Search found 94 matches

by Emmaraf 1K
Sat Mar 16, 2019 8:05 pm
Forum: Interesting Applications: Rechargeable Batteries (Cell Phones, Notebooks, Cars), Fuel Cells (Space Shuttle), Photovoltaic Cells (Solar Panels), Electrolysis, Rust
Topic: 6O3 7th edition
Replies: 1
Views: 95

6O3 7th edition

The questions asks which of Mn2+, Al3+, Ni2+, or Au3+ will be reduced in the presence of water when electrolyzed with water at pH 7. Reduction potential of water is -.42V at pH 7. Why is water reduced with the first 2 and why is the metal reduced for the last 2. I thought in electrolysis reactions, ...
by Emmaraf 1K
Sat Mar 16, 2019 7:49 pm
Forum: Interesting Applications: Rechargeable Batteries (Cell Phones, Notebooks, Cars), Fuel Cells (Space Shuttle), Photovoltaic Cells (Solar Panels), Electrolysis, Rust
Topic: What are the steps in the process of of rusting?
Replies: 1
Views: 85

What are the steps in the process of of rusting?

The textbook acts about the process of rusting 7th edition question 6N.21 and I wanted to know what the official steps are and why the formula for rust is Fe2O3 H2O and how both oxygen gas and water act as the oxidizing agents
by Emmaraf 1K
Fri Mar 15, 2019 10:16 pm
Forum: Arrhenius Equation, Activation Energies, Catalysts
Topic: What are the units for A?
Replies: 1
Views: 44

What are the units for A?

What are the units for the frequency factor, A?
by Emmaraf 1K
Thu Mar 14, 2019 7:44 pm
Forum: Entropy Changes Due to Changes in Volume and Temperature
Topic: Review Session-Thermo-files- Wednesday-Q11-clarification [ENDORSED]
Replies: 10
Views: 409

Re: Review Session-Thermo-files- Wednesday-Q11-clarification [ENDORSED]

I wanted to clarify since it's not entirely clear to me about question 11:
We wouldn't know whether to use the Cv or Cp value unless we were given the V-T or P-T diagram and saw whether volume or pressure was held constant, right?
by Emmaraf 1K
Thu Mar 14, 2019 4:44 pm
Forum: Reaction Mechanisms, Reaction Profiles
Topic: Molecularity
Replies: 1
Views: 29

Re: Molecularity

It doesn't really make sense to talk about the molecularity of the overall reaction. It only makes sense to talk about the molecularity of the elementary steps. Molecularity refers to how many and which molecules must collide with each other for the reaction to be carried out at each step.
by Emmaraf 1K
Wed Mar 13, 2019 10:46 pm
Forum: Reaction Mechanisms, Reaction Profiles
Topic: K = k/k'
Replies: 3
Views: 57

Re: K = k/k'

This statement is true for all equilibrium reactions.
by Emmaraf 1K
Wed Mar 13, 2019 10:29 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: When to put Pt(s) in a cell diagram?
Replies: 3
Views: 66

Re: When to put Pt(s) in a cell diagram?

If there is no solid metal in the anode or the cathode to carry a current, then you need to put Pt(s) in the cell diagram. Put it on the side lacking the solid metal (could be the cathode, anode, or both)
by Emmaraf 1K
Wed Mar 13, 2019 2:47 pm
Forum: Kinetics vs. Thermodynamics Controlling a Reaction
Topic: Molecularity
Replies: 2
Views: 86

Re: Molecularity

It's not necessarily the number of reactants but the number of molecules involved in the collision during each step of the reaction mechanism.
by Emmaraf 1K
Wed Mar 13, 2019 1:27 pm
Forum: Administrative Questions and Class Announcements
Topic: Chemistry community posts
Replies: 5
Views: 242

Chemistry community posts

I know that last quarter it didn't matter how many posts you did per week but you just had to do all 30 posts by the end of the quarter for full points. Is it the same for this quarter or did it change to only being counted by the week? Are the posts counted by the TA or by the computer system?
by Emmaraf 1K
Wed Mar 13, 2019 12:02 pm
Forum: Concepts & Calculations Using Second Law of Thermodynamics
Topic: enthalpy and spontaneity/favorability
Replies: 2
Views: 86

Re: enthalpy and spontaneity/favorability

Generally spontaneity is a measure of whether Delta G is positive or negative and is dependent on both S and H. Therefore, you need both factors to determine spontaneity. However, a negative H tends to lend itself to a negative G aka a .spontaneous reaction
by Emmaraf 1K
Wed Mar 13, 2019 12:02 pm
Forum: Concepts & Calculations Using Second Law of Thermodynamics
Topic: enthalpy and spontaneity/favorability
Replies: 2
Views: 86

