## Search found 50 matches

Tue Mar 13, 2018 4:50 pm
Forum: Calculating Standard Reaction Entropies (e.g. , Using Standard Molar Entropies)
Topic: 9.31? Determining which one has a higher entropy?
Replies: 1
Views: 303

### Re: 9.31? Determining which one has a higher entropy?

Iodine vapor has a larger entropy than bromine vapor because the element iodine is larger and more electrons, therefore, there is more possibility of obtaining higher states.
Tue Mar 13, 2018 4:39 pm
Forum: Arrhenius Equation, Activation Energies, Catalysts
Topic: Catalyst
Replies: 3
Views: 193

### Re: Catalyst

there would be no difference if the catalyst was homogeneous or heterogeneous that would change how the catalyst affects the activation energy or delta G.
Tue Mar 13, 2018 4:29 pm
Forum: Administrative Questions and Class Announcements
Topic: Organic Chem on Final
Replies: 9
Views: 736

### Re: Organic Chem on Final

There would be a high possibility that the ochem discussed in class would appear in the test because for the chem14a final with Lavelle, he had a question on hemoglobin that he briefly touched upon in lecture.
Fri Mar 09, 2018 11:44 am
Forum: First Order Reactions
Topic: Help on 15.3
Replies: 7
Views: 556

### Re: Help on 15.3

The answer should be in mmol/Lxs and there's no need to change L. If anything, you should just convert mmol to mol to get the answer in mol/LxS.
Fri Mar 09, 2018 10:49 am
Forum: Zero Order Reactions
Topic: Definition of Reaction Rate
Replies: 4
Views: 394

### Re: Definition of Reaction Rate

The reaction rate is given in M/s because its the change in concentration over time where M is molarity which could also be written as mol/L.
Thu Mar 01, 2018 10:35 am
Forum: Kinetics vs. Thermodynamics Controlling a Reaction
Topic: Hw 15.1 [ENDORSED]
Replies: 7
Views: 469

### Re: Hw 15.1[ENDORSED]

yes, it depends on the mole to mole ratio in the reaction.
Thu Mar 01, 2018 10:33 am
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Cell potential
Replies: 5
Views: 289

### Re: Cell potential

The best way to determine if something is an anode or cathode, you would look if the electrons are gained or lost.
Wed Feb 28, 2018 10:28 am
Forum: Balancing Redox Reactions
Topic: Oxidation state
Replies: 4
Views: 270

### Re: Oxidation state

Yes, you have to multiply the coefficient with the charges because the charge is only for one atom/molecule so if you have multiple of the same molecules/atom then you have to multiply the charge by the coefficient.
Wed Feb 28, 2018 10:24 am
Forum: Student Social/Study Group
Topic: Post All Chemistry Jokes Here
Replies: 8039
Views: 1410488

### Re: Post All Chemistry Jokes Here

Did you know that you can cool yourself to -273.15˚C and still be 0K?
Wed Feb 21, 2018 4:47 am
Forum: Balancing Redox Reactions
Topic: 14.5a
Replies: 4
Views: 281

### Re: 14.5a

O 3 is being reduced because you have to balance the half reaction of O 3 -> O 2 which would have H 2 O on the O 2 side which would then force there to be two hydrogen ions on the ozone side which means that it would also have 2e- on that side too. Therefore, ozone is reduced since it is gaining ele...
Wed Feb 21, 2018 4:41 am
Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
Topic: #14.23 finding n [ENDORSED]
Replies: 3
Views: 224

### Re: #14.23 finding n[ENDORSED]

In this case, n is the number of electrons involved in the reaction. You can determine it by balancing the half reactions.
Wed Feb 14, 2018 5:45 am
Forum: Gibbs Free Energy Concepts and Calculations
Topic: stability and +/- delta G
Replies: 1
Views: 2094

### Re: stability and +/- delta G

When the standard Gibbs free energy of formation is considered thermodynamically stable when it is negative because the pure compound is then considered to have a lower Gibbs free energy than the Gibbs free energy of the pure elements which would mean that the pure element would have the tendency to...
Wed Feb 14, 2018 5:30 am
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: q==q
Replies: 2
Views: 205

