## Search found 107 matches

Sat Mar 14, 2020 4:08 pm
Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
Topic: Test 2 #6 b
Replies: 1
Views: 20

### Re: Test 2 #6 b

If you add water, the volume goes up causing the concentration to go down. Concentration does affect cell potential as shown in the Nernst equation.
Fri Mar 13, 2020 7:43 pm
Forum: Arrhenius Equation, Activation Energies, Catalysts
Topic: Endgame 12
Replies: 1
Views: 30

### Endgame 12

How do you tell if something is a catalyst? For example, in endgame 12, why is D not a catalyst?
Fri Mar 13, 2020 7:24 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Endgame 5 and 7
Replies: 2
Views: 54

### Endgame 5 and 7

How comes in Endgame question 5, you were able to add the standard cell potentials to get -0.16V but you can't add the standard cell potentials in #7? Shouldn't you not be able to add them in 5 because cell potential isn't a state potential?
Fri Mar 13, 2020 10:38 am
Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
Topic: Endgame Q.2D
Replies: 2
Views: 48

### Re: Endgame Q.2D

For part D you should use the Nernst equation. E=Eo-(RT/nF) *lnQ
You have found Eo in part b. E is given as 2.20V. And Q=[Fe2+][Ce3+]^2/[Ce4+]^2 (products over reactants)
I believe the answer should be [Fe2+]=8.4*10^-6 M
Wed Mar 11, 2020 12:52 am
Forum: Administrative Questions and Class Announcements
Topic: ENDGAME Review Session
Replies: 71
Views: 2757

### Re: ENDGAME Review Session

Thank you for all your help these past two quarters, Lyndon! Thank you for putting in so much time and effort to get us through these courses. Congratulations on graduating and best of luck in the future!
Sat Mar 07, 2020 10:14 pm
Forum: General Science Questions
Topic: Reducing Math Errors
Replies: 7
Views: 147

### Re: Reducing Math Errors

Sometimes it helps to keep everything as variables and don't plug in numbers until you've isolated the variable you're trying to solve for. And of course, if you have extra time on a test, always be sure to double or triple check!
Sat Mar 07, 2020 10:12 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Reducing Mass of Electrode
Replies: 6
Views: 126

### Re: Reducing Mass of Electrode

Changing the mass of the electrode doesn't affect cell potential. Changing the concentration DOES change cell potential.
Sat Mar 07, 2020 10:11 pm
Forum: Reaction Mechanisms, Reaction Profiles
Topic: the intermediate in a reaction
Replies: 10
Views: 147

### Re: the intermediate in a reaction

Intermediates should not be a part of the rate law expression. Use the elementary reactions to find an equation you can set equal to the intermediate and plug it into the rate law equation.
Wed Mar 04, 2020 9:36 pm
Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
Topic: calculating K2?
Replies: 3
Views: 71

### Re: calculating K2?

You find K2 by using the Vant Hoff equation you wrote down: ln K2/K1=-ΔH°/R [1/T2-1/T1] After finding K2, square root it to find the H3O+ concentration. Use the concentration to find the pH. This pH is the neutral pH at 10 degrees C. Compare that number with 7 to see if a pH of 7 is acidic or basic...
Wed Mar 04, 2020 11:28 am
Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
Topic: calculating K2?
Replies: 3
Views: 71

### Re: calculating K2?

You find K2 by using the Vant Hoff equation you wrote down: ln K2/K1=-ΔH°/R [1/T2-1/T1] After finding K2, square root it to find the H3O+ concentration. Use the concentration to find the pH. This pH is the neutral pH at 10 degrees C. Compare that number with 7 to see if a pH of 7 is acidic or basic ...
Sat Feb 29, 2020 11:07 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: Outline of Thermodynamics #3
Replies: 2
Views: 57

### Re: Outline of Thermodynamics #3

Gibbs free energy depends on the equilibrium constant/reaction quotient as shown by these equations:
deltaGo=-RTlnK
deltaG=deltaGo+RTlnQ
Fri Feb 28, 2020 3:18 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: 6O1
Replies: 2
Views: 44

