## Search found 102 matches

Sun Mar 15, 2020 3:15 pm
Forum: Administrative Questions and Class Announcements
Topic: Athena
Replies: 34
Views: 1969

### Re: Athena

Dr. Lavelle,

Thank you for all of your hard work these past two quarters! I'll definitely be leaving with a lot of valuable lessons as a student.
Also, thank you for all of the epic poetry and DJ'ing –– a true Renaissance man right there.

Take care and stay healthy!
Sat Mar 14, 2020 5:17 pm
Forum: Reaction Mechanisms, Reaction Profiles
Topic: 7C.7
Replies: 2
Views: 26

### 7C.7

"The following mechanism has been proposed for the reaction between nitric oxide and bromine: Step 1 NO + Br 2 --> NOBr 2 (slow) Step 2 NOBr 2 + NO --> NOBr + NOBr (fast) Write the rate law for the formation of NOBr implied by this mechanism." Just to clarify, if we are given a problem lik...
Sat Mar 14, 2020 11:59 am
Forum: Arrhenius Equation, Activation Energies, Catalysts
Topic: Transition State Theory
Replies: 3
Views: 52

### Transition State Theory

Can someone explain to me what the transition state theory is, and how it differs from the collision theory? Thank you!
Fri Mar 13, 2020 9:52 am
Forum: Entropy Changes Due to Changes in Volume and Temperature
Topic: Entropy of Surroundings vs. System
Replies: 3
Views: 93

### Entropy of Surroundings vs. System

How do we know when the entropy of the surroundings is positive or negative in a volume expansion?
Fri Mar 13, 2020 9:46 am
Forum: Calculating Work of Expansion
Topic: Work without volume
Replies: 5
Views: 123

### Re: Work without volume

I think most of the problems that we do involve expansion work (so a change in volume is given), but since you can relate work with U = q + w, I assume you can find it through this equation given the internal energy and enthalpy.
Fri Mar 13, 2020 9:42 am
Forum: Reaction Mechanisms, Reaction Profiles
Replies: 2
Views: 22

Even though Lavelle said that we won't be using steady state, would we still need to know the basic idea behind it?
Tue Mar 03, 2020 3:23 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: 6M.5 part A
Replies: 1
Views: 34

### 6M.5 part A

For each reaction that is spontaneous under standard conditions, (K>1), write a cell diagram, determine the standard cell potential, and calculate ΔG°for the reaction: 2NO 3 - (aq) + 8H + (aq) + 6Hg(l) --> 3Hg 2 2+ (aq) + 2NO(g) + 4H2O (l) I was able to do most of this problem except for the cell di...
Mon Mar 02, 2020 9:55 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Relationship between E° + K
Replies: 1
Views: 20

### Relationship between E° + K

In the book, it says that when E°cell > 0, then K >1. What is the reasoning behind this?
Mon Mar 02, 2020 9:26 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: 6M.11
Replies: 1
Views: 12

### 6M.11

"Suppose that each of the following pairs of redox couples is combined to form a galvanic cell that generates a current under standard conditions. Identify the oxidizing agent and the reducing agent, write a cell diagram, and calculate the standard cell potential from the standard potentials of...
Mon Mar 02, 2020 5:05 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: 6N.3 a)
Replies: 1
Views: 54

### 6N.3 a)

Predict the potential of each of the following cells:

(a) Pt(s)|H2(g,1.0 bar) |HCl(aq, 0.075M) ||HCl(aq, 1.0 M) | H2(g, 1.0 bar)|Pt(s)

Can someone walk me through this problem? I'm having trouble with the half-reactions and setting up Q.
Sun Mar 01, 2020 2:18 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Cell Diagram (phases)
Replies: 2
Views: 41

### Cell Diagram (phases)

Is there a certain order/arrangement that phases (ex. solid, liquid, gases) are placed in the cell diagram? I do know that the cathode is on the right and anode is on the left.
Sun Mar 01, 2020 1:41 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: C(gr) state
Replies: 4
Views: 40

### C(gr) state

What does C(gr) mean?
Sun Mar 01, 2020 1:36 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Determining "n" (6L.1)
Replies: 1
Views: 33

