## Search found 61 matches

Thu Mar 14, 2019 7:54 pm
Forum: First Order Reactions
Topic: Edition 6 15.23
Replies: 2
Views: 148

### Re: Edition 6 15.23

It is a second order reaction, Im pretty sure that's a typo for that problem as in 15.39 they mention the same equation (2A --> B + C) and call it a second-order reaction
Tue Mar 12, 2019 7:02 pm
Forum: Van't Hoff Equation
Topic: Van't Hoff use
Replies: 13
Views: 1083

### Re: Van't Hoff use

You would use the Van't Hoff equation when there is a temperature change and you are looking to find an equilibrium constant.
Tue Mar 12, 2019 7:00 pm
Forum: First Order Reactions
Topic: Units of Rate Constant
Replies: 5
Views: 261

### Re: Units of Rate Constant

I wouldn't always convert the time units to seconds, because often times the units depend on the context of the problem. If the problem operates in hours or minutes, then you should use those units.
Tue Mar 12, 2019 6:53 pm
Forum: General Rate Laws
Topic: Rate Laws
Replies: 8
Views: 293

### Re: Rate Laws

I think you should have a general understanding of the derivation, but you shouldn't stress yourself out over studying that, as the formulas will be on the formula sheet.
Tue Mar 12, 2019 6:50 pm
Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
Topic: Log version vs ln Version
Replies: 7
Views: 296

### Re: Log version vs ln Version

It does not matter which one you use, however I would use the ln one, since that is the one that is included on the equation sheet that we are given on tests and the final
Tue Mar 12, 2019 6:49 pm
Forum: First Order Reactions
Topic: Rate dependency
Replies: 5
Views: 244

### Re: Rate dependency

We focus a lot on initial reactants, as that tells us about the initial rate.
Tue Mar 12, 2019 6:47 pm
Forum: Second Order Reactions
Topic: amounts of reactant and its affect on rate
Replies: 6
Views: 201

### Re: amounts of reactant and its affect on rate

Yes, that is precisely what happens.
Tue Mar 12, 2019 6:46 pm
Forum: Zero Order Reactions
Topic: zero order in rate law
Replies: 7
Views: 424

### Re: zero order in rate law

In this case, you would not need to include it since any number to the power of zero is one.
Tue Mar 12, 2019 6:38 pm
Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
Topic: Largest E°cell question test #2
Replies: 4
Views: 242

### Re: Largest E°cell question test #2

You would choose the largest reducing agent as well as the largest oxidizing agent
Mon Feb 25, 2019 2:42 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: Gibbs Free Energy
Replies: 7
Views: 303

### Re: Gibbs Free Energy

When a reaction is exergonic, energy is released from the system to the surroundings, and when a reaction is endergonic, energy is taken in (absorbed) from the surroundings
Mon Feb 25, 2019 2:41 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: Gibbs Free Energy Units
Replies: 5
Views: 200

### Re: Gibbs Free Energy Units

When the question gives you a chemical reaction or units with moles, I would use kJ/mol
Mon Feb 25, 2019 2:40 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: Free Energy is a state function?
Replies: 5
Views: 184

### Re: Free Energy is a state function?

Since Gibbs Free Energy is a combination of multiple state functions, the resulting function is also a state function.
Sat Feb 09, 2019 11:06 pm
Forum: Entropy Changes Due to Changes in Volume and Temperature
Topic: Converting Celsius to Kelvin
Replies: 7
Views: 288

### Converting Celsius to Kelvin

When we are given a temperature in degrees Celsius and we are required to convert to Kelvin, are we supposed to add 273 or 273.15?
Sat Feb 09, 2019 11:02 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: formulas given on midterm
Replies: 4
Views: 172

### Re: formulas given on midterm

It will be the same equation sheet that we've been given for previous tests. It's also on his website under "Constants and Equations"
Mon Feb 04, 2019 1:57 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Units
Replies: 7
Views: 269

### Re: Units

It would be J/C*mol
Mon Feb 04, 2019 1:55 pm
Forum: Phase Changes & Related Calculations
Topic: Type of systems
Replies: 12
Views: 588