Re: enthalpy and spontaneity/favorability

Generally spontaneity is a measure of whether Delta G is positive or negative and is dependent on both S and H. Therefore, you need both factors to determine spontaneity. However, a negative H tends to lend itself to a negative G aka a .spontaneous reaction
by Emmaraf 1K
Wed Mar 13, 2019 12:00 pm
Forum: Arrhenius Equation, Activation Energies, Catalysts
Topic: collision theory
Replies: 2
Views: 39

Re: collision theory

For a reaction to occur, the correct reactants must collide with each other with the correct orientation. If they collide with the incorrect orientation, the reaction won't occur. Additionally, the collision must collide with enough energy for the bonds that need to break to break for the reaction t...
by Emmaraf 1K
Tue Mar 05, 2019 4:36 pm
Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
Topic: Textbook Problem 6O #3
Replies: 1
Views: 53

Re: Textbook Problem 6O #3

Basically during electrolysis, one species is always reduced and another is always oxidized but in contrast to a galvanic cell, Ecell is negative, meaning it requires energy to power the reactions to happen. Therefore, when looking at the reduction potential of water and the reduction potential of a...
by Emmaraf 1K
Mon Mar 04, 2019 2:49 pm
Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
Topic: 6N7 7th edition
Replies: 1
Views: 45

6N7 7th edition

For part B, you must find Ecell for a concentration cell where at the anode and cathode is H2--> H+ and H+ -->H2 so when you balance them there should be the transfer of 2 electrons. However, when the question is solved, n=1. Why is this?
by Emmaraf 1K
Sun Mar 03, 2019 9:24 pm
Forum: Kinetics vs. Thermodynamics Controlling a Reaction
Topic: Study Advice
Replies: 30
Views: 360

Re: Study Advice

I personally prefer to go to the workshop sessions that are 2 hours long since they tend to go over all the material of the past week very in depth and you get to do plenty of practice problems which are similar to the tests. However, if you go to Lyndon's Workshop 7-9 on Mondays you should get ther...
by Emmaraf 1K
Tue Feb 26, 2019 12:25 am
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: 6L5(b) 7th edition
Replies: 2
Views: 38

Re: 6L5(b) 7th edition

If there is no solid metal at either the cathode or the anode to pass an electric current, Pt must be added. If there is no solid on the cathode side, Pt is added on the right and if there is no solid on the anode then Pt is added to the left. If there is no solid on either side then Pt is added to ...
by Emmaraf 1K
Mon Feb 25, 2019 11:51 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: ln(k2/k1)=(-delta H/R)(1/T2 - 1/T1)
Replies: 3
Views: 170

ln(k2/k1)=(-delta H/R)(1/T2 - 1/T1)

We learned this equation in class but to calculate K when not at 25 degrees C yet it's not on our formula sheet. Will it be on the test and if so how would it show up/would we have to memorize it?
by Emmaraf 1K
Mon Feb 25, 2019 11:47 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: Redox Reactions
Replies: 4
Views: 63

Re: Redox Reactions

The oxidizing agent is the element which really wants to be reduced. Therefore, it is the one with the highest positive standard potential.
by Emmaraf 1K
Mon Feb 25, 2019 11:45 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Cell Diagram Order
Replies: 3
Views: 80

Re: Cell Diagram Order

There is no solid metal to generate the electric current on that side of the voltaic cell so platinum metal must be present for the half reaction to occur.
by Emmaraf 1K
Wed Feb 20, 2019 11:13 pm
Forum: Balancing Redox Reactions
Topic: H2O
Replies: 3
Views: 65

Re: H2O

If you have more oxygen atoms on one side, add enough H2O to the other side so that both sides have the same number of oxygen atoms. Then, you will have a disproportionate number of H atoms on the side you added H2O to so add enough H+ to the other side of the reaction so that there are the same num...
by Emmaraf 1K
Thu Feb 14, 2019 10:27 pm
Forum: Thermodynamic Systems (Open, Closed, Isolated)
Topic: intensive and extensive
Replies: 2
Views: 142

Re: intensive and extensive

An extensive property is a value that changes depending on the amount of something (grams, moles, etc) whereas an intensive property doesn't change depending on amount. Heat capacity is extensive since it's units are only J/K whereas specific heat capacity is specific to a single gram of something (...
by Emmaraf 1K
Thu Feb 14, 2019 9:57 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: Degeneracy
Replies: 4
Views: 152

