Thu Jan 23, 2020 2:48 pm
Forum: Non-Equilibrium Conditions & The Reaction Quotient
Topic: 6C.1
Replies: 2
Views: 43

### Re: 6C.1

A proton transfer is just the tranfer of a hydrogen ion (H+) in solution. You would write it as hydronium (H3O+) on the product side and the conjugate base along with it.
Thu Jan 23, 2020 2:46 pm
Forum: Non-Equilibrium Conditions & The Reaction Quotient
Topic: Ka correlation to strength of an acid
Replies: 3
Views: 26

### Re: Ka correlation to strength of an acid

If the Ka is large it means it's a stronger acid. The greater the number the more it dissociates so more H+ will be in solution.
Thu Jan 23, 2020 2:36 pm
Forum: Non-Equilibrium Conditions & The Reaction Quotient
Topic: pKa to Kb
Replies: 12
Views: 144

### Re: pKa to Kb

Another way to do it is to turn the pKa into Ka first. Once you turn it into ka you can use the kw (water constant) to find the kb. Set the equation to be kb=kw/ka.
Thu Jan 23, 2020 2:29 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Chemical Equilibrium 1B Post-Assessment #19.b
Replies: 2
Views: 38

### Re: Chemical Equilibrium 1B Post-Assessment #19.b

The reaction is reversed, so the k value would become 1/k. Putting the k value you got in part A over 1 should get you D as the answer.
Thu Jan 23, 2020 2:21 pm
Forum: Phase Changes & Related Calculations
Topic: Systems and Surroundings
Replies: 3
Views: 34

### Re: Systems and Surroundings

A closed system gas a fixed amount of matter, which in that sense makes it closed. Although it can still exchange energy with its surroundings through heat work and transfer. These energy forms can be transferred across system boundaries.
Sat Jan 11, 2020 2:07 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: Decreasing pressure by increasing volume [ENDORSED]
Replies: 4
Views: 50

### Re: Decreasing pressure by increasing volume[ENDORSED]

I believe the trends are the same, just in the opposite direction. So the reaction will shift to the side that has less moles.
Sat Jan 11, 2020 1:56 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: 5I.19
Replies: 1
Views: 26

### Re: 5I.19

Since it is 60% you would multiply the value by 0.60 and take that as the change.
Sat Jan 11, 2020 1:50 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: 5H.3
Replies: 4
Views: 47

### Re: 5H.3

You make the two equations into composite equations. Use the two equations that has 2HCl as a product and Br2 + Cl2 as a product. Everything should cancel out and create the equation you are looking for. Make sure that when you add two chemical reactions together you multiply their k values. When I ...
Thu Jan 09, 2020 12:51 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: 5I.33
Replies: 2
Views: 48

### Re: 5I.33

I believe you use the conservation of mass and you don't need an ICE table. Since k = [NH3]^2 * [CO2] you would use the equilibrium value of 17.4mg of CO2 to find the molarity of that (divide by 0.250L). Since the amount of solid ammonium carbonate initially is 25.0g you just subtract 0.0174g of the...
Thu Jan 09, 2020 12:40 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Initial Concentrations of Reactants and Products
Replies: 2
Views: 25

### Initial Concentrations of Reactants and Products

I know that it doesn't matter what amount of reactants and products you begin with, and it still will have the same equilibrium concept, but I am still confused as to how that works? Does the reaction just continue until the ratio is reached?
Sat Dec 07, 2019 9:30 am
Forum: Shape, Structure, Coordination Number, Ligands
Topic: Identifying Polydentates
Replies: 1
Views: 51

### Re: Identifying Polydentates

A polydentate ligand refers to ligands with more than one donor atom, meaning its elements can occupy more than one binding site simultaneously. They are typically ligands that have a central atom with a lone pair. To determine the number, it is just how bonds the polydentate can form.
Sat Dec 07, 2019 9:28 am
Forum: Calculating pH or pOH for Strong & Weak Acids & Bases
Topic: Finding pH From Strong Acids/Bases
Replies: 1
Views: 19

