## Search found 103 matches

Sat Mar 14, 2020 1:33 pm
Forum: Arrhenius Equation, Activation Energies, Catalysts
Topic: Transition State Theory
Replies: 3
Views: 54

### Re: Transition State Theory

The transition state theory states there exists a state between the reactants and products where the compound is in its highest energy form called the activated complex. This is different from the collision theory as it states that the more frequent collisions the reactants go through the faster the...
Sat Mar 14, 2020 1:24 pm
Forum: Zero Order Reactions
Topic: 0 order
Replies: 6
Views: 126

### Re: 0 order

The order of a reaction signifies how the rate is dependent on the concentration of a reactant. Thus, a zero-order reaction means there is no dependence between rate of a reaction and concentration of a reactant.
Sat Mar 14, 2020 1:22 pm
Forum: Administrative Questions and Class Announcements
Topic: Printing for Final
Replies: 9
Views: 241

### Re: Printing for Final

I'm assuming we will have to print and then scan and send back as the problems will likely be free response. It would be very unlikely that he only asks for the final answer to be entered onto ccle. My guess is we will have to print it out and then scan and submit online so he can grade for partial ...
Sat Mar 14, 2020 1:20 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Electromotive force
Replies: 2
Views: 18

### Re: Electromotive force

Electromotive force is a difference in the potential of two reactions that give rise to an electric current. This concept was given in the first lecture of electrochemistry.
Sat Mar 14, 2020 1:14 pm
Forum: Zero Order Reactions
Topic: Equations for 0, 1st, and 2nd order reactions
Replies: 4
Views: 69

### Re: Equations for 0, 1st, and 2nd order reactions

1st: ln[A] = -kt + ln[A]o

2nd: (1/[A]) = kt + (1/[A]o)

0 order: [A] = -kt + [A]o
Fri Mar 06, 2020 6:40 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: 6.73
Replies: 1
Views: 52

### Re: 6.73

I had to look up the equations for an aluminum-air fuel cell because I couldn't find the cell equations, in the following pages after Focus six. anode: 6OH-(aq) + 2Al(s) --> 2Al(OH)3 (aq) + 6e- cathode: 3H2O(l) + (3/2)O2(g) + 6e ---> 6OH- (aq) overall: 3H2O(l) + 2Al(s) + (3/2)O2(g) --> 2Al(OH)3 (aq)...
Fri Mar 06, 2020 6:17 pm
Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
Topic: HW 6.65 [ENDORSED]
Replies: 3
Views: 84

### Re: HW 6.65[ENDORSED]

at pH=1, the denominator in the K should be 1x10^-14 M, which will give you the right answer.

pH=1: RT/nF (lnK)= .025693 V ln(1.0 mol.L^-1/ 1.0 x 10^-14 mol.L^-1)= +0.828V
Fri Mar 06, 2020 6:12 pm
Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
Topic: HW 6.63
Replies: 2
Views: 71

### Re: HW 6.63

Borate is a polyatomic ion with a charge of negative one and thus we can assume that there is a transfer of only one electron and thus in the formula n=1.
Fri Mar 06, 2020 6:03 pm
Forum: Reaction Mechanisms, Reaction Profiles
Topic: Molecularity
Replies: 4
Views: 57

### Re: Molecularity

I believe it is called tetramolecular; however, since the simultaneous collision is needed for the reactants to go forward with the reaction, it is very unlikely to have a tetramolecular reaction as four reactants colliding together is very rare.
Fri Mar 06, 2020 5:59 pm
Forum: Reaction Mechanisms, Reaction Profiles
Topic: pseudo rate law
Replies: 2
Views: 38

### Re: pseudo rate law

Psuedo rate law means one that has been modified to fit a certain order that was not already in its desired order, to begin with. For example, a pseudo-first-order reaction is one that was not originally first order, but the concentration of the reactants is altered in order to make it a first-order...
Mon Mar 02, 2020 1:19 am
Forum: First Order Reactions
Topic: zero, first, and second order
Replies: 3
Views: 52

### Re: zero, first, and second order

The proportion of rate to concentration is the difference. In a first order reaction, the rate is proportional to the concentration. In a second order reaction, rate is proportional to the concentration raised to a power of two. Lastly, a third order reaction, the rate is proportional to a concentra...
Mon Mar 02, 2020 1:12 am
Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
Topic: pH
Replies: 1
Views: 31

