## Search found 108 matches

Sat Mar 14, 2020 2:25 pm
Forum: General Rate Laws
Topic: Rate-determining step
Replies: 7
Views: 128

### Re: Rate-determining step

How can you identify which step of the reaction mechanism is the slowest step? Or will this just be given in the problem itself? If you are given the differential rate law and a proposed reaction mechanism (with its elementary steps), you can determine which elementary step is rate-determining by s...
Sat Mar 14, 2020 2:22 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Test 2 on Standard Cell Potential
Replies: 6
Views: 42

### Re: Test 2 on Standard Cell Potential

The half-reactions are Ce 4+ (aq) + e- = Ce 3+ (aq) Standard E = 1.44V Li+ (aq) + e- = Li (s) How do I know which one is the cathode and which one is the anode for me to use standard E cell = standard E cathode - standard E anode???? To determine which one is cathode and one which is anode, you hav...
Sat Mar 14, 2020 2:21 pm
Forum: Balancing Redox Reactions
Topic: Acid or base?
Replies: 5
Views: 147

### Re: Acid or base?

Will we always be given whether a solution is basic or acidic for balancing redox reactions? If we aren't, what are all the ways we'd be expected to know to determine if the solution is acidic or basic? I would expect that we would be given whether we are balancing the redox reactions in basic or a...
Sat Mar 14, 2020 2:19 pm
Forum: Reaction Mechanisms, Reaction Profiles
Topic: Mechanisms
Replies: 3
Views: 61

### Re: Mechanisms

Hi, I'm just really confused about what reaction mechanisms are and why they are relevant? A reaction mechanism is important because it shows how we derive the experimentally observed rate laws. Proposed reaction mechanisms show a series of elementary steps, which may be slow/fast, which help expla...
Sat Mar 14, 2020 2:18 pm
Forum: Student Social/Study Group
Topic: Curve?
Replies: 31
Views: 1371

### Re: Curve?

So the syllabus says that a 50% is required o pass the class with at least a C- but at the same time, "there's no curve" is what I've been hearing from most students so if I have a 75% in the class it'll remain the same but if I get a 50% it'll jump up to 70%? Based on what I've heard, a ...
Mon Mar 02, 2020 9:11 am
Forum: Kinetics vs. Thermodynamics Controlling a Reaction
Topic: Kinetics in Test 2?
Replies: 13
Views: 118

### Re: Kinetics in Test 2?

AngieGarcia_4F wrote:We're not going to be tested on kinetics in test 2 right?

For test 2, we only need to know the second page of Outline 4 and all of Outline 5 (Electrochemistry).
Mon Mar 02, 2020 9:10 am
Forum: Balancing Redox Reactions
Topic: Cell Diagrams
Replies: 5
Views: 78

### Re: Cell Diagrams

I know that the anode is on the left and cathode is on the right. My question is, that for species that are in the same phase, occurring in either cathode or anode, and separated by a comma, is there a particular order to them in the cell diagram? Eg Pb4+ +Sn2+ ---> Pb2+ +Sn4+ C(gr)| Sn4+(aq), Sn2+...
Mon Mar 02, 2020 9:08 am
Forum: Method of Initial Rates (To Determine n and k)
Topic: k
Replies: 10
Views: 96

### Re: k

Vuong_2F wrote:what are the units of k?

K does not have any units.
Mon Mar 02, 2020 9:08 am
Forum: Gibbs Free Energy Concepts and Calculations
Topic: free energy and work
Replies: 5
Views: 72

### Re: free energy and work

Jasleen Kahlon wrote:What is the relationship between free energy and work?

If Gibbs free energy, or delta G, is negative, then it releases free energy, which can then be put towards doing work. This is why we have the relationship delta G = -w(max).
Mon Mar 02, 2020 9:07 am
Forum: Thermodynamic Systems (Open, Closed, Isolated)
Topic: Kelvin or Celsius?
Replies: 47
Views: 967

### Re: Kelvin or Celsius?

Veronica Lu 2H wrote:when using PV=nRT is the temperature supposed to be celsius or kelvin?

The units for R are L*atm/mol*K. Based on this information, we can determine that R should be in Kelvin.

In general, most chemical reactions use temperature in Kelvin.
Sun Mar 01, 2020 4:43 pm
Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
Topic: finding n
Replies: 6
Views: 77

### Re: finding n

Clarice Chui 2C wrote:How do you find n from an equation for a reaction?

To find n for a reaction, write out the individual oxidation and reduction reactions. To balance the reaction, you have to include electrons to balance out the reaction. n correlates to this number of electrons.
Sun Mar 01, 2020 4:41 pm
Forum: Zero Order Reactions
Topic: Deriving Equations
Replies: 7
Views: 608

### Re: Deriving Equations

Will we have to know how to derive each single type of equation for the different orders into other equations or will some be given on the formula sheet? All of the formulas for the differential and integrated rate laws are on the formula sheet. However, for each rate law, it is not given which equ...
Sun Mar 01, 2020 4:40 pm
Forum: Kinetics vs. Thermodynamics Controlling a Reaction
Topic: how can you tell
Replies: 11
Views: 146

### Re: how can you tell

How can you tell whether kinetics or thermodynamics controls a reaction? For the reactions that are spontaneous but slow, I believe that kinetics control the reaction more. For reactions that are spontaneous but fast, I believe that thermodynamics control the reaction more. For reactions that are n...
Sun Mar 01, 2020 4:39 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: salt bridge
Replies: 11
Views: 100

### Re: salt bridge

Clarice Chui 2C wrote:What is the purpose of a salt bridge?

