## Search found 113 matches

Wed Mar 13, 2019 11:56 am
Forum: Arrhenius Equation, Activation Energies, Catalysts
Topic: collision theory
Replies: 2
Views: 75

### collision theory

Could someone possibly explain the collision theory to me please?
Tue Mar 12, 2019 10:40 pm
Forum: Balancing Redox Reactions
Topic: Coefficients
Replies: 3
Views: 198

### Re: Coefficients

They don’t affect the oxidation numbers, but it affects the charge of the molecule and thus, the number of electrons needed to balance the charges on both sides
Tue Mar 12, 2019 10:38 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: Ice melting
Replies: 4
Views: 384

### Re: Ice melting

I like to think of spontaneity as the ability of a reaction to occur on its own, meaning that the reaction does not require additional energy in order for the reaction to take place
Tue Mar 12, 2019 10:34 pm
Forum: Administrative Questions and Class Announcements
Topic: Sig Figs
Replies: 9
Views: 519

### Re: Sig Figs

I believe sig figs will be important on the exam. I believe TAs had checked for sig figs in the midterm, so I assume it’ll be the same for the final as well
Tue Mar 12, 2019 7:27 pm
Forum: Reaction Mechanisms, Reaction Profiles
Topic: Slow step in reaction mechanisms
Replies: 1
Views: 80

### Slow step in reaction mechanisms

does anyone happen to understand why the slow step determines the rate?
Tue Mar 12, 2019 7:25 pm
Forum: Reaction Mechanisms, Reaction Profiles
Topic: Units
Replies: 3
Views: 153

### Re: Units

the units vary depending on the order. rate has the units of mol/(L*s), and concentration has units of mol/L. Thus, to find the units of k, you need to first determine the order of the reaction. For example, if you had A + A -> Product, the rate = k[A]^2. To get the right side of the equal side equa...
Tue Mar 12, 2019 7:16 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Partial Pressure to Concentration
Replies: 3
Views: 117

### Re: Partial Pressure to Concentration

You can use the equation PV = nRT. Find the value of n (units = moles) then divide it by the volume (units = L) to find concentration
Tue Mar 12, 2019 7:14 pm
Forum: General Rate Laws
Topic: Rate Laws
Replies: 8
Views: 252

### Re: Rate Laws

I would recommend knowing how he derived in case there are conceptual questions about it. I would also be familiar with the graphs, such as which order has a linear graph, etc.
Sun Mar 10, 2019 7:44 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: What does K say about stability?
Replies: 5
Views: 594

### What does K say about stability?

For Q1 part c on the midterm, the question asked us to comment on the relative stability of the reactants and products, and the equilibrium constant (Kp) given was 3 x 10^4. The solutions said the formation of SO3- was more stable because Kp is a large number, but I don’t really understand why. Coul...
Sun Mar 10, 2019 4:53 pm
Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
Topic: question 5 on Test 2
Replies: 2
Views: 149

### question 5 on Test 2

This problem asked us to determine if a pH = 7 is acidic or basic when the temperature went from 25 Celsius to 10 C. Standard enthalpy was 58 kJ/mol and Kw at 25 Celsius = 10^-14, and the equation was 2H_{2}O (aq) \leftrightharpoons H3O^{+} (aq) + OH^{-} (aq) Does anyone happ...
Sun Mar 10, 2019 4:07 pm
Forum: Balancing Redox Reactions
Topic: increasing oxidation power
Replies: 2
Views: 144

### increasing oxidation power

On test 2, one of the questions asked us to place the following in order of increasing oxidation power going from their second oxidation state to neutral: Ti2+, Sn2+, Mg2+

I'm a bit confused how to rank them based on their oxidation power. Can someone explain please?
Sat Mar 09, 2019 10:53 am
Forum: Reaction Mechanisms, Reaction Profiles
Topic: Reaction mechanisms
Replies: 2
Views: 113

### Reaction mechanisms

Would we be expected to know how to write the intermediate steps for a certain compound/molecule?
Thu Mar 07, 2019 9:01 pm
Forum: Second Order Reactions
Topic: Final
Replies: 30
Views: 790

### Final

Will the final mainly be on the materials we learned after the Midterm and/or Test 2?
Mon Mar 04, 2019 7:56 am
Forum: Kinetics vs. Thermodynamics Controlling a Reaction
Replies: 73
Views: 3786