### Re: Finding pH From Strong Acids/Bases

If there is both a strong acid and a strong base then they need to be subtracted from each other, to find out what there is more of, H+ or OH-. If there are equal amounts the pH would be neutral, but once they are subtracted it is the left over H+ or OH- that did not get bounded together, thus influ...
Sat Dec 07, 2019 9:25 am
Forum: Calculating the pH of Salt Solutions
Topic: salts of weak bases/acids
Replies: 2
Views: 66

### Re: salts of weak bases/acids

Another way to determine how a salt will affect a solution is to write out the net ionic equation for the salt produced and separating the the cation and anion. If it produces a strong base, OH- will be produced (basic), and if the product is a strong acid, H+ will be produced (acidic).
Sat Dec 07, 2019 9:22 am
Forum: Lewis Acids & Bases
Topic: Strong Acids and Bases
Replies: 1
Views: 33

### Re: Strong Acids and Bases

You should know that groups 1 and 2 form strong bases. For the strong bases, you should probably know the 6 common strong acids: HClO4, HCl, HBr, HI, HNO3, H2SO4.
Sat Dec 07, 2019 9:20 am
Forum: Bronsted Acids & Bases
Topic: Homework J.7
Replies: 1
Views: 48

### Re: Homework J.7

Make sure you know that zinc nitrate is Zn(NO2)2 because Zn has a 2+ charge. Then you attach and 2 OH- to Zn2+ in the reactants and attach and H+ to NO2-. A neutralization always forms water and the salt, so balance the chemical equation.
Sat Dec 07, 2019 9:14 am
Forum: Hybridization
Topic: resonance structures
Replies: 1
Views: 53

### Re: resonance structures

Yes, they have unhybridized orbitals because resonance is the moving of pi orbitals, for various arrangements. The arrangement of pi bonds involves only unhyrbidized orbitals.
Sat Dec 07, 2019 9:08 am
Forum: Dipole Moments
Topic: Dipole Moments Cancel in Tetrahedral?
Replies: 5
Views: 167

### Re: Dipole Moments Cancel in Tetrahedral?

The tetrahedral shape is never non-polar unless all elements surrounding the central atom are identical. It's easies to see the 3-D shape, and how they would not be able to cancel out.
Fri Dec 06, 2019 12:36 am
Forum: Determining Molecular Shape (VSEPR)
Topic: VSEPR Formulas
Replies: 2
Views: 36

### VSEPR Formulas

Does SO2 have a bent molecular shape, and if so is the VSEPR formula AX2E2.
Wed Dec 04, 2019 8:49 pm
Forum: Conjugate Acids & Bases
Topic: Neutralization Reactions
Replies: 1
Views: 41

### Neutralization Reactions

For problems such as J.7, in order to select an acid or base it seems we would just add an H+ to the conjugate base and an OH- to the conjugate acid but would the same apply to the zinc nitrite? Would the zinc be the conjugate base, but Zn(OH)2 doesn't seem like a base that we're familiar with.
Tue Dec 03, 2019 11:20 am
Forum: Naming
Topic: Naming Coordination Compounds
Replies: 5
Views: 50

### Naming Coordination Compounds

Dr. Lavelle posted a link on his site https://lavelle.chem.ucla.edu/wp-conten ... pounds.pdf
I was wondering if anyone knew if we needed to memorize the anionic ligands?
Mon Dec 02, 2019 11:36 pm
Forum: Naming
Topic: [CO(SO4)(NH3)5]+
Replies: 2
Views: 429

### [CO(SO4)(NH3)5]+

How would we name this compound?
Mon Dec 02, 2019 6:45 pm
Forum: Lewis Acids & Bases
Topic: Acid Strength
Replies: 4
Views: 108

### Re: Acid Strength

The weaker the bond the stronger the acid. So the element that is the most electronegative (strong bond) will have a weak acid.
Mon Dec 02, 2019 6:28 pm
Forum: Bronsted Acids & Bases
Topic: Bronsted vs. Lewis
Replies: 1
Views: 29

### Re: Bronsted vs. Lewis

Bronsted acids are defined as substances that can donate a hydrogen ion (H+) whereas Lewis acids are seen as simply electron-pair donors, and not specifically hydrogen ions.
Wed Nov 20, 2019 2:45 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: London forces vs. dipole-dipole for halogen-containing molecules
Replies: 3
Views: 50

