## Search found 68 matches

Fri Mar 15, 2019 10:34 pm
Forum: Calculating pH or pOH for Strong & Weak Acids & Bases
Topic: Test 1 problem 5
Replies: 6
Views: 439

### Re: Test 1 problem 5

I have a different version of the test but I got the problem right. Could you post the full equation for the problem? What is the pH of a 0.020 M solution of sodium propionate? the pKa of c3h6o2 is 4.88 C3H5o2-(aq) + H20(l) --> C3H6O2(aq) + OH-(aq) I know how to do the problem I just want to make s...
Fri Mar 15, 2019 9:58 pm
Forum: Calculating pH or pOH for Strong & Weak Acids & Bases
Topic: Test 1 problem 5
Replies: 6
Views: 439

### Test 1 problem 5

I know its a little late but can someone tell me what the answer for number 5 on test 1? I want to make sure I got it right. I had my test on Wednesday and the problem asked about a 0.02 M solution with a pKa of 4.88. Thanks!
Fri Mar 15, 2019 7:54 pm
Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
Topic: Which cell potential?
Replies: 1
Views: 254

### Which cell potential?

When we are arranging different atoms in order of increasing/decreasing strength as reducing agents, how do we know which cell potential to use? some elements have several cell potentials depending on how many electrons are added (for example, Fe+ to Fe has a different cell potential than Fe2+ or Fe...
Mon Mar 11, 2019 10:03 pm
Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
Topic: 7th edition 6O.1
Replies: 2
Views: 130

### 7th edition 6O.1

how do you do this? and does someone know the equivalent problem in the 6th edition?
Mon Mar 11, 2019 10:02 pm
Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
Topic: 7th edition 6N.15
Replies: 1
Views: 120

### 7th edition 6N.15

I have no idea how to do this lol. I dont know the equivalent problem in the fact 6th edition so if someone knows can you put it in the replies so other people can look at it? Thanks!
Mon Mar 11, 2019 10:01 pm
Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
Topic: 7th edition 6N.7b
Replies: 1
Views: 105

### 7th edition 6N.7b

Can someone explain why n=1? When I write out the half reactions, 2 electrons are being transferred from the 2 H+ atoms to the H2 molecule.
Wed Mar 06, 2019 10:19 am
Forum: Reaction Mechanisms, Reaction Profiles
Topic: fast and slow elementary reactions
Replies: 3
Views: 152

### fast and slow elementary reactions

when finding the rate constant from elementary reactions, do we ignore the slow reaction or the fast reaction and why?
Mon Mar 04, 2019 3:23 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: E cell spontaneity
Replies: 5
Views: 238

### Re: E cell spontaneity

Is there a quick way to assume the sign of the Ecell? if I understand your question correctly, you can determine the sign of Ecell depending on whether or not the reaction is spontaneous. so if G for the reaction is negative, Ecell is positive and vice versa. and if the reaction favors the products...
Mon Mar 04, 2019 3:21 pm
Forum: Second Order Reactions
Topic: 7th edition 7B.13
Replies: 3
Views: 391

### 7th edition 7B.13

how do you find the time it takes for the second order reactions to take place in 7B.13? what formula do we need to use?
Mon Mar 04, 2019 3:19 pm
Forum: General Rate Laws
Topic: units of rates and rate constants
Replies: 4
Views: 189

### units of rates and rate constants

what are the basic units for rates and rate constants? are they different for different orders?
Wed Feb 27, 2019 9:50 am
Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
Topic: flipping the sign of Ecell
Replies: 5
Views: 215

### flipping the sign of Ecell

if the E cell for a half reaction in Appendix 2B has a positive value, but the half reaction used in the problem is the other way around, do we flip that value of Ecell?
Mon Feb 25, 2019 11:38 am
Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
Topic: trends in standard potential
Replies: 2
Views: 121

### trends in standard potential

what are the periodic trends for standard potential? specifically, can someone explain 7th edition 6M.7?
Mon Feb 25, 2019 11:32 am
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: order of cell notation
Replies: 1
Views: 82

### order of cell notation

does the order of the molecules on the left or right side matter when writing the ruction using cell notation? for example, if the anode half reaction has Fe2+ going to Fe3+, should we write Fe2+, Fe3+ or Fe3+, Fe2+? I know Lavelle said something about that but I can't remember what it was. also, ho...
Mon Feb 25, 2019 11:27 am
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: 7th 6L.7 / 6th #15 [ENDORSED]
Replies: 1
Views: 121