With the flow of electrons from the anode to the cathode, there is a charge buildup in each flask. To neutralize this excessive positive and negative charge, the salt cations and anions from the salt bridge neutralize the charge.
Sun Mar 01, 2020 4:38 pm
Forum: Zero Order Reactions
Topic: Order of Reactions
Replies: 4
Views: 74

### Re: Order of Reactions

What determines whether a reaction is zero, first, or second order? I would assume that it would be molar ratios but I've seen exceptions to this so I was wondering what the explanation is. To determine if the reaction is zeroth order, plot the concentration over time. If this results in a line, th...
Mon Feb 24, 2020 11:14 pm
Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
Topic: nernst equation
Replies: 3
Views: 63

### Re: nernst equation

what exactly does the nernst equation show? The Nernst equation allows us to calculate the Ecell value at non-standard conditions given the reaction quotient. At the same time, the Nernst equation can also be used to calculate the reaction quotient or the equilibrium constant given Ecell and Ecell ...
Mon Feb 24, 2020 11:13 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: 6N.17
Replies: 1
Views: 46

### Re: 6N.17

consider the cell Ag I Ag+ (aq. 5.0 mmol.L^-1)II Ag+ (aq 0.15 mol.L^-1)I Ag. can this cell do work? if so, what is the maximum work that it can perform (per mole of Ag)? This is an example of a problem using a concentration cell. The overall reaction for a concentration cell is Ag+ (0.15M) -> Ag+ (...
Mon Feb 24, 2020 11:10 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: gibbs free
Replies: 2
Views: 43

### Re: gibbs free

AMahadi wrote:what is the conceptual relationship between enthalpy, entropy, and temperature to give Gibbs Free Energy?

Gibbs free energy combines enthalpy and entropy in the equation delta G = delta H - T*delta S.
Mon Feb 24, 2020 11:09 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: Gibbs Free energy units
Replies: 4
Views: 81

### Re: Gibbs Free energy units

Does the Gibbs free energy have to be reported in kJ per mol or can we report in J per mol? Gibbs free energy is typically reported in kJ per mol because the values for Gibbs free energy are typically large enough to be reported in kJ per mol. Mathematically speaking, there is no difference between...
Mon Feb 24, 2020 11:08 pm
Forum: Balancing Redox Reactions
Replies: 7
Views: 73

In a redox reaction, how do you know how many electrons to add to each part of the reaction? And how do you know which side of the equation to add them on? Add electrons to the side of the equation with the greater positive charge. To determine how many electrons to add to each part of the reaction...
Tue Feb 18, 2020 9:01 pm
Forum: Thermodynamic Systems (Open, Closed, Isolated)
Topic: Constant R
Replies: 15
Views: 264

### Re: Constant R

Haley Dveirin 1E wrote:When do you use the constant R=8.314 vs 8.206x10^-2 and what are the units for each

To determine which R to use, look at the units provided in the problem. The units for R=8.314 are J/K*mol and the units for R = 0.08206 are L*atm/K*mol.
Tue Feb 18, 2020 9:00 pm
Forum: Administrative Questions and Class Announcements
Topic: Test #2
Replies: 4
Views: 144

### Re: Test #2

ayushibanerjee06 wrote:Does anyone know what Test #2 will cover, especially since it is next week?

It will likely cover the following concepts
1. Material from Friday lecture (relationship between delta G and K)
2. Redox reactions (i.e. balancing)
3. Galvanic Cells
Tue Feb 18, 2020 8:59 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: reaction at equilibrium
Replies: 6
Views: 64

### Re: reaction at equilibrium

Clara Cho 2K wrote:why is delta G equal to zero when a reaction is at equilibrium?

Gibbs Free Energy is a measure of the reaction's tendency to proceed in a given direction (i.e. towards the reactants or towards the products). Since neither side of the reaction is favored at equilibrium, delta G is equal to 0.
Tue Feb 18, 2020 8:57 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: 5G.13
Replies: 8
Views: 192

### Re: 5G.13

(a) Calculate the reaction Gibbs free energy of I2(g) -->2I(g) at 1200. K (K = 6.8) when the partial pressures of I2 and I are 0.13 bar and 0.98 bar, respectively. (b) Indicate whether this reaction mixture is likely to form reactants, is likely to form products, or is at equilibrium. Can someone g...
Tue Feb 18, 2020 8:51 pm
Forum: Entropy Changes Due to Changes in Volume and Temperature
Topic: converting T to kelvin
Replies: 21
Views: 320

### Re: converting T to kelvin

When calculating something involving changing temperature, it is okay to leave the temperature in celsius correct? That's correct - because change in degrees celsius is the same as the change in degrees Kelvin, you can leave the temperature in celsius. For example, if given a q=mC(delta T) problem,...
Sat Feb 15, 2020 10:21 pm
Forum: Entropy Changes Due to Changes in Volume and Temperature
Topic: P1/P2
Replies: 10
Views: 150

### Re: P1/P2

Why is it P1/P2 for delta S and V2/V1? According to Boyle's law, pressure and volume are inversely related. As such, if one variable increases, the other variable decreases. Since these two variables are in an inverse relationship, their ratios must also be inverses of each other. Thus, for delta S...
Sat Feb 15, 2020 10:20 pm
Forum: Entropy Changes Due to Changes in Volume and Temperature
Topic: S vs Stotal
Replies: 7
Views: 108

### Re: S vs Stotal

vanessas0123 wrote:What is the difference between delta S and delta S total?

