## Search found 107 matches

Sat Mar 14, 2020 9:08 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: Midterm Q.3B
Replies: 2
Views: 173

### Midterm Q.3B

Can someone explain this problem and how the Le Chatlier's principle helps solve for what combination of HCl and NaOH would produce the largest change in temperature?
Sat Mar 14, 2020 8:10 pm
Forum: General Science Questions
Topic: Test 2
Replies: 2
Views: 135

### Test 2

Since we couldn't get Test 2 back my TA said they'd post the answer key to study from, but where did they post it? I don't see it on Lavelle's website.
Fri Mar 13, 2020 8:36 pm
Forum: Method of Initial Rates (To Determine n and k)
Topic: 7B.1
Replies: 3
Views: 119

### Re: 7B.1

Why can you plug in the grams of the drug if you don't know what volume it is in? Since it's asking for concentration, how come you can plug in the 0.02 grams?
Fri Mar 13, 2020 7:54 pm
Forum: Method of Initial Rates (To Determine n and k)
Topic: 7B.1
Replies: 3
Views: 119

### 7B.1

For this problem, I'm confused on how to solve the rate equation with the given info. I know I'm supposed to use the equation with K=1/t*ln(A initial)/(A) but I don't get how the initial mass given is put into the equation to solve.
Wed Mar 11, 2020 6:31 pm
Forum: Zero Order Reactions
Topic: 7A.15A
Replies: 3
Views: 80

### 7A.15A

Do we know that the order of the reactant C is zero because when experiment 1 is compared to experiment 4, the increase in reactants does not influence the rate?
Mon Mar 09, 2020 10:30 pm
Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
Topic: 6N.15
Replies: 2
Views: 58

### 6N.15

For this problem are we supposed to use the equation standard E cell= (RT/F) ln K? It says to look at the 6I.1 table but also this table doesn't show the K value for just a Nickel rxn.
Wed Mar 04, 2020 10:48 pm
Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
Topic: reduction and oxidation
Replies: 4
Views: 92

### Re: reduction and oxidation

or is it the other way around?
Wed Mar 04, 2020 10:46 pm
Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
Topic: reduction and oxidation
Replies: 4
Views: 92

### reduction and oxidation

Is the element that is being reduced the one with a standard reduction that is the smallest or the most negative? and the one that is oxidized the one with the biggest or most positive standard reduction?
Wed Mar 04, 2020 7:03 pm
Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
Topic: 6N.5B
Replies: 1
Views: 103

### 6N.5B

For this equation when you solve for Q, the concentration of the H+ ion is found by doing 10^-pH which would be (10^-4) and then this is raised to the 16th power due to the stochiometric coefficient 16. But, this gives an answer of 1x10^-64 and then multiplied by conc. of the MnO4 and get 1x10^-68. ...
Wed Mar 04, 2020 12:01 pm
Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
Topic: equation for Q
Replies: 3
Views: 83

### equation for Q

Is the equation for Q from the cell diagram always going to be the anode over the electrode? Like for 6N.1 in the textbook with the rxn Mn(s)+Ti^2+---->Mn^2+ +Ti(s)? Or is it just like you'd normally do Q with products over reactants?
Tue Mar 03, 2020 5:36 pm
Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
Topic: 6L.7
Replies: 2
Views: 50

### 6L.7

For the single elements given, which standard reduction potentials should I use? Like for example one of the listed elements is Fe how should I know if I use the standard potential of Fe^3+ or Fe^2+???
Mon Mar 02, 2020 9:53 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: 6L.7
Replies: 3
Views: 115

### 6L.7

I'm so confused for like this whole problem because in the half rxns they include elements that aren't even in the entire redox rxn. Like, for part b the O2 included in the anode isn't in the whole redox rxn given. And for part a the Ag(s) wasn't in the full rxn either.
Mon Mar 02, 2020 9:34 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: 6L.3D
Replies: 3
Views: 82

### Re: 6L.3D

So, from the cell diagram, the two elements don't have to be on opposite sides of the rxn? Like since O2 and H+ on the anode side of the cell diagram doesn't have to have a half rxn of O2--->H+?
Mon Mar 02, 2020 9:31 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: 6L.7A
Replies: 1
Views: 35