It honestly depends on how you prefer to study. If you like going going through problems and solving them step by step, then the STEP UP sessions would be beneficial. However if you’re like me, where you’re confused about certain topics and would rather do problems on your own then ask questions, th...
Mon Mar 04, 2019 7:52 am
Forum: Method of Initial Rates (To Determine n and k)
Topic: Order of the reactant (n)
Replies: 4
Views: 183

### Re: Order of the reactant (n)

It’s essentially the coefficient in front of the reactant or product and it’s raised to the concentration of that reactant or product. For example, if given 2NO2 -> 2NO + O2, and asked to find the rate of consumption of NO2, it’ll be rate = k[NO2]^2.
Mon Mar 04, 2019 7:49 am
Forum: Zero Order Reactions
Topic: How to determine zero order rxts
Replies: 1
Views: 93

### How to determine zero order rxts

When given a reaction, how would we determine if a reactant or product is a zero order reactant or some other order reaction? For example, in the book, they said for 2NH3 -> N2 + 3H2 the rate of consumption of NH3 is a zero order reaction, so the rate is equal to k. How would we have known from the ...
Tue Feb 26, 2019 7:51 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Writing Cell Diagrams
Replies: 3
Views: 99

### Re: Writing Cell Diagrams

An UA told me you don't need it when you have a metal present on both sides of the salt bridge. However, if one or both sides lacked a metal, then you would insert Pt (s) on the side(s) without a metal
Tue Feb 26, 2019 7:48 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Calculating standard potential of cell
Replies: 1
Views: 66

### Re: Calculating standard potential of cell

When you switch the reaction, the standard potential sign is reversed. However, it is important to note that if you multiply an entire chemical equation by a number, you DO NOT multiple the standard potential by that number. You only that for standard gibb free energy of the reaction. For example if...
Tue Feb 26, 2019 7:38 pm
Forum: Balancing Redox Reactions
Topic: Oxidation states for Oxygen
Replies: 2
Views: 92

### Re: Oxidation states for Oxygen

One of the UAs told me that in order to figure out if O3 is being oxidized or reduced, you would need to know if the other element in the equation is being reduced or oxidized. For instance, if you had O3 + Br- -> O2 + BrO3-, Br- is being oxidized. Thus, if Br- is oxidized, that means O3 must be red...
Tue Feb 26, 2019 7:35 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: help on 14.24 b and c
Replies: 1
Views: 72

### help on 14.24 b and c

Does anyone happen to know how to write the half reactions for 14 b and c? I'm stuck 14.24) Predict the standard cell potential and calculate the standard reaction Gibbs free energy for galvanic cells having the following cell reactions: b) 2 H2(g) + O2(g) -> 2 H2O(l) in acidic solution c) 2 H2(g) +...
Sun Feb 24, 2019 9:09 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Help on 14.11d
Replies: 1
Views: 83

### Help on 14.11d

For 14.11 part d, the question asks us to write the half reactions and the balance redox reaction for the following galvanic cell: Pt(s) | O2 (g) | H+ (aq) || OH- (aq) | O2 (g) | Pt (g) I understand that the side to the left of the salt bridge represents oxidation and the side to the right represent...
Sat Feb 23, 2019 8:35 pm
Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
Topic: test 3
Replies: 10
Views: 361

### Re: test 3

everything from gibbs energy to the end of friday's lecture, which is section 14.6 in the 6th edition of the textbook
Sat Feb 23, 2019 8:32 pm
Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
Replies: 4
Views: 204

It's given on the formula sheet so you don't have to memorize it
Sat Feb 23, 2019 8:30 pm
Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
Topic: Standard Potentials and Equilibrium Constants
Replies: 2
Views: 92

### Re: Standard Potentials and Equilibrium Constants

I do not believe so since I don't recall Professor Lavelle going over that during lecture yet
Fri Feb 22, 2019 12:12 pm
Forum: Balancing Redox Reactions
Topic: oxidation state of MnO4-
Replies: 3
Views: 138

### oxidation state of MnO4-

For the example Professor Lavelle did in lecture Wednesday, 2/20/19, he said the oxidation state of MnO4- was +7. Can someone please explain why the oxidation number +7 please? I am confused how to find the oxidation state for metals in the d-block.
Wed Feb 20, 2019 7:48 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: Determining stability of a compound/reaction when there's an increase in temperature
Replies: 2
Views: 153

### Determining stability of a compound/reaction when there's an increase in temperature

What is the best way to determine if a compound or reaction is stable or unstable?