### Re: London forces vs. dipole-dipole for halogen-containing molecules

CHI3 has the higher boiling point because the molecule is larger. That overrides any of the IMF typically, and CHF3 does not have hydrogen bonding because the central atom is carbon so H and F are not bonded together.
Wed Nov 20, 2019 2:38 pm
Forum: Dipole Moments
Topic: lone pairs and polarity
Replies: 2
Views: 47

### Re: lone pairs and polarity

The lone pairs generally affect the polarity of a molecule because the long pairs distort the geometry of the molecule to be asymmetrical. When the molecule is not symmetrical it has polar properties. The arrows point toward H3 because the lone pairs repel the other atoms away.
Mon Nov 18, 2019 4:39 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Stronger IMF's
Replies: 2
Views: 37

### Re: Stronger IMF's

The bigger the molecule, the greater the IMF is a rule of thumb. The shape of the molecule is secondary to the amount of electrons, so we typically only compare that when they have the same number of electrons.
Mon Nov 18, 2019 4:38 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Molecular Shapes
Replies: 1
Views: 30

### Re: Molecular Shapes

I believe it's everything in the book, which includes part of the charts. I think we need to be familiar with the names and bond angles.
Fri Nov 15, 2019 11:51 am
Forum: Dipole Moments
Topic: Polarity
Replies: 6
Views: 94

### Re: Polarity

A polar molecule must have polar bonds with dipoles that do not cancel each other out. So the electronegativity of atoms must be evident and typically on the same side of the central atom. Draw a lewis structure and then determine its molecular shape. It is determined the symmetry of the molecule (l...
Fri Nov 15, 2019 11:46 am
Forum: Dipole Moments
Topic: Shape of Molecules affect boiling point?
Replies: 7
Views: 148

### Re: Shape of Molecules affect boiling point?

The rod shaped molecule is larger than the spherical shaped molecule, thus experiencing greater intermolecular london dispersion forces. Larger molecules=stronger attraction=harder to break bonds=higher boiling point.
Fri Nov 15, 2019 11:44 am
Forum: Sigma & Pi Bonds
Topic: One Sigma One Pi
Replies: 3
Views: 56

### Re: One Sigma One Pi

There can only be one sigma bond between two atoms because the orbitals form the two atoms overlapping it cannot bond again to share more electrons in another end to end overlap, therefore a pi bond is created instead (for orbitals to overlap side-to-side).
Fri Nov 15, 2019 11:40 am
Forum: Sigma & Pi Bonds
Topic: Sigma & Pi Bonds
Replies: 5
Views: 98

### Re: Sigma & Pi Bonds

Also remember that a triple bond has one sigma bond and two pi bonds!
Wed Nov 13, 2019 7:40 pm
Forum: Electronegativity
Topic: Problem 3F.15
Replies: 2
Views: 84

### Problem 3F.15

AsF3 has a higher boiling point than AsF5 because it has lone pairs that distort the geometry, therefore making the shape polar. But AsF5 is bigger, so does the dipole-dipole interaction have a greater influence in bond strength than the size of the molecule?
Wed Nov 13, 2019 7:35 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: Problem 3F.5
Replies: 3
Views: 65

### Problem 3F.5

I know the boiling point is higher for CHI3 than it is for CHF3 because CHI3 is the larger molecule so the dispersion forces are stronger and greater. But since Fluorine is more electronegative does that play any role in the strength of the forces, since it attracts the CH to it?
Wed Nov 13, 2019 7:13 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: Topic 3F.1
Replies: 3
Views: 41

### Re: Topic 3F.1

Also, another question on this problem. How do we know that H2SeO4 has a dipole-dipole intermolecular force, and not an ion-dipole intermolecular force. Are ion dipole just for the ion being an element?
Wed Nov 13, 2019 7:08 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: Topic 3F.1
Replies: 3
Views: 41