### Re: Type of systems

No, because they are two distinct types of systems. An isolated system does not allow energy or matter transfer, whereas a closed system allows energy transfer.
Mon Feb 04, 2019 1:52 pm
Forum: Thermodynamic Systems (Open, Closed, Isolated)
Topic: Midterm [ENDORSED]
Replies: 49
Views: 2131

### Re: Midterm[ENDORSED]

I would say definitely doing the homework problems and reading the textbook as well as class notes are the best way to prepare.
Sun Jan 27, 2019 10:47 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: Heat Capacity
Replies: 8
Views: 285

### Re: Heat Capacity

Heat Capacity is extensive
Sun Jan 27, 2019 10:44 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: pKa vs. pH
Replies: 15
Views: 2263

### Re: pKa vs. pH

This is because pKa is a the -log of Ka, the acid dissociation constant, it is a measure of acid strength. pH, on the other hand is a measure of the concentration of H+ ions.
Sun Jan 27, 2019 10:42 pm
Forum: Administrative Questions and Class Announcements
Topic: Advice from a Medical Student [ENDORSED]
Replies: 221
Views: 115707

### Re: Advice from a Medical Student[ENDORSED]

Sun Jan 27, 2019 10:40 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Standard Temperature
Replies: 7
Views: 268

### Re: Standard Temperature

I believe it is 25 degrees celsius, unless the problem says differently
Sun Jan 27, 2019 10:38 pm
Forum: Phase Changes & Related Calculations
Topic: Enthalpy signs
Replies: 13
Views: 484

### Re: Enthalpy signs

When Delta H is positive, it's endothermic and when it's negative, it's exothermic
Tue Jan 22, 2019 6:02 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Salt on Test 1
Replies: 5
Views: 206

### Re: Salt on Test 1

Yes, salts are going to be on the test, since they were on the lecture, meaning they are fair game for the test.
Tue Jan 22, 2019 5:45 pm
Forum: Non-Equilibrium Conditions & The Reaction Quotient
Topic: ignoring x
Replies: 10
Views: 327

### Re: ignoring x

You should ignore it when k is equal to or less than 10^-3
Tue Jan 22, 2019 5:41 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: What Happens to a Reaction if Inert Gas is Added?
Replies: 7
Views: 627

### Re: What Happens to a Reaction if Inert Gas is Added?

The reaction does not change if an inert gas is added
Sat Jan 12, 2019 5:01 pm
Forum: Non-Equilibrium Conditions & The Reaction Quotient
Topic: defining Q
Replies: 6
Views: 283

### Re: defining Q

Yes, it will continue until it reaches dynamic equilibrium.
Sat Jan 12, 2019 4:58 pm
Forum: Non-Equilibrium Conditions & The Reaction Quotient
Topic: Example in Class
Replies: 7
Views: 242

### Re: Example in Class

This is because the system would react in order to favor the production of NH3. Since you're removing NH3, it would allow the reactants to form more product
Sat Jan 12, 2019 4:53 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Solids and Liquids in Rxn
Replies: 6
Views: 280

### Re: Solids and Liquids in Rxn

If the reaction was only made up of solids and liquids, then K would be equal to 1.
Thu Dec 06, 2018 3:24 pm
Forum: Naming
Topic: Name to Formula
Replies: 1
Views: 124

### Name to Formula

When going from the name to formula, if there are multiple ligands, how do we know which order to put them in for the formula?
Thu Dec 06, 2018 3:23 pm
Forum: Naming
Topic: Spelling
Replies: 4
Views: 184

### Re: Spelling

It is spelled ammine.
Wed Dec 05, 2018 9:20 pm
Forum: Naming
Topic: cyanido vs cyano
Replies: 1
Views: 118

### cyanido vs cyano

When do we use cyanido vs cyano in naming?

For 9C.1 in the book, I thought the name of [Fe(CN)6]4- was hexacyanidoferrate(II), but the answer key has it as hexacyanoferrate(II).
Sun Dec 02, 2018 9:42 pm
Forum: Hybridization
Topic: Hybridization Notation
Replies: 10
Views: 349

### Re: Hybridization Notation

both ways of writing it are correct
Sun Dec 02, 2018 9:38 pm
Forum: Hybridization
Topic: Pi bonds in triple bond
Replies: 17
Views: 864

### Re: Pi bonds in triple bond

There is one sigma bond and two pi bonds in a triple bond.
Sun Dec 02, 2018 9:31 pm
Forum: Hybridization
Topic: S Hybridization?
Replies: 5
Views: 209