### 6O1

A 1.0 m NiSO4(aq) solution was electrolyzed by using inert electrodes. Write (a) the cathode reaction; (b) the anode reaction. (c) With no overpotential at the electrodes, what is the minimum potential that must be supplied to the cell for the onset of electrolysis? How do you find the minimum poten...
Tue Feb 25, 2020 3:22 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: 6L9
Replies: 2
Views: 51

### 6L9

Write balanced half reactions for the redox reaction of an acidified solution of potassium permanganate and iron(II) chloride.
Could someone help walk through how to get the half reactions? And why are the potassium and chlorines not included in the reactions?
Tue Feb 25, 2020 12:23 am
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Pt in cell diagram
Replies: 1
Views: 31

### Pt in cell diagram

When given a skeletal equation of a cell reaction, how do you know whether or not to include Pt? And which side would you include it on?
For example, in 6L5 why does a) Ni2+ +Zn -> Ni + Zn2+ not include platinum when b) Ce4+ + I- -> I2 +Ce3+ does
Mon Feb 24, 2020 9:37 pm
Forum: Balancing Redox Reactions
Topic: 6K. D
Replies: 3
Views: 104

### Re: 6K. D

The way i start this problem is by balancing the solution in acidic solution and then, at the end, adding OH- to both sides so the H+'s cancel out. The OH- + H+ turns into neutral H2O molecules (which may or may not cancel out. Therefore, Oxidation: 8OH- +P4 --> H2PO2-+4e- Reduction: 12e-+ 12H2O+ P...
Sun Feb 23, 2020 2:31 pm
Forum: Student Social/Study Group
Topic: Curve?
Replies: 31
Views: 1401

### Re: Curve?

I think grades are adjusted a bit at the end of the quarter based on the class averages. When I had him last quarter, my final grade ended up being a bit higher than my point total would've been.
Sun Feb 23, 2020 2:27 pm
Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
Topic: Coulomb Unit
Replies: 2
Views: 32

### Re: Coulomb Unit

One coulomb is the amount of electrical charge in 6.24*10^18 electrons. Coulomb is just a convenient unit that allows for the volt unit to be equal to 1J/C.
Sun Feb 23, 2020 2:23 pm
Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
Topic: test 2 material clarification
Replies: 10
Views: 117

### Re: test 2 material clarification

Yes, the Focus 5 topics listed under Outline 4 will be on test 2.
Sun Feb 23, 2020 2:22 pm
Forum: Administrative Questions and Class Announcements
Topic: Test 2 Material
Replies: 16
Views: 264

### Re: Test 2 Material

Test 2 will cover the second page of outline 4 (thermodynamics, focus 5) and outline 5 (electrochemistry)
Sat Feb 22, 2020 9:11 pm
Forum: General Science Questions
Topic: What are Workshops?
Replies: 10
Views: 279

### Re: What are Workshops?

I think both workshops and step up sessions go over the concepts but step ups might break down the concepts more and tend to go over more homework problems. Workshops sometimes have worksheets which are helpful.
Mon Feb 17, 2020 2:34 pm
Forum: Administrative Questions and Class Announcements
Topic: 14BL and 14C
Replies: 8
Views: 101

### 14BL and 14C

Hi! I was wondering if taking 14BL and 14C together is doable or is it too heavy of a workload/not recommended?
Thanks!
Wed Feb 12, 2020 3:04 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Pizza Roll's
Replies: 3
Views: 77

### Re: Pizza Roll's

Step one is raising the temperature of the reactants to 200C. Step 2 is the actual reaction at 200C (deltaH is given). Step 3 is cooling the products back down to 37C. Add all these values together to get the total change in enthalpy of the reaction.
Wed Feb 12, 2020 11:46 am
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Buffer Solution
Replies: 4
Views: 86

### Buffer Solution

This is a problem from Hannah's acid and base review session: What is the initial pH of a buffer solution consisting of .400M acetic acid (CH3COOH) and .250M KCH3CO2? The Ka for acetic acid is 1.78 x 10^-5 The answer I got was a pH of 4.545 and I was wondering if someone could confirm that this is c...
Tue Feb 11, 2020 9:03 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: Extensive and Intensive Properties
Replies: 12
Views: 227