For example, for 9.65, the question asks us to determine which of the compounds is less stable when temperature is raised: PCl5, HCN, NO, and SO2. How w ould I determine the stability of the compounds?
Wed Feb 20, 2019 7:41 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Potential Difference
Replies: 2
Views: 88

### Potential Difference

What exactly is potential? Dr. Lavelle mentioned potential and potential difference today in lecture, but I'm unsure what it is exactly.
Wed Feb 20, 2019 7:39 pm
Forum: Balancing Redox Reactions
Topic: Trends
Replies: 5
Views: 144

### Re: Trends

How would we figure put the oxidation number for the transition metals or the ones in the d-block, such as Mn for example? Will it be given to us on the exam?
Mon Feb 18, 2019 9:24 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: Molar Gibbs free energy
Replies: 3
Views: 189

### Molar Gibbs free energy

Is molar Gibbs free energy the same thing as the standard Gibbs free energy?
Mon Feb 18, 2019 5:09 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: Spontaneity and exothermic reactions
Replies: 3
Views: 160

### Spontaneity and exothermic reactions

Could someone please explain why exothermic reactions are mostly spontaneous?
Mon Feb 18, 2019 5:08 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: Delta G
Replies: 4
Views: 158

### Re: Delta G

I know for sure that Gibbs free energy itself is a state function. I’m not too sure about the change in G though.
Tue Feb 12, 2019 9:21 am
Forum: Concepts & Calculations Using First Law of Thermodynamics
Replies: 4
Views: 162

I believe you would need to convert it since U is supposed to be in terms of J or kJ. Like someone said, the formula to covert it is on the formula sheet so I would think that you need to convert it. I’m not sure if the TAs will take off points if you leave it in L•atm, but I would just convert it t...
Tue Feb 12, 2019 9:18 am
Forum: Thermodynamic Definitions (isochoric/isometric, isothermal, isobaric)
Topic: Residual energy
Replies: 2
Views: 302

### Residual energy

Could someone possibly explain residual energy? I’m still having a hard time understanding what it is exactly...
Tue Feb 12, 2019 9:17 am
Forum: Thermodynamic Definitions (isochoric/isometric, isothermal, isobaric)
Topic: delta U [ENDORSED]
Replies: 10
Views: 615

### Re: delta U[ENDORSED]

In lecture yesterday for one of the review problems that asked to calculate deltaS of an isothermal reaction, Lavelle mentioned that U = (3/2)nRT. Thus, If there’s no change in temperature, since n, R, and T are all constant, that means there’s no change in internal energy.
Tue Feb 12, 2019 9:11 am
Forum: Thermodynamic Definitions (isochoric/isometric, isothermal, isobaric)
Topic: Extensive vs Intensive
Replies: 5
Views: 224

### Extensive vs Intensive

Can someone please explain what an extensive and intensive property is?
Sun Feb 10, 2019 2:16 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: 8.73 Help (Bond Enthalpy)
Replies: 2
Views: 128

### 8.73 Help (Bond Enthalpy)

For part a, the questions asks us to find the reaction enthalpy for 3C2H2 (g) -> C6H6 (g). In the solutions manual, it says 6 moles of the C-C bonds are formed in the reaction. Where did they get 6 moles from? When I drew out the Lewis structure of C6H6, which came out to be a carbon ring with 6 hyd...
Fri Feb 08, 2019 5:41 pm
Forum: Entropy Changes Due to Changes in Volume and Temperature
Topic: Lecture Notes
Replies: 1
Views: 108

### Lecture Notes

Hello! I wasn't able to stay for the entire lecture today (2/8/19) since I had a meeting, so I was wondering if one of you guys could possibly send me photos of the lecture notes.

Thanks!
Thu Feb 07, 2019 1:23 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: when to solve for specific vs. molar heat capacity
Replies: 2
Views: 94

### when to solve for specific vs. molar heat capacity

How do you know to calculate for specific or molar capacity if it's not specified in the question? For instance, for 8.31, the question asks for us to "calculate the heat released by 5.025 g of Kr(g) at 0.400 atm as it cools from 97.6 C to 25.0 C at (a) constant pressure and (b) constant volu...
Thu Feb 07, 2019 11:46 am
Forum: Concepts & Calculations Using Second Law of Thermodynamics
Topic: Help on 9.5
Replies: 4
Views: 118

### Re: Help on 9.5

Entropy has the units energy over temperature, or joules per kelvin. You are correct that you need to add them together. However, you need to find the individual entropies by dividing the joules by their temperature in kelvin. Then add those values like the book to find entropy. hope this helps. Oh...
Thu Feb 07, 2019 11:43 am
Forum: Entropy Changes Due to Changes in Volume and Temperature
Topic: question on 9.11
Replies: 1
Views: 76