### 6L.7A

What is the cathode half-rxn for this ? I'm confused on what would make up this rxn.
Mon Mar 02, 2020 8:29 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: cell diagrams
Replies: 2
Views: 63

### cell diagrams

When you write the cell diagram do you always leave out stoichiometric coefficients? Also, how do you know when you need to add a platinum on the outsides?
Mon Mar 02, 2020 7:53 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: 6L.3D
Replies: 3
Views: 82

### 6L.3D

Can someone please explain the oxidation rxn with the anode for this one? I'm confused because the anode is O2 and H+ , how would this make up the anode rxn if it's not H20 to H+?
Mon Mar 02, 2020 12:05 pm
Forum: Balancing Redox Reactions
Topic: 6K.3 Part D
Replies: 5
Views: 153

### Re: 6K.3 Part D

Yeah, I'm pretty sure it's a typo and it's supposed to be Cl2 to Cl- not Cl2 to Cl2.
Sun Mar 01, 2020 9:57 pm
Forum: Balancing Redox Reactions
Topic: 6K.3 Part D
Replies: 5
Views: 153

### Re: 6K.3 Part D

The half rxn of Cl2--->Cl goes from a charge of 0 to a charge of -1 meaning the Cl is reduced. And in the other half rxn of Cl2--->HClO the chlorine is going from a 0 charge to a +1 charge and is oxidized. This is why it is both oxidized and reduced.
Thu Feb 27, 2020 12:47 pm
Forum: Concepts & Calculations Using Second Law of Thermodynamics
Topic: melting point and freezing point
Replies: 1
Views: 96

### melting point and freezing point

Is the melting point temperature the same as the freezing point temperature because for problem 4I.7 part b they use the freezing point temperature as the melting point temperature. Is this specifically for C2H5OH or is it for all compounds?
Thu Feb 27, 2020 12:35 pm
Forum: Entropy Changes Due to Changes in Volume and Temperature
Topic: Problem 4I.5
Replies: 2
Views: 176

### Problem 4I.5

When finding the equilibrium temperature of water I don't understand why you wouldn't multiply the grams given by the specific heat capacity for the how water and the cold water? Why do they just cancel?
Thu Feb 27, 2020 10:34 am
Forum: Equilibrium Constants & Calculating Concentrations
Topic: water in the equilibrium constant
Replies: 2
Views: 56

### water in the equilibrium constant

Which phases of water are included and not included in the equilibrium constant? Is it included when it's a gas and solid but not liquid?
Wed Feb 26, 2020 11:16 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Problem 5.55
Replies: 1
Views: 43

### Problem 5.55

Can someone please explain how to do this problem I don't know how to do it with all of the given values. I'm really lost because there is no Kc value given either.
Tue Feb 25, 2020 9:36 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: 5G.13 and 5G.19
Replies: 1
Views: 44

### 5G.13 and 5G.19

What is the difference between the two questions because they both ask for the Gibbs free energy of the rxn I2<-->2I but they have different answers. Can someone explain why they're different?
Mon Feb 24, 2020 3:03 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: cis and trans entropy
Replies: 3
Views: 142

### cis and trans entropy

For 4G.5, how is a cis molecule structurally supposed to be arranged? I know for the trans molecule it needs to have its X and Y molecules on opposite sides but I wasn't sure for cis.
Sun Feb 23, 2020 11:17 pm
Forum: Balancing Redox Reactions
Topic: Test 2 Topics
Replies: 7
Views: 157

### Re: Test 2 Topics

Lavelle said that Test 2 will include the 2nd page of Thermodynamics and all of Electrochemistry! :)
Sun Feb 23, 2020 11:14 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Balancing Equations
Replies: 5
Views: 81

### Re: Balancing Equations

The element or molecule that is being oxidized is the one that is losing electrons and whichever is being reduced is the one that is gaining electrons. My high school chem teacher taught us the acronym OIL RIG to help us remember (oxidation is loss of e- and reduction is gain of e-). Hope that helps...
Sun Feb 23, 2020 11:12 pm
Forum: Concepts & Calculations Using Second Law of Thermodynamics
Topic: 4F.13
Replies: 2
Views: 112