### 7th 6L.7 / 6th #15[ENDORSED]

can someone show me their work or explain how to do this problem? I'm confused on all three parts. it's 6L.7 from the 7th edition, and 15 from the 6th edition.
Mon Feb 25, 2019 10:49 am
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Pt in a cell diagram
Replies: 1
Views: 100

### Pt in a cell diagram

how do you know when you need to add Pt in the cell diagram? I thought it was when everything on one side of the diagram was in the same phase, but there was one example in the textbook that had solid and aqueous iodine which still had platinum. so how do you know if it needs platinum?
Wed Feb 20, 2019 10:35 am
Forum: Gibbs Free Energy Concepts and Calculations
Topic: Delta G a state function?
Replies: 23
Views: 835

### Re: Delta G a state function?

Aidan Ryan 1B wrote:What are things we have learned that are not state functions?

work and heat are the only things we've learned about that aren't state functions
Wed Feb 20, 2019 10:34 am
Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
Topic: Units for Gibbs
Replies: 8
Views: 329

### Re: Units for Gibbs

I dont think it matters, as long as it makes sense. For example, using joules would be better if you get something like 57 J, because that would be 0.057 kJ and it just looks neater with J. On the same note, if you get 57000 J, it might be better to convert that to 57 kJ
Wed Feb 20, 2019 10:32 am
Forum: Gibbs Free Energy Concepts and Calculations
Topic: 4J.15
Replies: 2
Views: 141

### Re: 4J.15

this would depend on what you get for the entropy of reaction. PCl5 is less stable at higher temperatures because the resulting entropy is negative. HCN is more stable at higher temperature because the entropy is positive.
Mon Feb 11, 2019 12:37 pm
Forum: Concepts & Calculations Using First Law of Thermodynamics
Replies: 4
Views: 167

I would assume that we would have to convert it to joules. since U is the internal energy, and energy is measured in joules, they would probably expect us to give the answer i joules. but the conversion from L*atm to joules is given on the formula sheet, so you don't have to memorize it, just rememb...
Mon Feb 11, 2019 12:30 pm
Forum: Concepts & Calculations Using Second Law of Thermodynamics
Topic: 3/2 R and 5/2 R
Replies: 3
Views: 153

### 3/2 R and 5/2 R

What types of problems would we be using 3/2 R, 5/2 R, 3R, 7/2 R, and 4R? what exactly do those values indicate, and what part of a word problem would indicate that our calculations require us to use those values?
Mon Feb 11, 2019 12:26 pm
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: 7th edition 4C.13
Replies: 1
Views: 114

### 7th edition 4C.13

for 4C.13, I tried calculating q(water)=-q(ice) using the mass of the ice and the specific heat of the ice, however, I wasn't getting the right answer. the solutions manual uses the molar heat of ice instead of the specific heat of ice. is there a reason why using the specific heat of ice would be w...
Mon Feb 04, 2019 11:02 pm
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: reaction constant P
Replies: 3
Views: 130

### Re: reaction constant P

the changes in pressure and volume have a minimal effect on solids and liquids because of how tightly packed the atoms are compared to gases. liquids and solids can not change volume if they are compressed, however atoms in gases are far enough apart that they are affected by compressions. the same ...
Mon Feb 04, 2019 10:52 pm
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: enthalpy of combustion vs formation
Replies: 3
Views: 163

### enthalpy of combustion vs formation

what is the enthalpy of combustion, and how is it different from the enthalpy of formation? how does it affect the calculation of reaction enthalpy? for example, in exercise 4D.15?
Mon Feb 04, 2019 10:49 pm
Forum: Concepts & Calculations Using Second Law of Thermodynamics
Topic: 7th edition 4F.7
Replies: 3
Views: 158

### 7th edition 4F.7

can someone explain why we use 5/2 R and 3/2 R in the calculation of entropy for problem 7? I dont quite understand what those values indicate.
Mon Jan 28, 2019 9:21 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: calorimeter
Replies: 2
Views: 109

### calorimeter

can someone explain how calorimeters and bomb calorimeters work? I dont really understand the explanation in the textbook. what do they do and what are we trying to calculate when doing problems?
Mon Jan 28, 2019 9:19 pm
Forum: Calculating Work of Expansion
Topic: Irreversible vs. Reversible Expansion
Replies: 2
Views: 120

### Re: Irreversible vs. Reversible Expansion

I think it depends on the surroundings of the reaction, for example certain containers allow it to be reversible, while others restrict it. I may be wrong, but this is what I understood from the homework problems. regardless, the homework seems to tell you whether or not its reversible, so I dont th...
Mon Jan 28, 2019 9:17 pm
Forum: Calculating Work of Expansion
Topic: value of R?
Replies: 4
Views: 185