### question on 9.11

The question asks us to calculate the change in entropy when the pressure of 1.50 mol Ne(g) is decreased isothermally from 15.0 atm to 0.500 atm while assuming ideal behavior. When I used the equation from the book \Delta S = nR\ln (P1/P2) , I got -42.416. However, in the back, the answer sa...
Thu Feb 07, 2019 9:17 am
Forum: Concepts & Calculations Using Second Law of Thermodynamics
Topic: Help on 9.5
Replies: 4
Views: 118

### Help on 9.5

The questions asks to find the TOTAL entropy change of a process in which 40 kJ of energy is transferred as heat from a large reservoir at 800 k to one at 200 k. I thought I had to just add them, but the solutions manual did it differently. They did -40000 J / 800 K and 40000 J / 200 K then added th...
Mon Feb 04, 2019 9:35 pm
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: qv vs qp
Replies: 9
Views: 387

### Re: qv vs qp

qv is heat at constant volume, while qp is heat at constant pressure, as denoted by the subscripts. The question would typically ask you which one to solve for or would typically state which one is constant. Hope this helps! just wondering, if a question asked us to solve for Qv or Qp, how would we...
Mon Feb 04, 2019 9:27 pm
Forum: Concepts & Calculations Using Second Law of Thermodynamics
Topic: residual energy
Replies: 3
Views: 210

### residual energy

Today in lecture, Professor Lavelle talked about residual energy. Could someone please explain what it is? I'm still a bit confused.

He also mentioned that CH4 had no residual energy, but CH3Cl had residual energy. Could someone explain how to determine if a molecule has residual energy please?
Mon Feb 04, 2019 1:58 pm
Forum: Concepts & Calculations Using Second Law of Thermodynamics
Topic: Degeneracy
Replies: 5
Views: 198

### Degeneracy

Today Professor Lavelle talked about dengenracy. I was wondering if someone could explain what degeneracy actually is. I’m having a hard time thinking about it conceptually? Is it just the number of possible outcomes?
Thu Jan 31, 2019 10:46 am
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Question on yesterday’s lecture
Replies: 2
Views: 113

### Question on yesterday’s lecture

For the lecture Wednesday, 1/30/19, Professor Lavelle started off with thermodynamics. Does anyone happen to know if this is still part of CH8 of the 6th edition (7th edition: CH4) or another chapter?
Tue Jan 29, 2019 8:34 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Help on 8.37a.
Replies: 1
Views: 91

### Help on 8.37a.

For this question, we are asked to find the enthalpy of vaporization of methane, given that the vaporization of .579 moles of CH4 (l) requires 4.76 kJ of heat? My friend told me that to find the answer, I need to divide heat by the moles (4.76 / .579), but I don't understand why. Can someone please ...
Tue Jan 29, 2019 6:57 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: Heat capacity vs. enthalpy
Replies: 4
Views: 164

### Heat capacity vs. enthalpy

Could someone please explain what the difference between heat capacity and enthalpy is? I’m still a bit confused.

Thanks!
Tue Jan 29, 2019 6:52 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: Exothermic vs. Endothermic
Replies: 10
Views: 1563

### Re: Exothermic vs. Endothermic

Professor Lavelle gave example of a hot/cold pack during lecture one day, and I thought it was helpful. Endothermic reactions require heat to obtain the products (delta H = positive) while exothermic reactions release heat during reactions (delta H = negative). Given that, with a hot pack, when you ...
Tue Jan 29, 2019 6:45 pm
Forum: Phase Changes & Related Calculations
Topic: Test #1
Replies: 11
Views: 387

### Re: Test #1

Yes, I believe we will be getting them back during discussion this week since our midterm is coming up. If not, then latest by next week or so.
Mon Jan 21, 2019 3:22 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Test 1 & homework
Replies: 2
Views: 111

### Re: Test 1 & homework

According to some TAs and UAs, Professor Lavelle should be providing the values for Ka, Kb, pKa, and pKb on the exam
Mon Jan 21, 2019 3:17 pm
Forum: Non-Equilibrium Conditions & The Reaction Quotient
Topic: Acid Strength
Replies: 3
Views: 118

### Re: Acid Strength

Strong Acid: Large Ka, small pKa; also means the conjugate base will be weak Weak Acid: Small Ka, large pKa; also means the conjugate base will be strong Strong Base: Large Kb, small pKb; also means the conjugate acid will be weak Weak: Small Kb, large pKb; also means the conjugate acid will be strong
Mon Jan 21, 2019 3:14 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: Change in temperature's effect on K
Replies: 4
Views: 154