### Re: Extensive and Intensive Properties

An extensive property depends on the amount you have. Heat capacity is extensive because the amount of energy required to raise the temperature by 1 degree is dependent on how much of the object you have. Molar and specific heat capacity are intensive because they have already defined the amount you...
Tue Feb 11, 2020 2:38 pm
Forum: Thermodynamic Definitions (isochoric/isometric, isothermal, isobaric)
Topic: delta H for isothermal reactions
Replies: 1
Views: 29

### delta H for isothermal reactions

Why is deltaH=0 for isothermal reactions?
Tue Feb 11, 2020 12:37 am
Forum: Phase Changes & Related Calculations
Topic: Heat of fusion and vaporization
Replies: 1
Views: 40

### Heat of fusion and vaporization

Since heat of fusion for water is 6.01kJ/mol, is it correct that the change in enthalpy when going from liquid to solid be -6.01kJ/mol? And similarly going from gas to liquid would be -40.7kJ/mol?
Tue Feb 11, 2020 12:30 am
Forum: Entropy Changes Due to Changes in Volume and Temperature
Topic: Irreversible Process
Replies: 1
Views: 33

### Irreversible Process

does an isothermal, irreversible free expansion mean there's no change in entropy of the surroundings?
Sat Feb 08, 2020 10:59 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: 4D9
Replies: 2
Views: 48

### Re: 4D9

Because N2 and O2 are already in their most stable form so their standard reaction of enthalpy by definition is 0.
Sat Feb 08, 2020 10:57 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: Negative Heat Capacity
Replies: 4
Views: 42

### Re: Negative Heat Capacity

No because it doesn't make sense for it to take negative energy to raise the temperature of a substance.
Sat Feb 08, 2020 10:54 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Bond Enthalpies
Replies: 3
Views: 30

### Re: Bond Enthalpies

Drawing the lewis structure helps a lot to visualize which bonds need to be broken and formed. In worst case scenario, you could calculate if all bonds were broken and all new bonds reformed.
Sat Feb 08, 2020 10:52 pm
Forum: Entropy Changes Due to Changes in Volume and Temperature
Topic: Units
Replies: 4
Views: 48

### Re: Units

Entropy is always in J/K. The units for the numbers you are finding the natural log of (volume, temperature, pressure) will always end up cancelling out.
Sat Feb 08, 2020 10:47 pm
Forum: Entropy Changes Due to Changes in Volume and Temperature
Topic: Irreversible and Reversible Processes
Replies: 2
Views: 33

### Irreversible and Reversible Processes

Can someone explain how irreversible and reversible processes affect entropy of the surroundings and universe? For example in 4I9, why does an isothermal, reversible expansion mean there's no change in total entropy? And why does an isothermal, irreversible free expansion mean there's no change in e...
Thu Jan 30, 2020 5:42 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Hess's Law vs. Standard Enthalpies of Formation
Replies: 5
Views: 72

### Hess's Law vs. Standard Enthalpies of Formation

How do we know when to use Hess's Law as opposed to standard enthalpies of formation where we do the enthalpies of product minus enthalpies of reactants?
Thu Jan 30, 2020 10:58 am
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: 4D19
Replies: 1
Views: 31

### 4D19

Calculate the reaction enthalpy for the synthesis of hydrogen bromide gas, H2(g)+Br2(l)->2HBr(g), NH3(g)+HBr(g)->NH4Br(s) dH=-188.32kJ N2(g)+3H2(g)->2NH3(g) dH=-92.22kJ N2(g)+4H2(g)+Br2(l) dH=-541.66kJ I was wondering why you don't have to divide 92.22 by 3 in order to get the reaction enthalpy for ...
Tue Jan 28, 2020 3:40 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: q vs deltaH
Replies: 6
Views: 64

### q vs deltaH

Could someone explain the difference between q and deltaH please? Thank you!
Mon Jan 27, 2020 11:48 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: 4D1
Replies: 2
Views: 43