### Re: pH

Usually, the final redox reaction will have H+ in the reactants or products. When using the Nernst equation, set up the ratios of products to reactants for lnQ. Then, substitute given values for the reaction quotient but leaving [H+] as it is to solve for. Isolate [H+], and then take -log [H+] to ge...
Mon Mar 02, 2020 1:08 am
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: electromotive force
Replies: 1
Views: 23

### Re: electromotive force

Electromotive force is a difference in potential, for example, reduction potential that gives rise to some sort of electric current that can be used to do work.
Mon Mar 02, 2020 1:06 am
Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
Topic: different values for RT/F
Replies: 1
Views: 35

### Re: different values for RT/F

The .0592 is used along with logQ, but the .025693 is used with lnQ. Both will give the same answer in the end.
Fri Feb 28, 2020 1:59 am
Forum: Equilibrium Constants & Calculating Concentrations
Topic: 5.55
Replies: 3
Views: 57

### Re: 5.55

Yes an ICE table is needed in part b. Once you find the moles of each substance using the given moles, use an ice table to find equilibrium concentrations.
Sun Feb 23, 2020 1:34 am
Forum: Entropy Changes Due to Changes in Volume and Temperature
Topic: Textbook question 4.45
Replies: 1
Views: 97

### Re: Textbook question 4.45

Dispersal of the matter is the idea that in a system energy will be spread over many particles rather than being concentrated, thus, if the substance can be dispersed into particles it will be in order to follow the laws of energy and spread it out over a greater area. Since KNO3 is an ionic compoun...
Sun Feb 23, 2020 1:21 am
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Homework 6L.3 part d
Replies: 1
Views: 38

### Re: Homework 6L.3 part d

I think for this one we should know that both H+ and O2 are on the same side of the reaction because together they form water which is the desired product on the right side of the equation. If either H+ or O2 was on the other side, the chemical reaction would not have made sense.
Sun Feb 23, 2020 1:13 am
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: 6M.1
Replies: 2
Views: 22

### Re: 6M.1

You have the numbers correct. but should double-check the arrangement of the final equation you are using to solve. Should be like this...

Ecell = E cathode - E anode (solving for E cathode...)
E cathode = E cell + E anode
E cathode = -.698V + .34V = -.349V
Fri Feb 21, 2020 1:45 pm
Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
Topic: Spontaneity
Replies: 7
Views: 108

### Re: Spontaneity

Higher cell potentials will indicate a greater level of spontaneity; however, spontaneity is a thermodynamic concept. It does not relate to kinetics, and thus, will not tell us anything about the speed of a reaction.
Thu Feb 20, 2020 1:05 am
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Cathode to the Right Rule
Replies: 6
Views: 65

### Re: Cathode to the Right Rule

I believe you can assume that the cathode will always be on the right. But, just to double-check when you assume this, at the cathode the reaction that takes place is always reduction. Thus, we should see a gain of electrons on the right side of the given statement. In this one, Ag+ goes to Ag.
Sat Feb 15, 2020 10:37 pm
Forum: Balancing Redox Reactions
Topic: Balancing Equations Order
Replies: 2
Views: 32

### Balancing Equations Order

When we balance half-reactions, I'm confused on the order in which we should balance them. Do we add H+ or H2O first?
Sat Feb 15, 2020 10:33 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: Hw 5G.19
Replies: 1
Views: 29

### Re: Hw 5G.19

b) you simply use the equation deltaGf = -RTlnK. In the problem it should look like this

deltaGf = -RTlnK = -(8.314 J/K mol)(298K)ln(1.1E-12) = 68 kJ/mol
--K was given in the problem
Sat Feb 15, 2020 10:30 pm
Forum: Balancing Redox Reactions
Topic: half reaction
Replies: 8
Views: 62

### Re: half reaction

A half-reaction is a partial breakdown of a full chemical redox reaction that shows each individual species being oxidized (loss of electrons, electrons on the product side) or being reduced (gain of electrons, electrons on the reactant side).
Sat Feb 15, 2020 10:29 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: 5G.21
Replies: 1
Views: 46

### Re: 5G.21

a) the delta G of formation for water is -228.57 kJ/mol.This should get you the correct answer when using it in the -RTlnK equation.

b) maybe recheck that you are using the correct delta G of formation values
CO2 --> -394.36 kJ/mol
CO --> -137.17 kJ/mol
Sat Feb 15, 2020 10:23 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: Gibbs Free Energy Calculations
Replies: 1
Views: 33

