Search found 68 matches

Sun Mar 17, 2019 10:24 pm
Forum: Thermodynamic Definitions (isochoric/isometric, isothermal, isobaric)
Topic: Bomb Calorimeter
Replies: 2
Views: 449

Re: Bomb Calorimeter

I thought so because the pressure and volume is constant!
Sat Mar 16, 2019 11:53 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: K
Replies: 3
Views: 218

Re: K

K is the equilibrium constant so yes!
Wed Mar 13, 2019 8:12 pm
Forum: Kinetics vs. Thermodynamics Controlling a Reaction
Topic: rate constants at equilibrium
Replies: 2
Views: 209

rate constants at equilibrium

When the reaction is at equilibrium, are the rate constants of the forward and reverse equal? In my discussion notes I have
K=1 so k=k' ?
Mon Mar 11, 2019 6:13 pm
Forum: Second Order Reactions
Topic: error for 15.39 sixth edition
Replies: 1
Views: 64

error for 15.39 sixth edition

So the question asks to determine the time required for each reaction to take place. For part 1 it gives the reaction 2A ---> B + C. It also says these reactions are second order. If it is second order isn't the equation supposed to be 1/[A]t = 2kt + 1/[A]initial since there is a coefficient of 2 in...
Sun Mar 10, 2019 10:09 pm
Forum: First Order Reactions
Topic: stoichiometry
Replies: 2
Views: 75

stoichiometry

How does stoichiometry come into kinetics? There are some questions in the book that ask about finding k constants when they give you the initial concentration of A but then give you a concentration of B at the some point in time?
Sun Mar 10, 2019 9:32 pm
Forum: Second Order Reactions
Topic: negative in front of k
Replies: 1
Views: 55

negative in front of k

I dont understand what happens to the negative in front of k for integrated 2nd order rate laws??
Sat Mar 09, 2019 9:09 pm
Forum: General Rate Laws
Topic: integrals
Replies: 8
Views: 158

integrals

can someone please explain integrals to me? I never took calculus or ap calculus and I am super confused? Why does ln come in?
Tue Mar 05, 2019 10:09 am
Forum: General Rate Laws
Topic: Order Reaction/Rate Law
Replies: 3
Views: 65

Re: Order Reaction/Rate Law

I think you use the rate law to find m and n which represent the order of the reactant.
Tue Mar 05, 2019 10:07 am
Forum: General Rate Laws
Topic: rate and dependence on [R]
Replies: 2
Views: 50

Re: rate and dependence on [R]

I think so since the initial concentrations are the reactant concentrations
Tue Mar 05, 2019 10:06 am
Forum: General Rate Laws
Topic: K and k [ENDORSED]
Replies: 2
Views: 84

K and k[ENDORSED]

What is the difference between capital K and lowercase k??
Tue Feb 26, 2019 12:10 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Cell diagram help.
Replies: 2
Views: 66

Re: Cell diagram help.

You add an inert metal when the ions of the same element are in the same solution or when you have a gas and ion in the same solution
Mon Feb 25, 2019 6:03 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: 6th edition 14.31
Replies: 1
Views: 66

6th edition 14.31

In the solutions manual for part d it says NO3- is the oxidizing agent and it is in the cathode, but how is this possible if it goes from NO3- to No2. Is it not losing an electron, therefore it is oxidizing so it is part of the anode??
Mon Feb 25, 2019 4:26 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: reversing reaction [ENDORSED]
Replies: 3
Views: 93

reversing reaction[ENDORSED]

how come for some of the homework problems in the solutions manual they reverse the reaction. What is the significance of this?
Tue Feb 19, 2019 10:31 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: O2
Replies: 5
Views: 88

Re: O2

O2 is a naturally occurring compound.
Wed Feb 13, 2019 10:51 am
Forum: Entropy Changes Due to Changes in Volume and Temperature
Topic: delta S
Replies: 7
Views: 179

delta S

under what conditions does delta S = 0
Wed Feb 13, 2019 10:07 am
Forum: Calculating Work of Expansion
Topic: Hotdog Midterm #6
Replies: 2
Views: 112

Hotdog Midterm #6

If you start at 100 L and end at 100 L then volume for the entire process is unchanging so if delta V is equal to 0 doesnt work = 0??
Wed Feb 13, 2019 12:54 am
Forum: Thermodynamic Definitions (isochoric/isometric, isothermal, isobaric)
Topic: Isothermal and reversible
Replies: 2
Views: 92