Delta S is simply the entropy of the system, while Delta S total accounts for the entropy of the system and the surroundings, or the universe.
Sat Feb 15, 2020 10:19 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: Equilibrium
Replies: 15
Views: 137

### Re: Equilibrium

Why is delta G naught 0 at equilibrium? By definition, equilibrium is when the forward and backward reaction rates are equal. If delta G naught is 0, this means that the thermodynamic potential is the same of both the reactants and products. As such, there is no favorable direction the reaction mus...
Sat Feb 15, 2020 10:16 pm
Forum: Concepts & Calculations Using Second Law of Thermodynamics
Topic: spontaneity
Replies: 34
Views: 637

### Re: spontaneity

What is most important in deciding if a reaction is spontaneous (ex enthalpy, entropy, Gibbs free energy)? Personally, I think that Gibbs free energy is the best indicator because it combines enthalpy and entropy. Moreover, it's extremely clear cut: if delta G is negative, it is spontaneous; if del...
Sat Feb 15, 2020 10:15 pm
Forum: Balancing Redox Reactions
Topic: Balancing Redox Reactions
Replies: 2
Views: 19

### Re: Balancing Redox Reactions

What should we keep in mind when balancing a redox reaction to ensure that we balance it correctly? Much like any other reaction, the first thing you should keep in mind is the law of conservation of mass - make sure that there are the same number of atoms of each respective element on both the rea...
Thu Feb 06, 2020 2:36 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: boltzmann constant
Replies: 2
Views: 28

### Re: boltzmann constant

the boltzmann constant will always be given to us on tests right? thanks! Yes - the Boltzmann constant will be found on the Constants and Formulas sheet in the exam. This is the link to the sheet, found on Dr. Lavelle's website: https://lavelle.chem.ucla.edu/wp-content/supporting-files/Chem14B/Cons...
Thu Feb 06, 2020 2:35 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: Boltzman Constant
Replies: 4
Views: 44

### Re: Boltzman Constant

Jada Brown 2H wrote:What are the units of the boltzman constant?

The units for the Boltzmann's Constant are J*K^-1. This can be found on Dr. Lavelle's formula sheet: https://lavelle.chem.ucla.edu/wp-conten ... ations.pdf
Thu Feb 06, 2020 2:34 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: -qsystem=qsurroundings
Replies: 2
Views: 25

### Re: -qsystem=qsurroundings

When I am doing calculations, I have a bit of trouble determining when to apply the "-qsystem=qsurroundings." How can you determine when to use this in a problem? Does anyone have any tips? Typically, if you see that heat is leaving the system and entering the surroundings, you will have ...
Thu Feb 06, 2020 2:33 pm
Forum: Thermodynamic Definitions (isochoric/isometric, isothermal, isobaric)
Topic: irreversible vs reversible
Replies: 3
Views: 19

### Re: irreversible vs reversible

can someone explain to me the difference between an irreversible and reversible path? thank you! In a reversible process, at each point along the path, the system is only slightly removed from being in thermodynamic equilibrium with its surroundings. This is because, in a reversible process, you ar...
Thu Feb 06, 2020 2:30 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Bond Enthalpy Values
Replies: 2
Views: 31

### Re: Bond Enthalpy Values

Megan Cao 1I wrote:Are broken bonds considered negative or do they still remain positive?

From what I've seen in the textbook, energy is required to break bonds. Thus, the bond enthalpy values will be positive because you are supplying heat to the system to break the bonds.
Wed Jan 29, 2020 7:00 pm
Forum: Phase Changes & Related Calculations
Topic: energy of a system
Replies: 4
Views: 67

### Re: energy of a system

can someone briefly explain the piston example the professor did in class today? how would the energy of the system decrease? Assuming that the piston can move, the system can increase its volume. In increasing volume, the system is doing work on the surroundings. In doing work on the surroundings,...
Wed Jan 29, 2020 6:59 pm
Forum: Thermodynamic Systems (Open, Closed, Isolated)
Topic: System vs Surroundings
Replies: 14
Views: 599

### Re: System vs Surroundings

I have a hard time determining what the system is in a reaction. Is there a way of easily identifying what it is or do we have to memorize that for certain examples one is the system and thus the other is the surroundings? The system is where the reaction is actually occurring. The surroundings are...
Wed Jan 29, 2020 6:56 pm
Forum: Calculating Work of Expansion
Topic: Converting gas volume to mols
Replies: 2
Views: 29

### Re: Converting gas volume to mols

When you convert a gas to mols, they said you turn it from Liters to Mols through the conversion factor of: 1mol/22.4 but I'm not entirely certain if this is accurate or not While this may be a reasonable approximation, I definitely think that it is best to use the ideal gas law: PV=nRT. In the pra...
Wed Jan 29, 2020 6:54 pm
Forum: Calculating Work of Expansion
Topic: Systems of Equilibrium Practice
Replies: 2
Views: 44