### Re: Gibbs Free Energy Calculations

I am not exactly sure, but the equilibrium constant, K, is a ratio of the products over reactants raised to the power of their respective molar coefficients. Thus, the moles of the product are already accounted for in the natural log of the equilibrium constant.
Sun Feb 09, 2020 11:14 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: 4D.7
Replies: 5
Views: 49

### Re: 4D.7

I think anytime there is no temperature we assume 25C (298K).
Sun Feb 09, 2020 11:14 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: 4D.7
Replies: 5
Views: 49

### Re: 4D.7

I think anytime there is no temperature we assume 25C (298K).
Sun Feb 09, 2020 11:14 pm
Forum: Entropy Changes Due to Changes in Volume and Temperature
Topic: Entropy of a close
Replies: 2
Views: 36

### Re: Entropy of a close

I believe because in the case of heat, as heat leaves the system entropy decreases which is absorbed by the surroundings. In general, what is lost by one is gained by the other part of a system.
Sun Feb 09, 2020 11:04 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: Heat capacity
Replies: 3
Views: 25

### Re: Heat capacity

Intensive properties are ones that depend on the size or amount of variables involved. Heat capacity depends on heat and temperature, both of which do not change in response to size of the system or amount of material. However, specific heat capacity depends on grams of a substance and molar heat ca...
Sun Feb 09, 2020 11:01 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Textbook Question 4D.1 example
Replies: 1
Views: 34

### Re: Textbook Question 4D.1 example

When you solve for the moles given from the .113g you get 1.45x10^-3 mol. However, the chemical equation starts off with 2 mol of C6H6 and thus you must use stoichiometry to convert to the proper number of moles to get the accurate deltaH in the end.
Fri Feb 07, 2020 12:19 am
Forum: Administrative Questions and Class Announcements
Replies: 7
Views: 90

It's fairly simple. The class is made up of homework points, discussion posts on chemistry community, and then the exams (Test 1, Midterm, Test 2, Final). The final grade has no weighted categories so it is simply how many points you earn out of all the total points possible in the class. The syllab...
Sat Feb 01, 2020 5:40 pm
Forum: Concepts & Calculations Using Second Law of Thermodynamics
Topic: entropy units
Replies: 2
Views: 19

### Re: entropy units

The SI unit for entropy is J/K.
Sat Feb 01, 2020 5:40 pm
Forum: Concepts & Calculations Using Second Law of Thermodynamics
Topic: microstates
Replies: 3
Views: 46

### Re: microstates

A compound can take many forms in which the atoms can have different placements. Each of the different positions the atoms can take makes up different microstates which all have the same energy.
Sat Feb 01, 2020 5:36 pm
Forum: Thermodynamic Definitions (isochoric/isometric, isothermal, isobaric)
Topic: kinetics
Replies: 8
Views: 55

### Re: kinetics

Kinetics is the study of the rate of reactions and how they are dependent on certain factors such as heat and time. Thermodynamics relates more to looking at the initial conditions and final conditions of a reaction.
Fri Jan 31, 2020 12:50 am
Forum: Gibbs Free Energy Concepts and Calculations
Topic: Delta G° vs Delta G
Replies: 2
Views: 28

### Re: Delta G° vs Delta G

Delta G° represents the standard free energy of a reaction, which is the gibbs free energy, or the energy available to do work, at the standard conditions of a reaction. The other Delta G is at any other point in the reaction which can be increased or decreased depending on how much products or reac...
Fri Jan 31, 2020 12:48 am
Forum: Thermodynamic Systems (Open, Closed, Isolated)
Topic: state property
Replies: 8
Views: 57

### Re: state property

A state property is a quantity that is independent of how the substance was prepared. For example, pressure and volume are both state properties that do not have anything to do with how a sample is prepared. Heat would not be a state function as it is dependent on what type of reaction takes place.
Thu Jan 23, 2020 10:55 pm
Forum: Phase Changes & Related Calculations
Topic: Celsius and Kelvin
Replies: 11
Views: 86

### Re: Celsius and Kelvin

Anytime you switch from celsius to Kelvin you must always use the conversion K=C + 273.
Thu Jan 23, 2020 10:54 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Titration
Replies: 1
Views: 19

### Re: Titration

Titrations are used to find the concentration of an unknown acidic solution by adding known concentrations of a basic solution, or vice versa. The base is added to the solution while there is an indicator added to the acid so that when the acid and base reaction reach equilibrium, moles of acid equa...
Wed Jan 22, 2020 3:37 pm
Forum: Administrative Questions and Class Announcements
Topic: 14A final solutions
Replies: 6
Views: 80

