## Search found 50 matches

Sun Mar 18, 2018 10:31 pm
Forum: General Science Questions
Topic: Grade
Replies: 8
Views: 937

### Re: Grade

I think the class is graded.
Sun Mar 18, 2018 2:59 pm
Forum: Student Social/Study Group
Topic: Post All Chemistry Jokes Here
Replies: 8039
Views: 1411080

### Re: Post All Chemistry Jokes Here

What do you do with a dead chemist?
Barium
Sun Mar 18, 2018 2:58 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: Putting an Ice cube into a glass of water
Replies: 4
Views: 850

### Re: Putting an Ice cube into a glass of water

Yes, need both deltaH fusion and deltaH for warming up liquid water to final temp.
Sun Mar 18, 2018 2:55 pm
Forum: Student Social/Study Group
Topic: Final
Replies: 11
Views: 1239

### Re: Final

Yeah was confused about that as well. Don't you need two unknown variables for a function?
Sun Mar 18, 2018 2:42 pm
Forum: Van't Hoff Equation
Topic: Van't Hoff
Replies: 9
Views: 642

### Re: Van't Hoff

I think that this equation can be used for different temperatures and also different Ea as well.
Sun Mar 18, 2018 2:38 pm
Forum: Thermodynamic Definitions (isochoric/isometric, isothermal, isobaric)
Topic: isothermal = no internal energy change
Replies: 4
Views: 433

### Re: isothermal = no internal energy change

Only isothermal reactions have u = 0 so q = -w. T being 0 does not always mean that q = 0. Isothermal reaction is when T = 0. This is because as work may be done by or done on the system, there is a supply or removal of heat from the system so that T = 0 and that the internal energy of the system re...
Sun Mar 18, 2018 2:32 pm
Forum: Student Social/Study Group
Topic: Post All Chemistry Jokes Here
Replies: 8039
Views: 1411080

### Re: Post All Chemistry Jokes Here

Making bad chemistry jokes because all the good ones Argon
Sun Mar 18, 2018 2:31 pm
Forum: Student Social/Study Group
Topic: Post All Chemistry Jokes Here
Replies: 8039
Views: 1411080

### Re: Post All Chemistry Jokes Here

What is the chemical formula for "coffee"?
CoFe2
Sat Mar 17, 2018 8:47 am
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: What has greater residual entropy at 0K?
Replies: 5
Views: 523

### Re: What has greater residual entropy at 0K?

I think NO has resonance meaning that there has multiple possible structures. So there are more possible structures for NO than for BF3 which is why there is more residual entropy.
Fri Mar 16, 2018 4:51 pm
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: What has greater residual entropy at 0K?
Replies: 5
Views: 523

### Re: What has greater residual entropy at 0K?

Things to look for when comparing entropy. The following will usually have higher entropy:
Gases in larger volume>smaller volume
Gases>liquids>solids
Larger mass>smaller mass
Greater complexity>less complex
Fri Mar 16, 2018 4:48 pm
Forum: General Rate Laws
Topic: Writing out states for rate laws
Replies: 4
Views: 516

### Re: Writing out states for rate laws

I'm pretty sure that we don't have to.
Fri Mar 16, 2018 4:45 pm
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: What has greater residual entropy at 0K?
Replies: 5
Views: 523

### Re: What has greater residual entropy at 0K?

Yes, you should draw out the lewis structures. If you do, you will see that NO is non-symmetric and has resonance. BF3 is symmetric and only has one configuration, so NO should have greater residual entropy.
Fri Mar 16, 2018 4:06 pm
Forum: Reaction Mechanisms, Reaction Profiles
Topic: Substitution Reactions
Replies: 2
Views: 220

### Re: Substitution Reactions

What do we have to know about the Sn2 organic reaction substitution nucleophile 2? I get that an atom is replaced by another, but what is the nucleophile?
Fri Mar 16, 2018 4:01 pm
Forum: Third Law of Thermodynamics (For a Unique Ground State (W=1): S -> 0 as T -> 0) and Calculations Using Boltzmann Equation for Entropy
Topic: Microstate Determination
Replies: 2
Views: 285

### Re: Microstate Determination

If the problem asks for calculating the number of microstates for one mole, make sure you use Avogadro's number for the number of atoms as the power.
Fri Mar 16, 2018 3:48 pm
Forum: Arrhenius Equation, Activation Energies, Catalysts
Topic: Collision Theory
Replies: 3
Views: 296