### Re: Change in temperature's effect on K

To remember which direction the reaction will favor if the reaction is endothermic or exothermic, I like to have a visual in mind. If the reaction is endothermic, that means the reaction requires heat to form its products. So in the chemical equation, on the side of the reactants, heat should be add...
Thu Jan 17, 2019 9:54 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Help on 12.45
Replies: 1
Views: 70

### Help on 12.45

The question asks us to arrange the bases in order of increasing strength based on the pKa values of their conjugate acids (given in paraentheses): ammonia (9.26), methylamine (10.56), ethylamine (10.81), aniline (4.63) Does anyone happen to know how to solve this? Would I need to convert the pKa va...
Thu Jan 17, 2019 9:10 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Writing the Phases in equation
Replies: 2
Views: 128

### Writing the Phases in equation

Does anyone happen to know if points will be taken off if we don't include the phases of the molecules when writing the chemical equations?
Thu Jan 17, 2019 9:07 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Sig Figs
Replies: 3
Views: 143

### Re: Sig Figs

Yes that is correct! I would not worry about significant figures too much for this class though. According to the TAs, they will not pay too much attention to significant figures this quarter, meaning they won't take off points if you use an incorrect number of sig figs. Unless the question specific...
Wed Jan 16, 2019 9:19 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Concentration
Replies: 4
Views: 179

### Re: Concentration

Adding on to what Andre said, if Q < K, then it means there's a greater concentration of reactants, which means the reaction will favor and produce more products (reaction goes to the right) since it'll want to balance out the equation. However, if Q > K, then it means there's a greater amount of pr...
Wed Jan 16, 2019 9:13 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: Test topics for next week
Replies: 3
Views: 122

### Re: Test topics for next week

I believe the test will cover everything from the first lecture to friday's lecture, which starts from chemical equilibrium to some of acids and bases (i think my TA said the professor might go over salts on friday)
Tue Jan 15, 2019 9:12 am
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Question on 12.41
Replies: 3
Views: 117

### Question on 12.41

For this question, it says to use tables 12.1 and 12.2 to place the bases in order of increasing strength: F-, NH3, CH3CO2-, and C5H5N.

Only C5H5N is present on the tables. How do I determine which base is stronger and weaker (F-, NH3, and CH3CO2-)?
Tue Jan 15, 2019 9:06 am
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Help on 12.39
Replies: 1
Views: 49

### Help on 12.39

For the sixth edition, CH12 #39, it says use tables 12.1 and 12.2 to place the following acids in order of increasing strength: HNO2, HCLO2, +NH3OH, and (CH3)2NH2+ +NH3OH and (CH3)2NH2+ aren’t included on the two tables. How do I figure out which is the stronger acid? Is there a way to figure this o...
Mon Jan 14, 2019 4:21 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Acids and Bases
Replies: 7
Views: 264

### Acids and Bases

I haven't taken Chem 14A in a long time, so I don't remember how to figure out if an acid/base is strong or weak. Can someone please explain how you could determine if an acid or base is strong or weak without being given the chemical equation? Also, in class,the Professor did an example where we ha...
Tue Jan 08, 2019 7:27 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Kc vs. Kp
Replies: 7
Views: 270

### Re: Kc vs. Kp

I would recommend you look at the values you're given in the problem first to determine if you solve for Kc or Kp. In the problem, if you're given values for the reactants and products and they're in units of bars, then that means you'll be solving for Kp since pressure is measured in bars. However,...
Mon Jan 07, 2019 3:09 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Help on 11.13
Replies: 2
Views: 84

### Help on 11.13

For this question, we are asked to find the reaction quotient Q. For part b, the equation is P_4S_10(s)+16H_2O(l)\rightleftharpoons 4H_3PO_4(aq)+10H_2S(aq) and the answer is [H3PO4]^4[H2S]^1^0 . I am confused why we still need to take aqueous solutions into account. I...
Mon Jan 07, 2019 2:54 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Help on 11.9: b and c
Replies: 4
Views: 141

### Help on 11.9: b and c

For this question, we are asked to balance then write the equilibrium expression Kc for the reactions For part b, the equation is I_2 (g) + F_2 (g) -> IF_5 . I balanced the equation and got I_2 (g) + 5F_2 (g) -> 2IF_5 . Then I used the equation in the book, K = (R...
Mon Jan 07, 2019 2:29 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Calculating Equilibrium Concentrations
Replies: 3
Views: 108