### Determining "n" (6L.1)

Calculate the standard reaction Gibbs free energy for the following cell reactions:

b) 6Fe3+(aq) + 2 Cr3+(aq) + 7 H2O(l) --> 6Fe2+(aq) + Cr2O72-(aq) + 14H+(aq)
where Ecell°= -1.29 V

Can someone walk me through how they found "n" for this problem?
Sat Feb 29, 2020 11:41 pm
Forum: Balancing Redox Reactions
Topic: 6K.5 Part B
Replies: 1
Views: 22

### 6K.5 Part B

"Balance each of the following skeletal equations by using oxidation and reduction half-reactions. All the reactions take place in basic solution. Identify the oxidizing agent and reducing agent in each reaction." b) Br 2 (l) --> BrO 3 - (aq) + Br - (aq) Can someone walk me through the bal...
Sat Feb 29, 2020 11:02 pm
Forum: Balancing Redox Reactions
Topic: 6K.3 Part D
Replies: 5
Views: 94

### 6K.3 Part D

"Balance each of the following skeletal equations by using oxidation and reduction half-reactions. All the reactions take place in acidic solution. Identify the oxidizing agent and reducing agent in each reaction." d) Cl 2 (g) ––> HClO(aq) + Cl 2 (g) For this reaction, why would Cl 2 be bo...
Sun Feb 23, 2020 8:37 pm
Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
Topic: Spontaneity
Replies: 8
Views: 81

### Spontaneity

If the cell potential of a battery is positive, does it mean that that Gibbs Free Energy would be negative too?
Sun Feb 23, 2020 5:14 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Calculating Cell Potential
Replies: 2
Views: 26

### Calculating Cell Potential

What did Dr. Lavelle say was his "recommended" way of solving for the cell potential? He mentioned it during lecture earlier this week but I did not write it down :/
Sun Feb 23, 2020 5:12 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Half reactions
Replies: 13
Views: 126

### Re: Half reactions

Half reactions are oxidation and reduction processes that occur in a redox reaction.

A great way to remember them is OIL RIG –– "oxidation is loss (of electrons), reduction is gain."

Hope this helps!
Sun Feb 23, 2020 1:35 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Notation of Species
Replies: 3
Views: 26

### Notation of Species

When would we use a comma versus a single line between the reactants and products?
Sun Feb 23, 2020 1:31 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Use of Platinum
Replies: 10
Views: 90

### Use of Platinum

How would we know when to use platinum as a cathode/anode in a battery?
Tue Feb 11, 2020 3:26 pm
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: Meaning of q=-w
Replies: 14
Views: 265

### Meaning of q=-w

I know when ΔU = 0, but in these cases, how do I interpret q=-w?
Tue Feb 11, 2020 3:24 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Units for Enthalpy
Replies: 2
Views: 21

### Units for Enthalpy

What are the units for enthalpy, exactly? Can they be written in the form of KJ/mol?
Mon Feb 10, 2020 5:58 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: Entropy between molecules
Replies: 3
Views: 100

### Entropy between molecules

Given two different molecular formulas, how would we determine which one has a higher residual entropy?
Mon Feb 10, 2020 5:56 pm
Forum: Concepts & Calculations Using Second Law of Thermodynamics
Topic: 4F.13
Replies: 1
Views: 51

### 4F.13

Use data in Table 4C.1 or Appendix 2A to calculate the entropy change for (a) the freezing of 1.00 mol H2O(l) at 0.00 8C; (b) the vaporization of 50.0 g of ethanol, C2H5OH, at 351.5 K.