Re: Degeneracy

Degeneracy never equals 0 since having a degeneracy equal to 0 is like saying something doesn't have a single state which it can occupy aka it doesn't exist. The question on the midterm I believe you are thinking about had a degeneracy=1 so entropy=0 because S=klnW and lnW = 0. The molecule could on...
by Emmaraf 1K
Wed Feb 13, 2019 3:33 pm
Forum: Administrative Questions and Class Announcements
Topic: Midterm Review Question
Replies: 10
Views: 305

Re: Midterm Review Question

Can you post the explanation to 14. I feel like you need the enthalpy of CH4? Would you calculate it by finding the change in entropy associated with the loss of CH4 and O2 by calculating their entropies/mol (step 1), then finding the change in entropy as the reaction proceeds by doing delta H of th...
by Emmaraf 1K
Tue Feb 12, 2019 7:28 pm
Forum: Administrative Questions and Class Announcements
Topic: Midterm Review Question
Replies: 10
Views: 305

Re: Midterm Review Question

Jim Brown 14B Lec1 wrote:
Jim Brown 14B Lec1 wrote:I think you need the bond enthalpy for ethane, then use it to heat water to 100º C and to reach its ∆Hvap

Enthalpy of combustion*


Okay that makes 10x more sense . Thanks!
by Emmaraf 1K
Tue Feb 12, 2019 6:46 pm
Forum: Administrative Questions and Class Announcements
Topic: Midterm Review Question
Replies: 10
Views: 305

Re: Midterm Review Question

I am completely lost on #12. How would you even start?
by Emmaraf 1K
Tue Feb 12, 2019 6:25 pm
Forum: Entropy Changes Due to Changes in Volume and Temperature
Topic: 7th ed. 4I9
Replies: 2
Views: 64

7th ed. 4I9

For part b, you are asked to find S of surroundings, system, and total for an irreversible isothermal expansion. In the solution, it says w=0 since it's a free expansion (what does this mean?) and that delta U=0 (but why if it is irreversible?). It later says delta S surroundings = 0 and total entro...
by Emmaraf 1K
Tue Feb 12, 2019 6:22 pm
Forum: Phase Changes & Related Calculations
Topic: Slope of heating curve
Replies: 8
Views: 208

Re: Slope of heating curve

A higher heat capacity means a substance can better withstand and input of heat and will not increase its temperature as easily. Hence, a higher heat capacity means a less steep slope.
by Emmaraf 1K
Tue Feb 12, 2019 5:33 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Enthalpy of formation
Replies: 2
Views: 60

Re: Enthalpy of formation

Any element in its most stable state has an enthalpy of formation of 0. If you look at a periodic table which has states of matter labelled, the element in that state of matter has an enthalpy of formation of 0 except for diatomics which must have 2 atoms present at their most stable state of matter...
by Emmaraf 1K
Tue Feb 12, 2019 5:31 pm
Forum: Entropy Changes Due to Changes in Volume and Temperature
Topic: Entropy Calculations
Replies: 1
Views: 31

Re: Entropy Calculations

I believe you are talking about calculating entropy of say the vaporization of water at 298K. We don't know any equation for the entropy of the vaporization of water at 298 degrees, we only know it at water's boiling point 373K. However, enthalpy is a state function so if we can undergo a bunch of p...
by Emmaraf 1K
Tue Feb 12, 2019 10:07 am
Forum: Calculating Standard Reaction Entropies (e.g. , Using Standard Molar Entropies)
Topic: Assume Ideal Behavior
Replies: 3
Views: 120

Re: Assume Ideal Behavior

Tbh I think some of the textbook questions forgot to include number of moles. That phrase is used to denote to use the 3/2 R and 5/2 R values for C in the entropy equations.
by Emmaraf 1K
Tue Feb 12, 2019 10:01 am
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: Irreversible and Reversible Expansion
Replies: 2
Views: 52

Re: Irreversible and Reversible Expansion

In irreversible expansion, the outer pressure will suddenly drop from say 2 to 1 ATM and so the piston will constantly be pushing against 1 ATM of pressure. In reversible expansion, the pressure outside slowly drops bit by bit from 2 to 1.9 to 1.8 to 1.7 (not actually by .1 but by an infitesimally s...
by Emmaraf 1K
Tue Feb 12, 2019 9:10 am
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: Problem 4C.3 (7th ed.)
Replies: 1
Views: 34

Re: Problem 4C.3 (7th ed.)