### 4D1

Carbon disulfide can be prepared from coke and elemental sulfur: 4C(s)+S8(s) --> 4CS2(l) deltaH=+358.8kJ (b) Calculate the heat absorbed in the reaction of 197g of carbon with an excess of sulfur. Can someone explain why we have to divide by 4 moles of carbon to get the answer? And should we normall...
Mon Jan 27, 2020 11:46 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: 4E.5c
Replies: 1
Views: 26

### Re: 4E.5c

The answer is 0kJ/mol for the reason you stated
Wed Jan 22, 2020 3:23 pm
Forum: Administrative Questions and Class Announcements
Topic: 14A final solutions
Replies: 6
Views: 80

### 14A final solutions

Does anyone know if the 14A final solutions are posted anywhere?
Wed Jan 22, 2020 12:08 am
Forum: Acidity & Basicity Constants and The Conjugate Seesaw
Topic: Homework 6C.5
Replies: 2
Views: 126

### Re: Homework 6C.5

Wed Jan 22, 2020 12:06 am
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Homework 6D.7a
Replies: 3
Views: 65

### Re: Homework 6D.7a

I believe you have to search up the Ka value. I found it to be 3.0*10^-8. Use the hydronium concentration you found and plug it into the ice table. Then take the values from the ice table and set up an equation equal to Ka to solve for the initial concentration
Tue Jan 21, 2020 11:59 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: 5.33
Replies: 4
Views: 44

### Re: 5.33

I think that catalysts only speed up reactions. They don't cause more product to form.
Tue Jan 21, 2020 11:57 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: 5.61a
Replies: 3
Views: 43

### Re: 5.61a

5.61 The overall photosynthesis reaction is 6 CO2(g) + 6 H2O(l) -- C6H12O6(aq) + 6 O2(g), and H = 12802 kJ. Suppose that the reaction is at equilibrium. State the effect that each of the following changes will have on the equilibrium composition: tends to shift toward the formation of reactants, te...
Sun Jan 19, 2020 2:22 pm
Forum: Non-Equilibrium Conditions & The Reaction Quotient
Topic: Homework 6E.3
Replies: 3
Views: 36

### Re: Homework 6E.3

I think if the second Ka value is less than 10^-3 then the second protonation can be ignored
Sun Jan 19, 2020 2:18 pm
Forum: Identifying Acidic & Basic Salts
Topic: Identifying salts
Replies: 2
Views: 83

### Re: Identifying salts

A salt is produced by the neutralization of a base by an acid. Oftentimes a cation will act as the acid and an anion as the base.
Sun Jan 19, 2020 2:14 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: 5.61a
Replies: 3
Views: 43

### Re: 5.61a

I believe that increasing the partial pressure of O2 is achieved by means of adding more O2 gas particles. And remember that P (partial pressure) = concentration * R * T (temperature). Doesn't increasing the partial pressure have the same effect as increasing the concentration? Why doesn't the equi...
Thu Jan 16, 2020 10:24 pm
Forum: Polyprotic Acids & Bases
Topic: Polyprotic Acid pH
Replies: 1
Views: 65

### Polyprotic Acid pH

Is it right to say that the second deprotonations of all polyprotic acids (but sulfuric acid) can be ignored when calculating pH?
Tue Jan 14, 2020 11:56 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: delta H
Replies: 5
Views: 37

### delta H

Do we have to know how to calculate delta H? If yes, how?
Sat Jan 11, 2020 9:37 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Hw 5I.1
Replies: 4
Views: 60

### Re: Hw 5I.1

For this problem, you can just set the given K value equal to [products]/[reactants] and solve for the [Br2]
Sat Jan 11, 2020 9:32 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Table 5G.2
Replies: 5
Views: 50

### Re: Table 5G.2

EllieSchmidtke_4I wrote:For problem 5I.3, why would you use Kc = 160 from Table 5G.2 instead of Kc = 794 or Kc = 54?