### 4F.13

For this problem, why do I have to multiply the - change in enthalpy of fusion by the amount of moles? I thought enthalpy was a state function why does it have to be multiplied by the amount of moles of H20?
Sun Feb 23, 2020 10:47 pm
Forum: Entropy Changes Due to Changes in Volume and Temperature
Topic: entropy with change of temperature
Replies: 2
Views: 136

### entropy with change of temperature

I was a little confused about entropy because I thought that if the temperature was higher, there would be more disorder and entropy considering under conditions of high temp. the molecules would move around faster and be more "disordered". But, the entropy equation says otherwise since th...
Sun Feb 23, 2020 10:42 pm
Forum: General Science Questions
Topic: test 2
Replies: 1
Views: 164

### test 2

I know Lavelle said he's moving test 2 to week 9, but does that mean we're going to have it the same week as our final? Isn't that finals week?
Thu Feb 20, 2020 6:19 pm
Forum: Concepts & Calculations Using Second Law of Thermodynamics
Topic: units for entropy with Boltzmann's constant
Replies: 2
Views: 149

### units for entropy with Boltzmann's constant

When your using the entropy equation with delta S= KblnW the units that W converts to is J/s but I was confused because if you use the Kb the units cancel to leave 1/K*s. Aren't the units for entropy supposed to be J/K?
Wed Feb 12, 2020 2:11 pm
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: Pizza Rolls 3E
Replies: 4
Views: 85

### Pizza Rolls 3E

Can someone explain why it is false that removing heat from the system is exothermic and the temperature will decrease?
Wed Feb 12, 2020 12:49 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: units for heat capacity
Replies: 2
Views: 170

### units for heat capacity

Whenever you're asked for heat capacity are you suppose to always give an answer in J/g/Celsius ? Do you do this even if they give you a q that's in KJ?
Wed Feb 05, 2020 8:34 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: enthalpy of formation
Replies: 2
Views: 32

### enthalpy of formation

Is the enthalpy of formation of all diatomic molecules 0 ?
Tue Feb 04, 2020 10:51 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: assuming temperature
Replies: 2
Views: 48

### assuming temperature

Do we always assume the temperature is 298 K when we have to use the equation (change in enthalpy) = (change in internal energy) + (change in moles) RT? And if so why?
Tue Feb 04, 2020 10:26 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: enthalpy equations
Replies: 1
Views: 34

### enthalpy equations

For 4D.5 why is the change in enthalpy equal to the heat supplied if there was expansion work done? I thought there had to be no expansion for the change in enthalpy to equal q.
Mon Feb 03, 2020 8:49 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Replies: 1
Views: 33

In 4C.13 why do you add enthalpy to the heat supply of the ice??? I understand why the heat gained by the ice is equal to the heat lost by the water. But, I don't get why the change in enthalpy is being added to the head gained by the ice.
Mon Feb 03, 2020 7:20 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: asking for final temp
Replies: 2
Views: 30

### asking for final temp

When a question asks for final temperature how do you find that? What equation do you use? Do you use the enthalpy equations?
Sun Feb 02, 2020 4:52 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Enthalpy units
Replies: 5
Views: 96

### Re: Enthalpy units

In the equations that Lavelle did in class when he was showing different methods to find enthalpy he used kJ with Hess's Law.
Sun Feb 02, 2020 4:50 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: thermochemistry equations
Replies: 5
Views: 90

### thermochemistry equations

I'm kind of stressing out because I feel like I'm not going to be able to remember all these different equations and when to use them. Like the different equations for work and internal energy. How do you memorize all of them???
Sun Feb 02, 2020 4:42 pm
Forum: Phase Changes & Related Calculations
Topic: reverse fusion
Replies: 1
Views: 42

### reverse fusion

When something goes from a solid to a liquid instead of liquid to solid in fusion, why is it still going go be a positive enthalpy value?
Wed Jan 29, 2020 10:26 am
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: internal energy
Replies: 4
Views: 79