For q=mcdeltaT, use Cv under constant volume and Cp under constant pressure.
by Emmaraf 1K
Tue Feb 12, 2019 9:08 am
Forum: Phase Changes & Related Calculations
Topic: Specific Heat of Ice
Replies: 3
Views: 104

Re: Specific Heat of Ice

Be aware of the heat/temperature curve for water. A lot of the problems we have done have had ice at zero degrees so it will just start to melt when heat is added since zero is the melting point. If we start at less than zero degrees, say -3, then to get to the melting point we need to raise the tem...
by Emmaraf 1K
Tue Feb 12, 2019 9:06 am
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: assuming no work
Replies: 2
Views: 48

Re: assuming no work

If volume does not change then work is 0
by Emmaraf 1K
Tue Feb 12, 2019 9:04 am
Forum: Entropy Changes Due to Changes in Volume and Temperature
Topic: Entropy
Replies: 1
Views: 33

Re: Entropy

Yes entropy changes. I believe the equation you gave is for isothermal expansion so temperature is constant over the course of the process. However in the equation S=q/T it is evident that temperature does matter.
by Emmaraf 1K
Sun Feb 10, 2019 11:00 pm
Forum: Administrative Questions and Class Announcements
Topic: Lyndon's HOTDOG MIDTERM REVIEW SESSION!! FINALLY!
Replies: 49
Views: 2620

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

Temperature is supposed to be given for #6 I believe.
EDIT: Okay the review system I went to did end up giving us the temperature but you can calculate it n your own using PV=nRT where pressure and volume is the pressure and volume of the system after the isochoric step so V=10l and P=10atm
by Emmaraf 1K
Sat Feb 09, 2019 11:04 pm
Forum: Concepts & Calculations Using Second Law of Thermodynamics
Topic: Spontaneity
Replies: 2
Views: 44

Re: Spontaneity

It would be nonspontaneous since entropy is negative and Gibbs free energy is also positive since deltaG=deltaH-TdeltaS
by Emmaraf 1K
Wed Feb 06, 2019 2:14 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Heat vs Enthalpy
Replies: 1
Views: 39

Re: Heat vs Enthalpy

Enthalpy is heat at a constant pressure. When pressure changes, the amount of final heat within a system is dependent on how the pressure has changed so pathway does matter in this scenario.
by Emmaraf 1K
Mon Feb 04, 2019 4:15 pm
Forum: Thermodynamic Definitions (isochoric/isometric, isothermal, isobaric)
Topic: Negative or Positive Work
Replies: 3
Views: 60

Re: Negative or Positive Work

When stuff is happening from the outside on the system, work is positive. When the working is doing stuff on its own accord, work is negative. It is similar to how when there is an input of heat from the outside, heat is positive and when heat is released by the system, q is negative.
by Emmaraf 1K
Thu Jan 31, 2019 9:09 pm
Forum: Thermodynamic Systems (Open, Closed, Isolated)
Topic: reversible expansion
Replies: 3
Views: 51

Re: reversible expansion

The volumes are normally given to you. Also, sometimes the question will say that the system expands by x amount in which case you add the initial volume and x to get the secondary volume.
by Emmaraf 1K
Mon Jan 28, 2019 12:56 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: Water specific heat capacity
Replies: 2
Views: 33

Re: Water specific heat capacity

Water contains hydrogen bonds which require a lot of heat in order to break so its temperature doesn't rise very easily because most of the energy goes into just trying to break these hydrogen bonds. Therefore, water has a high boiling point because it is hard to generate the heat necessary to overc...
by Emmaraf 1K
Thu Jan 24, 2019 4:11 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Autoprotolysis
Replies: 3
Views: 74

Autoprotolysis

At what concentration of equilibrium hydronium ions must we consider the autoprotolysis of water as being an important factor in pH calculation. Is it 10^-6 or 10^-7?
by Emmaraf 1K
Tue Jan 22, 2019 11:44 am
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Given Equilibruim Partial Pressures and a Volume
Replies: 2
Views: 45

Re: Given Equilibruim Partial Pressures and a Volume

Yes. Although if you are referring to a certain problem it seems odd to me they would give you volume with partial pressures unless there was a second part to the question but for your purposes you are right.
by Emmaraf 1K
Tue Jan 22, 2019 11:43 am
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: Changing Pressure
Replies: 6
Views: 124

Re: Changing Pressure

Yes, changing the volume is like compressing/decompressing the container which the reaction is taking place so pressure and volume have an inverse relationship. A decrease in volume is an increase in pressure and an increase in volume is a decrease in pressure. Therefore a volume decrease/pressure i...
by Emmaraf 1K
Mon Jan 21, 2019 1:38 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: 5G9 7th ed.
Replies: 1
Views: 18

5G9 7th ed.