### Re: Systems of Equilibrium Practice

Are there any problems in the homework that uses the equation for work in a system of equilibrium (the integral equation that Dr. Lavelle went over in the lecture today)? Thanks! Technically, you could use that formula to calculate the work in a system of equilibrium. However, we will learn another...
Wed Jan 29, 2020 6:52 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Enthalpy and Entropy
Replies: 3
Views: 30

### Re: Enthalpy and Entropy

I'm just a little confused but can someone tell me the difference between enthalpy and entropy in regards to when to use them? Enthalpy is a measure of the total heat content of a system. It is equal to the internal energy of the system plus the product of pressure and volume. On the other hand, en...
Tue Jan 21, 2020 1:58 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Question 6.19
Replies: 1
Views: 24

### Re: Question 6.19

In this problem, part a asks if lactic acid were to increase, what would happen to HbO2 in the reaction H3O+HbO2->HHb+H2O+O2 I said that HbO2 would decrease since more H3O would be produced when lactic acid dissociates. However, is my statement accurate since we don't know the Ka of lactic acid and...
Tue Jan 21, 2020 1:56 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: 51.13 Part C
Replies: 1
Views: 27

### Re: 51.13 Part C

5I.13 (a) In an experiment, 2.0 mmol Cl2(g) was sealed into a reaction vessel of volume 2.0 L and heated to 1000. K to study its dissociation into Cl atoms. Use the information in Table 5G.2 to calculate the equilibrium composition of the mixture. (b) If 2.0 mmol F2 was placed into the reaction ves...
Tue Jan 21, 2020 1:53 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: ICE table
Replies: 5
Views: 58

### Re: ICE table

How do you determine the change in partial pressure ("C")? The "change" in any ICE table is the same regardless of if you are calculating Kp or Kc. To calculate the change, you simply look at the stoichiometric coefficient. Be careful when determining if the change is positive/a...
Tue Jan 21, 2020 1:52 pm
Forum: Ideal Gases
Topic: Acid and Bases
Replies: 16
Views: 140

### Re: Acid and Bases

To clarify, what is the pH scale for acidity? The most acidic is a lower pH, meanwhile the more basic is a higher pH right? That's correct. The same reasoning can be used for the pOH scale. The higher the OH- concentration, and thus, the more "basic" a substance is, the lower the pOH. On ...
Tue Jan 21, 2020 1:51 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: 5J 5: increase in pressure
Replies: 4
Views: 59

### Re: 5J 5: increase in pressure

So I understand the basic set up of the question, but I am confused on the answer for D. To me it seems like there's more moles on the left side so the reaction would favor the products?? I'm also confused about B :( For Part D, you have to take the stoichiometric coefficients into account. Thus, o...
Mon Jan 13, 2020 5:44 pm
Forum: Non-Equilibrium Conditions & The Reaction Quotient
Topic: PV=nRT
Replies: 9
Views: 93

### Re: PV=nRT

When do we use the equation PV=nRT? And how would we use it? In the context of what we learned, we use the PV=nRT equation to convert between pressure and molarity (and vice versa). In this class, we use this equation to convert between Kp and Kc. For example, if the question gives you concentratio...
Mon Jan 13, 2020 5:38 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: The Value of Kw
Replies: 3
Views: 24

### Re: The Value of Kw

Can the value of Kw ever change? I remember Professor Lavelle talking about temperature being able to change Kw but I don't really recall why or if temperature was the only factor that could change its value. He discussed this some more today. Temperature is the only factor that can change Kw. Thus...
Mon Jan 13, 2020 5:36 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Autoprotolysis
Replies: 6
Views: 34

### Re: Autoprotolysis

Does autoprotolysis only happen with water or can it be other molecules as well? It can occur in molecules other than water. By definition, autoprotolysis is when a a substance can act as both an acid and a base, and there is proton transfer between the same molecule. Water is one of the most promi...
Mon Jan 13, 2020 5:31 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Kc and Kp
Replies: 8
Views: 83

### Re: Kc and Kp

when a question simply asks for "the equilibrium constant" or "K" does that mean related to concentration or pressure? and why is this so easily interchangeable? When a question asks for the equilibrium constant, you have to look at the context of the question to determine if yo...
Mon Jan 13, 2020 5:28 pm
Forum: Ideal Gases
Topic: Kc and Kp
Replies: 5
Views: 52

### Re: Kc and Kp

Ghadir Seder 1G wrote:Why and how are Kc and Kp calculated the same way but represent different values?

Kc is calculated using concentrations. Kp is calculated using pressure. Because the constants are calculated using different values, the values of Kc and Kp, the constants are also going to be different.
Wed Jan 08, 2020 2:32 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Small K value and Large K value
Replies: 10
Views: 108

### Re: Small K value and Large K value

What is the cut off for the value of K to say that the reaction strongly favors the formation of reactions and the reaction strongly favors the formation of products? Thank you in advance. Dr. Lavelle said that the cutoff is 10^-3 and 10^3 respectively. Thus, if K < 10^-3, then the reactants are st...
Wed Jan 08, 2020 2:30 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Homework Question 5G.1 D
Replies: 1
Views: 43

### Re: Homework Question 5G.1 D

The question asks whether the following statement is t/f: "If one starts with higher concentrations of reactants, the equilibrium concentrations of the products will be larger". I wasn't quite sure how the concentrations of the reactants correlates with that of products. Also was this som...
Wed Jan 08, 2020 2:28 pm
Forum: Non-Equilibrium Conditions & The Reaction Quotient
Topic: Reaction Direction
Replies: 5
Views: 76