### internal energy

When a question asks what is the change in the internal energy of a reaction, what are they asking you to find? Are they asking for the work?
Wed Jan 29, 2020 10:10 am
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: work equations
Replies: 5
Views: 80

### work equations

For the work formula for expansion it is - P x change of volume but for the other formula it has P x a x d. I was just wondering why the second equation doesn't have a negative sign in it.
Sat Jan 25, 2020 7:52 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Ka of strong acid
Replies: 3
Views: 47

### Ka of strong acid

Is the Ka of a strong acid like HCL just 1 since it fully dissociates?
Tue Jan 21, 2020 5:18 pm
Forum: Non-Equilibrium Conditions & The Reaction Quotient
Topic: suggestions
Replies: 16
Views: 186

### suggestions

Does anyone have some good Youtube video suggestions for someone who's super confused on weak acids and bases and salts?
Tue Jan 21, 2020 5:12 pm
Forum: Non-Equilibrium Conditions & The Reaction Quotient
Topic: polyprotic acids
Replies: 2
Views: 54

### polyprotic acids

In 6E. for #1 the H2SO4 in its second protonation for the ICE table it's supposed to have a concentration of 0.15 for H3O+ the same as the H2SO4 initial concentration. But for #3 when H2CO3 is protonated, the H3O+ concentration is not 0.01 like the initial of H2CO3. I was wondering what made them di...
Tue Jan 21, 2020 3:25 pm
Forum: Non-Equilibrium Conditions & The Reaction Quotient
Topic: Acids and Bases
Replies: 7
Views: 67

### Acids and Bases

How do you know whether a molecule is an acid or a base? I was doing the problems in 6D and I didn't know how to set up some of the equilibrium equations because I didn't know if they were acids or bases. Is there a way to tell?
Sun Jan 19, 2020 8:50 pm
Forum: General Science Questions
Topic: test 1
Replies: 8
Views: 110

### test 1

Is the test the Tuesday we get back from the weekend on Jan 21st? And is it just on Chemical Equilibria and Acid & Base Equilibria?
Thu Jan 16, 2020 8:16 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: 5E.2 table??
Replies: 3
Views: 43

### 5E.2 table??

On the problem 5.39 it tells me to refer to 5E.2 table but I looked in 5E chapter and there's only one table and it's 5E.1. Does anyone know where to find the table?
Thu Jan 16, 2020 6:18 pm
Forum: Non-Equilibrium Conditions & The Reaction Quotient
Topic: rearranging for quadratic
Replies: 3
Views: 57

### Re: rearranging for quadratic

Sorry I meant to say I got -2.92 for b in the quadratic formula
Thu Jan 16, 2020 6:17 pm
Forum: Non-Equilibrium Conditions & The Reaction Quotient
Topic: rearranging for quadratic
Replies: 3
Views: 57

### rearranging for quadratic

In the homework 5I.27 for part c, for the quadratic I got -2.92 instead of -4.92 and I'm not sure why. Can anyone help?
Thu Jan 16, 2020 11:59 am
Forum: Non-Equilibrium Conditions & The Reaction Quotient
Topic: percentage reacted
Replies: 3
Views: 63

### percentage reacted

In the homework problem 5I.19 it asks for the equilibrium constant for the reaction of H2+I2<--->2HI if initially there is 0.4 mol of H2 and 1.6 mol of I2 in a 3.0 L container. They say that 60% of the hydrogen has reacted. When you are doing the ice table for the problem I thought that since the hy...
Wed Jan 15, 2020 8:50 pm
Forum: Non-Equilibrium Conditions & The Reaction Quotient
Topic: ICE tables
Replies: 4
Views: 40

### ICE tables

How do you know when a question requires an ICE table? I know that an ICE table is only used when they don't give you the equilibrium initial concentration. But, will they tell you they're not the concentrations at equilibrium? How will the problem usually be worded for ones that require ICE tables?
Sun Jan 12, 2020 9:41 pm
Forum: Non-Equilibrium Conditions & The Reaction Quotient
Replies: 2
Views: 55