### value of R?

what is the value of the constant R? in one of the homework problems, we used R=0.08206 in the n=PV/RT formula, but then we used R=8.314 in the w=-nRTlnV1/V2 formula. why is the value of R different?
Tue Jan 22, 2019 8:38 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: 7th edition 5.35
Replies: 1
Views: 89

### 7th edition 5.35

does anyone understand how to do 5.35? thats the one with the graph
Tue Jan 22, 2019 5:39 pm
Forum: Calculating pH or pOH for Strong & Weak Acids & Bases
Topic: determining x for weak acids and bases
Replies: 6
Views: 395

### determining x for weak acids and bases

when we calculate x for weak acid/base problems, we can disregard x in the denominator when Ka is less than 10^-3, because it doesn't add any significant change to the concentration of the reactants. does this same logic apply to the problems we solved for the chemical equilibrium section?
Tue Jan 22, 2019 5:22 pm
Forum: Calculating pH or pOH for Strong & Weak Acids & Bases
Topic: pH vs pKa
Replies: 1
Views: 313

### pH vs pKa

what is the difference between the pH and the pKa? what does each one calculate? and the same with pOH and pKb?
Mon Jan 14, 2019 1:16 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Forward vs. Reverse Reactions
Replies: 4
Views: 245

### Re: Forward vs. Reverse Reactions

if Q is less than K, that means that there are currently more reactants than products, which means that products will continue to form until the solution reaches K, which is equilibrium. if Q is greater than K, it means that the concentrations of the products are higher than the equilibrium concentr...
Mon Jan 14, 2019 1:04 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: 7th edition 5I.35
Replies: 1
Views: 120

### 7th edition 5I.35

can someone explain how to do this problem?
Mon Jan 14, 2019 12:58 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: 7th edition 5I.29
Replies: 1
Views: 71

### 7th edition 5I.29

for this problem, in the solutions manual, it says "because the equilibrium constant is small, assume that x<<0.22"

what does this mean?
Tue Jan 08, 2019 10:44 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: 5G3
Replies: 2
Views: 115

### Re: 5G3

I believe that the format of (P^x) is for partial pressures of gases, while the format of [C]^x is for concentrations of solute. I'm not sure if they can be interchanged however, can someone clarify that?
Tue Jan 08, 2019 10:39 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Leaning to the left/right
Replies: 4
Views: 179

### Leaning to the left/right

what does it mean when the reaction is leaning to the left or the right? or when a reaction is shifted to the left/right? there were some questions about it in the first video module, but I dont really understand the concept.
Tue Jan 08, 2019 10:37 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: 7th edition 5G.5
Replies: 3
Views: 103

### 7th edition 5G.5

I am working through the homework for this section and I dont understand how to do 5G.5, especially part c. Can someone explain the logic behind solving this problem?
Sat Dec 08, 2018 3:49 pm
Forum: Identifying Acidic & Basic Salts
Topic: salts of weak acids and bases
Replies: 4
Views: 441

### salts of weak acids and bases

can someone explain why salts of weak bases produce acidic solutions and salts of weak acids produce basic solutions?
Sat Dec 08, 2018 3:48 pm
Forum: Air Pollution & Acid Rain
Topic: Acid Rain and Respiratory Acidosis
Replies: 1
Views: 272

### Acid Rain and Respiratory Acidosis

what do we need to know about acid rain and respiratory acidosis for the final?
Tue Dec 04, 2018 1:05 pm
Forum: Bronsted Acids & Bases
Topic: Determining Acidity
Replies: 3
Views: 191

### Determining Acidity

How do you determine how acidic an acid is? for example, if you had to put HClO3, HClO, HClO2, and HClO4 in order from least to most acidic, how would you go about doing that? how would you do it for bases?
Tue Dec 04, 2018 1:03 pm
Forum: *Molecular Orbital Theory (Bond Order, Diamagnetism, Paramagnetism)
Topic: C2 bond??
Replies: 1
Views: 324

### C2 bond??

I was looking at an old final and saw a question about the C2+ bond and the C2- bond. What would the lewis structures of C2+ and C2- look like? and which has a stronger bond? How do you calculate bond order?
Tue Dec 04, 2018 1:01 pm
Forum: Lewis Acids & Bases
Topic: How to Identify Lewis acid and Bases
Replies: 4
Views: 558