The problem tells you the equilibrium mixture is at 500K which is why you use Kc=160
Sat Jan 11, 2020 9:27 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: 5J.13
Replies: 2
Views: 23

### Re: 5J.13

The problem also tells you that K=7.8*10^-5 at 700K which is less than K at 600K. Therefore more ammonia (the product) would be formed at 600K since a greater K value means a greater ratio of products to reactants.
Fri Jan 10, 2020 11:27 am
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: 5.61b
Replies: 3
Views: 23

### 5.61b

6CO2(g) + 6H2O(l)->C6H12O6(aq) + 6O2(g) is at equilibrium
How comes when you compress this system, there will be little to no effect on the system? Would the reaction not shift to the formation of reactants because there's less moles?
Tue Jan 07, 2020 10:42 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: 5J.11b Halogens
Replies: 1
Views: 48

### 5J.11b Halogens

Predict whether each of the following equilibria will shift toward products or reactants with a temperature increase:
X2(g) -> 2X(g), where X is a halogen

How do halogens affect equilibrium?
Sat Dec 07, 2019 9:24 pm
Forum: Bronsted Acids & Bases
Topic: 6C.19
Replies: 2
Views: 95

### Re: 6C.19

HClO4 is a stronger acid than HPO4. The only differing atom between them is the chlorine and phosphorus. Chlorine is more electronegative so it will help to stabilize the negative charge that will be created after the molecule gives up a proton. Chlorine is able to pull electron density towards it a...
Sat Dec 07, 2019 12:12 am
Forum: Shape, Structure, Coordination Number, Ligands
Topic: Chelate vs Polydentate
Replies: 6
Views: 108

### Re: Chelate vs Polydentate

Chelates form a ring around the central atom, whereas polydentate ligands allow more than one of its binding sites to be occupied. I think that a polydentate ligand can be a chelate, but they are not necessarily a chelate. In the review session i'm pretty sure Matthew said all polydentate ligands c...
Fri Dec 06, 2019 11:40 pm
Forum: Shape, Structure, Coordination Number, Ligands
Topic: Chelate vs Polydentate
Replies: 6
Views: 108

### Chelate vs Polydentate

How do you define chelate and polydentate and how are they different?
Thu Dec 05, 2019 6:02 pm
Forum: Conjugate Acids & Bases
Topic: Conjugate Acid
Replies: 1
Views: 29

### Conjugate Acid

Could someone explain why the conjugate acid of a strong base such as NaOH doesn't affect pH? Thanks!
Wed Dec 04, 2019 9:35 pm
Forum: Shape, Structure, Coordination Number, Ligands
Topic: Polydentate
Replies: 2
Views: 65

### Polydentate

Hi,
Could someone explain the placement of lone pairs necessary on ligands for the ligand to be polydentate?
Wed Dec 04, 2019 9:31 pm
Forum: Amphoteric Compounds
Topic: Amphoteric vs Amphiprotic
Replies: 9
Views: 99

### Re: Amphoteric vs Amphiprotic

Amphiprotic means that a substance can both accept and donate a proton or H+. Amphoteric means that a substance can act as both an acid and a base. All amphoteric substances are amphiprotic because if a molecule can either donate or accept a proton, that means it can act as both an acid or a base. ...
Wed Dec 04, 2019 9:28 pm
Forum: Amphoteric Compounds
Topic: Amphoteric vs Amphiprotic
Replies: 9
Views: 99

### Re: Amphoteric vs Amphiprotic

ALegala_3I wrote:What does the term polyprotic mean? Can a molecule be both polyprotic and amphiprotic?

Polyprotic means an acid that can give more than one proton
Tue Dec 03, 2019 10:55 pm
Forum: Amphoteric Compounds
Topic: Amphoteric vs Amphiprotic
Replies: 9
Views: 99

### Amphoteric vs Amphiprotic

Hi,
Is it correct to say that all amphiprotic substances are amphoteric? If so, what are some compounds that are amphoteric but not amphiprotic?
Fri Nov 29, 2019 10:43 pm
Forum: Calculating pH or pOH for Strong & Weak Acids & Bases
Topic: Strong vs Weak Acids and Bases
Replies: 5
Views: 127

### Strong vs Weak Acids and Bases

Is there a way to determine if an acid/base is strong or weak when only given their chemical formula?
Thu Nov 28, 2019 5:52 pm
Forum: Bronsted Acids & Bases
Topic: 6A9
Replies: 2
Views: 45