For 5I.13 I did the ice table correctly and got 0.0001-x for Cl2 and +2x for 2Cl. I did the quadratic to find x and got 5.6*10^-6 and then plugged it in to get 1.12*10^-5 for the 2Cl but it's not the right answer. I'm not sure what I'm doing wrong.
Sun Jan 12, 2020 6:29 pm
Forum: Ideal Gases
Topic: partial pressures
Replies: 7
Views: 83

### partial pressures

In 5G.9 it says in two containers, one with 0.1 mol of O3 and the other with 0.5 mol of O3 with the rxn 2O3(g)<--->3O2(g) taking place will ratio of PO2/PO3 be the same (part b). I understand that the ratio won't be the same for the two containers because the partial pressures of the O3 as well as t...
Sun Jan 12, 2020 6:23 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: memorization
Replies: 12
Views: 198

### memorization

Does anyone know if we have to memorize certain K values? Like some of the homework problems don't give the K value and ask for you to refer to the table in 5G. Would we have to memorize that table?
Sun Jan 12, 2020 5:26 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Gibbs free energy
Replies: 3
Views: 36

### Re: Gibbs free energy

Okay, that makes a lot of sense!!!! Thank you :)
Wed Jan 08, 2020 12:50 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Gibbs free energy
Replies: 3
Views: 36

### Gibbs free energy

The problem 5G.1 (d) asks if it's true or false that the gibs free energy is greater than the standard gibs free energy will proceed to equilibrium. Isn't this false because the gibs free energy must go to 0 to reach equilibrium rather than be bigger?
Wed Jan 08, 2020 12:39 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Composite Equations
Replies: 3
Views: 51

### Composite Equations

For the homework problem 5H.3, it asks for the K value at 300 kelvin for the reaction 2BrCl(g) + H2(g) > Br2(g) + 2HCl(g) using the Table 5G.2. I wanted to combine H2+Cl2>2HCl which had a K of 4.0x10^31 at 300K and then Br2>2Br. But for the Br equation the kelvins listed were either 1000 or 1200. Is...
Sun Dec 08, 2019 12:06 am
Forum: Formal Charge and Oxidation Numbers
Topic: best lewis structure
Replies: 1
Views: 115

### best lewis structure

If the atoms in a lewis structure have formal charges that add to zero is this more stable than having one atom with a formal charge of 0 and the other with a charge? Like say for (C2)-2. You could have a double bond and have a carbon with a 2+ charge and carbon with 0 or a triple bond and have a ch...
Sat Dec 07, 2019 11:30 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: AXE formula
Replies: 7
Views: 266

### AXE formula

Is the E in the AXE the lone pairs on the central atom or all of the atoms?
Sat Dec 07, 2019 11:29 pm
Forum: Acidity & Basicity Constants and The Conjugate Seesaw
Topic: pkA and kA
Replies: 1
Views: 66

### pkA and kA

how are pkA and kA related and how do they relate to how strong an acid is?
Sat Dec 07, 2019 8:13 pm
Forum: Resonance Structures
Topic: when there is resonance
Replies: 5
Views: 225

### when there is resonance

Is it possible for a molecule with only two atoms to have resonance?
Sat Dec 07, 2019 8:08 pm
Forum: Properties of Electrons
Topic: z effective
Replies: 2
Views: 381

### z effective

I went to a late quantum review session and they showed this equation z effective which is supposed to represent the number of protons multiplied by e which is charge of proton and electrons. And then there was another equation with (z effective) x (e) = (z theoretical) - (electron electron repulsio...
Sat Dec 07, 2019 7:32 pm
Forum: Lewis Structures
Topic: Lewis for carbon monoxide
Replies: 3
Views: 534