Can someone walk me through this problem? Thanks!
Sat Feb 08, 2020 6:20 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Using the 5% rule
Replies: 1
Views: 28

### Using the 5% rule

What is the minimum value that K has to be for it to be considered "small" (so the 5% rule can be used?)
Sat Feb 08, 2020 3:35 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: 4D.1
Replies: 2
Views: 30

### 4D.1

Carbon disulfide can be prepared from coke (an impure form of carbon) and elemental sulfur: 4C(s) + S 8 (s) --> 4 CS2(l) ΔH°= +358.8 kJ (b) Calculate the heat absorbed in the reaction of 197 g of carbon with an excess of sulfur. (c) If the heat absorbed in the reaction was 415 kJ, how much CS2 was p...
Sat Feb 08, 2020 2:07 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: Nonlinear vs linear molecules
Replies: 4
Views: 52

### Nonlinear vs linear molecules

What's the difference between nonlinear and linear molecules for heat capacity?
Fri Feb 07, 2020 5:23 pm
Forum: Concepts & Calculations Using Second Law of Thermodynamics
Topic: Entropy + Disorder
Replies: 3
Views: 29

### Entropy + Disorder

Why does Lavelle avoid using the term "disorder" when he explains entropy? If we were asked to describe it on an exam, how should I define it?
Wed Feb 05, 2020 7:03 pm
Forum: Thermodynamic Definitions (isochoric/isometric, isothermal, isobaric)
Topic: Isothermal expansion
Replies: 2
Views: 46

### Isothermal expansion

Why is ∆U = 0 for isothermal expansion (or compression) of an ideal gas?
Sun Feb 02, 2020 9:16 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Enthalpy
Replies: 7
Views: 61

### Enthalpy

When exactly does enthalpy equal "q"? Are there certain conditions we need to follow?
Sun Feb 02, 2020 9:12 pm
Forum: Thermodynamic Systems (Open, Closed, Isolated)
Topic: Expansion Work
Replies: 2
Views: 34

### Expansion Work

Can someone explain to me the difference between non-expansion and expansion work? Also, how does this concept of expansion pertain to enthalpy?
Sat Feb 01, 2020 3:08 pm
Forum: Calculating Work of Expansion
Topic: 4A.3 (HW)
Replies: 2
Views: 52

### 4A.3 (HW)

Air in a bicycle pump is compressed by pushing in the handle. The inner diameter of the pump is 3.0 cm and the pump is depressed 20. cm with a pressure of 2.00 atm. (a) How much work is done in the compression? (b) Is the work positive or negative with respect to the air in the pump? (c) What is the...
Sat Feb 01, 2020 2:45 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: Calorimeter + Heat Transfer
Replies: 4
Views: 21

### Calorimeter + Heat Transfer

In the book, it states that the heat lost in an reaction is heat gained by the calorimeter (-q=qcal). Can someone explain why this is?
Sat Feb 01, 2020 2:42 pm
Forum: Calculating Work of Expansion
Topic: Changing external pressure
Replies: 1
Views: 30

### Changing external pressure

Can someone explain the "reversible process" that they talk about in section 4A.3 of the reading? I was thrown off when they mentioned how a "reversible reaction can be reversed by an infinitely small change in a variable".
Sun Jan 26, 2020 2:10 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Polyprotic Acids
Replies: 2
Views: 20

### Polyprotic Acids

Do we need to know how to calculate equilibrium concentrations for polyprotic acids?
Sun Jan 26, 2020 2:08 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Temperature (K)
Replies: 4
Views: 28

### Temperature (K)

For temperature increases in a system that is in equilibrium, why would the K value change?
Sun Jan 26, 2020 2:07 pm
Forum: Ideal Gases
Topic: PV=NRT
Replies: 7
Views: 80

### Re: PV=NRT

We don't really need to know this concept; as long as you know what values you plug into for the formula you should be fine.
Tue Jan 21, 2020 4:04 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: 6D.15
Replies: 1
Views: 47

### 6D.15

For this question, I'm stuck on part b:

Calculate the pH of ... (b) 0.055 M AlCl3(aq).