### Re: 14A final solutions

The final solutions should be posted on his website but on the previous 14A website. I'm not sure if we have access to his 14A website anymore.
Tue Jan 21, 2020 9:10 pm
Forum: Non-Equilibrium Conditions & The Reaction Quotient
Topic: 6A.19c
Replies: 1
Views: 32

### Re: 6A.19c

I think this may be a typo as the given concentration does not say X 10^-3. We can ask Lavelle or TAs in class tomorrow.
Tue Jan 21, 2020 9:08 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: HW 6D. 9
Replies: 2
Views: 44

### Re: HW 6D. 9

If the problem says a certain molarity of an acidic or basic solution it is referring to its initial concentration. If it was the equilibrium concentration, it would have definitely specified.
Tue Jan 21, 2020 9:06 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Post Assessment Part 1B number 18
Replies: 1
Views: 14

### Re: Post Assessment Part 1B number 18

Since the values are given as gas pressures, you would just have to calculate Kp without converting it to Kc.
Thu Jan 16, 2020 12:47 am
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: Le Chatelier overview
Replies: 3
Views: 31

### Re: Le Chatelier overview

Le Chatelier's encompasses all three mentioned in relation to adding a stress or removing a reactant or product, whether it may be concentration or pressure. If a stress is added to a reaction, according to LeChatelier's principle, the reaction will move away from that stressor to regain equilibrium...
Thu Jan 16, 2020 12:45 am
Forum: Acidity & Basicity Constants and The Conjugate Seesaw
Topic: kA and kB
Replies: 3
Views: 100

### Re: kA and kB

Yes that is correct. The higher Ka and Kb, mean that more of the acid or base dissociated, which indicates a higher strength. Due to the math, (log function), the pKa becomes the inverse and lower pKa and pKb values correspond to a greater strength.
Thu Jan 16, 2020 12:43 am
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: Module 4 Q15
Replies: 2
Views: 28

### Re: Module 4 Q15

I believe when considering LeChatliers principle, you must take into account all reactants and products. But, when writing the equilibrium constant equations, liquids and solids are not accounted for.
Thu Jan 16, 2020 12:41 am
Forum: Calculating pH or pOH for Strong & Weak Acids & Bases
Topic: Approximation
Replies: 6
Views: 117

### Re: Approximation

I think there is no official reason why it is 5%; however, the approximation check is used to make sure that X is such a small number that it allows to consider it insignificant when add or subtracting to another number.
Wed Jan 15, 2020 11:03 am
Forum: Student Social/Study Group
Topic: Discussion Sec 2A, 2C, 2J
Replies: 2
Views: 66

### Re: Discussion Sec 2A, 2C, 2J

I attached a picture of my notes.
Wed Jan 08, 2020 2:17 pm
Forum: Ideal Gases
Topic: Gas Law
Replies: 6
Views: 59

### Re: Gas Law

The gas law is an expression that relates P and V to concentration. Thus it allows you to convert between partial pressures and concentration of a reactant or product that is in equilibrium during a reaction.
Wed Jan 08, 2020 2:10 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: solids and liquids
Replies: 2
Views: 29

### Re: solids and liquids

Solids and liquids are not used in equilibrium because they do not affect the reactant amount at equilibrium and therefore should not be expressed in the equilibrium constant.
Wed Jan 08, 2020 1:59 pm
Forum: Ideal Gases
Topic: Q and K
Replies: 7
Views: 73

### Re: Q and K

Q and K are both calculated the same way — products/reactants. K is specifically referring to when the chemical reaction is in equilibrium. Q describes the reaction at any other point in time other than equilibrium.
Wed Jan 08, 2020 1:56 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Partial Pressure vs. Concentration
Replies: 4
Views: 33

### Re: Partial Pressure vs. Concentration

In the problem, they will either give you the partial pressures of some of the reactants and products, which you would use to solve for Kp. If they give you the concentrations of the components of the reaction, then solve for Kc. Both are calculated the same way, products/reactants.
Wed Jan 08, 2020 1:55 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: Le Chatelier's Principle
Replies: 3
Views: 50

### Re: Le Chatelier's Principle

This principle states that if a side of a equation increases in concentration, then the reaction will shift toward the other direction. For example, if the concentration of the reactions is increased, the forward reaction will be favored to produce more product to maintain equilibrium. Likewise, if ...
Thu Dec 05, 2019 9:45 pm
Forum: Calculating pH or pOH for Strong & Weak Acids & Bases
Topic: Sig Figs?
Replies: 1
Views: 28