### Re: q==q

it would all depend on which side is losing heat or not. the side that loses heat would be the one with the negative sign.
Wed Feb 14, 2018 5:27 am
Forum: Concepts & Calculations Using Second Law of Thermodynamics
Topic: 9.15 Question
Replies: 2
Views: 210

### Re: 9.15 Question

Yes, it is because you are going from liquid to ice which is the opposite of fusion. You could also think of this in terms of the molecules gaining or losing heat since the molecule is going from liquid to ice, it is losing heat so deltaH would be negative.
Wed Feb 14, 2018 5:24 am
Forum: Concepts & Calculations Using Second Law of Thermodynamics
Topic: 9.37d
Replies: 1
Views: 2859

### Re: 9.37d

There is no relationship between the number of moles and entropy for 9.37d. Instead, it is because there is a tendency for disorder based on the second law of thermodynamics, therefore, the reaction would tend towards becoming more disordered. The key word in the problem is that it says it is decomp...
Wed Feb 14, 2018 5:15 am
Forum: Concepts & Calculations Using Second Law of Thermodynamics
Topic: Calculating Degeneracy
Replies: 3
Views: 316

### Re: Calculating Degeneracy

You would calculate the degeneracy by the general formula: $\large (number of orientations)^{number of molecules}$
However, this is only true when you are given the number of molecules; if you are given the moles then you just do basic stoichiometry where 1 mole = 6.023x10^23 molecules.
Wed Feb 14, 2018 5:10 am
Forum: Thermodynamic Definitions (isochoric/isometric, isothermal, isobaric)
Topic: Laws of Thermodynamics
Replies: 2
Views: 250

### Re: Laws of Thermodynamics

First Law: The conservation of energy (deltaU = w + q) Second Law: nature of entropy increases over time; tend toward disorder (deltaS = q/t) Third Law: the entropy of perfect crystal at absolute zero is equal to 0 (eqn derived from second law) It is perfectly fine to think it the way you have howev...
Wed Feb 14, 2018 5:01 am
Forum: Thermodynamic Definitions (isochoric/isometric, isothermal, isobaric)
Topic: Relationship between Internal Energy, Temperature, Work, and Heat
Replies: 1
Views: 200

### Re: Relationship between Internal Energy, Temperature, Work, and Heat

Isothermal processes are processes at a constant temperature throughout the whole process so the temperature remains the same at the end. This would mean that the change in temperature would be the same values subtracting from each other which would equate to 0. Furthermore, the kinetic energy and p...
Wed Jan 31, 2018 4:32 am
Forum: Gibbs Free Energy Concepts and Calculations
Topic: Gibbs Free Energy [ENDORSED]
Replies: 6
Views: 777

### Re: Gibbs Free Energy[ENDORSED]

Gibbs free energy determines the favorability of a reaction whereas S shows the change in entropy/"disorder".
Wed Jan 31, 2018 4:26 am
Forum: Entropy Changes Due to Changes in Volume and Temperature
Topic: sign of entropy
Replies: 11
Views: 668

### Re: sign of entropy

You determine the sign of entropy by the direction of heat flow.
Wed Jan 31, 2018 4:24 am
Forum: Gibbs Free Energy Concepts and Calculations
Topic: Gibbs Free Energy: State Function? [ENDORSED]
Replies: 4
Views: 768

### Re: Gibbs Free Energy: State Function?[ENDORSED]

Gibbs free energy is considered a state function because Gibbs free energy is defined by the equation: G= H-TS where entropy and enthalpy are considered state functions therefore Gibb free energy is a state function.
Mon Jan 29, 2018 9:08 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: Gibbs free energy equations
Replies: 4
Views: 276

### Re: Gibbs free energy equations

They are essentially the same thing. The only difference is what element/molecule is part of the reaction.
Mon Jan 29, 2018 8:45 pm
Forum: Calculating Standard Reaction Entropies (e.g. , Using Standard Molar Entropies)
Topic: calculating specific heat
Replies: 5
Views: 319