### Re: Collision Theory

For the activated complex model, I think we need to know how to identify the slowest step (rate determinant step), which will be the highest peak. Additionally, to know the position of the atoms in a reaction as it progresses, like if the transition state will have atoms closer to the position that ...
Fri Mar 16, 2018 3:40 pm
Forum: Arrhenius Equation, Activation Energies, Catalysts
Topic: Collision Theory
Replies: 3
Views: 296

### Re: Collision Theory

I think we need to know the 3 concepts
(1) molecules must collide
(2) must collide with sufficient energy to break bonds-overcome energy barrier or activation energy
(3) must collide in the correct orientation
Wed Mar 14, 2018 7:03 pm
Forum: Reaction Mechanisms, Reaction Profiles
Topic: Slow Step
Replies: 4
Views: 246

### Re: Slow Step

I don't think the second step would be considered to be in equilibrium. If the first step is the slow step, the second step would just proceed normally. The rate is determined by the slow step so just the first. The reason why when the second step is slower, that the first step is considered to be i...
Wed Mar 14, 2018 4:09 pm
Forum: *Enzyme Kinetics
Topic: Catalysts and Intermediates
Replies: 5
Views: 816

### Re: Catalysts and Intermediates

The main difference is that catalysts occur in the beginning and the end of the reaction. They may both be cancelled out, but catalysts occur in the beginning and may be consumed in one of the elementary steps, but in the end the catalyst will reform as it was in the beginning. An intermediate will ...
Wed Mar 14, 2018 4:05 pm
Forum: Reaction Mechanisms, Reaction Profiles
Topic: Elementary reactions
Replies: 6
Views: 392

### Re: Elementary reactions

It says in the lecture notes that the rate law for each elementary step follows directly from molecularity, which is the number of species. Because of that, we can determine that an elementary step with a first order rate law is unimolecular meaning one species, a second order rate law is bimolecula...
Wed Mar 14, 2018 3:58 pm
Forum: Arrhenius Equation, Activation Energies, Catalysts
Topic: Chapter 15.12?
Replies: 4
Views: 248

### Re: Chapter 15.12?

I think that the equation is lnk = -Ea/RT + lnA with the negative sign.
Wed Mar 14, 2018 3:57 pm
Forum: Arrhenius Equation, Activation Energies, Catalysts
Topic: Chapter 15.12?
Replies: 4
Views: 248

### Re: Chapter 15.12?

Also know that there in a graph with lnk and 1/T as its axes, the slope will be linear and will equal -Ea/R.
Wed Mar 14, 2018 3:39 pm
Forum: Arrhenius Equation, Activation Energies, Catalysts
Topic: Catalysts vs Intermediates
Replies: 2
Views: 227

### Re: Catalysts vs Intermediates

The catalyst usually appears in the beginning of the reaction and the end of the reaction. So if it is consumed, it will reappear in the end. The intermediate does not appear in the beginning or the end of the reaction-it is both formed and consumed in the middle of the reaction.
Wed Mar 14, 2018 3:34 pm
Forum: General Rate Laws
Topic: Test #3 Q3
Replies: 3
Views: 623

### Re: Test #3 Q3

When we use the (change in concentration)/(change in time) equation does that mean that it is 1st order?
Wed Mar 14, 2018 3:28 pm
Forum: Kinetics vs. Thermodynamics Controlling a Reaction
Topic: units
Replies: 4
Views: 436

### Re: units

Also for kinetics specifically make sure you know that the units for a rate constant can vary depending on the order of the equation. The rate should be in mol/L*s so you can determine the rate constant from there depending on the order. Or we might have to get the order of a reaction when we are gi...
Wed Mar 14, 2018 3:20 pm
Forum: *Amines
Topic: amine
Replies: 2
Views: 502

### amine

Today in lecture, Dr. Lavelle said that for amines each atom that the N is bonded to could be replaced with a CH3, so it was drawn a single N with a lone pair and three CH3 groups. But in my notes it shows a that the functional group has a NH2. Does the N not have to be bonded to two H atoms?
Wed Mar 14, 2018 3:14 pm
Forum: *Alkanes
Topic: Naming compounds
Replies: 3
Views: 2873