### Re: S Hybridization?

Yes, however we don't really use s hybridization since we focus on more complex molecules that typically involve p orbitals as well.
Sun Dec 02, 2018 9:27 pm
Forum: Hybridization
Topic: CH2O hybridization
Replies: 9
Views: 8352

### Re: CH2O hybridization

Since there are 3 hybrid orbitals and 3 regions of electron density, the hybridization is sp2.
Sun Dec 02, 2018 9:23 pm
Forum: Hybridization
Topic: lone pairs
Replies: 20
Views: 713

### Re: lone pairs

Yes, Lone pairs do indeed count as an area of electron density, so yes, they count for hybridization.
Wed Nov 28, 2018 9:01 pm
Forum: Hybridization
Topic: Sp3d or dsp3
Replies: 4
Views: 693

### Re: Sp3d or dsp3

I don't think it matters which order it is written, but I prefer to do sp3d
Mon Nov 26, 2018 9:02 pm
Forum: Dipole Moments
Topic: TEST 3: Polarity
Replies: 7
Views: 287

### Re: TEST 3: Polarity

I believe the arrow should always point to the negative, and thats the way Lavelle did it in class, so I would probably do it that way
Mon Nov 26, 2018 8:56 pm
Forum: Formal Charge and Oxidation Numbers
Topic: Formal Charge
Replies: 8
Views: 2634

### Re: Formal Charge

The one I find the most helpful is # of valence electrons - (Lone electrons + Bonds)
Mon Nov 26, 2018 8:53 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Can an octahedral be polar?
Replies: 4
Views: 460

### Re: Can an octahedral be polar?

No, an octahedral cannot be polar, because the shape is symmetric
Mon Nov 19, 2018 11:55 am
Forum: Ionic & Covalent Bonds
Topic: delta positive delta negative
Replies: 15
Views: 845

### Re: delta positive delta negative

Delta negative is the one that accepts electrons, while Delta positive is the one that gives electrons
Mon Nov 19, 2018 11:40 am
Forum: Determining Molecular Shape (VSEPR)
Topic: Bond Angles in 7E 2E.13.b
Replies: 4
Views: 167

### Re: Bond Angles in 7E 2E.13.b

Double bonds don't have nearly the same effect on bond angles that lone pairs do. Double bonds and single bonds both are the same electron density thus it doesn't affect the bond angle
Mon Nov 19, 2018 11:35 am
Forum: Determining Molecular Shape (VSEPR)
Topic: Rotation from Sigma and Pi bonds
Replies: 2
Views: 148

### Re: Rotation from Sigma and Pi bonds

Sigma bonds have their electron density along the bond axis, while pi bonds have their electron density above and below the bond axis. Therefore, pi bonds cannot rotate the same way as sigma bonds since rotation would break the pi bond interaction.
Mon Nov 19, 2018 11:33 am
Forum: Determining Molecular Shape (VSEPR)
Topic: Bond Angle
Replies: 8
Views: 328

### Bond Angle

Is there a set degree amount a lone pair causes bond angles to change? I know it lessens the angles, but is there a specific amount?
Mon Nov 19, 2018 11:25 am
Forum: Determining Molecular Shape (VSEPR)
Topic: Dipole moments
Replies: 8
Views: 2131

### Re: Dipole moments

As long as each dipole moment is equal in charge and opposite in direction, then they will cancel each other out.
Mon Nov 05, 2018 3:37 pm
Forum: Formal Charge and Oxidation Numbers
Topic: Why does PCl5 break the Octet Rule?
Replies: 8
Views: 936

### Re: Why does PCl5 break the Octet Rule?

This is because Phosphorous is in the 3rd energy level, which means it can access the d-orbitals in order to have an expanded octet and form more than 4 bonds.
Mon Nov 05, 2018 12:41 am
Forum: Sigma & Pi Bonds
Topic: Midterm1
Replies: 10
Views: 621

### Re: Midterm1

That information wasn't covered in the sections we are required to know for the midterm, nor have we gone over the material in class, so they will not be on the midterm.
Mon Nov 05, 2018 12:36 am
Forum: Formal Charge and Oxidation Numbers
Topic: Alternative version of formula
Replies: 7
Views: 618