### Re: calculating specific heat

Volume would not be necessary because specific heat capacity is in the units of Joules per grams and Celsius or Kelvin.
Mon Jan 29, 2018 8:40 pm
Forum: Calculating Standard Reaction Entropies (e.g. , Using Standard Molar Entropies)
Topic: formula for standard entropy
Replies: 5
Views: 387

### Re: formula for standard entropy

Yes, they are the same because they are both state functions.
Mon Jan 22, 2018 7:53 pm
Forum: Thermodynamic Systems (Open, Closed, Isolated)
Topic: Is there a way specific way to approach into seeing if open closed or isolated?
Replies: 9
Views: 497

### Re: Is there a way specific way to approach into seeing if open closed or isolated?

you should always consider if first energy is being transferred such as heat/work then it narrows down the possible systems to the open or closed system. after you have to consider if matter is being transferred from the system to the surrounding.
Mon Jan 22, 2018 7:51 pm
Forum: Thermodynamic Systems (Open, Closed, Isolated)
Topic: System Types
Replies: 7
Views: 405

### Re: System Types

open system = matter and energy exchanged with the surrounding
closed system = only energy exchanged with the surrounding
isolated system = no matter or energy is exchanged with the surrounding
Wed Jan 17, 2018 4:44 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Hess Law
Replies: 4
Views: 273

### Re: Hess Law

Yes, you can because enthalpy is a state function.
Wed Jan 17, 2018 4:43 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: K vs C
Replies: 6
Views: 280

### Re: K vs C

When you're calculating for the change in temperature, it doesn't matter what units of temperature it is in.
Wed Jan 17, 2018 4:41 pm
Forum: Phase Changes & Related Calculations
Topic: 8.5
Replies: 5
Views: 240

### Re: 8.5

Yes, it would be 524 + 340 because internal energy is the total store of energy in a system.
Wed Jan 17, 2018 4:34 pm
Forum: Phase Changes & Related Calculations
Topic: 8.17
Replies: 3
Views: 232

### Re: 8.17

For melting, work is negative because work is done by the system. For condensation, work is positive because work is done on the system. Furthermore, enthalpy and heat are correlated with work.
Tue Dec 05, 2017 4:42 pm
Forum: Calculating pH or pOH for Strong & Weak Acids & Bases
Topic: Difference between pH and pKa?
Replies: 4
Views: 483

### Re: Difference between pH and pKa?

pH is the measure of the concentration of hydrogen ions whereas pKa the acid dissociation constant and is able to predict what a molecule would do at specific pH.
Tue Dec 05, 2017 4:21 pm
Forum: Bronsted Acids & Bases
Topic: Bronsted vs. Lewis
Replies: 4
Views: 327

### Re: Bronsted vs. Lewis

For a bronsted-lowry acid, the acid is a electron donor, whereas in a lewis acid, it is an electron acceptor.
Fri Dec 01, 2017 11:29 am
Forum: Shape, Structure, Coordination Number, Ligands
Topic: Dentates
Replies: 6
Views: 419

### Re: Dentates

You can figure out if a molecule is monodentate, bidentate, tridentate, etc if you just draw out the lewis dot structure and see where there are lone pairs on the central atom.
Tue Nov 28, 2017 4:20 pm
Forum: Naming
Topic: Oxidation
Replies: 1
Views: 127

### Re: Oxidation

You would say Iron (II) however, you only use Ferrate (II) when you are naming the coordination compound.
Thu Nov 23, 2017 11:47 pm
Forum: Non-Equilibrium Conditions & The Reaction Quotient
Topic: Using the ICE Box
Replies: 2
Views: 215

### Re: Using the ICE Box

[] indicates the concentration of something. For example, [x] is the concentration of x in molarity.
Thu Nov 23, 2017 11:40 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Expanded octet
Replies: 6
Views: 390

### Re: Expanded octet

You know an element has an expanded octet when it has any d orbitals. This is because d orbitals are able to hold more electrons than s and p orbitals.
Thu Nov 16, 2017 12:32 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Bond Angle
Replies: 7
Views: 428