### 6A9

Which of the following can be classified as reactions between Bronsted acids and bases? For those that can be so classified, identify the acid and the base. a) NH4I + H2O -> NH3 + H3O+ + I- b) NH4I -> NH3 + HI c) CH3COOH + NH3 -> CH3CONH2 + H2O d) NH4I + KNH2 -> KI + 2NH3 Could someone explain how t...
Mon Nov 25, 2019 9:33 pm
Forum: Shape, Structure, Coordination Number, Ligands
Topic: Transition Metals
Replies: 4
Views: 95

### Transition Metals

Can coordination compounds only be made with transition metals? Or can other metals act as the central metal atom?
Mon Nov 25, 2019 9:29 pm
Forum: Shape, Structure, Coordination Number, Ligands
Topic: OH2 vs H2O
Replies: 4
Views: 83

### OH2 vs H2O

Would we get marked down if we were to write H2O instead of OH2 when the central metal is binding to the O?
Mon Nov 25, 2019 12:06 am
Forum: Shape, Structure, Coordination Number, Ligands
Topic: Shape
Replies: 2
Views: 45

### Shape

How do we know when a coordination complex is tetrahedral as opposed to square planar?
Sun Nov 24, 2019 10:59 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Polar vs. Nonpolar
Replies: 3
Views: 53

### Re: Polar vs. Nonpolar

if a central atom has two different pairs of elements attached to it, those dipoles would not cancel out because of the molecule's tetrahedral shape. The atoms are not all on one plane
Sun Nov 24, 2019 10:56 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Final
Replies: 10
Views: 112

### Re: Final

Sun Nov 24, 2019 10:49 pm
Forum: Hybridization
Topic: hybridization
Replies: 1
Views: 35

### hybridization

could someone explain the different hybrid orbitals? for example, would there be a hybrid orbital with p4? what would be the orbital with 6 electron densities? 7?
Fri Nov 22, 2019 9:16 pm
Forum: Lewis Acids & Bases
Topic: Week 9 Homework
Replies: 5
Views: 73

### Week 9 Homework

What section should we complete for week 9's homework?
Mon Nov 18, 2019 11:40 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: seesaw
Replies: 5
Views: 76

### seesaw

Are the angles of a seesaw molecule 90 and 120 degrees? Or should they be slightly less than 90 and 120.
The textbook answer key says it should be 90 and 120 exactly, but shouldn't the lone pair repulsion cause the angles to be slightly smaller?
Sat Nov 16, 2019 11:01 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: VSEPR notation
Replies: 8
Views: 114

### Re: VSEPR notation

AX3 because there are 3 atoms (3 oxygens) attached to the central atom (nitrogen)
Sat Nov 16, 2019 10:58 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: VSEPR notation
Replies: 6
Views: 97

### Re: VSEPR notation

yes, those are correct :)
Sat Nov 16, 2019 10:56 pm
Forum: Dipole Moments
Topic: 3F15
Replies: 2
Views: 53

### 3F15

For 3F15, why does AsF3 have a higher boiling point than AsF5?
I guess my question is also: how is AsF5 polar while AsF3 not, as the answer key says?
Fri Nov 15, 2019 6:40 pm
Forum: Dipole Moments
Topic: CH
Replies: 3
Views: 60

### CH

When carbon and hydrogen are bonded, is there a dipole moment?
Thu Nov 14, 2019 9:16 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Bond Angles
Replies: 8
Views: 88

### Bond Angles

Are we just supposed to memorize that a tetrahedral angle is 109.5 degrees and that trigonal planar angles are 107 degrees, etc? Or is there a way that these angles were calculated?
Sat Nov 09, 2019 10:38 pm
Forum: Resonance Structures
Topic: Resonance Structures
Replies: 18
Views: 394

### Re: Resonance Structures

Resonance structures are alternate Lewis structures for a single compound. They're all correct and often just have double/triple bonds at different locations.
Sat Nov 09, 2019 10:36 pm
Forum: Formal Charge and Oxidation Numbers
Topic: How to know where a double bond should go?
Replies: 10
Views: 151

### Re: How to know where a double bond should go?

Count all the total number of valence electrons and arrange them around the atoms. Then as you calculate formal charge, you can rearrange the lone pairs and see where there are double bonds.
Sat Nov 09, 2019 10:35 pm
Forum: Electronegativity
Topic: Periodic Trend
Replies: 13
Views: 178