### Re: How to Identify Lewis acid and Bases

From what I understand, this is correct. Lewis bases have lone pairs that they are able to donate to a bond, while the acids have room to accept that electron pair. I found this online: "A Lewis acid is a chemical species that contains an empty orbital which is capable of accepting an electron ...
Tue Nov 27, 2018 10:27 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Seesaw Shape Bond Angles
Replies: 8
Views: 347

### Re: Seesaw Shape Bond Angles

I think its less than both 90 and 120 but I might be wrong
Tue Nov 27, 2018 9:21 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: 7th edition 2E.13b
Replies: 2
Views: 66

### 7th edition 2E.13b

for 7th edition 2E.13b, which is N2O, how can we assume that N is the central atom, and not O?
Tue Nov 27, 2018 9:07 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: AX3E2
Replies: 2
Views: 131

### AX3E2

for molecules with an AX3E2 shape, why do the electron pairs take equatorial positions and not axial positions? since the lone pair-lone pair repulsion is the strongest, wouldn't it make sense that the two lone pairs would distance themselves as much as possible, and therefore take axial positions? ...
Mon Nov 19, 2018 10:51 pm
Forum: Hybridization
Topic: Hybridized vs. Unhybridized Orbitals
Replies: 4
Views: 1528

### Re: Hybridized vs. Unhybridized Orbitals

hybridized orbitals have energy that is between unhybridized orbitals, it can be seen as a blend of different orbitals. such as the sp3 hybridized orbital, which is a blend of the s orbital and the 3 p orbitals, and has an energy that is between the s and p orbitals. this also results in a different...
Mon Nov 19, 2018 10:48 pm
Forum: Hybridization
Topic: Sigma and Pi Bonds [ENDORSED]
Replies: 12
Views: 464

### Re: Sigma and Pi Bonds[ENDORSED]

sigma bonds involve a single overlap, such as when two s orbitals overlap, or one s overlaps with a p orbital. pi bonds involve a double overlap, such as when two p orbitals overlap side by side, so that they are inflexible. this is why pi bonds are stronger
Mon Nov 19, 2018 10:42 pm
Forum: Hybridization
Topic: D-orbital
Replies: 5
Views: 188

### Re: D-orbital

either is fine although im not sure if one is preferred over the other
Sun Nov 11, 2018 11:25 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: 7th edition 2E.5
Replies: 1
Views: 106

### 7th edition 2E.5

Can someone explain how to do this problem? what does the lewis structure look like and how can we determine the bond angle based off of that?
Sun Nov 11, 2018 11:23 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Polar and Non-polar
Replies: 3
Views: 133

### Re: Polar and Non-polar

a general rule of them that I use for polarity is whether or not the molecule is symmetrical. for examples, something like CH4 would not be polar because it is symmetrical. also, polarity has to do with the electronegativity charges of the atoms in the bond. if a molecule consists of a very electron...
Sun Nov 11, 2018 11:21 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Bond angles
Replies: 3
Views: 166

### Bond angles

how do you know what the bond angles between atoms are from just knowing the structure? for example for 7th edition 2E.7 part c, how do you know that there is a 109.5 degree angle?
Mon Nov 05, 2018 10:30 pm
Forum: Bond Lengths & Energies
Topic: Lengths of Bonds
Replies: 9
Views: 260

### Re: Lengths of Bonds

because the larger number of shared electrons draw the atoms in closer together
Mon Nov 05, 2018 10:20 pm
Forum: Formal Charge and Oxidation Numbers
Topic: formal charge on most electronegative atom
Replies: 3
Views: 245

### Re: formal charge on most electronegative atom

yes since the most electronegative atom is the central atom, it is bonded to most of the other atoms on the compound. in order for it to be the most stable, the central atom should have a formal charge as close to 0 as possible
Mon Nov 05, 2018 10:16 pm
Forum: Electronegativity
Topic: Electron Affinity vs. Ionization Energy
Replies: 8
Views: 381

### Re: Electron Affinity vs. Ionization Energy

electron affinity is the energy it takes for an atom to gain an electron. ionization energy is the energy needed for an atom to lose an electron. the trend for both is the same, it increases across a group and decreases down a period.
Tue Oct 30, 2018 10:57 am
Forum: Ionic & Covalent Bonds
Topic: Octet Rule
Replies: 7
Views: 288

### Re: Octet Rule

The exceptions are the first few atoms because they usually lose electrons to fill just the 1s orbital. I think other exceptions are like the example from class with SO4, where sulfur had more than 8 electrons because they went into the 3d orbital of sulfur.
Tue Oct 30, 2018 10:54 am
Forum: Lewis Structures
Topic: Drawing Lewis Structures
Replies: 14
Views: 673