### Re: Reaction Direction

How do you determine what direction of the reaction goes given K and the concentrations of all reactants and products? Using the concentrations of all reactants and products, find Qc. Then, compare Qc to K. If Q < K, then the products are favored and the reaction proceeds forward. If Q > K, then th...
Wed Jan 08, 2020 2:25 pm
Forum: Ideal Gases
Topic: K and Q
Replies: 13
Views: 111

### Re: K and Q

When do you use Q and when do you use K? What are the differences between them? K is the equilibrium constant. Q is calculated the same way as K, but it can be used at any time - regardless of if the reaction is at equilibrium or not. By comparing the two, you can find the direction the reaction is...
Wed Jan 08, 2020 2:22 pm
Forum: Ideal Gases
Topic: Gas Law
Replies: 6
Views: 58

### Re: Gas Law

How does the gas law apply to chemical equilibrium? The ideal gas law is PV = nrt. So, if you are given the pressures of a gas in a problem, and it asks you to find Kc, you can plug the pressure into PV = nRT, and solve for n/V (moles/volume, or molarity). Using this value, you can find Kc. Similar...
Wed Dec 04, 2019 4:55 pm
Forum: Calculating pH or pOH for Strong & Weak Acids & Bases
Topic: Marshmallow Packet pH
Replies: 3
Views: 191

### Re: Marshmallow Packet pH

Lyndon sees his crush and panics, accidentally dropping 382.7 mg of HCl and 147.1 mg CaO into a 1L flask. After filling that last with water up to the 1L mark, what is the pH of the resulting solution? how do we find pH given these values? did we go over this in class or is there a section in the b...
Wed Dec 04, 2019 4:51 pm
Forum: Shape, Structure, Coordination Number, Ligands
Topic: How to tell which ligands can be polydentrate
Replies: 4
Views: 181

### Re: How to tell which ligands can be polydentrate

Can a ligand be polydentate if it has two lone pairs on the same atom? Such as an oxygen atom? Even if the ligand has two lone pairs, I don't think the ligand can be polydentate. One such example is 9C.5 (c). Water, for example, has 2 lone pairs - however, due to its geometry, only one of the lone ...
Wed Dec 04, 2019 4:48 pm
Forum: Shape, Structure, Coordination Number, Ligands
Topic: Shape
Replies: 2
Views: 56

### Re: Shape

PriscillaLi_3G wrote:Which shapes do we need to know for the class?

For coordination compounds, we only went over three shapes in class:
1. Octahedral (6 ligands)
2. Tetrahedral (4 ligands)
3. Square Planar (4 ligands)
Wed Dec 04, 2019 4:47 pm
Forum: Bronsted Acids & Bases
Topic: Strong vs Weak Acids (6C.19)
Replies: 2
Views: 52

### Re: Strong vs Weak Acids (6C.19)

Decide which acid in each of the following pairs is the stronger and explain why: (a) HF or HCl; (b) HClO or HClO2; (c) HBrO2 or HClO2; (d) HClO4 or H3PO4; (e) HNO3 or HNO2; (f) H2CO3 or H2GeO3. Could someone provide brief justifications for which acid is stronger in each example? To consider the s...
Tue Dec 03, 2019 1:11 pm
Forum: Naming
Topic: Naming Coordination Compounds that Are Polydentate
Replies: 1
Views: 41

### Naming Coordination Compounds that Are Polydentate

Would we be expected to know how to name coordination compounds with ligands that are bi, tri, and/or polydentate? We didn't go over any examples such is that in class, but problem 9C.9 from the textbook deals with this issue.
Wed Nov 27, 2019 2:29 pm
Forum: Conjugate Acids & Bases
Topic: Determining Conjugate Acid and Bases
Replies: 2
Views: 46

### Re: Determining Conjugate Acid and Bases

What is the best way to determine in a reaction on which of the following elements are the acids, conjugate acids, bases, and conjugate bases? Is it possible to find out whether there are more than one of each type if there are more than two reactants/products (ie when the precipitation of a solid ...
Wed Nov 27, 2019 2:26 pm
Forum: Hybridization
Topic: sigma or pi?
Replies: 20
Views: 274

### Re: sigma or pi?

For hybridized orbitals, how do we know if a bond is sigma or pi just based on lewis structures? Are all hybrid orbitals sigma bonds? Everyone in the comments above has already mentioned that the first bond is a sigma bond and that subsequent bonds are pi bonds. To add onto that, know that a single...
Wed Nov 27, 2019 2:23 pm
Forum: Properties & Structures of Inorganic & Organic Acids
Topic: Acids
Replies: 13
Views: 219

### Re: Acids

What acids are we expected to know? As mentioned above, I don't think there is a specific list of acids that we are expected to know. However, in lecture today, Dr. Lavelle did go over trends on acid/base strength. Based on that, I think he would probably expect us to know acid/base strength not ba...
Wed Nov 27, 2019 2:19 pm
Forum: Amphoteric Compounds
Topic: Amphoteric characteristics
Replies: 3
Views: 52