Although I know the process of finding the pH, I'm not sure how to write the equilibrium reaction for this salt. Can someone walk me through it?
Tue Jan 21, 2020 4:01 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Gases (units based on K)
Replies: 2
Views: 22

### Gases (units based on K)

For reactions that are in homogeneous equilibrium (all reactants and products are gases, in this case) how would we know whether we need to use partial pressure units or molar concentration?
Sun Jan 19, 2020 5:51 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: Endo vs. Exothermic
Replies: 5
Views: 43

### Endo vs. Exothermic

How can we tell if a reaction is endothermic or exothermic besides looking at the sign of ΔH?
Sun Jan 19, 2020 5:18 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: 5J.1
Replies: 4
Views: 41

### 5J.1

I have a question on one part of this question: Consider the equilibrium CO(g) + H 2 O(g) <--> CO 2 (g) + H 2 (g). b) If the partial pressure of CO is decreased, what happens to the partial pressure of CO 2 ? Why would the partial pressure of CO 2 decrease if the moles of gas on each side are equal?
Sat Jan 18, 2020 7:54 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: Temperature
Replies: 2
Views: 25

### Temperature

I still can't quite understand how equilibrium works with temperature (the "exothermic" and "endothermic" seem to be throwing me off). I've been trying to read the textbook for help but I'm quite lost. Can someone explain the process to me?
Thu Jan 16, 2020 8:23 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: Solids and Liquids in Le Chatelier
Replies: 5
Views: 76

### Solids and Liquids in Le Chatelier

Do solids and liquids apply to Le Chatelier's principle? For example, if we removed a solid reactant, would there be any effect on the equilibrium?

Thanks!
Wed Jan 15, 2020 6:12 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Ka + Kb
Replies: 6
Views: 40

### Ka + Kb

During lecture, Dr. Lavelle mentioned how as Ka increases, Kb decreases. What is the reason for this?
Tue Jan 14, 2020 9:39 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: 5I.19
Replies: 2
Views: 35

### 5I.19

A reaction mixture that consisted of 0.400 mol H 2 and 1.60 mol I 2 was introduced into a flask of volume 3.00 L and heated. At equilibrium, 60.0% of the hydrogen gas had reacted. What is the equilibrium constant K for the reaction H 2 (g) + I 2 (g) <=> 2 HI(g) at this temperature? Can someone help ...
Sun Jan 12, 2020 10:16 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: K Expression for Reverse Reaction
Replies: 3
Views: 38

### K Expression for Reverse Reaction

When we write the K expression of a reverse reaction, would we flip the products or reactants around? Or would the expression remain the same?
Sun Jan 12, 2020 10:10 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Q
Replies: 10
Views: 108

### Re: Q

Q, or the "reaction quotient", measures the relative amount of reactants and products at a certain time. It essentially describes a reaction when it's not in equilibrium and what direction will be taken for it for equilibrium to be restored (hence the favoring of a forward or reverse react...
Sun Jan 12, 2020 6:08 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Example 5I.3 (page 556 on pdf)
Replies: 3
Views: 25

### Example 5I.3 (page 556 on pdf)

I was able to understand and follow most of this example, but I noticed that in Step Four that they removed the "-2x" and "-x" from the (3.21 - 2x)2 and (6.21 - x) from the K expression. What is the reasoning behind this?
Sun Jan 12, 2020 5:25 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Units and Conversions of Kp
Replies: 3
Views: 35

### Units and Conversions of Kp

For several problems, I noticed how they used either "bar" or "Pa" for the units of partial pressure. Which set of units is the "default" one? Also, how would we convert between bar and Pa (kPa as well)?
Sun Jan 12, 2020 4:44 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Different types of K
Replies: 9
Views: 65

### Different types of K

What's the difference between K and Kc?
Sat Dec 07, 2019 10:37 am
Forum: Shape, Structure, Coordination Number, Ligands
Topic: Coordination Number + Polydentate
Replies: 1
Views: 40

### Coordination Number + Polydentate

Does the coordination number have any correlation to whether a ligand is polydentate?
Sat Dec 07, 2019 9:47 am
Forum: Naming
Topic: "Cyano" vs. "Cyanido"
Replies: 1
Views: 37

### "Cyano" vs. "Cyanido"

In some of the naming coordination compounds on the homework set, I noticed how some complexes had the name "cyano-" or "cyanido". How do we know when to use which?
Thu Dec 05, 2019 10:59 pm
Forum: Air Pollution & Acid Rain
Topic: Acid Rain
Replies: 1
Views: 92

### Acid Rain

What page in the textbook can we refer to acid rain?
Tue Dec 03, 2019 2:47 pm
Forum: Shape, Structure, Coordination Number, Ligands
Topic: 9C.5
Replies: 4
Views: 66