### Re: Sig Figs?

Yes, sig figs is still used in pH and pOH calculations. However, the rules are slightly different. For pH and pOH sig figs are started to be counted after the decimal. For example, 6.5 pH is only 1 sig fig.
Thu Dec 05, 2019 9:39 pm
Forum: Properties & Structures of Inorganic & Organic Acids
Topic: Acid Strength
Replies: 2
Views: 51

### Re: Acid Strength

Looking at the chemical formula, pay attention to the anion. If the anion, is larger that means the bond between the elements is weaker. If the bond is weaker that means the acid will dissociate more, thus indicating it is a strong acid.
Thu Dec 05, 2019 9:30 pm
Forum: Properties & Structures of Inorganic & Organic Acids
Topic: Solubility rules
Replies: 1
Views: 50

### Re: Solubility rules

I don't think we will be expected to know solubility rules as none of the problems nor his lecture mentioned anything about knowing precipitation rules. Just to make sure, maybe we should clarify with him tomorrow.
Thu Dec 05, 2019 9:25 pm
Forum: Properties & Structures of Inorganic & Organic Acids
Topic: Stronger acid
Replies: 1
Views: 30

### Re: Stronger acid

The weaker the bond is the easier it is to break apart into ions and dissociate. We know that the more an acid dissociates the stronger it will be; thus, the fact that HCl has a weaker bond it will be able to dissociate easier making it the stronger acid. Similar to bases, the weaker bond the base h...
Thu Dec 05, 2019 9:23 pm
Forum: Naming
Topic: Adding -ate to end of transition metal
Replies: 2
Views: 31

### Re: Adding -ate to end of transition metal

Yes this is correct. Any time the coordination complex has a negative charge you add -ate to the end of the name.
Wed Nov 27, 2019 12:32 pm
Forum: Bronsted Acids & Bases
Topic: Difference between bronsted and lewis acid/base?
Replies: 6
Views: 56

### Re: Difference between bronsted and lewis acid/base?

We don't neccessarily use one or the other to define them. A bronsted acid is a proton donor, and a bronsted base is a proton acceptor. A Lewis acid is a electron acceptor and a lewis base is an electron donor.
Wed Nov 27, 2019 12:32 pm
Forum: Bronsted Acids & Bases
Topic: Difference between bronsted and lewis acid/base?
Replies: 6
Views: 56

### Re: Difference between bronsted and lewis acid/base?

We don't neccessarily use one or the other to define them. A bronsted acid is a proton donor, and a bronsted base is a proton acceptor. A Lewis acid is a electron acceptor and a lewis base is an electron donor.
Mon Nov 25, 2019 10:52 pm
Forum: Naming
Topic: Order of Ligands
Replies: 4
Views: 61

### Re: Order of Ligands

I believe both of the examples you have given might be incorrect. The Cl is the anion and thus must be written outside of the big brackets.
Mon Nov 25, 2019 8:45 pm
Forum: Naming
Topic: naming complexes
Replies: 3
Views: 30

### Re: naming complexes

When looking at the chemical name, the ligand will be the one that is written inside the parenthesis.
Mon Nov 25, 2019 8:43 pm
Forum: Shape, Structure, Coordination Number, Ligands
Topic: shape
Replies: 3
Views: 40

### Re: shape

It would be really hard to distinguish from only the formula you would need to draw the lewis structure to find out if it has lone pairs.
Mon Nov 25, 2019 8:06 pm
Forum: Shape, Structure, Coordination Number, Ligands
Topic: Online Textbook
Replies: 6
Views: 74

### Re: Online Textbook

Yes, there should be an online code that came with the book purchase. But, there was an exchange for the code you got for a new one. Check with the textbook renting center in ackerman to get some help with that.
Fri Nov 22, 2019 12:19 am
Forum: Interionic and Intermolecular Forces (Ion-Ion, Ion-Dipole, Dipole-Dipole, Dipole-Induced Dipole, Dispersion/Induced Dipole-Induced Dipole/London Forces, Hydrogen Bonding)
Topic: QUiz 2
Replies: 2
Views: 65