Given the equilibrium equation 2O3 <--> 3O2, why will the Partial pressure O2/Partial pressure O3 value change if you start with a different concentration of O3?
by Emmaraf 1K
Wed Jan 16, 2019 5:43 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: partial pressure v concentration
Replies: 4
Views: 62

Re: partial pressure v concentration

You can always use either but make sure you use Kp for partial pressure and Kc for concentration.
by Emmaraf 1K
Wed Jan 16, 2019 5:41 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: pH of Hydronium Ion
Replies: 1
Views: 30

Re: pH of Hydronium Ion

Basically what was meant in lecture is that when you get the hydronium ion concentration is less than 10^-7, this value is really representing the change in hydronium ion concentration (think "x" in the ICE table) from the initial hydronium ion concentration, which was 10^-7. Therefore, si...
by Emmaraf 1K
Wed Jan 16, 2019 5:34 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: Question on Problem 6A.19C in 7th Edition
Replies: 3
Views: 32

Re: Question on Problem 6A.19C in 7th Edition

I emailed my TA about some of the issues with negative pH in the 7th edition textbook and she agreed that it looked odd and would ask Dr. Lavelle about it. I think the solutions manual is just wrong in a few cases.
by Emmaraf 1K
Tue Jan 15, 2019 12:10 am
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: Question on Problem 6A.19C in 7th Edition
Replies: 3
Views: 32

Re: Question on Problem 6A.19C in 7th Edition

I'm going to email my TA about this tomorrow but I think some questions in the 7th edition are incorrect in the cases where the pH/pOH aren't in the range of 0 to 14 since there are a few problems in the textbook (I remember one of them was a table where H+ and OH- concentration were 1.5M) where the...
by Emmaraf 1K
Mon Jan 14, 2019 2:30 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: 7th Edition 5H 3
Replies: 2
Views: 32

Re: 7th Edition 5H 3

Looking at the table, you have to divide the reaction into two parts so imagine the reaction happening in two steps to get to the final equation. The first step will have a K value as will the second step. Therefore, to find the final K value, multiply the Ks from the first and second step to get th...
by Emmaraf 1K
Fri Jan 11, 2019 1:25 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: What do you do if all products are pure substances?
Replies: 2
Views: 39

Re: What do you do if all products are pure substances?

Yes, you would just put 1 (but in the numerator since the products are in the numerator and the reactants are in the denominator)
by Emmaraf 1K
Fri Jan 11, 2019 1:12 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: Can you cause a shift in equilibrium by increasing pressure by adding in a non-gas?
Replies: 2
Views: 36

Can you cause a shift in equilibrium by increasing pressure by adding in a non-gas?

It is my understanding that adding in an inert gas doesn't affect equilibrium/create a shift because it will behave as an ideal gas meaning it won't have a volume. If volume isn't changing, then the concentration isn't changing so the equilibrium stays where it is. However, what happens if say a liq...
by Emmaraf 1K
Fri Jan 11, 2019 1:08 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: Inert gases
Replies: 4
Views: 267

Re: Inert gases

I don't believe adding an inert gas changes the equilibrium regardless of whether it is an open or closed system. Assuming the inert gas behaves as an ideal gas, the gas is said to take up no space aka that it has no volume. Therefore, if volume isn't changing then the concentration isn't changing i...
by Emmaraf 1K
Fri Jan 11, 2019 1:00 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: ICE Table Help
Replies: 3
Views: 73

Re: ICE Table Help

I think you might be looking back at the problem in the wrong order from when we took the notes. It was given that the dead muscle tissue has an ATP concentration at equilibrium 7.214x10^-11 but that originally it was 8.435x10^-3. We didn't solve for the 7.214x10^-11 value since it was give to us. W...
by Emmaraf 1K
Thu Dec 06, 2018 11:12 pm
Forum: Bronsted Acids & Bases
Topic: 7th ed. 6A9
Replies: 2
Views: 58

Re: 7th ed. 6A9

NH4I(s) --> NH3(g) + HI(g)
I clearly see that if the NH4I was separate as ions the NH4 gives a proton/hydrogen to the I but they don't exist as separate ions and isn't that necessary since otherwise why does the textbook give a hint to write the net ionic equation?
by Emmaraf 1K
Thu Dec 06, 2018 3:47 pm
Forum: Calculating pH or pOH for Strong & Weak Acids & Bases
Topic: 7th ed. 6C17
Replies: 1
Views: 42

7th ed. 6C17

How do you determine which is the strong base out of BrO- and C17H19O3N? Did the solutions manual just use the list of pKa values in the textbook?
by Emmaraf 1K
Thu Dec 06, 2018 3:45 pm
Forum: Amphoteric Compounds
Topic: 7th ed. 6A17
Replies: 3
Views: 81

7th ed. 6A17

How do you know Bi2O3 is an amphoteric compound? Do you just assume because Bi is close to the metalloids even though it isn't one itself?
by Emmaraf 1K
Thu Dec 06, 2018 3:44 pm
Forum: Bronsted Acids & Bases
Topic: 7th ed. 6A9
Replies: 2
Views: 58

