Search found 93 matches

by sarahforman_Dis2I
Tue Feb 18, 2020 8:46 am
Forum: Gibbs Free Energy Concepts and Calculations
Topic: ∆G = ∆Gº + RT lnQ
Replies: 12
Views: 52

Re: ∆G = ∆Gº + RT lnQ

Hi, I'm having trouble understanding the difference between the ∆G and ∆Gº terms in the equation ∆G = ∆Gº + RT lnQ. Is ∆Gº the standard Gibb's free energy difference between the reactants and products, and ∆G the Gibb's free energy difference between the initial state and equilibrium (since we deri...
by sarahforman_Dis2I
Tue Feb 18, 2020 8:39 am
Forum: Calculating Standard Reaction Entropies (e.g. , Using Standard Molar Entropies)
Topic: Hc vs Hf
Replies: 3
Views: 12

Re: Hc vs Hf

Is there a difference between Hc and Hf? Would you use them exactly them say as in products minus reactants? Hf would be used to calculate the overall enthalpy of the reaction. You would calculate this using sum of Hf (products) - sum of Hf (reactants) Hc is the enthalpy of combustion. In other wor...
by sarahforman_Dis2I
Tue Feb 18, 2020 8:36 am
Forum: Van't Hoff Equation
Topic: Van't Hoff Temperature Dependence
Replies: 4
Views: 16

Re: Van't Hoff Temperature Dependence

Can someone explain to me why we are taking the natural log of Temperature in Van't Hoff's equation? I'm confused as to what the equation also is trying to convey also because I was confused about the in class example. Thank you! The reason you take ln(K) is because you are assuming that the reacti...
by sarahforman_Dis2I
Tue Feb 18, 2020 8:27 am
Forum: Gibbs Free Energy Concepts and Calculations
Topic: Free Energy and Work
Replies: 4
Views: 17

Re: Free Energy and Work

What is the relationship between free energy and work? This is one of the learning objectives from Thermodynamics. From what I understand, the free energy is the amount of energy that is available to do work. When talking about energy, energy can be in the form of heat, friction ext. Free energy is...
by sarahforman_Dis2I
Tue Feb 18, 2020 8:25 am
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: isothermal reactions
Replies: 8
Views: 22

Re: isothermal reactions

Rhea Shah 2F wrote:Why is internal energy equal to 0 in an isothermal reaction?


One way that a TA explained this concept to me, is the U is a function of T, meaning that if the temperature changes, then the internal energy must change as well (because the molecules will have more motion).
by sarahforman_Dis2I
Mon Feb 10, 2020 12:23 pm
Forum: Phase Changes & Related Calculations
Topic: Reversible and Irreversible
Replies: 3
Views: 12

Re: Reversible and Irreversible

What is the difference between reversible and irreversible expansions? Along with what the other student said, the difference was explained to me as such. If you have two scales with a bunch of pebbles on them, an irreversable expansion would be similar to taking all of the pebbles off of the scale...
by sarahforman_Dis2I
Mon Feb 10, 2020 12:19 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: 4D.23 homework help
Replies: 4
Views: 27

Re: 4D.23 homework help

Why does the solution manual (6th edition) put "The reaction we want is N2 (g) + 5/2 O2 (g) -> N2O5 (g)" when there's no N2 in the reactions given? Shouldn't we create a reaction that does include the reactants and products of the 2 reactions given, which will be 2NO (g) + 3/2 O2 (g) -> N...
by sarahforman_Dis2I
Mon Feb 10, 2020 12:11 pm
Forum: Concepts & Calculations Using Second Law of Thermodynamics
Topic: Entropy Equations
Replies: 3
Views: 27

Re: Entropy Equations

When do we use ΔS=qrev/T versus ΔS=nRln(V2/V1) or ΔS=nRln(P1/P2)? In the lecture these equations were derived from an isothermal reversible expansion so does that mean it can only be used for those types of reactions? Also just to clarify, which entropy equations are used for irreversible reactions...
by sarahforman_Dis2I
Mon Feb 10, 2020 12:05 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Difference between ΔH, ΔH°, ΔH(rxn)°, and ΔH(f)°
Replies: 2
Views: 16

Re: Difference between ΔH, ΔH°, ΔH(rxn)°, and ΔH(f)°

Can someone explain the difference between all these notations: ΔH, ΔH°, ΔH(rxn)°, and ΔH(f)°? I feel like some questions refer to ΔH°as the same as ΔH(rxn)°but some don't so I'm utterly confused. It would also help if you explain this with the units correlating to each because I know some has &quo...
by sarahforman_Dis2I
Mon Feb 10, 2020 11:57 am
Forum: Entropy Changes Due to Changes in Volume and Temperature
Topic: How do you change the internal energy of an ideal gas?
Replies: 3
Views: 15

Re: How do you change the internal energy of an ideal gas?

I'm confused can someone explain to me how the internal energy of an ideal gas changes? Does doing work on the system affect it at all? You can change the work done on the gas through changing the volume (making delta V not equal to zero). Like someone else said, you can also change the temperature...
by sarahforman_Dis2I
Tue Feb 04, 2020 6:01 pm
Forum: Concepts & Calculations Using Second Law of Thermodynamics
Topic: Statistical Entropy
Replies: 1
Views: 9

Statistical Entropy

Can someone please explain what statistical entropy is and how it is different from thermodynamic entropy?
by sarahforman_Dis2I
Mon Feb 03, 2020 2:01 pm
Forum: Calculating Work of Expansion
Topic: Degeneracy and Volume
Replies: 6
Views: 30

Re: Degeneracy and Volume

905373636 wrote:Is W2/W1 always equal to V2/V1?