### Re: QUiz 2

Yes, the ion ion interactions could be on the test, but the main forces are dipole-dipole interactions, London Dispersion forces, and hydrogen bonding.
Fri Nov 22, 2019 12:10 am
Forum: Determining Molecular Shape (VSEPR)
Topic: 2E.5
Replies: 5
Views: 70

### Re: 2E.5

The molecule will be bent with bond angles slightly less than 120 degrees. Looking at the Lewis structure will tell you that this molecule has 2 bonding atoms and 1 lone pair, thus it is bent. If the molecule had 3 bonding atoms and 0 lone pairs, it would have been trigonal planar.
Fri Nov 22, 2019 12:07 am
Forum: Sigma & Pi Bonds
Topic: Coordination # and Steric #
Replies: 2
Views: 40

### Re: Coordination # and Steric #

Steric # and coordination # are the same thing as they both refer to the number of bonded atoms and lone pairs around an atom.
Fri Nov 22, 2019 12:02 am
Forum: Determining Molecular Shape (VSEPR)
Topic: AXE Format
Replies: 34
Views: 280

### Re: AXE Format

If there is only one, simply writing just the letter X or E is enough. The subscript of 1 is redundant.
Thu Nov 21, 2019 11:59 pm
Forum: Shape, Structure, Coordination Number, Ligands
Topic: Ligands
Replies: 2
Views: 32

### Re: Ligands

I'm almost certain the binding site will be on a protein of some sort.
Fri Nov 15, 2019 2:25 am
Forum: Determining Molecular Shape (VSEPR)
Topic: Symmetry and Polarity
Replies: 13
Views: 139

### Re: Symmetry and Polarity

You have to be careful because Lewis structures are not meant to be drawn to an accurate representation of the shape of a molecule. Although a Lewis structure may be drawn as symmetrical, we must first consider the VSEPR shape first. If we were to use the shape and symmetry of the VSEPR structure, t...
Fri Nov 15, 2019 2:22 am
Forum: Determining Molecular Shape (VSEPR)
Topic: 2E.19 (b)
Replies: 3
Views: 32

### Re: 2E.19 (b)

For an atom to have 120-degree bond angles, the molecule must be identified as trigonal planar. For this shape, the molecule must have one central atom and three surrounding bonded atoms. The molecule you have described only has two surrounding molecules and thus is not a trigonal planar with 120-de...
Fri Nov 15, 2019 2:20 am
Forum: Interionic and Intermolecular Forces (Ion-Ion, Ion-Dipole, Dipole-Dipole, Dipole-Induced Dipole, Dispersion/Induced Dipole-Induced Dipole/London Forces, Hydrogen Bonding)
Topic: Why does SO2 molecules have dipole-dipole interations?
Replies: 4
Views: 41

### Re: Why does SO2 molecules have dipole-dipole interations?

Yes, the presence of lone pairs usually renders a molecule to be polar since the atom with the lone pairs will be a more negative charge. Another example would be water!
Fri Nov 15, 2019 2:18 am
Forum: Determining Molecular Shape (VSEPR)
Topic: Polar vs Nonpolar molecules
Replies: 4
Views: 71

### Re: Polar vs Nonpolar molecules

Hi, let's take a trigonal planar molecule for example. As per your comment, if all the dipoles are facing outward meaning the more positive atom is on the center, then this symmetrical distribution of dipoles will render the molecule nonpolar. If even one of the dipoles was facing the opposite direc...
Fri Nov 15, 2019 2:16 am
Forum: Interionic and Intermolecular Forces (Ion-Ion, Ion-Dipole, Dipole-Dipole, Dipole-Induced Dipole, Dispersion/Induced Dipole-Induced Dipole/London Forces, Hydrogen Bonding)
Topic: How do we determine bond angles?
Replies: 4
Views: 40

### Re: How do we determine bond angles?

You have to predict its shape first using the rules we learned in the lecture. Then, you will know the bond angles. If the molecule is linear, then the angles will be 180 degrees. Trigonal planar - 120 degrees. Tetrahedral - 109.5 degrees.
Sun Nov 10, 2019 4:41 pm
Forum: Electronegativity
Topic: Electronegativity Exceptions
Replies: 3
Views: 35

### Re: Electronegativity Exceptions

There are no electronegativity exceptions to my understanding. Electronegativity increases going up a family and also increases going down a period towards Fluorine.
Sun Nov 10, 2019 4:39 pm
Forum: Lewis Structures
Topic: More than 8 electrons in structure?
Replies: 4
Views: 69