### Re: Calculating Equilibrium Concentrations

I believe Professor Lavelle will give us the concentrations on the exams.
Thu Jun 14, 2018 2:09 pm
Forum: Octet Exceptions
Topic: do we nee to memorize the octet exceptions?
Replies: 6
Views: 562

### Re: do we nee to memorize the octet exceptions?

i think all you need to know is that elements in period 3 and below can have expanded octets, and that H, Li, Be, and He don't have full octets
Thu Jun 14, 2018 2:07 pm
Forum: Shape, Structure, Coordination Number, Ligands
Topic: Charge on ligands? [ENDORSED]
Replies: 2
Views: 279

### Re: Charge on ligands?[ENDORSED]

It would help to know the charges on the ligands. There's a chart on page 742 that gives you all the common ligands and their charges. Once you know the overall charge on the ligand, to find the oxidation number of the transition metal, then you would need to see what number added to the ligand char...
Sun Jun 10, 2018 4:52 pm
Forum: Shape, Structure, Coordination Number, Ligands
Topic: Ligands to Memorize for the Final
Replies: 2
Views: 151

### Re: Ligands to Memorize for the Final

I'm not too sure which ones exactly, but I was told to look at the chart on pg. 742 in the textbook
Fri Jun 08, 2018 5:03 pm
Forum: Lewis Acids & Bases
Topic: HW 12.17 [ENDORSED]
Replies: 4
Views: 424

### HW 12.17[ENDORSED]

For this problem, we are being asked to state if the following oxides are acidic, basic, or amphoteric of BaO, SO3, As2O3, and Bi2O3.

How do you determine if it’s acidic, basic, or amphoteic if we’re just given the molecule? Do we just draw out the Lewis structure and see from there?
Thu Jun 07, 2018 8:15 pm
Forum: Shape, Structure, Coordination Number, Ligands
Topic: coordination number=polydentate number?
Replies: 5
Views: 254

### Re: coordination number=polydentate number?

Yes, I believe it does. My TA said coordination number is not equal to the number of ligands, but it's equal to the number of LIGAND ATTACHMENTS (or bonds) to the central atom.
Thu Jun 07, 2018 10:40 am
Forum: Shape, Structure, Coordination Number, Ligands
Topic: Polydentate
Replies: 5
Views: 251

### Re: Polydentate

Could someone please explain how you know if a molecule is polydentate or not? I’m still confused on this. For example, in 17.33, we’re asked if the given molecules are polydenatate or not, and if they are, how many places can it bind simultaneously? Two of the molecules given were (b) CO3 -2 And (c...
Thu Jun 07, 2018 9:14 am
Forum: Shape, Structure, Coordination Number, Ligands
Topic: Question on an example we did in class [ENDORSED]
Replies: 1
Views: 144

### Question on an example we did in class[ENDORSED]

In class, we had this example I believe: [Fe(CN)6] I know the coordination number is 6 since there are 6 ligand attachments to the central atom, but I believe Professor Lavelle said the oxidation state of Fe was +1. How is it +1? I know the charge on the CN ion is -1, but since Fe is attached to 6 l...
Thu Jun 07, 2018 9:08 am
Forum: Shape, Structure, Coordination Number, Ligands
Topic: Oxidation number
Replies: 4
Views: 271

### Re: Oxidation number

Oxidation number is the same as formal charge except bonding pairs are not split equally. They are both assigned to the more electronegative atom. Oxidation number = V - LPE - (BE shared with less electronegative atoms) Will we be expected to remember the charges of common polyatomic compounds for ...
Wed Jun 06, 2018 12:28 pm
Forum: Hybridization
Topic: strength of sigma and pi bonds
Replies: 10
Views: 646

### Re: strength of sigma and pi bonds

Yes, a sigma bond is stronger than a pi bond. This is because the length of a sigma bond is shorter than a pi bond, and it takes more energy to break a sigma bond. Wait but aren't sigma bonds single bonds? Wouldn't sigma bonds be weaker since single bonds are weaker than double bonds (which is what...
Wed May 30, 2018 3:04 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: 4.1
Replies: 5
Views: 293

### Re: 4.1

The first figure can have a lone pair because based on what Professor Lavelle said in the lecture the other day, if the central atom has two other atoms surrounding it, it shuld be linear, such as the figure shown in b. However, in a, the molecule has a bent shape. That means the molecule must have ...
Wed May 30, 2018 1:55 pm
Forum: Hybridization
Topic: hybridization example
Replies: 3
Views: 200

