## Search found 67 matches

Sat Mar 16, 2019 11:04 am
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Concentration cells Ecell
Replies: 1
Views: 87

### Re: Concentration cells Ecell

Yes. For concentration cells, the Enot is always zero.
Sat Mar 16, 2019 10:49 am
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Concentration Cells
Replies: 1
Views: 110

### Re: Concentration Cells

In concentration cells there is no need to identify which side is oxidized or reduced. Just realize that the one with the smaller concentration is always the product and the one with the higher concentration is the reactant.
Sat Mar 16, 2019 10:24 am
Forum: Arrhenius Equation, Activation Energies, Catalysts
Topic: Activated structure [ENDORSED]
Replies: 2
Views: 89

### Re: Activated structure[ENDORSED]

Dr. Lavelle said we don't need to know how to draw structures for 14B.
Sun Mar 10, 2019 11:00 pm
Forum: First Order Reactions
Topic: reaction orders
Replies: 3
Views: 145

### Re: reaction orders

Yes. There is a possibility in which the order can be any sign and any fraction.
Sat Mar 09, 2019 9:51 pm
Forum: Second Order Reactions
Topic: rate constant k
Replies: 3
Views: 141

### Re: rate constant k

Rate constants are never negative in any reactions. The value of k will always be positive.
Sat Mar 09, 2019 3:54 pm
Forum: Method of Initial Rates (To Determine n and k)
Topic: negative and k
Replies: 3
Views: 169

### Re: negative and k

The "k" value can never be negative. For a first order reaction, the slope=-k. Since the slope is negative, k is the opposite sign of what ever the slope is.
Sun Mar 03, 2019 11:54 pm
Forum: Van't Hoff Equation
Topic: Sample problem
Replies: 2
Views: 335

### Re: Sample problem

It is useful in problems to fine K at a different temperature if delta H is known.
Sun Mar 03, 2019 11:52 pm
Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
Topic: Class on 2/27 and 3/1
Replies: 2
Views: 112

### Re: Class on 2/27 and 3/1

Last Wednesday we finished electrochemistry and began Kinetics.
Sun Mar 03, 2019 2:32 pm
Forum: Reaction Mechanisms, Reaction Profiles
Topic: Molecularity
Replies: 1
Views: 111

### Re: Molecularity

The number of reactants ultimately determines molecularity.
For example:
A-->products is unimolecular
A+A---> products is bimolecular
A+B--->products is also bimolecular
A+B+B---> products is termolecular
A+B+C----> products is also termolecular
Sun Mar 03, 2019 1:31 pm
Forum: First Order Reactions
Topic: Possiility
Replies: 2
Views: 123

### Re: Possiility

Yes, it is possible to have all reactants be in first order.
Sun Feb 24, 2019 1:51 pm
Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
Topic: cell potential
Replies: 2
Views: 85

### Re: cell potential

We need to know how to calculate standard reduction potentials of cells from given reactions.
Sat Feb 23, 2019 11:10 pm
Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
Topic: Finding n in Delta G = -nFE
Replies: 3
Views: 156

### Re: Finding n in Delta G = -nFE

You find n by finding the number of moles of electrons transferred in a reaction.
Fri Feb 22, 2019 10:27 am
Forum: Gibbs Free Energy Concepts and Calculations
Topic: Spontaneity
Replies: 6
Views: 265

### Re: Spontaneity

When delta G is negative, the forward reaction is spontaneous and the products are more stable.
Thu Feb 21, 2019 11:46 pm
Forum: Balancing Redox Reactions
Topic: Balancing / Skeletal Equations
Replies: 4
Views: 211

### Re: Balancing / Skeletal Equations

We sometimes add H2O or H+ to balance redox reactions to ensure to correct amount of oxygens and hydrogens are balanced on each side.
Sun Feb 17, 2019 1:49 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: spontaneity
Replies: 2
Views: 122

### Re: spontaneity

When reactions are spontaneous, they do not need anything extra to occur. Therefore, these reactions will naturally form products.
Sun Feb 17, 2019 1:38 pm
Forum: Van't Hoff Equation
Topic: Different Constants of Eqn
Replies: 3
Views: 175

### Re: Different Constants of Eqn

Yes, we need a constant temperature to use that equation.
Sat Feb 16, 2019 2:47 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: Homework question 9.55
Replies: 1
Views: 74

### Re: Homework question 9.55

The default temperature when dealing with standard energy is usually 25 degrees Celsius unless otherwise noted.
Sun Feb 10, 2019 9:41 pm
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: DeltaU=q+w
Replies: 5
Views: 159

### Re: DeltaU=q+w

q and w inherently denote change because it is a transfer of energy.
Sun Feb 10, 2019 12:21 am
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: Units
Replies: 6
Views: 490