### 9C.5

Which of the following ligands can be polydentate? If the ligand can be polydentate, give the maximum number of places on the ligand that can bind simultaneously to a single metal center: (a) HN(CH 2 CH 2 NH 2 ) 2 ; (b) CO 3 -2 ; (c) H 2 O; (d) oxalate How can we tell if something is mono or polyden...
Tue Dec 03, 2019 1:36 pm
Forum: Shape, Structure, Coordination Number, Ligands
Topic: Tetrahedral vs. Square Planar
Replies: 1
Views: 30

### Tetrahedral vs. Square Planar

How do we know if a coordination compound has a tetrahedral or square planar shape?
Tue Dec 03, 2019 1:24 pm
Forum: Naming
Topic: Oxidation Number
Replies: 3
Views: 40

### Oxidation Number

How do we determine the oxidation state of the metal atom / ion in a complex?
Sun Dec 01, 2019 7:56 pm
Forum: Hybridization
Topic: Hybridization (Lone Pairs)
Replies: 4
Views: 72

### Hybridization (Lone Pairs)

Do molecules with a shape such as bent or seesaw have hybrid orbitals?
Sun Dec 01, 2019 5:00 pm
Forum: Hybridization
Topic: 2F.3
Replies: 3
Views: 37

### 2F.3

How many sigma bonds and how many pi bonds are there in (a) H2S and (b) SO2?

For SO2, the answer says that there are two sigma bonds and one pi bond. Why do they use the Lewis structure with one double bond and one single bond rather than the one with two double bonds?
Sun Dec 01, 2019 4:38 pm
Forum: Hybridization
Topic: Writing the hydrization
Replies: 10
Views: 212

### Re: Writing the hydrization

Can you explain how to find the hybridization? I've always struggled with it I would recommend looking at the example listed in 2F.3 (page 122 on the pdf). You should first identify the molecular shape about the central atom - the number of atomic orbitals it has is equivalent to the hybridized orb...
Sun Dec 01, 2019 2:04 pm
Forum: Sigma & Pi Bonds
Topic: Ionic bond --> sigma and pi bonds
Replies: 8
Views: 299

### Ionic bond --> sigma and pi bonds

In the textbook, it says that all single covalent bonds are sigma bonds. If this is the case, how would we define the bond for an ionic compound such as NaCl?
Sun Dec 01, 2019 1:42 pm
Forum: Sigma & Pi Bonds
Topic: Drawing Sigma and Pi bonds
Replies: 7
Views: 110

### Drawing Sigma and Pi bonds

When you have a double bond, is it correct to label it as "σ + π"? Also, given a molecule with multiple single bonds, is it correct to label every single bond with a "σ"? I didn't get my test back last week (since I left campus early) and this question has been buzzing around my ...
Tue Nov 19, 2019 1:14 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Bond Angles
Replies: 4
Views: 56

### Bond Angles

When can we tell when a bond angle is "slightly less than" what is expected?
For example, if we look at CH3- from problem 2E.15, why are the bond angles considered to be "slightly less than 109.5 degrees"?
Mon Nov 18, 2019 3:58 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: Strength of IMF
Replies: 1
Views: 34

### Strength of IMF

I read in the textbook that the hydrogen bond is the strongest intermolecular force; however, other sources I've looked at said that the ion-dipole interaction is the strongest force. Which one is stronger?
Mon Nov 18, 2019 3:31 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: London dispersion
Replies: 4
Views: 49

### Re: London dispersion

The strength of London Dispersion Forces is determined by the polarizability - or how easy the electron cloud is distorted - of an atom. Remember that larger atoms have higher polarizabilities because more electrons means more shielding from nuclear charge. Therefore, the larger the molecule, the st...
Mon Nov 18, 2019 3:15 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: CHI3 vs CHF3
Replies: 2
Views: 73

### CHI3 vs CHF3

Why does CHI3 have the higher boiling point if CHF3 is more polar (higher electronegativity)?
Mon Nov 18, 2019 3:00 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: 3F.5
Replies: 2
Views: 66