### Drawing Lewis Structures

When drawing Lewis structures, how do you know where the atoms are? Like what angles the atoms are? Sometimes they're all in a straight line, but other times they're at 90 degree angles.
Tue Oct 30, 2018 10:53 am
Forum: Resonance Structures
Topic: Resonance
Replies: 8
Views: 389

### Resonance

What does it mean when the bonds of the resonance structures are all the same length? How does that compare to a molecule with bonds that have different lengths? And how do we know which of the resonance structures exist in real life?
Mon Oct 22, 2018 11:00 pm
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: Test 2 Question
Replies: 3
Views: 209

### Test 2 Question

On the study guide summary it says we need to knowhow to: Describe the interpretation of atomic orbitals in terms of probability.

What does this mean?
Mon Oct 22, 2018 10:59 pm
Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
Topic: Frequency Condition
Replies: 2
Views: 174

### Frequency Condition

Instead of using this: En = - h R / n^2
Can we use this: frequency = R(1/n1^2 - 1/n2^2)

What's the difference? Prof Lavelle uses the first one but the textbook uses the second.
Mon Oct 22, 2018 10:55 pm
Forum: *Shrodinger Equation
Topic: Schrodinger's Equation
Replies: 6
Views: 729

### Schrodinger's Equation

This is what it says on the list of things we need to know for the upcoming test: Understand the relationship between Schrodinger's equation (H ψ = E ψ), wave functions, and orbitals. I know we don't need to know any calculations, but what do we need to know about schrodingers equation? Can someone ...
Wed Oct 17, 2018 11:41 pm
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: Problem 1D 13
Replies: 2
Views: 105

### Problem 1D 13

For 1D 13 part d, how do you know that there are 4 sub shells for a shell with n=6?
Wed Oct 17, 2018 11:39 pm
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: Problem 1D 23
Replies: 2
Views: 152

### Problem 1D 23

How do you do 1D 23? Can someone explain the concepts behind it as well as explain the answers?
Wed Oct 17, 2018 11:38 pm
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: Determining Orbitals
Replies: 1
Views: 132

### Determining Orbitals

How do you determine how many orbitals an atom has based on whether its s, p, d, or f? For example, problem 1D 19?
Tue Oct 09, 2018 10:13 am
Forum: Properties of Light
Topic: Exam
Replies: 7
Views: 262

### Re: Exam

So far, I have just been repeating problems from the textbook in order to see what areas I'm weak in. I personally didn't like the audio visual modules because the answers were multiple choice, which isn't what we're going to have on the test. I will also do more problems from the book that aren't a...
Tue Oct 09, 2018 10:11 am
Forum: Photoelectric Effect
Topic: Photoelectric Effect and Experiment
Replies: 2
Views: 88

### Photoelectric Effect and Experiment

Can someone explain what the photoelectric experiment and effect are in simpler terms? I had a hard time following the lecture.
Tue Oct 09, 2018 10:09 am
Forum: Administrative Questions and Class Announcements
Topic: Test 1 Study Plan
Replies: 6
Views: 325

### Test 1 Study Plan

I am taking Test 1 this Thursday. What is the best study plan? Should I focus on Test 1 topics until the test, and start Ch 1 homework after the test, or should I start working on Ch 1 at the same time as reviewing for Test 1? What are you all doing?
Tue Oct 02, 2018 11:40 am
Forum: Empirical & Molecular Formulas
Topic: Solving For Empirical and Molecular Formulas
Replies: 4
Views: 1643

### Re: Solving For Empirical and Molecular Formulas

If you first find the mass %, you can then easily assume that there is 100g of sample in order to determine the empirical formula. Then, you can use the mass percentages to find the number of moles of Co and F. After that, divide both values by the smaller of the two values in order to determine the...
Tue Oct 02, 2018 11:33 am
Forum: Empirical & Molecular Formulas
Topic: Chemical Equations?
Replies: 4
Views: 269

### Re: Chemical Equations?

The coefficient is showing the ratio of each molecule in a chemical equation. It's easier to understand if you think of it like the number of atoms or molecules in an equation, but if you are doing any calculations, it would be considered the number of moles. It technically is the number of moles fo...
Tue Oct 02, 2018 11:23 am
Forum: SI Units, Unit Conversions
Topic: formula units [ENDORSED]
Replies: 69
Views: 24638

### Re: formula units[ENDORSED]

The way I understand it is: formula units can mean atoms or molecules, depending on what the question is asking for. For example, if you need to find the number of formula units in a a certain mass of H2O, you calculate the number of H2O molecules. But if it asks you to find the number of hydrogen a...