### Re: Units

There are no units for Keq or Kc or Kp.
Sat Feb 09, 2019 5:02 pm
Forum: Entropy Changes Due to Changes in Volume and Temperature
Topic: Spontaneity
Replies: 1
Views: 68

### Re: Spontaneity

Phase changes can be spontaneous or non spontaneous.
Sun Feb 03, 2019 10:52 pm
Forum: Phase Changes & Related Calculations
Topic: Heating Curve
Replies: 4
Views: 200

### Heating Curve

I had trouble understanding why steam creates a more severe burn then hot water. Can someone explain this concept again please?
Sat Feb 02, 2019 9:48 am
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Test Question
Replies: 4
Views: 218

### Re: Test Question

You would usually use Kp when dealing with gases. However, if the question explicitly states find the Kc, then just use Kc when doing calculations.
Thu Jan 31, 2019 9:55 pm
Forum: Calculating Work of Expansion
Topic: Equations for w
Replies: 5
Views: 212

### Re: Equations for w

Dr. Lavelle was basically showing us the proof behind the work equation which is why he got the integral.
Sat Jan 26, 2019 5:22 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: method 1
Replies: 3
Views: 125

### Re: method 1

Yes. The 2NO's cancel each other which is why NO is not in the final reaction.
Sat Jan 26, 2019 5:19 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: method 2
Replies: 2
Views: 93

### Re: method 2

You have it flipped. It requires energy to break the bonds on the reactant side, and it releases energy when bonds are formed on the product side.
Wed Jan 23, 2019 9:16 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Kw - applies to solutions other than 100% water?
Replies: 3
Views: 123

### Re: Kw - applies to solutions other than 100% water?

The question implies that it is about water since it has hydroxide and hydronium ion.
Tue Jan 22, 2019 6:18 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: Salts
Replies: 4
Views: 219

### Re: Salts

A salt has a anion and cation. For example, NaF is a salt since Na+ is a cation and F- is an anion.
Sun Jan 20, 2019 6:10 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Ionization and deprotonation
Replies: 3
Views: 55

### Re: Ionization and deprotonation

Yes. The two terms mean the exact same thing.
Wed Jan 16, 2019 9:54 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: Le Chatelier's Principle
Replies: 4
Views: 178

### Re: Le Chatelier's Principle

Without adding more reactants, you would have to decrease the amount of products (NH3) in order to yield more products.
Wed Jan 16, 2019 4:03 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: Temperature and Equilibrium
Replies: 3
Views: 145

### Re: Temperature and Equilibrium

Because endothermic reactions require heat in the reactants, increasing the temperature will result in the reaction sitting to the products in order to relieve the stress added to reaction. The same goes for exothermic reactions as the reaction will lay to the reactants if temperature is increased.
Wed Jan 16, 2019 3:59 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: Pure Solids and Pure Liquids
Replies: 4
Views: 198

### Re: Pure Solids and Pure Liquids

The equilibrium constant is not affect by pure liquids or solids. Only gases and aqueous solutions affect equilibrium.
Wed Jan 16, 2019 12:04 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: Test topics for next week
Replies: 3
Views: 136

### Re: Test topics for next week

Test 1 will cover chemical equilibrium and most of acid/base.
Sat Jan 12, 2019 11:32 pm
Forum: Ideal Gases
Topic: Homework Week 2
Replies: 10
Views: 429

### Re: Homework Week 2

Yes. From now on the homework is due in discussion every week.
Fri Jan 11, 2019 9:36 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: Effect of Pressure
Replies: 3
Views: 90

### Re: Effect of Pressure

The information you googled was briefly mentioned in class, but Dr. Lavelle made it clear that this is only true if the pressure changes by also changing the volume. If the pressure changes by inserting an inert gas, then there is no equilibrium shift.
Fri Jan 11, 2019 5:22 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: ICE
Replies: 2
Views: 96

### Re: ICE

I-initial concentration
C-change
E-equilibrium concentration
Thu Jan 10, 2019 11:44 pm
Forum: Non-Equilibrium Conditions & The Reaction Quotient
Topic: 5G.11 b
Replies: 3
Views: 149

### Re: 5G.11 b

The main rule is that liquids and solids are not included in the equilibrium constant expression. Aqueous solutions and gases are included.
Thu Dec 06, 2018 10:56 am
Forum: Conjugate Acids & Bases
Topic: Inverse Proportional
Replies: 2
Views: 137

### Re: Inverse Proportional

Yes, a weak acid has a strong conjugate base. And a strong base has a weak conjugate acid.
Thu Dec 06, 2018 10:54 am
Forum: Calculating the pH of Salt Solutions
Topic: Calculating pH of Acid/Base
Replies: 1
Views: 260