### Topic 3F.1

Do we need to draw out the lewis structure every time we are determining what intermolecular forces are present for a molecule?
Sun Nov 03, 2019 5:43 pm
Forum: Trends in The Periodic Table
Topic: Ionization Energy Exceptions
Replies: 2
Views: 41

### Re: Ionization Energy Exceptions

The two exceptions from the general trend are the ionization energies of B is less than Be and O is less than N. They have greater electron shielding.
Sun Nov 03, 2019 5:15 pm
Forum: Bond Lengths & Energies
Topic: Bond Length
Replies: 2
Views: 46

### Re: Bond Length

The distance is the distance from one nucleus to another. It doesn't have a direct relation to electrons, but since the longer (weaker) the bond length, the easier it is broken, and it is more likely involved in a reaction (this is where the electrons come in).
Sun Nov 03, 2019 5:13 pm
Forum: Photoelectric Effect
Topic: Work function of an atom
Replies: 4
Views: 65

### Re: Work function of an atom

So I used two different equations to derive the energy because it's not asking for the energy of an electron, which is what the kinetic energy formula finds. I used E=hv, but found v first using v=c/lamda for part a.
Sun Nov 03, 2019 5:05 pm
Forum: Coordinate Covalent Bonds
Topic: coordinate covalent bond
Replies: 2
Views: 44

### Re: coordinate covalent bond

A coordinate covalent bond is when a shared pair of electrons comes from the same atom, and not a sharing between two different atoms. In a normal covalent bond each atom contributes one electron to make a pair. A coordinate covalent bond is held together because the electron pair is attracted by bo...
Sun Nov 03, 2019 4:59 pm
Forum: Dipole Moments
Topic: drawing dipole moments
Replies: 5
Views: 81

### Re: drawing dipole moments

Dipole moments are determined by the shape and structure of a molecule. So if there is charged asymmetry there is an electric field thus making it dipole. The equation u = q * d gives a mathematical representation. But if the molecule is asymmetric it has a dipole moment because the charges create t...
Sun Nov 03, 2019 4:38 pm
Forum: Ionic & Covalent Bonds
Topic: Distortion
Replies: 4
Views: 44

### Re: Distortion

Polarizability measures how easily an electron cloud distorted by an electron field (typically caused by cation and anion). If the electron cloud is easy to distort, it's polarizable.
Sun Nov 03, 2019 4:37 pm
Forum: Ionic & Covalent Bonds
Topic: Distortion
Replies: 4
Views: 44

### Re: Distortion

Polarizability measures how easily an electron cloud distorted by an electron field (typically caused by cation and anion). If the electron cloud is easy to distort, it's polarizable.
Fri Oct 25, 2019 11:32 am
Forum: Lewis Structures
Topic: Lewis Structures: Lone pairs as dots or lines?
Replies: 5
Views: 62

### Re: Lewis Structures: Lone pairs as dots or lines?

I would stick to using dots as lone pairs since lines indicate single bonds and double bonds between two electrons, just to avoid confusion.
Fri Oct 25, 2019 11:26 am
Forum: Ionic & Covalent Bonds
Topic: Bond length
Replies: 11
Views: 119

### Re: Bond length

The longer the bond length the lower the energy it takes to break that bond. The further away the element is from the nucleus of the central atom, then the easier it is to break.
Fri Oct 25, 2019 11:21 am
Forum: Trends in The Periodic Table
Topic: Electron Affinty
Replies: 5
Views: 54

### Electron Affinty

Since electron affinity is a neutral atom's likelihood of gaining an electron, what is the periodic trend? Does this have to do with filling its valence shell?
Tue Oct 22, 2019 2:34 pm
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: Energy of Electrons
Replies: 6
Views: 79

### Energy of Electrons

Does the energy of an electron increase when it moves up an energy level/orbital?
Fri Oct 18, 2019 4:54 pm
Forum: Photoelectric Effect
Topic: The Work Function
Replies: 15
Views: 175

### The Work Function

E=hv is also equal to the work function. What exactly is the work function and is it the threshold energy for the electron or for an element?
Fri Oct 18, 2019 4:53 pm
Forum: *Shrodinger Equation
Topic: Balmer and Lyman Series
Replies: 1
Views: 40