### 3F.5

For a) HCl vs. NaCl, why does NaCl have the higher boiling point? What factors do we use to compare these two?
Sun Nov 17, 2019 3:43 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: 2E.21 (two central atoms)
Replies: 1
Views: 23

### 2E.21 (two central atoms)

Draw the Lewis structure and give the approximate bond angles of

a) C2H4
...
d) N2H4

Although drawing the Lewis structures wasn't difficult, how do I determine the shape of these molecules since they have two central atoms?
Sun Nov 17, 2019 3:12 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: 2E.7 help
Replies: 1
Views: 19

### 2E.7 help

I'm a little stuck on part b of this question:

b) How many different OSCl bond angles are there in this molecule (SOCl2)?

How do I interpret this question?
Sun Nov 17, 2019 3:07 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Linear Molecular Shape
Replies: 1
Views: 24

### Re: Linear Molecular Shape

An example of a linear molecular shape would be N3-. It's from 2E.17.

Remember that a linear molecular shape has a bond angle of 180, so it should appear as a straight line.
Sun Nov 17, 2019 12:33 pm
Forum: Lewis Structures
Topic: Drawing Lewis Structures (Multiple Atoms)
Replies: 3
Views: 58

### Drawing Lewis Structures (Multiple Atoms)

Are there any tricks to drawing Lewis Structures for molecules with three or more different types of atoms?
Ex. CH2F2
Thu Nov 14, 2019 3:57 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: Vapor Pressure + IMF
Replies: 3
Views: 71

### Vapor Pressure + IMF

What is vapor pressure exactly, and how can we determine if a molecule has a "high" or "low" vapor pressure based on its intermolecular forces?
Thu Nov 14, 2019 3:34 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: Polarizability and Polar
Replies: 4
Views: 51

### Polarizability and Polar

Does polarizability have any connection to a molecule being polar?
Wed Nov 06, 2019 11:30 am
Forum: Polarisability of Anions, The Polarizing Power of Cations
Topic: Polarizing Power (Trends)
Replies: 3
Views: 80

### Polarizing Power (Trends)

What trends can we use to determine the polarizing power of an atom?
Tue Nov 05, 2019 12:13 pm
Forum: Trends in The Periodic Table
Topic: Ionization Energy (Oxygen)
Replies: 1
Views: 45

### Ionization Energy (Oxygen)

Why is the ionization energy of oxygen lower than that of nitrogen?
Mon Nov 04, 2019 3:07 pm
Forum: Polarisability of Anions, The Polarizing Power of Cations
Topic: 2D.5 - Electronegativity
Replies: 4
Views: 98

### 2D.5 - Electronegativity

For each pair, determine which compound has bonds with greater ionic character: (a) HCl or HI; (b) CH4 or CF4; (c) CO2 or CS2 For (c), I looked at the answer key and I noticed that the CO2 was considered the most ionic because "C" and "S" have nearly identical electronegativities...
Mon Nov 04, 2019 2:51 pm
Forum: Ionic & Covalent Bonds
Topic: 2D.1
Replies: 2
Views: 77

### 2D.1

Place the following elements in order of increasing electronegativity: antimony, tin, selenium, and indium.

Why does Selenium have the biggest electronegativity out of all of them if it has less protons?
Mon Nov 04, 2019 2:33 pm
Forum: Polarisability of Anions, The Polarizing Power of Cations
Topic: Ionic and Covalent character
Replies: 2
Views: 54

### Ionic and Covalent character

What does it actually mean to have "ionic" or "covalent" character?
Sun Nov 03, 2019 9:39 pm
Forum: Photoelectric Effect
Topic: Work function + Threshold energy
Replies: 2
Views: 68

### Re: Work function + Threshold energy

You are correct! They are interchangeable terms - basically you should instantly know that it's the minimum energy required to eject an electron from a metal!
Sun Nov 03, 2019 9:32 pm
Forum: Trends in The Periodic Table
Topic: Run Down of Trends
Replies: 4
Views: 105

### Re: Run Down of Trends

When I think about the trends, I like to think about them conceptually! Going across a row (L to R), the electrons occupy the same shell, so there is less shielding from the nucleus. As a result, they have a greater pull to the nucleus and are much smaller in radius. When you go down a group, the el...
Sun Nov 03, 2019 9:14 am
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: Nodal Planes
Replies: 1
Views: 40