Re: Isothermal and reversible

One of the TA's in the review session said it is possible to have a irreversible isothermal expansion but we do not need to worry about in this class.
Tue Feb 12, 2019 10:36 pm
Forum: Entropy Changes Due to Changes in Volume and Temperature
Topic: clarification
Replies: 1
Views: 75

clarification

To clarify, when the reaction is reversible delta S is 0?
Tue Feb 12, 2019 11:46 am
Forum: Administrative Questions and Class Announcements
Replies: 179
Views: 8502

Can someone explain how to do #1. I found the heat gained by the water but without the final temperature of the metal how would I find the specific heat??
Tue Feb 12, 2019 10:30 am
Forum: Administrative Questions and Class Announcements
Topic: Lyndon's HOTDOG MIDTERM REVIEW SESSION!! FINALLY!
Replies: 49
Views: 3229

Re: Lyndon's HOTDOG MIDTERM REVIEW SESSION!! FINALLY!

Mya Majewski 1L wrote:For #6, how did we get w=9.119 x 10^3 J?

For the first part it says you preform an isobaric compression to 10L. Isobaric is constant pressure so work is equal to -PdV. So pressure is 1.00 atm and the change of V is 10-100 so -90. This comes to -90 L.atm you then convert this to Joules
Sun Feb 10, 2019 10:26 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: Heat Capacity
Replies: 4
Views: 96

Re: Heat Capacity

Yes it just depends what units you are working with!
Sun Feb 10, 2019 10:25 pm
Forum: Entropy Changes Due to Changes in Volume and Temperature
Topic: Occupying positions
Replies: 2
Views: 73

Re: Occupying positions

In a solid the molecules are not as free to move around as in a liquid, because in a solid molecules are more tightly packed so they occupy less positions
Wed Feb 06, 2019 5:48 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: 6th edition 6.41
Replies: 1
Views: 45

6th edition 6.41

In the solutions manual they add the reaction enthalpy of fusion to the equation q=mCdeltaT when calculating heat of the ice cube. Can someone please explain why this is done?
Sun Feb 03, 2019 5:38 pm
Forum: Thermodynamic Systems (Open, Closed, Isolated)
Topic: HW
Replies: 3
Views: 75

Re: HW

I think you can still do hw on thermochemistry since we recently started to cover thermodynamics.
Sat Feb 02, 2019 9:28 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: delta H vs q
Replies: 9
Views: 172

Re: delta H vs q

delta H is change in enthalpy and q is heat added to the system
Sat Feb 02, 2019 9:25 pm
Forum: Calculating Work of Expansion
Topic: Calculus in Chem
Replies: 1
Views: 51

Calculus in Chem

Hi! I never took calculus in high school let alone AP calculus. Can someone explain to me why we need integrals? I know Professor Lavelle answered this question in class but I didn't get the answer. Thank you!
Thu Jan 24, 2019 11:23 am
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Acid/ Base
Replies: 1
Views: 51

Re: Acid/ Base

Ka is the constant relating to acids and its dissociation while Kb is the concentration related to bases and their ionization
Thu Jan 24, 2019 11:21 am
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: pKa vs. pH
Replies: 15
Views: 543

Re: pKa vs. pH

pKa is a the -log of the acid dissociation constant, it is a measure of acid strength. pH is a measure of the concentration of H+ ions.
Thu Jan 24, 2019 11:19 am
Forum: Phase Changes & Related Calculations
Topic: outline 3
Replies: 1
Views: 55

outline 3

Will next weeks homework be on textbook questions from outline 3?
Sun Jan 20, 2019 11:49 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Error in Solutions manual [ENDORSED]
Replies: 1
Views: 43

Error in Solutions manual[ENDORSED]

I have the 6th edition and for 12.35, it says list the acids in order of increasing strength, and it says the larger the Ka value, the stronger the acid, yet the list of acids is in the wrong order and it should be the other way around. Is this an error or am I thinking about this wrong?
Sat Jan 19, 2019 6:12 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: Le Chateliers Principle
Replies: 4
Views: 113

Le Chateliers Principle

How does the affect of temperature and pressure differ when it comes to changing the equilibrium?
Sat Jan 19, 2019 6:08 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Post Assessment Part 2
Replies: 1
Views: 43