### Re: Calculating pH of Acid/Base

Lavelle said we do not need to worry about those specific calculations because that is more 14B. All we need to know is the regular pH calculation of an acid or base based on its concentration.
Tue Dec 04, 2018 8:01 pm
Forum: Acidity & Basicity Constants and The Conjugate Seesaw
Topic: K
Replies: 3
Views: 156

### Re: K

K means constant.
Thu Nov 29, 2018 11:16 am
Forum: Shape, Structure, Coordination Number, Ligands
Topic: coordination sphere
Replies: 1
Views: 32

### Re: coordination sphere

A coordinate sphere is the area in a transition metal complex where the ligands are directly attached to the central atom.
Tue Nov 27, 2018 9:06 pm
Forum: Lewis Structures
Topic: 3.71 6th edition
Replies: 1
Views: 42

### Re: 3.71 6th edition

You will need to calculate formal charge to see which one is favorable.
Tue Nov 27, 2018 4:31 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Sigma and Pi bonds
Replies: 2
Views: 76

### Re: Sigma and Pi bonds

A sigma bond has two orbitals that interact end to end to form the bond. Sigma bonds allow rotation of atoms. A pi bond has two orbitals that overlap side to side to form the bond. Pi bonds do not allow the atoms to rotate. When two atoms are bound by more than one covalent bond, the additional orbi...
Sat Nov 24, 2018 10:14 am
Forum: Resonance Structures
Topic: Resonance in VSEPR Theory
Replies: 1
Views: 265

### Re: Resonance in VSEPR Theory

Resonance does occur in vsepr structures. However, resonance does not change the name or structure of the molecule.
Sat Nov 24, 2018 10:12 am
Forum: Hybridization
Topic: hybridization problems
Replies: 4
Views: 164

### Re: hybridization problems

To find the hybridization of an atom in a molecule, count the number of regions of electron density. If there are two regions, then the hybridization is sp. If three, then it is sp2. If four, then it is sp3. If there are five regions, then it is sp3d.
Sat Nov 24, 2018 10:09 am
Forum: Determining Molecular Shape (VSEPR)
Topic: double and triple bonds
Replies: 10
Views: 414

### Re: double and triple bonds

Double and triple bonds are still only one region of electron density; therefore, it does not affect the naming of the molecule or the vsepr structure.
Fri Nov 23, 2018 11:33 am
Forum: Interionic and Intermolecular Forces (Ion-Ion, Ion-Dipole, Dipole-Dipole, Dipole-Induced Dipole, Dispersion/Induced Dipole-Induced Dipole/London Forces, Hydrogen Bonding)
Topic: Distinctions between intermolecular forces
Replies: 2
Views: 137

### Re: Distinctions between intermolecular forces

Those three forces are used interchangeably.
Thu Nov 15, 2018 8:56 pm
Forum: *Molecular Orbital Theory (Bond Order, Diamagnetism, Paramagnetism)
Topic: 6th edition 4.31
Replies: 1
Views: 117

### Re: 6th edition 4.31

sp has two electron density groups which is a linear orientation. sp2 has three electron density groups which is a trigonal planar orientation.
Wed Nov 14, 2018 5:46 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Electrons and VSEPR
Replies: 4
Views: 143

### Re: Electrons and VSEPR

Lone pair electrons do affect the shape of molecules. They also slightly decrease the angle of the atoms.
Wed Nov 14, 2018 4:26 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Dipole moments and VESPR
Replies: 3
Views: 140

### Re: Dipole moments and VESPR

Dipole moments aren't directly related to VSEPR theory, but they will determine whether a molecule is polar or nonpolar.
Wed Nov 07, 2018 4:32 pm
Forum: Dipole Moments
Topic: dispersion forces vs. london forces
Replies: 2
Views: 126

### Re: dispersion forces vs. london forces

They are the same type of attractive forces. In other words, those terms can be used interchangeably.
Wed Nov 07, 2018 4:31 pm
Forum: Bond Lengths & Energies
Topic: bond lengths and strengths
Replies: 9
Views: 365

### Re: bond lengths and strengths

Single bonds are the weakest because they are the longest. Double and triple bonds are stronger because they are smaller and held tighter to the atoms.
Wed Nov 07, 2018 4:29 pm
Forum: Octet Exceptions
Topic: List of octect exceptions
Replies: 6
Views: 314

### Re: List of octect exceptions

The first four elements (H, He, Li, Be) are exceptions along with radicals and elements in the third period and below.
Fri Nov 02, 2018 10:18 pm
Forum: Ionic & Covalent Bonds
Topic: Ionic and Covalent bonds with covalent/ionic characteristics
Replies: 3
Views: 149