7th ed. 6A9

Why does letter b showcase a reaction between a Bronsted acid and a base? The hint says to give a net ionic equation so you can clearly identify the reactants and where the movement of the proton is but in the question, NH4I won't be separated in the net ionic equation since it's a solid. Therefore,...
by Emmaraf 1K
Thu Dec 06, 2018 3:27 pm
Forum: Naming
Topic: 7th ed. 9C9
Replies: 1
Views: 35

7th ed. 9C9

How do you determine the oxidation numbers for Pt and Cr? What does the "en" and "edta" mean?
by Emmaraf 1K
Thu Dec 06, 2018 3:25 pm
Forum: Naming
Topic: 9C1 7th edition
Replies: 2
Views: 69

9C1 7th edition

Why do the answers for b and d not include "ate" at the end of the transition metal so why isn't it "cobaltate"? The solution manual for some of them includes the "ate" like for letters a and c and then all of them include "ion" at the end. Why is this?
by Emmaraf 1K
Thu Dec 06, 2018 12:47 pm
Forum: Identifying Acidic & Basic Salts
Topic: Neutral salt
Replies: 3
Views: 121

Re: Neutral salt

Yes, if the cation is a conjugate acid of a strong base and the anion of the salt is a conjugate acid of a strong acid then the salt will have no effect on pH
by Emmaraf 1K
Wed Dec 05, 2018 6:49 pm
Forum: Amphoteric Compounds
Topic: List of amphoteric compounds
Replies: 2
Views: 39

List of amphoteric compounds

Without seeing reactions which show a compound as and acid and then a base, is there any way to tell an amphoteric compound just by looking at its Lewis structure? Is there a general way to tell? Also since the metalloids are generally amphoteric is there a list we should know?
by Emmaraf 1K
Wed Dec 05, 2018 6:41 pm
Forum: Conjugate Acids & Bases
Topic: Strong acids and bases to memorize
Replies: 9
Views: 252

Strong acids and bases to memorize

Since conjugate bases of weak acids form basic solutions and conjugate acids of weak bases form acidic solutions does anyone have just a clean list of strong acids and bases to memorize where we just can assume if the acid/base isn't on the list then it's weak? I believe for strong bases it's those ...
by Emmaraf 1K
Wed Dec 05, 2018 6:34 pm
Forum: Polyprotic Acids & Bases
Topic: Defintion
Replies: 5
Views: 148

Re: Defintion

A polyprotic acid is one which can break off a hydrogen ion more than once so if an acid contains more than one hydrogen atoms then it is polyprotic such as H2SO4 or H3PO4
by Emmaraf 1K
Sat Nov 24, 2018 1:18 pm
Forum: Hybridization
Topic: Specific steps for 2.45 7th Ed.
Replies: 1
Views: 37

Specific steps for 2.45 7th Ed.

Could someone go through the specific steps for solving 2.45 on the 7th Ed. How do you determine whether hybrid orbitals or unhybridized orbitals are used in the sigma or pi bonds and how do you determine the lone pairs?
by Emmaraf 1K
Wed Nov 21, 2018 9:52 am
Forum: Hybridization
Topic: predicting hybrids
Replies: 3
Views: 45

Re: predicting hybrids

You can only figure out VSEPR structure by knowing the hybridization type since hybridizations just tell you the numbers of regions of electron density. d2sp3 is octahedral, dsp3 is trigonal bipyramidal, sp3 is tetrahedral, sp2 is trigonal planar, and sp is linear. To get molecular geometry, you nee...
by Emmaraf 1K
Sun Nov 11, 2018 7:19 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Interaction Potential Energy
Replies: 1
Views: 35

Re: Interaction Potential Energy

The negative sign indicates attraction and all these interactions are attractive.
by Emmaraf 1K
Thu Nov 08, 2018 11:00 am
Forum: Bond Lengths & Energies
Topic: HW 2.25 part a
Replies: 3
Views: 143

Re: HW 2.25 part a

If I recall correctly, the HCN has a triple bond between the C and N while the other molecule only has a single bond. Single bonds are longer/weaker than triple bonds.
by Emmaraf 1K
Wed Nov 07, 2018 6:27 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: Why are larger hydrocarbons more solid?
Replies: 2
Views: 53

Re: Why are larger hydrocarbons more solid?