Post Assessment Part 2

There is a question in this post assessment asking about finding the equilibrium constant of reaction 2BrCI <-> Br2 + Cl2. The question says something about 18.3% of the BrCI gas remains at equilibrium. However, no matter how many times I attempt the question I cant get the answer. Can someone expla...
Fri Jan 11, 2019 11:58 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Problem 11.7
Replies: 2
Views: 39

Re: Problem 11.7

The flasks are in order of time. So to get the answer you just count the amount of diatomic molecules present in each flask. And if you do this you will notice both flask 3 and 4 both have 5 diatomic molecules. So the reaction reached equilibrium at flask 3 because that is where the reactants stay c...
Fri Jan 11, 2019 11:51 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: ice table
Replies: 4
Views: 86

ice table

Today in lecture, professor Lavelle gave an example with the reaction PCI5, PCI3, and CI2. When he made the ICE table he made the change in concentration +x. How do we know to put +x? Can someone please explain, thank you!
Wed Jan 09, 2019 4:23 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: finding K Value
Replies: 3
Views: 49

finding K Value

In some questions they ask to find the K value from reactions where the coefficients were either divided or multiplied by a certain number, such a 2. How come when you multiply by 2, you have to square the given K value, and when you divide by 2, you square root the given K value?
Fri Dec 07, 2018 10:03 pm
Forum: Bronsted Acids & Bases
Topic: strong acid
Replies: 2
Views: 75

strong acid

I am still confused on how to tell if an acid is strong or not. Does electronegativity play a role in acid strength??
Tue Dec 04, 2018 11:06 am
Forum: Amphoteric Compounds
Topic: amphoteric substances
Replies: 3
Views: 121

amphoteric substances

How can you tell a substance is amphoteric by just looking at it? or is there a way you can figure it out?
Thu Nov 29, 2018 7:33 am
Forum: Determining Molecular Shape (VSEPR)
Topic: Molecular Shape
Replies: 2
Views: 91

Re: Molecular Shape

I dont think there will be a chart provided since Dr Lavelle said you are expected to memorize the bond angles and shape names. Try memorizing the formulas for molecular shape (e.g AX3E, which correpsonds to trigonal pyramid)
Thu Nov 29, 2018 7:30 am
Forum: Determining Molecular Shape (VSEPR)
Topic: Resonancy and VSEPR
Replies: 1
Views: 36

Re: Resonancy and VSEPR

Resonancy is not totally important when it comes to molecular shape because it does not matter which lewis structure you consider. Since all of the resonance structures will have the same shape it doesnt matter which one you focus on since single and multiple bonds are counted as one bond
Thu Nov 29, 2018 7:26 am
Forum: Naming
Topic: coordination compound
Replies: 1
Views: 45

coordination compound

So within a coordination compound, are the ligands always going to be lewis bases, and the central atom or ion is the lewis acid or can it be switched around??
Sun Nov 18, 2018 9:58 pm
Forum: Polarisability of Anions, The Polarizing Power of Cations
Topic: polarizing power and polarizability
Replies: 2
Views: 93

polarizing power and polarizability

Is it safe to say that polarizing power is indirectly proportional to atomic radius and directly proportional to electronegativity? and is polarizability indirectly proportional to electronegativity and directly proportional to atomic radius??
Sat Nov 17, 2018 7:54 pm
Forum: Bond Lengths & Energies
Topic: 6th edition 3.87
Replies: 2
Views: 84

6th edition 3.87

can someone please explain this question to me I don't get it at all
Thu Nov 15, 2018 11:38 am
Forum: Determining Molecular Shape (VSEPR)
Topic: Arrangement vs Shape
Replies: 3
Views: 107

Arrangement vs Shape

Can someone please clarify what the difference is when asked for arrangement vs when asked for molecular shape? I know it has something to do with the lone pairs but im not entirely sure
Mon Nov 12, 2018 1:48 pm
Forum: Polarisability of Anions, The Polarizing Power of Cations
Topic: Cations and polarizing power
Replies: 2
Views: 98

Re: Cations and polarizing power

Higher polarizing power refers to "atoms and ions that CAN cause large distortions." I capitalized "can" because that word made me understand what is meant by polarizing power. So basically the higher poloarizing power an atom has, the more it can pull electrons toward it. Small,...
Mon Nov 12, 2018 1:44 pm
Forum: Electronegativity
Topic: Ionic Character
Replies: 2
Views: 57