### Lewis for carbon monoxide

Why does the most stable structure for carbon monoxide have a triple bond between carbon and oxygen and 1 lone pair on each? I thought it would be a double bond between carbon and oxygen with one lone pair on carbon and one lone pair on oxygen because this gave me a formal charge of 0 on both carbon...
Sat Dec 07, 2019 6:03 pm
Forum: Interionic and Intermolecular Forces (Ion-Ion, Ion-Dipole, Dipole-Dipole, Dipole-Induced Dipole, Dispersion/Induced Dipole-Induced Dipole/London Forces, Hydrogen Bonding)
Topic: example of dipole induced dipole
Replies: 1
Views: 96

### Re: example of dipole induced dipole

A dipole induced dipole describes the forces between a polar molecule and a molecule with no charge. An example is HCL and Ar. Argon has no charge and HCL has a positive dipole on hydrogen and a negative dipole on chlorine. The Argon's electrons will be drawn to the positive charge on the hydrogen b...
Sat Dec 07, 2019 4:41 pm
Forum: Electron Configurations for Multi-Electron Atoms
Topic: Electron config for copper
Replies: 2
Views: 154

### Electron config for copper

Can someone please explain to me why the electron configuration 1s2 2s2 2p6 3s2 3p6 3d10 4s1 is copper and not potassium?
Sat Dec 07, 2019 3:55 pm
Forum: Interionic and Intermolecular Forces (Ion-Ion, Ion-Dipole, Dipole-Dipole, Dipole-Induced Dipole, Dispersion/Induced Dipole-Induced Dipole/London Forces, Hydrogen Bonding)
Topic: hydrogen bonding
Replies: 3
Views: 142

### hydrogen bonding

I'm kind of confused as to when a molecule has hydrogen bonding. Like, is hydrogen bonding present whenever there is a hydrogen in the molecule?
Thu Dec 05, 2019 1:35 am
Forum: Heisenberg Indeterminacy (Uncertainty) Equation
Topic: when to use Heisenberg
Replies: 2
Views: 123

### when to use Heisenberg

I know that we're given the equation for Heisenberg on the constant sheet but do we need to know how to use it?? Like if we know a problem has uncertainty according to the Heisenberg uncertainty principle do we just state how it applies and that's it? How would you answer the question?
Thu Dec 05, 2019 1:32 am
Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
Topic: different Rydberg
Replies: 3
Views: 194

### different Rydberg

I know on the constant sheet they write the Rydberg formula as En=-hR/n^2 but the other way to write it is v=R(1/n1^2)(1/n2^2). When do you use one versus the other? Like what kind of problems would you have where you would need to use the other version?
Thu Dec 05, 2019 1:27 am
Forum: Quantum Numbers and The H-Atom
Topic: Midterm question with Rydberg
Replies: 1
Views: 125

### Midterm question with Rydberg

In the question where it asks to determine whether the change in energy will be positive or negative in the hydrogen atom that is excited by a photon with a wavelength of 102.557nm. . . I found the change in energy was 1.9x10^-18 and the E initial was -2.18x10^-18. For the E final I used the equatio...
Tue Dec 03, 2019 11:40 pm
Forum: Naming
Topic: cations and anions with naming
Replies: 1
Views: 64

### cations and anions with naming

I'm trying to name K2 [Ni(CN)4] but I was confused because I know you're supposed to start the name with the prefix for how many ligands there are, so in this case tetra since there are 4 CN. Then, I thought I was supposed to do the TM cation name but I was confused because in the formula isn't the ...
Tue Dec 03, 2019 10:44 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: vsepr formula
Replies: 7
Views: 240

### vsepr formula

When a question asks for the VSEPR formula, is it asking for me to explain how the vsepr theory of electron repulsion relates to the molecule? What does it mean by formula?
Tue Dec 03, 2019 10:42 pm
Forum: Ionic & Covalent Bonds
Topic: polarity of shapes
Replies: 4
Views: 192

### polarity of shapes

If the shape of a molecule is square planar with two lone pairs, what are the bond angles? Do the lone pairs affect the bond angle ? Would it have the bond angle of an octahedron since it has 6 areas of electron density?
Tue Dec 03, 2019 10:39 pm
Forum: Ionic & Covalent Bonds
Topic: polarity of shapes
Replies: 3
Views: 165