### Re: Bond Angle

Usually, you would just memorize the bond angles for the standard molecular shapes and when there is a lone pair, you know that the angles would be slightly less than the standard bond angle.
Thu Nov 16, 2017 12:26 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: 4.1 Lone pairs
Replies: 6
Views: 492

### Re: 4.1 Lone pairs

In the second diagram posted above, can someone please explain the significance of the thicker line and the dotted line? The thicker line indicates that the bond is towards us and the dotted line shows that the bond is going away from us. This is to help represent the 3D shape of the molecule which...
Fri Nov 10, 2017 10:14 pm
Forum: Lewis Structures
Topic: Shape
Replies: 5
Views: 317

### Re: Shape

As long as you have the correct electron distribution and number of electrons, the shape shouldn't matter that much to Dr. Lavelle.
Fri Nov 10, 2017 2:57 pm
Forum: Polarisability of Anions, The Polarizing Power of Cations
Topic: Polar vs nonpolar vs ionic
Replies: 11
Views: 7919

### Re: Polar vs nonpolar vs ionic

yes, it's covalent because the electronegativity difference is literally 0, where its considered nonpolar.
Mon Nov 06, 2017 9:40 pm
Forum: Octet Exceptions
Topic: Noble gas exception
Replies: 4
Views: 556

### Re: Noble gas exception

Unlike s and p orbitals, d orbitals can expand beyond the octet rule and xenon is so low on the periodic table, therefore, Xe is able to hold more than 8 electrons.
Mon Nov 06, 2017 9:34 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Midterm
Replies: 8
Views: 549

### Re: Midterm

No, only fundamentals and chapter 1-3 are going to be on the midterm.
Sun Oct 22, 2017 4:04 am
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: 4s to 3d
Replies: 5
Views: 401

### Re: 4s to 3d

The reason why the two statements contradict is due to the fact that 4s orbital is lower in energy when 3d is only partially filled however when 3d is completely filled then it becomes lower than the 4s orbital.
Sat Oct 21, 2017 9:22 pm
Forum: Electron Configurations for Multi-Electron Atoms
Topic: Periodic Table
Replies: 2
Views: 170

### Re: Periodic Table

This is because for 3d and 4s orbitals, 4s orbitals must all be filled for 3d to be completely filled too.
Sat Oct 21, 2017 5:03 pm
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: Electric Spin
Replies: 5
Views: 302

### Re: Electric Spin

When you draw the electron configuration, it will determine if the electron is spin up or down.
Sat Oct 21, 2017 4:52 pm
Forum: DeBroglie Equation
Topic: Should velocity always be in m.s. when solving? [ENDORSED]
Replies: 11
Views: 1034

### Re: Should velocity always be in m.s. when solving?[ENDORSED]

Yes, velocity should be in meters per second.
Mon Oct 16, 2017 4:21 pm
Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
Topic: Homework Problem 1.15
Replies: 4
Views: 357

### Re: Homework Problem 1.15

After you solve for frequency, you use Rydberg's formula which is v (frequency) = R($\frac{1}{n1^{2}}$-$\frac{1}{n2^{2}}$). You always assume that n1 = 1, so you just plug in Ryberg's constant, n1 and frequency to solve for n2.
Sat Oct 14, 2017 3:34 pm
Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
Topic: Change in energy of an electron [ENDORSED]
Replies: 3
Views: 248

### Re: Change in energy of an electron[ENDORSED]

When we're solving for the change in energy, it gives us the energy emitted by the electrons because of E (photon) - E (energy remove e-) = $E_{K}$ which is the energy of the electron emitted.
Sat Oct 14, 2017 3:15 pm
Forum: Photoelectric Effect
Topic: Conversions for units in work function [ENDORSED]
Replies: 2
Views: 219

### Re: Conversions for units in work function[ENDORSED]

Lavelle said in class that it would be given to us with the constant but my TA said that we should still know the conversion factors for future reference.
Wed Oct 11, 2017 4:41 pm
Forum: Properties of Light
Topic: Clarification on C=λv
Replies: 10
Views: 1681

### Re: Clarification on C=λv

Wavelength and frequency are inversely proportional to each other which means if frequency increases then wavelength decreases or vice versa.