Re: Ionic Character

As you go down a group, atomic radius increases, so there is less pulling power on the electrons. CO2 is more ionic because oxygen is in the second period so its atomic radius is small which means there is more pulling on the elctrons by the nucleus. Therefore, Oxygen is very high in electronegtivit...
Mon Nov 12, 2018 1:39 pm
Forum: Formal Charge and Oxidation Numbers
Topic: 3.39b 6th edition
Replies: 2
Views: 120

Re: 3.39b 6th edition

Potassium and Phosphorus have a high difference in electronegativity so they have more ionic so they are not covalently bonded so the Potassium atoms are separate.
Sat Nov 03, 2018 12:09 am
Forum: Empirical & Molecular Formulas
Topic: Mass Composition
Replies: 3
Views: 137

Mass Composition

Okay so there are many questions that give you the mass composition of each element in a compound and ask to find the empirical or molecular formula. The percentage of each element adds up to a 100%. What if they did not add up to 100%, how we would go about solving the problem??
Fri Nov 02, 2018 11:40 pm
Forum: Quantum Numbers and The H-Atom
Topic: Electrons in Orbitals
Replies: 2
Views: 96

Re: Electrons in Orbitals

For example when n=3 and l=2 we know this corresponds to 3d. Since l is equal 2 we know the values for ml can be: -2,-1,0,1,2. This tells us how many orbitals there are. In this case it is 5 orbitals. Since there are 2 electrons in each orbital, there are 10 electrons
Mon Oct 29, 2018 11:26 pm
Forum: Ionic & Covalent Bonds
Topic: 6th edition 3.9 and 3.11
Replies: 1
Views: 57

6th edition 3.9 and 3.11

Can someone please explain the answers to these two questions. I do not understand them at all. Thank you in advance!
Mon Oct 29, 2018 12:21 am
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: 2.25 6th Edition
Replies: 2
Views: 126

Re: 2.25 6th Edition

For this question you just take the number of orbitals and multiply by 2 to get the number of electrons that can occupy that specific orbital. So for example the 4p orbital corresponds to the angular momentum quantum number 1. This number can have 3 values of the magnetic quantum number -1,0,1. Thsi...
Mon Oct 29, 2018 12:14 am
Forum: Properties of Light
Topic: Photoelectric Effect
Replies: 7
Views: 288

Re: Photoelectric Effect

Intensity is what effects the amount of electrons. So as intensity increases, quantity of electrons being removed increases
Sun Oct 21, 2018 5:39 pm
Forum: Einstein Equation
Topic: HW Problem 1.25 (6th Edition)
Replies: 2
Views: 107

Re: HW Problem 1.25 (6th Edition)

For part b, convert 5.00 mg to g. Then using the equation m=nM, find n, which is amount in moles. Then use the equation N=nNa to find N, which is number of sodium atoms. Use the answer from part a and multiple that number by the number of sodium atoms. For part c, just divide the answer from part a ...
Sun Oct 21, 2018 5:34 pm
Forum: Einstein Equation
Topic: Chapter 1 Question 27
Replies: 2
Views: 155

Re: Chapter 1 Question 27

First convert 420 nm to m. Then solve for the energy per photon by using the equation E=hc/(wavelength). Once you have that answer, you can divide the total energy which is 64J (1 W= 1 J.s, so 32 x 2=64 J) and divide that by the energy per photon. This will get you the amount in photons. To solve fo...
Sun Oct 21, 2018 2:00 pm
Forum: Quantum Numbers and The H-Atom
Topic: 6th edition 2.1
Replies: 1
Views: 66

Re: 6th edition 2.1

When the electron in a hydrogen atom makes a transition from the 1s orbital to a 2p orbital the atom's radius is increasing because the number of enegry levels is increasing, and so is the number of electrons. Each energy level is getting farther from the nucleus. So when a electron moves from 1s, w...
Sat Oct 20, 2018 10:00 pm
Forum: Quantum Numbers and The H-Atom
Topic: test 2 topics
Replies: 3
Views: 131

test 2 topics

This was probably already asked, but will electron configurations be on test 2? For example, will we need to know the ground state electron configuration of an element??
Fri Oct 19, 2018 12:20 am
Forum: *Shrodinger Equation
Topic: Orbitals, Lobes, e- density
Replies: 3
Views: 303

Orbitals, Lobes, e- density

The last time I took chemistry was 10th grade, so I am a little lost on the whole orbital concept and the wave function. Can someone give me a simple explanation? If you can me it as simple as possible that would be great.
Sun Oct 14, 2018 6:51 pm
Forum: Properties of Electrons
Topic: Energy Level Question
Replies: 4
Views: 85