### Nodal Planes

Although I know that nodal planes are where there is zero electron density (and they are in p- and d- orbitals), what's their significance? What can we understand about an orbital through the nodal plane?
Sun Nov 03, 2019 9:06 am
Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
Topic: Bohr Frequency Condition
Replies: 1
Views: 55

### Bohr Frequency Condition

On the learning outcomes for the Quantum world, one of the guidelines was "Use the Bohr frequency condition to explain the origin of the lines in the spectrum of an element". What exactly is Bohr's Frequency condition?
Tue Oct 29, 2019 4:18 pm
Forum: Ionic & Covalent Bonds
Topic: 2A.5 (d-block configurations)
Replies: 4
Views: 42

### 2A.5 (d-block configurations)

For Cu+, why is the configuration written as [Ar]3d10 instead of [Ar]3d84s2? Could someone also explain the configuration rules regarding the d-block?
Sat Oct 26, 2019 1:06 pm
Forum: Electron Configurations for Multi-Electron Atoms
Topic: 1E.21
Replies: 1
Views: 36

### 1E.21

"How many unpaired electrons are predicted for the ground-state configuration of each of the following atoms: (a) Bi; (b) Si; (omit C) (d) Ni?" Can someone walk me through this problem? My logic for "unpaired" electrons were the orbitals with only a single electron, but I don't t...
Sat Oct 26, 2019 11:57 am
Forum: Electron Configurations for Multi-Electron Atoms
Topic: Calculating Effective Nuclear Charge
Replies: 1
Views: 30

### Re: Calculating Effective Nuclear Charge

I don't think that we need to calculate the effective nuclear charge - I think as long as you know the basic concept of it you will be fine.

Effective nuclear charge is the pull that the nucleus has on an electron, taking into account the shielding from other electrons.
Sat Oct 26, 2019 11:45 am
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: oribital numbers
Replies: 7
Views: 82

### Re: oribital numbers

You can generally memorize the number of orbitals, but if you want to be technical... You can figure out the number of orbitals per sub shell through the quantum numbers! The subshells are depicted by l = 0,1,2,3 (which is s,p,d, and f, respectively). The magnetic quantum number m represents the ind...
Sat Oct 26, 2019 10:58 am
Forum: Electron Configurations for Multi-Electron Atoms
Topic: 1E.9
Replies: 1
Views: 26

### 1E.9

For this question, one of the parts stumped me: "Of the following sets of four quantum numbers { n , l , m l , m s }, identify the ones that are forbidden for an electron in an atom and explain why they are invalid: b) (5, 0, -1, +1/2)" Why is the m l invalid for this question? Wouldn't -1...
Sat Oct 26, 2019 10:22 am
Forum: Electron Configurations for Multi-Electron Atoms
Topic: 1E.5
Replies: 1
Views: 27

### 1E.5

For this question - which asks if the following statements in each listed part are true - part "c" stumped me the most: c) Electrons having l = 2 are better at shielding than electrons having l = 1. According to the answer key, this statement is false, since p-electrons are "less able...
Thu Oct 17, 2019 2:53 pm
Forum: Properties of Light
Topic: Vacuum
Replies: 3
Views: 57

### Re: Vacuum

A vacuum is a container with low pressure or virtually no matter. If you can recall, the photoelectric experiment was carried under a vacuum so the photons (light) wouldn't be intercepted by particles in the air.
Thu Oct 17, 2019 2:47 pm
Forum: Properties of Light
Topic: EM Spectrum
Replies: 3
Views: 64

### EM Spectrum

Are we responsible for knowing the regions (and their respective wavelengths) of the EM spectrum? Or we given them during an exam?
Thu Oct 17, 2019 2:41 pm
Forum: DeBroglie Equation
Topic: Question on applications of the equation
Replies: 2
Views: 45

### Re: Question on applications of the equation

The DeBroglie equation doesn't apply to photons because, like what the previous poster said, they do not have a measurable mass.