### Balmer and Lyman Series

How do we know that the Balmer series starts at n=2 and how the n= is found for the lyman series and what that ultimately means. Does this change how the other orbitals are calculated?
Fri Oct 18, 2019 4:47 pm
Forum: Electron Configurations for Multi-Electron Atoms
Topic: How to Name Electron Configurations
Replies: 5
Views: 69

### How to Name Electron Configurations

I'm not entirely sure how to write the electron configurations using previous elements on the periodic table. How do we know when to use the previous elements.
Fri Oct 18, 2019 4:39 pm
Forum: Properties of Light
Topic: 1D.13
Replies: 1
Views: 43

### 1D.13

b)How many values of ml are allowed for an electron in the 6d subshell?

I am not sure how to start this. Should we find the l orbital first?
Tue Oct 15, 2019 5:26 pm
Forum: Properties of Electrons
Topic: 1B.3
Replies: 3
Views: 75

### 1B.3

Which observation shows that the electromagnetic radiation is particle like and not wavelike? -Black-body radiation -Electron diffraction -Atomic Spectra -The photoelectric effect I'm having trouble figuring out which one shows particle properties because everything seems to describe wave properties...
Sun Oct 13, 2019 10:00 am
Forum: Properties of Electrons
Topic: 1E.10
Replies: 2
Views: 21

### Re: 1E.10

You need to use the definition of the quantum numbers to describe the location and spin of an atom. The d sub shell in c (described by l=2) can only hold a total of 5 orbitals, so c is not a valid set of numbers since the absolute value of the magnetic quantum number cannot exceed the value of the a...
Sun Oct 13, 2019 9:52 am
Forum: Properties of Electrons
Topic: Quantum electrons
Replies: 2
Views: 26

### Re: Quantum electrons

Is there a specific problem, or just a general question? Typically electrons are assigned quantum numbers when the orbitals are needed for the equations or you want to know the size of the orbital that the electron resides in. This creates different properties and energy required needed to remove th...
Sun Oct 13, 2019 9:45 am
Forum: Properties of Light
Topic: de broglies equation
Replies: 6
Views: 115

### Re: de broglies equation

De Broglie's equation is used to determine if matter has wavelength properties, but it is only noticed for moving objects with momentum (p) and objects with extremely small mass. The wavelength can be measured using this equation, where mass determines the outcome. Make sure that these calculations ...
Sun Oct 13, 2019 9:38 am
Forum: Limiting Reactant Calculations
Topic: Fundamentals M Homework Problem M.11
Replies: 3
Views: 258

### Re: Fundamentals M Homework Problem M.11

There are multiple ways to finding the limiting reagent. You could also start with the grams of water and see how much water is needed in moles or grams to complete the reaction (since it is the product) and then find how much o2 we already have. You can compare those values and see how much is exce...
Thu Oct 10, 2019 5:22 pm
Forum: Limiting Reactant Calculations
Topic: Fundamentals M.5
Replies: 3
Views: 180

### Fundamentals M.5

For part b of the problem that states: Estimate how many moles of each product will be produced and how many moles of the excess reactant will remain, how do we find the amount that remains. I understand the excess reactant is the BrF3 and found that 2 moles of Br2 is produced, but where do I go fro...
Mon Oct 07, 2019 8:53 pm
Forum: Balancing Chemical Reactions
Topic: Fundamentals H.11
Replies: 3
Views: 68

### Fundamentals H.11

For question H.11 it states: "In a second stage, the Fe3O4 reacts further with carbon monoxide to produce solid elemental iron and carbon dioxide. Write the balanced equation for each stage in the process." For the first part I balanced the equation and got 2 moles of Fe3O4. Does this numb...
Thu Oct 03, 2019 12:38 pm
Forum: Limiting Reactant Calculations
Topic: Chemical Principles Section M Question 7b
Replies: 2
Views: 58

### Re: Chemical Principles Section M Question 7b

It doesn't really matter that boron is diatomic because you are just finding the grams of all the boron in the compound! It is essentially already taking into consideration that boron is diatomic, so it doesn't affect your calculations. The moles of the element stays the same regardless of how "...