### Re: hybridization example

Yes he was only referring to the valence electrons of carbon. And I believe my TA told me that there was a hybridization question on one of the past finals, so there’s a chance we will see it on our final. I think the only type of question that we’d be asked is what the hybridization of the orbitals...
Wed May 30, 2018 1:44 pm
Forum: Lewis Structures
Topic: Test 3 Q2
Replies: 1
Views: 168

### Re: Test 3 Q2

When it's asking for stability, you need to consider if all atoms in the molecule have a full octet and if it has a low formal charge. For the way you did it with C having a pair of lone e- and having it be double bonded to O, which has two lone pair e-, O would have a full octet but C would not. C ...
Fri May 25, 2018 7:00 am
Forum: Ionic & Covalent Bonds
Topic: Help on 3.5
Replies: 2
Views: 189

### Re: Help on 3.5

The best way to approach these questions is to first write the electron configuration of Bi. The electron configuration for Bi is [Xe]4f14 5d10 6s2 6p3. But because the question is asking for the elec. config. of Bi 3+, that means you must remove 3 e- from the outermost shell or the highest e- level...
Fri May 25, 2018 6:54 am
Forum: Lewis Structures
Topic: chapter 3 hw #57 question
Replies: 5
Views: 289

### Re: chapter 3 hw #57 question

I believe the formula for perchlorate for given to us in a chart/diagram in Fundamentals Section D
Fri May 25, 2018 6:48 am
Forum: Lewis Structures
Topic: Lewis acid and base
Replies: 1
Views: 103

### Re: Lewis acid and base

I was told you should at least know or understand what a Lewis acid and base is for the test
Thu May 24, 2018 3:13 pm
Forum: General Science Questions
Topic: Chapter 6
Replies: 3
Views: 265

### Re: Chapter 6

Yes, we started Chapter 6 on Friday, but it was only a brief section on hydrogen bonds.
Thu May 17, 2018 11:25 pm
Forum: Ionic & Covalent Bonds
Topic: Help on 3.19
Replies: 1
Views: 94

### Re: Help on 3.19

The easiest way to approach these problems is to write out the normal electron configuration for the element first. The electron configuration for Sb is [Kr]4d1055s25p3. To find the configuration of Sb+3, you need to remove the e- from the highest energy level, which is the 5p subshell, so the confi...
Thu May 17, 2018 11:14 pm
Forum: Lewis Structures
Topic: Test #3
Replies: 11
Views: 640

### Re: Test #3

I believe there are some topics in Chapter 3 that we didn't touch upon, so I would say the test encompasses everything Professor Lavelle talked about during lecture (Lewis structures, bond strenth, etc.)
Thu May 17, 2018 12:36 am
Forum: Lewis Structures
Topic: HW 3.41
Replies: 2
Views: 128

### HW 3.41

For part b, we are asked to draw the Lewis structure of CH3OH. I drew it differently (see image below) from the book, but I still got a formal charge of 0 for each atom. Is the way I drew it still right or no?
Diagram for 3.41b
Thu May 17, 2018 12:14 am
Forum: Lewis Structures
Topic: Central atom
Replies: 7
Views: 413

### Re: Central atom

Wait, where are you guys getting ionization energy from? I thought the central atom has to be the element that was the least electronegative, which is why C is the central atom since it has the electronegativity
Tue May 08, 2018 11:26 am
Forum: Quantum Numbers and The H-Atom
Topic: 2.29
Replies: 9
Views: 601

### Re: 2.29

I still don't understand letters b and d. For the explanation for letter d, what do you mean by "only one orbital can exist in that location in space"? If l=2 aren't there 5 orbitals (ml)? And doesn't n=3 and l=2 refer to row 3 in the d block? Thank you and sorry if the questions are conf...
Tue May 08, 2018 11:05 am
Forum: Quantum Numbers and The H-Atom
Topic: Midterm Question
Replies: 2
Views: 211

### Re: Midterm Question

I'm positive my TA told us last week that points will be docked off for having an incorrect number of significant figures.
Tue May 08, 2018 11:01 am
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: spd orbitals and electron config.
Replies: 3
Views: 235

### Re: spd orbitals and electron config.

I think it also depends on the question, so be sure to read the question carefully! I believe if the question asks for the FULL electron configuration, you would need to write out all the subshells. But if the question just asks for the ground state, I believe you could use the noble gas abbreviatio...
Tue May 08, 2018 10:57 am
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: Ground state elec. config.
Replies: 3
Views: 190