### Re: Naming compounds

Will we be required to draw the functional groups?
Tue Mar 06, 2018 9:06 am
Forum: Method of Initial Rates (To Determine n and k)
Topic: K'
Replies: 7
Views: 449

### Re: K'

Sorry, the equation is k = k'/([B initial]m [C initial]l)
Tue Mar 06, 2018 9:03 am
Forum: Method of Initial Rates (To Determine n and k)
Topic: K'
Replies: 7
Views: 449

### Re: K'

There is also an equation if you are solving for k' for rate = k [A] [C], k = k'/[initial B]m [initial C]l[/b] when [B] and [C] are in surplus,
Tue Feb 20, 2018 11:32 am
Forum: Balancing Redox Reactions
Topic: Balancing REDOX reactions
Replies: 5
Views: 332

### Re: Balancing REDOX reactions

Because Eo is an intensive property, voltage difference is the same and does not depend on how many times the reaction occurs.
Tue Feb 20, 2018 11:27 am
Forum: Balancing Redox Reactions
Topic: Anode vs Cathode and their Equations
Replies: 2
Views: 211

### Re: Anode vs Cathode and their Equations

The anode has the element that is most likely oxidized while the cathode has the element that is reduced. The half-reaction with the element that is most likely reduced has a higher standard potential (more V) so it forms the cathode. The half-reaction with the element that is less likely reduced ha...
Sun Dec 10, 2017 9:05 pm
Forum: Conjugate Acids & Bases
Topic: % Ionization [ENDORSED]
Replies: 3
Views: 566

### Re: % Ionization[ENDORSED]

Is the hydrogen proton concentration the same as the conjugate base concentration for an acid?
Sun Dec 10, 2017 9:02 pm
Forum: Lewis Acids & Bases
Topic: Strength [ENDORSED]
Replies: 5
Views: 665

### Re: Strength[ENDORSED]

Stronger acids tend to have a greater percent ionization because its conjugate base will tend to stay in that form and be more stable.
Sun Dec 10, 2017 8:53 pm
Forum: Properties & Structures of Inorganic & Organic Acids
Topic: Strong Bases? [ENDORSED]
Replies: 2
Views: 490

### Re: Strong Bases?[ENDORSED]

Yes, strong bases have very stable conjugate acids because the strength of a base can be measured in how likely the conjugate acid is to stay an acid. This is because a strong base completely dissociates
Sun Dec 10, 2017 8:44 pm
Forum: Amphoteric Compounds
Topic: Amphoteric [ENDORSED]
Replies: 4
Views: 583

### Re: Amphoteric[ENDORSED]

Yes, amphiprotic compounds are included in amphoteric compounds because they can act as an acid or base. Amphiprotic compounds act as acids or bases by either donating or receiving protons.
Sun Dec 03, 2017 11:42 pm
Forum: Ideal Gases
Topic: Q and K [ENDORSED]
Replies: 35
Views: 1677

### Re: Q and K[ENDORSED]

Q is the formula for concentration of products/reactants at any time. K is the ratio of products to reactants at equilibrium and they use the same formulas
Sun Dec 03, 2017 11:39 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Chemical Equilibrium
Replies: 3
Views: 302

### Re: Chemical Equilibrium

The solvent is the material that contains the solute and concentration change in the solvent is assumed to be negligible, so it is not included in the chemical equilibrium expressions
Sun Nov 26, 2017 10:46 pm
Forum: Hybridization
Topic: 4.41
Replies: 4
Views: 751

### Re: 4.41

I think a good way to look at it is also remembering the regions of electron density. Sp2 has three regions of electron density so it is trigonal planar. Sp has two regions of electron density so it is linear
Sun Nov 26, 2017 10:38 pm
Forum: Hybridization
Topic: Filling the hybrid orbitals?
Replies: 12
Views: 859

### Re: Filling the hybrid orbitals?

Doesn't sp^2 hybridization have three regions of electron density?
Sun Nov 19, 2017 11:28 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Octahedral vs Trigonal Bypyramidal family
Replies: 3
Views: 319

### Re: Octahedral vs Trigonal Bypyramidal family

Yes pretty sure there is axial and equatorial plane. Lone pairs start occupying axial planes to make square pyramidal and square planar.
Sun Nov 19, 2017 11:17 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Predicting bond angles
Replies: 4
Views: 369