### Re: Periodic Trend

Electronegativity increases to the right and going up. Electronegativity is the electron-pulling power of an atom. So as you go to the right on the table, the outer electron shell becomes increasingly full so the atom would want an electron more because it's closer to becoming stable with a full ele...
Tue Nov 05, 2019 5:06 pm
Forum: Lewis Structures
Topic: CN-
Replies: 2
Views: 56

### CN-

Does CN- have a triple bond? If yes, why a triple bond and not a double bond with 2 lone pairs on nitrogen?
Tue Nov 05, 2019 12:38 am
Forum: Resonance Structures
Topic: Resonance Structures
Replies: 2
Views: 57

### Resonance Structures

Are resonance structures only the lowest energy structures with the best formal charge? Or can they be structures with non-optimal formal charges?
Mon Nov 04, 2019 3:18 pm
Forum: DeBroglie Equation
Topic: Week 3 Lyndon's Workshop
Replies: 1
Views: 176

### Week 3 Lyndon's Workshop

Hi,
Does anyone have the answers to the worksheet from Lyndon's workshop during week 3 10/14? They'd be much appreciated, thank you!!
Sat Nov 02, 2019 7:58 pm
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: Orbitals
Replies: 3
Views: 188

### Re: Orbitals

i believe this is how you do it: a) 103 because ml can be any value between [-l, l] so there are 51*2+1 possible orbitals bc) 1 because they give you a ml value so there's only one possible orbital d) if n=57 then there are 57 possible l values and for each of them they'd have l*2+1 orbitals (or ju...
Sat Nov 02, 2019 7:53 pm
Forum: Lewis Structures
Topic: Formal Charge for Lewis Structures
Replies: 4
Views: 61

### Re: Formal Charge for Lewis Structures

We should always use formal charge but remember that the sum of the formal charges of all the atoms should equal the charge of the compound. Check that the octet rule is satisfied and keep in mind that certain elements can have expanded or incomplete octets too.
Sat Nov 02, 2019 7:50 pm
Forum: Heisenberg Indeterminacy (Uncertainty) Equation
Topic: dino nuggets 13 (c)
Replies: 1
Views: 92

### Re: dino nuggets 13 (c)

the equation we would use is mass*indeterminacy of velocity*indeterminacy of position should be greater than or equal to h/4pi Plug in 0.0028kg for mass and 0.68 for indeterminacy of velocity because the velocity could be 0.34m/s above or below the given value. Isolate and solve for the position and...
Sat Nov 02, 2019 7:44 pm
Forum: Administrative Questions and Class Announcements
Topic: Midterm
Replies: 16
Views: 194

### Re: Midterm

htatshwe_3L wrote:So it's everything including material from test 1, not everything after test, right?

Yup, from week 0 to the end of focus 2D
Wed Oct 30, 2019 11:24 pm
Forum: Properties of Light
Topic: Waves
Replies: 4
Views: 85

### Waves

How long does an object's wavelength have to be to be considered to have wavelike properties?
Sat Oct 26, 2019 10:24 pm
Forum: Lewis Structures
Topic: Homework 2B 1a)
Replies: 2
Views: 33

### Re: Homework 2B 1a)

Carbon has a lower ionization energy.
Carbon is 153.9 kJ mol‑1 while chlorine is 349.0 kJ mol‑1. Chlorine is also closer to the top right corner of the periodic table which means it has higher ionization energy
Sat Oct 26, 2019 10:21 pm
Forum: Lewis Structures
Topic: 2B.1
Replies: 2
Views: 45

### Re: 2B.1

Because ONF is a neutral compound, you would want the formal charges to equal 0
Sat Oct 26, 2019 10:18 pm
Forum: Trends in The Periodic Table
Topic: Question on 2A.23 part a
Replies: 2
Views: 25

### Re: Question on 2A.23 part a

Magnesium has 2 valence electrons so it will generally give them up to atoms with almost full electrons. Arsenic has 5 valence electrons so it needs 3 more to complete its shell. Therefore if you have 3 magnesium atoms, there will be 6 electrons to give. And with 2 arsenic atoms, it needs 6 electron...
Sat Oct 26, 2019 10:14 pm
Forum: Trends in The Periodic Table
Topic: Question on 2A. 17 part c
Replies: 1
Views: 29