### Re: Ionic and Covalent bonds with covalent/ionic characteristics

In the case of NaCl, the cation Na+ exerts an electrostatic attraction on the electrons surroundings the anion Cl-. Therefore, the anion's electrons are pulled into the bonding region which creates a shared region of electrons between the bond of NaCl. As a result, this salt has some covalent charac...
Wed Oct 31, 2018 11:49 pm
Forum: Ionic & Covalent Bonds
Topic: Multi-Electron Atom
Replies: 3
Views: 172

### Re: Multi-Electron Atom

This cannot be applied to a hydrogen atom because hydrogen is not a multi electron atom. In other words, it must have more than one electron.
Wed Oct 31, 2018 11:42 pm
Forum: Resonance Structures
Replies: 5
Views: 253

Yes. This is because radicals only have one free electron instead of an electron pair.
Fri Oct 26, 2018 10:55 pm
Forum: Trends in The Periodic Table
Topic: Ionization Energy and Electron Affinity
Replies: 9
Views: 1004

### Re: Ionization Energy and Electron Affinity

Ionization energy is the amount of energy needed to remove an electron from an atom. Atoms that form cations have lower IE because they want to give away their electrons, which requires less energy. Electron affinity is the energy released when an electron is added to an atom. In simple terms, atoms...
Thu Oct 25, 2018 9:05 pm
Forum: Trends in The Periodic Table
Topic: Electron Affinity Trend
Replies: 9
Views: 370

### Re: Electron Affinity Trend

The elements on the top right of the periodic table have a negative (-) charge, which means they really want one electron to be neutral. This means they also have a high electron affinity.
Wed Oct 24, 2018 9:28 pm
Forum: Trends in The Periodic Table
Topic: Sizes of ions and neutral atoms
Replies: 4
Views: 242

### Re: Sizes of ions and neutral atoms

Since anions gain electrons while maintaining the same number of protons, the electron cloud enlarges and there is more electron-electron repulsion.
Sat Oct 20, 2018 10:51 pm
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: HW: 2.13
Replies: 1
Views: 31

### Re: HW: 2.13

We do not need to know how to depict/draw the orbitals and their orientations. It is just too complicated to draw free hand.
Sat Oct 20, 2018 10:48 pm
Forum: *Shrodinger Equation
Topic: Book Example 1.8:
Replies: 4
Views: 243

### Re: Book Example 1.8:

Dr. Lavelle said that we do not need to know how to do any calculations with Schrodinger's Equation. He just wants us to have a conceptual idea of the wave model. Calculations won't be on the test.
Wed Oct 17, 2018 8:43 pm
Forum: Heisenberg Indeterminacy (Uncertainty) Equation
Topic: Heisenberg Uncertainty Equation
Replies: 3
Views: 152

### Re: Heisenberg Uncertainty Equation

It really just depends on what the question is asking for. If it gives you the momentum (p), then solve for the uncertainty in position (x). And visa versa.
Thu Oct 11, 2018 11:31 pm
Forum: Properties of Electrons
Topic: Quantum World
Replies: 6
Views: 249

### Re: Quantum World

Correct. Frequency and wavelength are inversely proportional. As one increases, the other decreases.
Thu Oct 11, 2018 4:16 pm
Forum: Einstein Equation
Topic: Question 9; 6th edition
Replies: 3
Views: 161

### Re: Question 9; 6th edition

The standard units for frequency are Hertz (Hz). Also the standard units for wavelength is meters. You always want to convert the units to this standard when using them for calculations.
Wed Oct 10, 2018 9:51 pm
Forum: Properties of Electrons
Topic: Bohr frequency condition equation
Replies: 2
Views: 331

### Re: Bohr frequency condition equation

When an electron goes from a high energy level and drops to a lower energy level, the difference in energy (ΔE) is given off as a photon.
Thu Oct 04, 2018 11:47 pm
Forum: SI Units, Unit Conversions
Topic: 6th Edition E27, First Part
Replies: 5
Views: 261

### Re: 6th Edition E27, First Part

All you do is divide 1 by Avogadro's number. The calculation should looks like this: 1/(6.02 x 10^23).
Thu Oct 04, 2018 11:14 am
Forum: Empirical & Molecular Formulas
Topic: Molar mass and molecular weight
Replies: 3
Views: 280

### Re: Molar mass and molecular weight

Just to clarify, the molar mass measures the weight of 6.02 x 10^23 particles of a substance.
Thu Oct 04, 2018 10:52 am
Forum: Molarity, Solutions, Dilutions
Topic: measuring mols vs grams in dilutions
Replies: 2
Views: 71

### Re: measuring mols vs grams in dilutions

To find the mols in a molarity problem, you can multiply the concentration by the number of liters. Then you can convert to number of mols to grams.