### Re: Amphoteric characteristics

What differentiates amphoteric compounds from acids and bases? We can also use the Bronsted and Lewis definitions of acids and bases to answer this question. So, for example, H2O is known to be amphoteric. It can act as a Bronsted acid OR base because it can either donate an H+ (to become OH-) or a...
Wed Nov 27, 2019 2:13 pm
Forum: Calculating pH or pOH for Strong & Weak Acids & Bases
Topic: How to take the log to get the pH?
Replies: 8
Views: 81

### Re: How to take the log to get the pH?

If you were given a Hydrogen concentration of [H+]=0.1M, for example, and asked to find the pH, you would plug the concentration into the formula pH=-log[H+]; pH=-log[0.1M], and just plug it into your calculator. So would our answer just be 1? Also, would this be interpreted as our pH being 1? Yes ...
Wed Nov 20, 2019 4:51 pm
Forum: Student Social/Study Group
Topic: Lydon's Week 8 Learning Session
Replies: 4
Views: 144

### Re: Lydon's Week 8 Learning Session

How do we know how many atoms are in the same plane (problem 17)?
Mon Nov 18, 2019 10:36 pm
Forum: Interionic and Intermolecular Forces (Ion-Ion, Ion-Dipole, Dipole-Dipole, Dipole-Induced Dipole, Dispersion/Induced Dipole-Induced Dipole/London Forces, Hydrogen Bonding)
Topic: hydrogen bonds
Replies: 4
Views: 31

### Re: hydrogen bonds

Are hydrogen bonds also considered a dipole dipole interaction? Yes - hydrogen bonds are also considered a dipole-dipole interaction. Thus, if you ever observe hydrogen bonding, there is also dipole-dipole interactions. You can also think about it this way: In a polar molecule, Hydrogen will have a...
Mon Nov 18, 2019 10:32 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Exact Bond Angles for Test 1
Replies: 3
Views: 46

### Re: Exact Bond Angles for Test 1

Do we need to know the exact bond angles for molecular shapes that have lone electron pairs or can we just say slightly less than 109.5 degrees for AX3E and AX2E2 (NH3 and H2O)? Professor Lavelle actually talked about this in lecture. It's practically impossible for us to know what the angle is unl...
Mon Nov 18, 2019 10:30 pm
Forum: Dipole Moments
Topic: Net Dipole Moment
Replies: 4
Views: 56

### Re: Net Dipole Moment

Does BrF 6 have a net dipole moment? I know that F is more electronegative, so the dipole moment travels from the central Br to each F atom. When I draw all of these vectors out, I think they sum up to be 0. Is this correct? Is there another way to look at this? One way to see that the net dipole m...
Mon Nov 18, 2019 10:28 pm
Forum: Ionic & Covalent Bonds
Topic: HS vs HO
Replies: 4
Views: 67

### Re: HS vs HO

Is HS more tightly bound or is HO? why? The first thing I would do when determining if a molecule is more/less tightly bound is by seeing what type of bond is present between the atoms - i.e. is there a single, double, triple bond. In this case, both molecules have single bonds. In this situation, ...
Mon Nov 18, 2019 10:25 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: ion dipole interactions
Replies: 3
Views: 39

### Re: ion dipole interactions

Do ion atoms dissolve in molecules that have dipole forces(polar molecules) ? for example, CL- and H20? I know the rule is that that "like dissolves like" but in this case is an ion polar? Im confused Yes - ions do dissolve in molecules that have dipole forces. The best example of this is...
Wed Nov 13, 2019 9:00 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: VESPR Model of H2O
Replies: 12
Views: 205

### Re: VESPR Model of H2O

I was looking up the VESPR model of H2O and it wasn't linear, which I expected it to be. Are there new models we are going to learn? Kind of - right now we have only considered the VSEPR model by looking at atoms. However, we also need to consider lone pairs when determining the molecular geometry ...
Wed Nov 13, 2019 8:55 pm
Forum: Interionic and Intermolecular Forces (Ion-Ion, Ion-Dipole, Dipole-Dipole, Dipole-Induced Dipole, Dispersion/Induced Dipole-Induced Dipole/London Forces, Hydrogen Bonding)
Topic: Topic 3F.1
Replies: 3
Views: 39

### Re: Topic 3F.1

Do we need to draw out the lewis structure every time we are determining what intermolecular forces are present for a molecule? It's not about "need," but rather that it's beneficial to draw out the Lewis structure when you are determining what intermolecular forces are present for a mole...
Wed Nov 13, 2019 8:51 pm
Forum: *Liquid Structure (Viscosity, Surface Tension, Liquid Crystals, Ionic Liquids)
Topic: Viscosity
Replies: 16
Views: 401

### Re: Viscosity

This means that the intermolecular bonds are stronger, and thus the liquid is "thicker". It will not flow as well. what are the differences between intermolecular and intramolecular forces Intermolecular forces are forces between two separate molecules. This includes, but is not limited t...
Wed Nov 13, 2019 8:49 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Test 2
Replies: 15
Views: 231

### Re: Test 2

What topics should we expect to show up on test #2? From what I've heard, Test 2 will cover material up until Friday's lecture. Based on this, questions on Test 2 can appear from any material up until VSEPR. This includes, but is not limited to: 1. Review of high school chemistry 2. Quantum 3. Chem...
Wed Nov 13, 2019 8:44 pm
Forum: Ionic & Covalent Bonds
Topic: Electronegativity
Replies: 7
Views: 99