Larger hydrocarbons have more electrons which means greater polarizability which means greater attractive forces/stronger bonds between molecules. Stronger bonds/greater attractive forces between molecules results in the molecules forming a solid because solids are more tightly held together.
by Emmaraf 1K
Wed Nov 07, 2018 6:25 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: Greater polarizability of larger molecules
Replies: 6
Views: 90

Greater polarizability of larger molecules

I get that larger molecules have more electrons, but why does that cause greater polarizability? Is it because the more electrons there are, the more chances there are for electrons to become unequally distributed to create a partial negative and partial positive charge within the molecule?
by Emmaraf 1K
Wed Nov 07, 2018 6:22 pm
Forum: Bond Lengths & Energies
Topic: 2.25 Homework Problem
Replies: 4
Views: 93

Re: 2.25 Homework Problem

The answer is a combination of the other two posts. For one, P has a larger atomic radius, thereby making the bond longer. Secondly, N has a higher electronegativity meaning it pull electrons in the bond closer to it thereby making the bond shorter.
by Emmaraf 1K
Wed Nov 07, 2018 6:13 pm
Forum: Bond Lengths & Energies
Topic: problem 3.85b
Replies: 1
Views: 49

Re: problem 3.85b

Bond length isn't related to the number of bonds in the molecule. The bonds within SO2 and SO3 are all double bonds so the bond strength/bond length is considered equal. You can think of the bond lengths as averages of the lengths of all the bonds in the molecule and so given the length of an S=O bo...
by Emmaraf 1K
Thu Nov 01, 2018 10:51 am
Forum: Ionic & Covalent Bonds
Topic: Finding out the likely ion that forms
Replies: 2
Views: 52

Finding out the likely ion that forms

For question 2A15, the anticipated ion formed by Cadmium is a +2 which I understand because it has 2 electron in its 5s orbital which it wants to get rid of but what about the exceptions to electron configurations in the transition metals like copper and chromium (since while we don't need to know t...
by Emmaraf 1K
Thu Nov 01, 2018 10:32 am
Forum: Lewis Structures
Topic: The Number of Valence Electrons in Transition Metals
Replies: 2
Views: 73

Re: The Number of Valence Electrons in Transition Metals

But @Sara Lakamsani 4C why do you include the 3d orbitals in the number of valence electrons? Doesn't valence electrons only come from the outermost shell which would be when n=4 for Mn? I understand the correct answer is 7 but why do you count the 2 4s electrons and the 5 3d electrons when counting...
by Emmaraf 1K
Wed Oct 31, 2018 6:21 pm
Forum: Lewis Structures
Topic: Periodic Table Trends
Replies: 2
Views: 63

Re: Periodic Table Trends

I think another rule to follow is if formal charges are all else equal (in terms of magnitude), then the correct structure should have the negative formal charges on the atoms with the largest electron affinities.
by Emmaraf 1K
Wed Oct 31, 2018 6:17 pm
Forum: Octet Exceptions
Topic: Max # of bonds
Replies: 4
Views: 127

Max # of bonds

Since the atoms which can have an expanded octet do so by accessing their d orbitals, does that mean some atoms could form 9 bonds (since 1 s orbital, 3 p orbitals, and 5 d orbitals? Then, for some atoms which can access their f orbitals, could they even form 16 bonds (1 s orbital, 3 p orbitals, 5 d...
by Emmaraf 1K
Wed Oct 31, 2018 5:06 pm
Forum: Resonance Structures
Topic: Resonance merging
Replies: 3
Views: 98

Re: Resonance merging

Lewis dot structures are inaccurate because electrons don't actually just stay stagnant in bonds but are found throughout the molecule and can move/have momentum. Therefore, the electron density at different points in time is constantly changing but on average, there is an equal electron density at ...
by Emmaraf 1K
Wed Oct 31, 2018 4:58 pm
Forum: Formal Charge and Oxidation Numbers
Topic: Formal Charge variables?
Replies: 2
Views: 69

Re: Formal Charge variables?

Another easy way to calculate formal charge is to just do Valence electrons - # of bonds - number unpaired electrons = formal charge since then you don't have to divide by 2 when counting# bonded electrons. It speeds up the calculation and makes you less prone to making mistakes in my opinion.
by Emmaraf 1K
Thu Oct 25, 2018 12:35 am
Forum: Trends in The Periodic Table
Topic: Ionization energies
Replies: 9
Views: 182

Re: Ionization energies

The electron shielding doesn't outweigh the increase in nuclear charge when moving left to right on the periodic table. Therefore, since the electrons are pulled stronger into the nucleus, it's harder to remove and electron so ionization energy is greater. The added electron shielding going from Cs ...
by Emmaraf 1K
Thu Oct 25, 2018 12:30 am
Forum: Trends in The Periodic Table
Topic: Ionic radius
Replies: 2
Views: 44