### polarity of shapes

Are molecules that are trigonal planar usually non polar?
Mon Dec 02, 2019 4:47 pm
Forum: Photoelectric Effect
Topic: midterm problem
Replies: 1
Views: 140

### midterm problem

On the midterm there was a question about the longest wavelength needed to remove an electron from gold. But, they only give the work function. I tried rearranging and combining formulas but I always end up with two unknown variables. How would I solve this problem? Does anyone know what combination...
Sat Nov 30, 2019 1:54 am
Forum: General Science Questions
Topic: test bank
Replies: 2
Views: 58

### test bank

I wanted to study from previous exams given by Lavelle. I heard that I can find them at the test bank. Where is the test bank?
Sat Nov 30, 2019 12:25 am
Forum: General Science Questions
Topic: test taking nervousness
Replies: 19
Views: 477

### test taking nervousness

I think I have the concepts down pretty well from lecture and I do all of the homework problems. But, when I take the tests I kind of blank and I think it's because I get kind of nervous. Does anyone have any advice for that?
Sat Nov 30, 2019 12:22 am
Forum: General Science Questions
Topic: study tips for the final
Replies: 3
Views: 80

### study tips for the final

For the midterm, I used the dino nuggets practice review. Is there one similar to that for the final exam. Also, does anyone have tips on how to study besides the review sessions???
Tue Nov 26, 2019 12:28 am
Forum: Shape, Structure, Coordination Number, Ligands
Topic: abbreviations
Replies: 2
Views: 38

### abbreviations

I was doing homework problem 9C.9 where I'm supposed to find the coordination number. But, I didn't know what en or edta stood for in the compounds. Like one was [PtCl2(en)2] and the other [Cr(edta)]. What molecules are en and edta ?
Tue Nov 19, 2019 9:51 am
Forum: Ionic & Covalent Bonds
Topic: bond lengths
Replies: 4
Views: 276

### bond lengths

For tests are we supposed to memorize certain bond lengths or are they given to us in order to do the calculations?
Mon Nov 18, 2019 10:43 pm
Forum: Lewis Structures
Topic: Organic Compounds
Replies: 2
Views: 64

### Organic Compounds

How do you draw lewis structures for complex organic compounds? Like for example CH2CHCN? Do you draw you connect all of the carbons first or do you like draw parts of the compound separately and then see where they can fit together? I'm pretty lost on how to draw it to be honest. Any help would be ...
Mon Nov 18, 2019 8:59 pm
Forum: Lewis Structures
Topic: lone pairs
Replies: 7
Views: 341

### lone pairs

How do you know when the central atom will have lone pairs instead of more bonds?
Mon Nov 18, 2019 8:52 pm
Forum: Lewis Structures
Topic: double and triple bonds
Replies: 6
Views: 269

### Re: double and triple bonds

Why does arsenic have lone pairs? And how would you know it would have lone pairs being the central atom?
Mon Nov 18, 2019 7:42 pm
Forum: Lewis Structures
Replies: 3
Views: 97

How do you know when a compound is radical and which atom will have the unpaired electrons?
Mon Nov 18, 2019 7:33 pm
Forum: Lewis Structures
Topic: double and triple bonds
Replies: 6
Views: 269

### double and triple bonds

I'm still pretty confused on when to do double and triple bonds on a Lewis structure. For example in the compound AsF3, I'm not sure if it's supposed to have a double bond on two of the fluorines. I calculated formal charge and with the double bonds on two fluorines, I get a formal charge of 0 on ar...
Wed Nov 13, 2019 2:22 pm
Forum: Administrative Questions and Class Announcements
Replies: 4
Views: 89

Where do we check our midterm grade since it's not on CCLE? Sorry if this is an obvious question...
Tue Nov 05, 2019 10:42 pm
Forum: SI Units, Unit Conversions
Topic: HELP WITH UNITS
Replies: 9
Views: 1857

### HELP WITH UNITS

For questions for chem in general, do you give the answer in the units that the question uses? I've been converting everything to the standard units (meters, liters, Kelvin, kilograms, seconds) regardless of what the equation gives. Am I supposed to keep the answer in the units that the question has...
Sat Nov 02, 2019 1:32 am
Forum: Electron Configurations for Multi-Electron Atoms
Topic: orbitals
Replies: 1
Views: 34