### Re: Electronegativity

Are we given an electronegativity chart for Test 2 to compare electronegativity difference? I don't think we'll be given a chart. However, based on periodic trends, you should be able to figure out the relative electronegativity difference. Just remember that electronegativity increases as you go u...
Mon Nov 04, 2019 10:35 am
Forum: Dipole Moments
Topic: Induced dipole induced dipole interaction
Replies: 2
Views: 50

### Re: Induced dipole induced dipole interaction

If one dipole is induced and the induces another dipole, how does this interaction even begin? I am having trouble rationalizing this conceptually because I don't see how these molecules can induce a dipole when there is not something with a charge to incite it. The way Dr. Lavelle explained it in ...
Mon Nov 04, 2019 10:29 am
Forum: Trends in The Periodic Table
Topic: 3rd IE?
Replies: 2
Views: 60

### Re: 3rd IE?

If between K and Ca.. Ca has the stronger IE and K has the stronger 2nd IE would Ca have the stronger 3rd IE since it'll be at [Ar] while K would now have [Ne](3s^2)(3p^5)?? Yes. Since all atoms want to get to that 'noble gas' state, it would very difficult to remove an electron from Ca once it has...
Mon Nov 04, 2019 10:27 am
Forum: Bond Lengths & Energies
Topic: Covalent Bond Lengths
Replies: 1
Views: 41

### Re: Covalent Bond Lengths

What are different factors that affect covalent bond lengths? Bond length can be affected by many things, including (but not limited to): 1. Bond order - is it a single bond? Double bond? Triple bond? As the bond order increases, the length of the covalent bond decreases. 2. Electronegativity/Elect...
Mon Nov 04, 2019 10:23 am
Forum: Lewis Structures
Topic: 2a on mini dino nuggets sheet
Replies: 1
Views: 39

### Re: 2a on mini dino nuggets sheet

For the Lewis structures of CH3F and CH3Br, the drawn structures do not contain valence electrons around the halogens and therefore do not meet the total amount of electrons. Why is this? Is this because we are focusing on dipole moments rather then proper lewis structure? Sometimes, for the sake o...
Mon Nov 04, 2019 10:19 am
Forum: Photoelectric Effect
Topic: Work Function Units
Replies: 1
Views: 50

### Re: Work Function Units

Sometimes the work function is given with units kJ/mol so you know to convert to J/atom, but what if no units are given? Should you assume you're given the energy to eject a mol or one electron? I think it's very infrequent for a problem to give you the work function without units. Every problem I'...
Mon Oct 28, 2019 4:55 pm
Forum: Lewis Structures
Topic: Resonance Structures
Replies: 2
Views: 38

### Re: Resonance Structures

When drawing the possible Lewis Structures for ClNO2, why can only the oxygens be double bonded, and not the chlorine? Ideally, because Chlorine has seven valence electrons, it only needs one more electron to complete the octet. Thus, Chlorine only requires one more bond in the lowest energy state....
Mon Oct 28, 2019 4:52 pm
Forum: Trends in The Periodic Table
Topic: Noble Gas
Replies: 4
Views: 63

### Re: Noble Gas

Do all trends disregard noble gases or is there some that do? Electronegativity: The noble gases are disregarded for electronegativity. Ionization Energy: I believe the noble gases are included (it would be harder to remove an electron as you move to the upper right of the periodic table). Electron...
Mon Oct 28, 2019 4:49 pm
Forum: Trends in The Periodic Table
Topic: Ionization Energy
Replies: 3
Views: 37

### Re: Ionization Energy

Is it possible that the first ionization energy of any atom could be more than the second? I'm just wanting to clarify for my notes. I don't think it is possible for the first ionization energy of any atom to be more than the second ionization energy. Simply theoretically speaking, it is easier to ...
Mon Oct 28, 2019 4:45 pm
Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
Topic: The Wrong Rydberg's Equation
Replies: 1
Views: 39

### Re: The Wrong Rydberg's Equation

If we show how we denoted the correct Rydberg equation into the wrong one (as specified in class), could we technically use it for the test? I think it depends on what your TA prefers. However, I think it would be best (for the purposes of your understanding), that you use the equation that Profess...
Mon Oct 28, 2019 4:43 pm
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: Orbital Shapes
Replies: 1
Views: 34

### Re: Orbital Shapes

Two questions technically, but are orbital shapes going to be something we need to know how to draw, and is there a possibility that we will need to know the shapes of orbitals beyond the 4 we were shown in class? Professor Lavelle discussed this in class - he said that we are not going to need to ...
Mon Oct 21, 2019 4:01 pm
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: 1D-15
Replies: 3
Views: 49

### Re: 1D-15

Can somebody explain how you find angular momentum quantum numbers like in this question? What are the principal and orbital angular momentum quantum numbers for each of the following orbitals: (a) 6p; (b) 3d; (c) 2p; (d) 5f? To find the principal quantum number, just look at the number before the ...
Mon Oct 21, 2019 3:58 pm
Forum: Electron Configurations for Multi-Electron Atoms
Topic: Exceptions (Cr and Cu)
Replies: 3
Views: 58