Re: Ionic radius

Look at the nuclear charge of the isoelectric anions/cations/atoms. The higher the nuclear charge, the smaller the atom/cation/anion will be because the electrons will have a stronger pull inward thereby making the radius smaller.
by Emmaraf 1K
Thu Oct 25, 2018 12:28 am
Forum: Electron Configurations for Multi-Electron Atoms
Topic: Ordering of electrons in d-shell
Replies: 2
Views: 56

Re: Ordering of electrons in d-shell

You put the subshells in order of their principal quantum number and then their angular momentum quantum number. Going from the s to the d subshells, for example the 4s and 3d, the 4s subshell becomes a higher energy when the 3d starts to be filled which is why the 4s should be written afterwards wh...
by Emmaraf 1K
Wed Oct 24, 2018 11:28 pm
Forum: Trends in The Periodic Table
Topic: Ionization Energy
Replies: 6
Views: 134

Re: Ionization Energy

Are you referring to a specific question? Looking at a chart online for ionization energies, it says the ionization energy for sulfur is less than oxygen.
by Emmaraf 1K
Tue Oct 23, 2018 7:50 pm
Forum: Electron Configurations for Multi-Electron Atoms
Topic: 3d and 4s
Replies: 2
Views: 88

3d and 4s

Do we know the reason why the 4s subshell is a lower energy than the 3d UNTIL the 3d subshell starts to be filled. What causes the switch in energy to occur?
by Emmaraf 1K
Tue Oct 23, 2018 7:45 pm
Forum: Electron Configurations for Multi-Electron Atoms
Topic: Test Two: Electron Configuration
Replies: 6
Views: 129

Re: Test Two: Electron Configuration

Response to Lily Smith on electron spin: In addition to the other commenter, electron spin is more of a concept to help us understand the nature of electrons and why it's possible to have two electrons in a single orbital. Technically, electrons don't exactly "spin" in the traditional sens...
by Emmaraf 1K
Tue Oct 23, 2018 7:36 pm
Forum: Electron Configurations for Multi-Electron Atoms
Topic: Why do we always start with "up" spin?
Replies: 2
Views: 36

Why do we always start with "up" spin?

When writing electron configurations for atoms in their ground state, why do we always start with electrons having an up spin when filling a subshell? If the ground state just denotes the lowest energy state of the atom, why does it matter whether we fill one orbital with up spin and then the next o...
by Emmaraf 1K
Tue Oct 23, 2018 7:22 pm
Forum: Trends in The Periodic Table
Topic: Question 2.67 6th edition
Replies: 1
Views: 28

Re: Question 2.67 6th edition

There are certain exceptions to those trends for electron affinity and ionization energy. Carbon and nitrogen is one of those exceptions for electron affinity (as is all of group 4 vs group 5 elements). The exception arises because nitrogen has a half filled p subshell whereas carbon's p subshell on...
by Emmaraf 1K
Tue Oct 23, 2018 6:32 pm
Forum: *Particle in a Box
Topic: Purpose of Particle in a Box
Replies: 2
Views: 250

Re: Purpose of Particle in a Box

Particle in a Box questions give us the right mindset to apply the Schrodinger's Equation since we can think of electrons as being the particles inside the box which is a molecule. We use the box concept to denote that that the particle can't be found outside the box (which is why the PE inside the ...
by Emmaraf 1K
Tue Oct 23, 2018 6:27 pm
Forum: Electron Configurations for Multi-Electron Atoms
Topic: Building- Up Principle
Replies: 5
Views: 105

Re: Building- Up Principle

It is believed that the half filled d subshell and half filled s subshell is a more stable configuration than when the s is completely filled but the d shell only has 4 electrons since having a half filled subshell increases stability.
by Emmaraf 1K
Tue Oct 23, 2018 6:15 pm
Forum: Electron Configurations for Multi-Electron Atoms
Topic: Electron Configuration for Tungsten
Replies: 1
Views: 40

Re: Electron Configuration for Tungsten

We don't need to know anything past the 3d subshell for the test but after looking information about Tungsten up, it oddly doesn't follow the half-filled d subshell exception like chromium so you do the electron configuration normally, including the lanthanides which represent the 4f orbitals.Theref...
by Emmaraf 1K
Tue Oct 23, 2018 5:55 pm
Forum: Properties of Electrons
Topic: Difference between electron's particle like and wave like characteristics
Replies: 5
Views: 184

Re: Difference between electron's particle like and wave like characteristics

Various experiments displayed the wave-particle duality of electrons. The photoelectric effect showed how electrons acted as particles because when a photon with a certain threshold frequency was absorbed by an electron, the electron was shot out like a particle (kind of like billiards). In contrast...

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