### Re: Ground state elec. config.

For ground state electron, you need to order the subshells from lowest to highest energy first, so the electron configuration of Sn would be [Kr] 4d^10 5s^2 5p^2. When it's written this way, it's easier to see which subshell, at least for me, the electrons are removed from, which is outermost shell ...
Tue May 08, 2018 10:41 am
Forum: Ionic & Covalent Bonds
Topic: Midterm Topics [ENDORSED]
Replies: 33
Views: 2633

### Re: Midterm Topics[ENDORSED]

Will we need to be able to explain the existence of orbitals using the Heisenberg Uncertainity Principle or anything about the uncertainty principle for that matter? We will need to know how to do problems concerning the uncertainty principle, but I am not too sure about using it to explain the exi...
Thu May 03, 2018 1:17 pm
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: 2.43
Replies: 7
Views: 4865

### Re: 2.43

Also, could someone please explain to me why for part e, tungsten is [Xe]4f^14 5d^4 6s^2? If you follow the logic stated in some of the previous replies of how 4d^5 and 4^10 are more stable than 4d^9, then shouldn’t the ground state electron configuration of tungsten be [Xe]4f^14 5d^5 6s^1 instead o...
Thu May 03, 2018 12:33 pm
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: 2.43
Replies: 7
Views: 4865

### Re: 2.43

So how do we know when the element’s a “special case”? Do we only write, for example, 4d^10 5s^1 instead of 4d^9 5^2 when the element is near 4d^5 or 4d^10?
Thu May 03, 2018 10:41 am
Forum: Quantum Numbers and The H-Atom
Topic: 2.39
Replies: 4
Views: 392

### Re: 2.39

For further explanation for the whole question, (a, Carbon) shows 2 electrons in one p orbital when there are empty p orbitals, so it is in an excited state because ground state electrons want to be in separate orbitals. For (b, Nitrogen), one electron has opposite spin compared to the other two, b...
Thu May 03, 2018 9:54 am
Forum: Quantum Numbers and The H-Atom
Topic: Energy of electron vs. Energy Level
Replies: 2
Views: 194

### Energy of electron vs. Energy Level

If an atom undergoes a transition from say 1s to 2p, does the energy of the electron also increase? I know the energy state increases for sure since it’s going from the s-orbital to the p-orbital, but does that also mean the energy of th ELECTRON also increases? Can someone please explain why or why...
Thu May 03, 2018 9:38 am
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: Explanation to the answer of the question 2.31
Replies: 4
Views: 223

### Re: Explanation to the answer of the question 2.31

I’m confused as to why 4g can’t exist. Can someone explain this to me please?
Thu May 03, 2018 8:45 am
Forum: Quantum Numbers and The H-Atom
Topic: 2.29
Replies: 9
Views: 601

### Re: 2.29

Could someone explain part a and b please? I’m confused why the answer for a is 6 and 2 for part b. The question’s asking “how many electrons can have the following numbers in an atom.” For part a, we’re given that n=2 and l=1, so it’s referring to the 2p shell. I know that the p shell can hold a ma...
Thu May 03, 2018 8:33 am
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: Clarification on magnetic quantum number
Replies: 6
Views: 321

### Clarification on magnetic quantum number

I was wondering if someone could clarify my confusion about the magnetic quantum number (ml). I understand ml goes from l to -l. So if for example, ml = -2, -1, 0, 1, and 2, do each of the numbers correspond to an orbital? For instance, is -2 referencing to the d-orbitals along the negative x, y, z ...
Sun Apr 29, 2018 6:14 am
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: Difference between a shell, subshell, and orbital
Replies: 4
Views: 882

### Difference between a shell, subshell, and orbital

Could someone please explain what the difference between a shell, subshell, and orbital is? I don’t really see the difference between them.
Fri Apr 27, 2018 9:46 pm
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: Why does the 4s orbital come before the 3d?
Replies: 7
Views: 490

### Re: Why does the 4s orbital come before the 3d?

I am curious,why exactly does 3d have a lower energy level than 4s?
Fri Apr 27, 2018 3:56 pm
Forum: Electron Configurations for Multi-Electron Atoms
Topic: Ground State Configuration
Replies: 3
Views: 248

### Re: Ground State Configuration

Is there a difference between the electron configuration and the ground state configuration? Is ground state config. just another term for electorn config.?
Fri Apr 27, 2018 3:44 pm
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: Why does the 4s orbital come before the 3d?
Replies: 7
Views: 490

### Re: Why does the 4s orbital come before the 3d?

I was confused about this too. I don't understand the exact reason why 3d comes before 4s when writing the electron configuration.