### Re: Question on 2A. 17 part c

Cobalt is in group 9 so it has 9 valence electrons in its neutral state. Then because the charge the 3+, it means there are 3 less electrons than it does during its neutral state so there are 6 valence electrons.
Sat Oct 26, 2019 10:07 pm
Forum: Lewis Structures
Topic: 2B3d
Replies: 1
Views: 23

### 2B3d

How do we know that bromine gets 10 valence electrons?
Mon Oct 21, 2019 4:59 pm
Forum: Electron Configurations for Multi-Electron Atoms
Topic: 1E25c
Replies: 1
Views: 27

### 1E25c

Give the notation for the valence-shell configuration (including the outermost d-electrons) of Group 5 transition metals

Thank you!
Sun Oct 20, 2019 4:20 pm
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: Orbitals
Replies: 3
Views: 188

### Re: Orbitals

i believe this is how you do it: a) 103 because ml can be any value between [-l, l] so there are 51*2+1 possible orbitals bc) 1 because they give you a ml value so there's only one possible orbital d) if n=57 then there are 57 possible l values and for each of them they'd have l*2+1 orbitals (or jus...
Sun Oct 20, 2019 4:12 pm
Forum: Electron Configurations for Multi-Electron Atoms
Topic: paired and parallel electrons
Replies: 3
Views: 53

### paired and parallel electrons

could some please explain how electrons are paired and parallel? in what situations are they paired and when are they parallel?
Thu Oct 17, 2019 5:46 pm
Forum: Photoelectric Effect
Topic: Different metals
Replies: 2
Views: 47

### Re: Different metals

I believe the photoelectric effect works the same way but different metals have different threshold energies/energy required to remove an electron.
Thu Oct 17, 2019 5:42 pm
Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
Topic: Balmer and Lyman series
Replies: 5
Views: 57

### Re: Balmer and Lyman series

The Balmer series includes all spectral line emissions that have a final n value of 2 while the Lyman series includes all spectral line emissions with a final n value of 1. Because they are all emission lines, the initial n value must be greater than 2 and 1 respectively.
Wed Oct 16, 2019 5:35 pm
Forum: Properties of Electrons
Topic: orbitals, shells, subshells
Replies: 4
Views: 88

### orbitals, shells, subshells

could someone explain the difference between orbitals, shells, and subshells please? thank you!
Sun Oct 13, 2019 9:21 pm
Forum: Properties of Light
Topic: 1B #7
Replies: 1
Views: 44

### Re: 1B #7

a) lambda = c/v 589*10^-9 m = 3.0*10^8 m/s (v) v = 5.09 * 10^14 Hz E=hv E=6.626*10^34m^2kg/s * 5.09 * 10^14 Hz E=3.37 * 10^-19 J (per atom) b) 5.0 mg * (1g/1000mg)*(1 mol/22.99g) * (6.022*23 atoms/1mol) = 1.3096 atoms 1.3096 atoms * (3.37*10^-19J) = 44.2 J c) 1 mol * (6.022*23 atoms/1mol) * (3.37*10...
Sun Oct 13, 2019 9:05 pm
Forum: Properties of Electrons
Topic: 1B 15C
Replies: 1
Views: 33

### Re: 1B 15C

We know that the E(photon)=threshold energy + E(kinetic) Threshold energy is the amount of energy required to remove an electron from a metal which is what we found in (b) to be 1.66*10^-17 J E(kinetic)=1/2mv^2 where m=9.11*10^-31 kg (mass of electron) and v=3.6 * 10^3 km/s or 3.6*10^6m/s so E(kinet...
Sun Oct 13, 2019 3:59 pm
Forum: Properties of Light
Topic: Memorization of Electromagnetic Spectrum
Replies: 3
Views: 71

### Re: Memorization of Electromagnetic Spectrum

A UA told me we have to memorize the order of the spectrum. And for visible light know that violet has the shortest wavelength while red has the longest.