### orbitals

Can someone explain to me why s-electrons have a lower energy than p or d electrons. I knew that inner electrons shield the outer electrons from electrostatic attraction of the positive nucleus so I thought this meant they needed a higher energy to shield.
Thu Oct 24, 2019 5:54 pm
Forum: Properties of Light
Topic: photoelectric effect
Replies: 4
Views: 119

### photoelectric effect

In the photoelectric experiment when they doubled the intensity of light, electrons were still not ejected. What is intensity? Is the intensity the frequency or the wavelength?
Sun Oct 20, 2019 11:08 pm
Forum: DeBroglie Equation
Topic: equation conversions
Replies: 2
Views: 61

### equation conversions

I've seen the equation for the energy of a photon joined with the debroglie equation but I never understood how. Can someone explain how they can be put together?
Sun Oct 20, 2019 11:05 pm
Forum: Properties of Light
Topic: speed of light and velocity
Replies: 6
Views: 80

### speed of light and velocity

I've seen the speed of light equation also be written with velocity in place of c. Are velocity and speed always used interchangeably or is it only for speed of light because light only travels in one direction?
Sun Oct 20, 2019 11:03 pm
Forum: Properties of Light
Topic: Balmer and Lyman Series
Replies: 5
Views: 106

### Balmer and Lyman Series

In the spectral line series, the series is describing how the hydrogen transitions from a higher energy level to a lower energy level and emits light. If the hydrogen atom is going from a high energy level to a lower energy level, then why is n1 the lower energy level? Wouldn't n2 be the lower one s...
Mon Oct 14, 2019 10:17 pm
Forum: DeBroglie Equation
Topic: How to find work function
Replies: 2
Views: 58

### How to find work function

On the homework for problem 1B.15, the equation gives the velocity of the photon. I used the velocity to find the kinetic energy of the photon. However, the problem asks me to find the wavelength. But, there is no given work function or energy of the photon. How am I suppose to solve for the wavelen...
Mon Oct 14, 2019 9:01 pm
Forum: Einstein Equation
Topic: Homework Problem B.5
Replies: 2
Views: 66

### Homework Problem B.5

In this problem, the given information is that a y-ray has energy of 140.11 keV and I'm supposed to find the wavelength. I know I'm supposed to use Einstein's equation. But, what is keV? What is this unit? I've never seen it before so I have no idea how to convert it or if I even have to.
Mon Oct 07, 2019 9:07 pm
Forum: *Black Body Radiation
Topic: Black Body
Replies: 5
Views: 114

### Black Body

I know that a black body is an idealized object that absorbs all incoming light. But does it also hypothetically reflect light as well? And if so does it reflect light of all wavelengths?
Mon Oct 07, 2019 1:52 pm
Forum: Properties of Light
Topic: Planck's Law
Replies: 4
Views: 83

### Re: Planck's Law

Or what is the difference between quanta and a photon?
Mon Oct 07, 2019 1:47 pm
Forum: Properties of Light
Topic: Planck's Law
Replies: 4
Views: 83

### Planck's Law

Just checking but in Planck's Law the electromagnetic energy is in the form of quanta and quanta is also a photon right? Quanta and photon can be used interchangeably? They are the same thing?
Fri Oct 04, 2019 6:01 pm
Forum: Properties of Light
Topic: Emission and Absorption
Replies: 1
Views: 39

### Emission and Absorption

When light goes from high energy to low energy does it emit light? And when it goes from low energy to high energy does it absorb light? Or is it the other way around?
Fri Oct 04, 2019 5:54 pm
Forum: Einstein Equation
Topic: Planack's constant
Replies: 8
Views: 215

### Planack's constant

Dr. Lavelle mentioned Planack's constant is h=6.63x10^-34 J.s in lecture. What is Planack's constant used for or what is it a constant for?
Fri Oct 04, 2019 5:00 pm
Forum: Accuracy, Precision, Mole, Other Definitions