It applies to any particles with a mass - not just electrons! One homework problem in 1B asked for the wavelength of a proton and neutron using the equation.
Thu Oct 17, 2019 2:38 pm
Forum: Photoelectric Effect
Topic: relation of photoelectric effect to equations
Replies: 2
Views: 63

### Re: relation of photoelectric effect to equations

When scientists first carried out the photoelectric experiment, they first shone a longer wavelength (or smaller frequency) of high intensity light on a metal. However, this didn't eject any electrons. It wasn't until they increased the frequency of the light (or shorter wavelength) that the electro...
Tue Oct 15, 2019 1:27 pm
Forum: Photoelectric Effect
Topic: Question on Example 1B.3
Replies: 1
Views: 46

### Question on Example 1B.3

(Page 15 in the book, 152 on the pdf.) Here is the question: "Suppose you are developing a radiation detector to be used on a spacecraft and decide to use a thin layer of metallic potas- sium to detect certain ranges of electromagnetic radiation. You need to make some estimates of the physical ...
Sun Oct 13, 2019 10:37 pm
Forum: Properties of Light
Topic: Balmer vs. Lyman Lines (1A.11)
Replies: 3
Views: 52

### Balmer vs. Lyman Lines (1A.11)

While I was reading the text, I noticed the following statement about Lyman and Balmer lines: "The Balmer series consists of the lines with n1 = 2 (and n2 = 3, 4, . . .). The Lyman series is a set of lines in the ultraviolet region of the spectrum with n1 = 1 (and n2 = 2, 3, . . .)." Altho...
Sun Oct 13, 2019 10:13 pm
Forum: Properties of Light
Topic: When to use the Planck's Constant?
Replies: 6
Views: 52

### Re: When to use the Planck's Constant?

You can use Planck's constant when you are determining the energy of a photon (E = hv) and the energies at different n levels ( En = -hR / n^2)
It is also used in De Broglie (lambda = h/p).
Sun Oct 13, 2019 10:04 pm
Forum: Properties of Light
Topic: 1A.3
Replies: 2
Views: 40

### 1A.3

"Which of the following happens when the frequency of electromagnetic radiation decreases? Explain your reasoning.

[I was able to get a, b, and d]

c) The extent of the change in the electrical field at a given point decreases."

How do I interpret this problem?
Thu Oct 10, 2019 4:41 pm
Forum: Properties of Light
Topic: "Work Function" (from Post-Assessment Module)
Replies: 4
Views: 62

### "Work Function" (from Post-Assessment Module)

My question refers to a problem from the post-assessment module: "Light hits a sodium metal surface and the velocity of the ejected electron is 6.61 x 10^5 ms-1. The work function for sodium is 150.6 kJ mol-1...." In this question, what does the "work function" refer to? Is it su...
Thu Oct 10, 2019 4:37 pm
Forum: Properties of Light
Topic: Photoelectric Effect: Post-Assessment Question
Replies: 2
Views: 31

### Photoelectric Effect: Post-Assessment Question

Molybdenum metal must absorb radiation with a minimum frequency of 1.09 x 10^15 s^-1 before it can emit an electron from its surface. A. What is the minimum energy needed for this effect? B. If the metal is irradiated with 194 nm of light, what is the maximum KE of emitted electrons? I was able to s...
Sun Oct 06, 2019 5:30 pm
Forum: Molarity, Solutions, Dilutions
Topic: Help on G21
Replies: 1
Views: 48

### Help on G21

Question: A solution is prepared by dissolving 0.500 g of KCl, 0.500 g of K2S, and 0.500 g of K3PO4 in 500. mL of water. What is the concentration in the final solution of (a) potassium ions; (b) sulfide ions? Can someone walk me through this problem? I've walked through it (part a, specifically) by...
Sun Oct 06, 2019 2:47 pm
Forum: Molarity, Solutions, Dilutions
Topic: Question G7
Replies: 2
Views: 41

### Question G7

Question G7 asks how much of each mass component we would need to prepare 510 g of an aqueous solution (containing 5.45% KNO3 by mass). What are the mass components besides KNO3? Can someone walk me through this problem?
Thu Oct 03, 2019 2:42 pm
Forum: Significant Figures