### Re: Exceptions (Cr and Cu)

I know that Dr. Lavelle mentioned that Cr and Cu are exceptions to the rules and have electron configurations of [Ar] 3d5 4s1 and [Ar] 3d10 4s1 respectively. Does this extrapolate to the whole group 6 and group 11 where an electron is always taken from the 4s orbital? However, while doing the Homew...
Mon Oct 21, 2019 3:56 pm
Forum: Trends in The Periodic Table
Topic: Neon
Replies: 3
Views: 35

### Re: Neon

When professor Lavelle was demonstrating isoelectronic atoms, through Na+, Mg2+, and F-, what was the significance of the element Neon? Thank you All of these ions were isoelectronic - they all had the same number of electrons. In this case, Na+, Mg2+, and F- all had the same number of electrons as...
Mon Oct 21, 2019 3:54 pm
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: Shell vs. Orbital
Replies: 3
Views: 41

### Re: Shell vs. Orbital

What is the difference between a shell, a subshell and an orbital? Are the terms subshell and orbital interchangeable? The differences between these terms becomes increasingly clear when you look at the respective quantum numbers. The shell is represented by "n," or the principal quantum ...
Mon Oct 21, 2019 3:51 pm
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: Are electrons always removed from the 4s orbital before the 3d orbital?
Replies: 6
Views: 80

### Re: Are electrons always removed from the 4s orbital before the 3d orbital?

I know the 4s orbital fills first before the 3d orbital because the 4s orbital is lower in energy, but are electrons always removed from the 4s orbital first as well? And I think this becomes even more clear when you write the electron configuration of a given atom. Whenever, you write the electron...
Tue Oct 15, 2019 9:30 pm
Forum: DeBroglie Equation
Topic: HW 1B.15
Replies: 1
Views: 59

### Re: HW 1B.15

The velocity of an electron emitted from a metallic surface by a photon is 3.6*10^3 km/s. What is the wavelength of the ejected electron? I know we use the formula wavelength=h/mv which would give me (6.626*10^-34 J/s)/[(9.11x10^-31 kg)(3.6*10^6 m/s)]. However, after using this formula, how do we k...
Tue Oct 15, 2019 9:26 pm
Forum: *Shrodinger Equation
Topic: Schrondiger's Wave Function Equation
Replies: 4
Views: 84

### Re: Schrondiger's Wave Function Equation

Lavelle had mentioned that psi represents the height of a wave function at position x, y, and x. While (psi)^2 represents the probability of finding an electron. I wasn't sure what he meant; does he mean it represents the probability of finding an electron in a certain orbital? Based on what I unde...
Tue Oct 15, 2019 9:22 pm
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: Quantum Numbers
Replies: 2
Views: 72

### Re: Quantum Numbers

What do the 4 quantum numbers represent as in n, l, ml and ms? n represents the shell in which the electron is found. For example, in the unexcited state, Hydrogen's electron is found in n=1, or the 1st shell/orbital. l represents the orbital angular momentum, or the shape of the orbital. ml repres...
Tue Oct 15, 2019 9:19 pm
Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
Topic: Rydbergs Equation
Replies: 3
Views: 59

### Re: Rydbergs Equation

Use the equation that Lavelle gave us in the lecture E=(-hR/n^2) as the Rydberg equation. Lavelle didn't want us to use a different version of this equation that was given in the textbook, which is v=R{(1/n^2)-(1/n^2)}. He said that if we use this equation, we will just be plugging in numbers and w...
Tue Oct 15, 2019 9:17 pm
Forum: Properties of Light
Topic: Defraction patters
Replies: 3
Views: 79

### Re: Defraction patters

I am a bit confused about diffraction patters and wavelike properties. Do both light and electrons have wave like properties? If so, does that mean they both have Diffraction patterns. Also, what are diffraction patters? Yes - both light and electrons have wave-like properties. This was proven by D...
Mon Oct 07, 2019 2:26 pm
Forum: Properties of Light
Topic: Work Function
Replies: 4
Views: 75

### Re: Work Function

What is the difference between the work function and the threshold energy? From my understanding, the work function relates the photon's total energy, the required amount of threshold energy, and the kinetic energy. Essentially, it states that some of the photon's total energy is first used up to m...
Mon Oct 07, 2019 2:23 pm
Forum: Photoelectric Effect
Topic: light intensity and kinetic energy
Replies: 3
Views: 46

### Re: light intensity and kinetic energy

if you increase the intensity of a light source, what happens to the kinetic energy? We actually went over this topic in lecture today. According to the quantum model, if you increase the intensity of a light source, you are increasing the number of photons of light. This should have no effect on t...
Mon Oct 07, 2019 2:18 pm
Forum: SI Units, Unit Conversions
Topic: #E9- Formula Units
Replies: 3
Views: 94

### Re: #E9- Formula Units

In Chemistry, a formula unit can refer to an atom, a compound, or a molecule. Basically, a formula unit just refers to the 'thing' that the question is asking about. So, if a question asks, for example, how many formula units of NaCl there are in one mole of NaCl, they are asking how many NaCl's are...
Mon Oct 07, 2019 2:10 pm
Forum: Limiting Reactant Calculations
Topic: Question about Calculating Limiting Reactants
Replies: 5
Views: 77

### Re: Question about Calculating Limiting Reactants

Are you allowed to simply calculate the moles of each reactant and then compare them to find the limiting reagent? Yes - just make sure to account for the mole ratios when determining which reactant is the limiting reagent. Another way to determine which substance is the limiting reagent is to calc...