### Re: Predicting bond angles

After figuring out how many bonding areas there are, you still need to distinguish from atoms and lone pairs. Can't just rely on geometric shape to find bond angles because lone pairs affect the angles but only atoms are used to name the shape
Sun Nov 12, 2017 9:49 pm
Forum: Formal Charge and Oxidation Numbers
Topic: Formal Charge and stability [ENDORSED]
Replies: 7
Views: 4100

### Re: Formal Charge and stability[ENDORSED]

Also important to note that the most stable structures are those that have lower energy. Atoms form bonds in order to reach a state of lower energy which is why it takes energy to break bonds.
Sun Nov 12, 2017 6:15 pm
Forum: Formal Charge and Oxidation Numbers
Topic: Formal Charge
Replies: 8
Views: 611

### Re: Formal Charge

It is also really rare to have a formal charge of -2 in a stable lewis structure, so if the formal charge ends up being -2, try reducing the formal charge by adding bonds or drawing them a different way.
Sun Nov 05, 2017 11:53 pm
Forum: *Molecular Orbital Theory (Bond Order, Diamagnetism, Paramagnetism)
Topic: Paramagnetic- Q3F 2013 Final
Replies: 3
Views: 525

### Re: Paramagnetic- Q3F 2013 Final

Does the first electron to enter an orbital always have an upwards magnetic spin?
Sun Nov 05, 2017 11:48 pm
Forum: Hybridization
Topic: Atomic orbitals [ENDORSED]
Replies: 3
Views: 432

### Re: Atomic orbitals[ENDORSED]

It's also interesting because s has a magnetic quantum number of 0. And there's only one orbital for s because it is the orbital with symmetrical e- density. However p would have magnetic quantum numbers of -1, 0, and 1 because it has orbitals in the orientation of xy, yz. xz that line up on those n...
Sun Oct 29, 2017 11:10 pm
Forum: Hybridization
Topic: Principle Quantum Number in D-Block [ENDORSED]
Replies: 4
Views: 463

### Re: Principle Quantum Number in D-Block[ENDORSED]

Why do electrons fill up the 4s shells before the 3d shells in Potassium and Scandium if 3d is lower energy?
Sun Oct 29, 2017 11:04 pm
Forum: *Molecular Orbital Theory (Bond Order, Diamagnetism, Paramagnetism)
Topic: Relationship between Electronegativity and Orbital Energy
Replies: 4
Views: 1408

### Re: Relationship between Electronegativity and Orbital Energy

I think that the more electronegative an atom is, the more easy it is to attract electrons. This goes up in a diagonal trend, so increase as group goes to the right and as period goes up, disregarding noble gases. The atomic radius will increase as group goes to the left and period goes down. There ...
Sun Oct 15, 2017 4:18 pm
Forum: Properties of Light
Topic: Understanding the Rydberg Formula [ENDORSED]
Replies: 6
Views: 562

### Re: Understanding the Rydberg Formula[ENDORSED]

Frequency should always be positive so the negative sign is used when the change between initial and final is negative
Sun Oct 15, 2017 4:13 pm
Forum: Properties of Light
Topic: How to use the Rydberg Formula? [ENDORSED]
Replies: 6
Views: 574

### Re: How to use the Rydberg Formula?[ENDORSED]

I'm pretty sure all equations that we need on the test will be provided on the equations sheet. It is negative because some people switch the n1 with the n2 and to keep frequency as a positive number, they use the negative sign.
Tue Oct 03, 2017 10:46 pm
Forum: Balancing Chemical Reactions
Topic: Balancing Process
Replies: 11
Views: 652

### Re: Balancing Process

Yes I think it's just a guideline to follow to make it easier. I think when he says balance first the element that appears the least, he means the amount of times in the equation, not the number of moles.
Tue Oct 03, 2017 10:34 pm
Forum: Significant Figures
Topic: All students read this sig fig post [ENDORSED]
Replies: 131
Views: 17145

### Re: All students read this sig fig post[ENDORSED]

Hi, when there are numerous instances in a problem when multiplication/division is needed, can we just find the final answer and do the sig fig in the end after all the multiplication? Also, is a problem with both addition and multiplication different because you have to recount the sig figs after ...

Go to advanced search