### Re: More than 8 electrons in structure?

Yes, the d-block allows the elements that are at the far right of the periodic table to extend their octet as they will put the extra electrons in the following d orbitals.
Sun Nov 10, 2019 4:37 pm
Forum: Dipole Moments
Topic: Polarity
Replies: 8
Views: 70

### Re: Polarity

If the molecule consists of two atoms and the electronegativity of one atom is significantly higher than the other, the molecule can be considered polar. For molecules with 3 or more atoms, drawing the structure and then writing the dipole arrows will allow you to assess if the molecule is polar.
Sun Nov 10, 2019 4:28 pm
Forum: Bond Lengths & Energies
Topic: Bond strength
Replies: 4
Views: 54

### Re: Bond strength

Hello, when talking about single bonds, a greater difference in electronegativity is directly related to the strength in bonds. But, as you said, a double bond is stronger than a single bond, and thus, a triple bond is stronger than a double bond due to increased attraction between each atom.
Sun Nov 10, 2019 4:26 pm
Forum: Dipole Moments
Topic: HYDROGEN BONDING
Replies: 3
Views: 32

### Re: HYDROGEN BONDING

Hello, compounds with Hydrogen bonded to N, O, F always have a hydrogen bond due to the high electronegativity from the anions. The electrons are pulled toward the anion and create a partial positive on the hydrogen atom. The partially positive hydrogen bond the bonds to the partially negative anion.
Sat Nov 02, 2019 3:56 pm
Forum: Formal Charge and Oxidation Numbers
Topic: Formal Charges
Replies: 3
Views: 43

### Re: Formal Charges

I am sure we will only need to write the formal charges if the problem asks which model is more favorable if there are resonance structures.
Sat Nov 02, 2019 3:42 pm
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: Probabilty
Replies: 1
Views: 44

### Re: Probabilty

One of the TA's had mentioned a past exam question stating what is the probability of finding an electron in the center of a p orbital? The probability of this is 0 because a p orbital has 1 node (as well as a d orbital). Electrons cannot be found at the nodes only in the orbital space.
Sat Nov 02, 2019 3:34 pm
Forum: Electronegativity
Topic: Oxygen and Electronegativity
Replies: 5
Views: 62

### Re: Oxygen and Electronegativity

Oxygen only needs two more electrons to fill its valence shell and therefore it means that it has a high power to attract electrons in order to complete its final energy shell. Fluorine is the most electronegative atom since it only requires one more to fill its shell.
Sat Nov 02, 2019 3:30 pm
Forum: Lewis Structures
Topic: Drawing Structures for Ionic Bonds
Replies: 2
Views: 31

### Re: Drawing Structures for Ionic Bonds

You would draw each ion separate in brackets next to each other. For example, the lewis structure for ammonium chloride would be as follows:

[*lewis structure for NH4+] [Cl-]
Sat Nov 02, 2019 3:28 pm
Forum: Lewis Structures
Topic: Topic 2C question 5
Replies: 2
Views: 31

### Re: Topic 2C question 5

Hi, since Cl already has 7 valence electrons and O is more electronegative, the unpaired electron will be on the oxygen atom.
Sun Oct 27, 2019 4:11 pm
Forum: Electron Configurations for Multi-Electron Atoms
Topic: The exceptions
Replies: 2
Views: 34

### Re: The exceptions

Chromium's d orbital technically rests in 3d4, however, due to electron stability, the element is more table when an electron from the s orbital is transferred into the d orbital to make the configuration 3d54s1. A half d orbital is more stable and therefore the s orbital will lose an electron that ...
Sun Oct 27, 2019 4:06 pm
Forum: Resonance Structures
Topic: Resonance Structures
Replies: 5
Views: 72

### Re: Resonance Structures

Yes that is correct.The correct structure would be the one with the lowest formal charges. The other oones can be drawn to show your reasoning in order to prove that the lowest formal charges are the correct answer. However, the one to report as your final answer should be the one with the lowest fo...
Tue Oct 22, 2019 10:18 pm
Forum: Administrative Questions and Class Announcements
Topic: Online Modules
Replies: 7
Views: 94

### Re: Online Modules

Hi, I believe the online modules were only for week 1 and 2 material and nothing further than that.
Tue Oct 22, 2019 10:16 pm
Forum: Electron Configurations for Multi-Electron Atoms
Topic: 4s and 3d
Replies: 5
Views: 72