Re: Energy Level Question

When an electron jumps from a lower energy level to a higher energy level (ex. n=1 to n=3) then energy is absorbed. Therefore, the electron gains energy since it is moving away from the nucleus. When an electron goes down to a lower energy level (returning to ground state) it emits energy. Therefore...
Sun Oct 14, 2018 6:45 pm
Forum: Properties of Light
Topic: wavelengths and energy of a photon
Replies: 2
Views: 69

Re: wavelengths and energy of a photon

When the size of the wavelength increases (more far apart) then frequency decreases and I believe this causes energy to decrease. If the wavelength decreases(less space in between), then frequency increases therefore energy increases, specifically electromagnetic radiation. I found this on wikipedia...
Sun Oct 14, 2018 6:39 pm
Forum: Properties of Light
Topic: Test 2
Replies: 17
Views: 331

Test 2

Does anyone know if test 2 will cover both chapter 1 and 2 of the textbook or just chapter 1?
Mon Oct 08, 2018 11:03 pm
Forum: Limiting Reactant Calculations
Topic: Test 1
Replies: 2
Views: 180

Re: Test 1

Hi Katherine! First tests are always scary because it's hard to know what to expect, but just be confident and don't worry too much! My UA session is Tuesday 6-8pm and I go over practice test questions that are based off of previous exam questions, so that could be helpful. Doing problems is always...
Mon Oct 08, 2018 11:02 pm
Forum: Limiting Reactant Calculations
Topic: How to find the limiting reactant easily and quickly
Replies: 5
Views: 427

Re: How to find the limiting reactant easily and quickly

Okay first balance the equation given if it is not already. Then if given the mass of the two reactants convert both to moles. Then divide each of those amounts by the number of moles in the equation. For example 2Al+6HCI --> 2AlCI3 + 3H2 If given the grams of Al and HCI you convert to moles. In thi...
Mon Oct 08, 2018 9:25 pm
Forum: Limiting Reactant Calculations
Topic: Test 1
Replies: 2
Views: 180

Test 1

I am really nervous about Test 1, and I have done all the homework problems about 4 times. Is there anything else I can study? Or what is the most difficult topic for students to comprehend or a topic students have the most questions on?
Mon Oct 08, 2018 10:05 am
Forum: Empirical & Molecular Formulas
Topic: Converting Units
Replies: 5
Views: 131

Re: Converting Units

For me personally, it is much easier to convert all units to the correct units in the beginning instead of at the end. I don't know if that is the best way but it has worked for me!
Sat Oct 06, 2018 10:32 am
Forum: Limiting Reactant Calculations
Topic: Finding Limiting Reactants
Replies: 3
Views: 80

Finding Limiting Reactants

Is the limiting reactant always going to be the one with the least moles? or do you have to take into account the molar ratio? and if you do take into account the molar ratio how would you work that into finding the limiting reactant??
Fri Oct 05, 2018 11:40 pm
Forum: Properties of Light
Topic: Classical vs Quantum
Replies: 2
Views: 76

Classical vs Quantum

Can someone please explain the difference between classical mechanics vs quantum mechanics because I was totally lost in lecture about the whole pouring water from a flowering can example??
Wed Oct 03, 2018 11:36 am
Forum: Accuracy, Precision, Mole, Other Definitions
Topic: Question E 15
Replies: 2
Views: 75

Re: Question E 15

When you subtract the molar mass of the metal of the two hydroxide atoms from the molar mass of the metal hydroxide, you get a molar mass of 40.084. And the metal matching this molar mass is calcium (40.078) so now you take find the molar mass of calcium sulfide!
Tue Oct 02, 2018 3:51 pm
Forum: Empirical & Molecular Formulas
Topic: problem F13
Replies: 3
Views: 124

problem F13

Problem F13 in the textbook asks "In an experiment, 4.14g of phosphorus combined with chlorine to produce 27.8g of a white solid compound. What is the empirical formula of the compound? In the solutions manual it skips the step of finding mass percentage of each element. So instead of dividing ...
Tue Oct 02, 2018 3:10 pm
Forum: Significant Figures
Topic: Significant Figures
Replies: 6
Views: 176

Significant Figures

Can someone explain addition and subtraction with significant figures? We went over it in discussion today but I was still confused about how many significant figures should be in the final answer?