### Re: Alternative version of formula

Yes, your formula work, but I prefer to use FC = Valence Electrons - (Lone Electrons + Shared Electrons/2)
Mon Nov 05, 2018 12:33 am
Forum: DeBroglie Equation
Topic: DeBroglie Equation Units
Replies: 4
Views: 469

### Re: DeBroglie Equation Units

All of the equations use SI units in order for them to all follow the same units. That's why its in meters, because meters is the SI unit for measurement of length.
Mon Nov 05, 2018 12:32 am
Forum: Properties of Light
Topic: Practice Midterm 8b
Replies: 3
Views: 294

### Re: Practice Midterm 8b

Make sure to use wavelength = h/p in order to find the velocity of the electron. Once you find the velocity, you then plug the values into KE = E - work function in order to solve for E. Once you find E, you use E = hV, in order to solve for frequency.
Mon Nov 05, 2018 12:13 am
Forum: Resonance Structures
Topic: Bond Lengths
Replies: 7
Views: 419

### Bond Lengths

When there are double bonds in a structure, for example the Nitrate ion, NO3 2-, and chemists observe the actual N-O bond length, is every bond length the same length, despite the fact that we draw it with one double bond and two single bonds indicating that they are different lengths?
Sun Nov 04, 2018 6:55 pm
Forum: Administrative Questions and Class Announcements
Topic: MIDTERM PRACTICE - Garlic Bread Review Session [ENDORSED]
Replies: 121
Views: 7070

### Re: MIDTERM PRACTICE - Garlic Bread Review Session[ENDORSED]

For number 11, part b why would delta E be a negative value? If the problem is asking for the change in energy from n = 6 to n = 4, and the formula is
E = -hR(1/n1^2 - 1/n2^2), the energy released from n = 6 to n = 4 equals 7.5689 x 10^-20 J. So, why is the answer negative?
Sun Oct 28, 2018 9:44 pm
Forum: Lewis Structures
Topic: General Q on Lewis Structures
Replies: 2
Views: 85

### General Q on Lewis Structures

Is there a difference between using a line to represent bonds rather than 2 dots? Is there a chemical difference?
Sun Oct 28, 2018 9:39 pm
Forum: Electron Configurations for Multi-Electron Atoms
Topic: px,py,pz???
Replies: 6
Views: 774

### Re: px,py,pz???

px, py, and pz are helpful also to remember to follow Hund's Rule where every orbital in a subshell is singly occupied with one electron before any one orbital is doubly occupied. Thus 1px, 1py, 1pz instead of 2px, 1py.
Sun Oct 28, 2018 9:27 pm
Forum: Lewis Structures
Topic: octets
Replies: 13
Views: 497

### Re: octets

An electron must have a full octet before It goes to the next energy level. Hydrogen and Helium are satisfied with only two electrons in their outermost valence shell.
Mon Oct 22, 2018 11:45 am
Forum: Properties of Electrons
Topic: Test on Wednesday
Replies: 3
Views: 244

### Re: Test on Wednesday

The test will only cover material that we went over in class until last Friday's lecture. The lecture on Monday will not be on the upcoming test.
Mon Oct 22, 2018 11:45 am
Forum: Properties of Light
Topic: Test 2 Equations
Replies: 14
Views: 530

### Re: Test 2 Equations

I believe we will be given the same first sheet with many equations and constants as we were given during the first test.
Mon Oct 22, 2018 11:42 am
Forum: Properties of Light
Topic: TEST 2
Replies: 7
Views: 407

### Re: TEST 2

I believe we will be given the same first sheet as we were during the first test where it provides us with many equations and constants.
Sun Oct 14, 2018 6:57 pm
Forum: Properties of Electrons
Topic: Energy Q
Replies: 4
Views: 152

### Energy Q

What does it mean that energy is quantized?
Sun Oct 14, 2018 6:53 pm
Forum: Properties of Electrons
Topic: Electron Question
Replies: 6
Views: 290

### Electron Question

Why can an electron only exist on specific energy levels?
Sun Oct 14, 2018 6:45 pm
Forum: Properties of Electrons
Topic: Energy Level Question
Replies: 4
Views: 152

### Energy Level Question

How does the wavelength of an electron change as it jumps to a new energy level?