### Re: 4s and 3d

Hi, when writing the electron configuration 3d actually comes first before 4s since 3d electrons are at a lower electron shell level.
Tue Oct 22, 2019 10:14 pm
Forum: Trends in The Periodic Table
Replies: 4
Views: 63

Why does the trend going across a period start from bigger radii to smaller, and then once you hit the anions it again returns to a big radius and then decreases to small?
Thu Oct 17, 2019 10:13 pm
Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
Topic: Rydberg constant
Replies: 3
Views: 51

### Re: Rydberg constant

Yes, the R constant can only be used when dealing with Hydrogen as the constant was determined based on experimental data for H.
Thu Oct 17, 2019 10:09 pm
Forum: *Shrodinger Equation
Topic: Nodal Planes
Replies: 6
Views: 66

### Re: Nodal Planes

F orbitals have 3 nodal planes.
Thu Oct 17, 2019 1:46 am
Forum: Quantum Numbers and The H-Atom
Topic: spin up and spin down
Replies: 7
Views: 68

### Re: spin up and spin down

Yes, that is correct, the numbers do not play an important role in this situation. The only thing we need to pay attention to is the sign indicating the spin, the 1/2 value does not matter.
Thu Oct 17, 2019 1:44 am
Forum: Properties of Light
Topic: Rydberg's Equation [ENDORSED]
Replies: 4
Views: 56

### Re: Rydberg's Equation[ENDORSED]

We would use this equation in questions that ask us about a change in energy levels (n1 to n2). i.e. How much energy is required to excite an electron from energy levels 1 to 4? If ##J energy were used to excite an electron off of ground state, what will be the final energy level of the electron?
Thu Oct 17, 2019 1:39 am
Forum: Quantum Numbers and The H-Atom
Topic: Ground State [ENDORSED]
Replies: 5
Views: 125

### Re: Ground State[ENDORSED]

When an atom is in the ground state it means it is in its lowest electron shell and has not been excited to a higher energy level. The way to get it out of the ground state is to excite the atom with a photon or heat.
Sat Oct 12, 2019 2:57 pm
Forum: Properties of Light
Topic: Light Intensity
Replies: 6
Views: 50

### Re: Light Intensity

Yes, that is exactly correct. The intensity of light is directly related to the number of photons not the common mistake of thinking about energy. Once enough energy from the photon has been put in, the electron will be ejected with a kinetic energy of 1/2mv^2. Each photon will eject one electron if...
Sat Oct 12, 2019 2:56 pm
Forum: DeBroglie Equation
Topic: De Broglie equation
Replies: 5
Views: 42

### Re: De Broglie equation

The mass also has to be in kg because whenever doing a calculation it should always be done in SI units which for mass is kg.
Tue Oct 08, 2019 9:15 pm
Forum: Properties of Light
Topic: Intensity and the number of photons
Replies: 3
Views: 1086

### Re: Intensity and the number of photons

Increasing light intensity will increase the number of photons. If the energy in the photon is sufficient enough to eject an electron then increasing the intensity will increase the number of photons, and therefore will excite a greater number of electrons.
Tue Oct 08, 2019 9:11 pm
Forum: Properties of Light
Topic: What does n stand for in quantum
Replies: 4
Views: 97

### What does n stand for in quantum

IN the textbook, it talks about Balmer series as well as others. Each of them are given an "n" value. What does the n represent?
Tue Oct 08, 2019 8:58 pm
Forum: Photoelectric Effect
Topic: Kinetic Energy from the Photoelectric Effect
Replies: 5
Views: 68

### Re: Kinetic Energy from the Photoelectric Effect

When a photon is shot at a metal surface, if there is sufficient energy the electron will be removed with a kinetic energy equaling 1/2 x (mass of e-) x (velocity of e-)^2.
Sat Oct 05, 2019 11:59 pm
Forum: Accuracy, Precision, Mole, Other Definitions
Topic: Determining the amount of formula units in a certain amount of mass
Replies: 2
Views: 43

### Re: Determining the amount of formula units in a certain amount of mass

Formula Units are used to denote an ionic compound. In an ionic compound, 1 mole of the compound has 6.022x10^23 formula units. In this problem. first find the moles of MgSO4 and then use Avogadro's number in a stoichiometric conversion to find the number of formula units.
Sat Oct 05, 2019 11:55 pm
Forum: Molarity, Solutions, Dilutions
Topic: Symbols for Molarity
Replies: 8
Views: 211

### Re: Symbols for Molarity

Yes, they are similar. M and c both refer to the number of moles of solute divided by the total volume in Liters.