The proportion between W2/W1 and V2/V1 will always be equal, although the value of W2 and V2 will be different.
by sarahforman_Dis2I
Mon Feb 03, 2020 12:45 pm
Forum: Thermodynamic Definitions (isochoric/isometric, isothermal, isobaric)
Topic: Reversible Reaction
Replies: 5
Views: 21

Reversible Reaction

Can someone please explain what makes a reaction reversible. I am just a little confused about qualifies as a reversible reaction.
by sarahforman_Dis2I
Mon Feb 03, 2020 12:32 pm
Forum: Thermodynamic Definitions (isochoric/isometric, isothermal, isobaric)
Topic: Formula for isothermal, reversible equilibrium
Replies: 4
Views: 29

Re: Formula for isothermal, reversible equilibrium

Brian Tangsombatvisit 1C wrote:When using the equation -nRTln(V2/V1) for reversible reactions, does n stand for the change in moles after the reaction takes place or does it stand for the total number of moles?


I believe n stands for the net amount of moles produced in the reaction (so final amount of moles-initial moles).
by sarahforman_Dis2I
Mon Feb 03, 2020 12:31 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: First Law
Replies: 6
Views: 35

Re: First Law

Jarrett Peyrefitte 2K wrote:What is the first law of thermodynamics? How is it used and why?


Also, the equation for the first law of thermodynamics is
Delta U=w+q
This equation can have various ways of being expressed depending on the surroundings (whether pressure is constant ext..)
by sarahforman_Dis2I
Mon Feb 03, 2020 12:29 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: Residual Entropy
Replies: 3
Views: 18

Re: Residual Entropy

When would you use residual entropy? Why is this value useful?
by sarahforman_Dis2I
Mon Jan 27, 2020 12:24 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Methods to Calculate Enthalpies
Replies: 6
Views: 33

Re: Methods to Calculate Enthalpies

How do we know which method to use when calculating the total enthalpy of a reaction? Just like someone said above, it depends on what the problem gives you. Hess's method can be used if you are given all of the chemical equations of the intermediates with their respective changes in enthalpy. If y...
by sarahforman_Dis2I
Mon Jan 27, 2020 12:17 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: "Breaking bonds is always endothermic"
Replies: 6
Views: 26

Re: "Breaking bonds is always endothermic"

It states in the book that breaking bonds is always endothermic and requires energy. However in biology, breaking a phosphate group from ATP to form ADP releases energy. Can someone help me understand this? It is important to understand that the when an reaction is exothermic or exergonic the amoun...
by sarahforman_Dis2I
Mon Jan 27, 2020 12:14 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Signs for enthalpy
Replies: 8
Views: 16

Re: Signs for enthalpy

Since enthalpy is a measure of the heat released or gained in chemical reactions, it can be negative. If a reaction has a negative enthalpy, that means it is losing enthalpy to the surroundings (releasing heat), meaning it is exothermic
by sarahforman_Dis2I
Mon Jan 27, 2020 12:09 pm
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: Units for temperature?
Replies: 11
Views: 27

Re: Units for temperature?

When calculating from the specific heat capacity using the formula q=C(m) (delta T), do we use units for temperature as degree celsius or Kelvin? I believe you use celsius because the heat capacity (C in the equation) has units of J/(cg). Using the constant you are given, make sure that the units c...
by sarahforman_Dis2I
Mon Jan 27, 2020 12:05 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Negative pH
Replies: 9
Views: 35

Re: Negative pH

Why can the pH sometimes be negative? What's going on conceptually? If the concentration of H3O+ is greater than 1M, the pH will be 0 (if it is equal to 1) or negative. The reason that the scale is 1-14 is because in most systems, the concentration of H3O+ does not exceed 1M. Conversely, if the con...
by sarahforman_Dis2I
Mon Jan 20, 2020 12:27 pm
Forum: Ideal Gases
Topic: R constant for PV=nRT
Replies: 7
Views: 31

Re: R constant for PV=nRT

What is the the value of R in PV=nRT? I've seen two different values and don't know which is which. Yes, you are correct that there are two values for R. The difference between these values are the units that are used. This means that you need to be very careful when you are using the ideal gas law...
by sarahforman_Dis2I
Mon Jan 20, 2020 12:22 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Delta H
Replies: 10
Views: 38

Re: Delta H

When delta H is positive, is it endothermic or exothermic? And if H is negative? If delta H is positive, that means the sum of the enthalpy of reactants is LARGER than the sum of the enthalpy of products. This means that the reaction is endothermic, or uses heat. If delta H is negative, the sum of ...
by sarahforman_Dis2I
Mon Jan 20, 2020 12:19 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: Conjugate Acids and Bases
Replies: 4
Views: 11

Re: Conjugate Acids and Bases

How do you identify conjugate acids and bases in a chemical reaction? How do they differ from their respective acids and bases? A conjugate acid/base in a reaction is what is left over after the proton is donated or accepted from water. For example, in the dissociation of HCl, Cl- and H3O+ ions are...
by sarahforman_Dis2I
Mon Jan 20, 2020 12:15 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: Shifts vs Different K values
Replies: 3
Views: 15

Re: Shifts vs Different K values

When discussing the shifts in equilibrium from Le Chatelier's Principle, does this simply mean that the concentration will revert to the same K value or will it obtain a different K value? It is important to note that the only reason that the actual value of K can change is through a change in temp...
by sarahforman_Dis2I
Mon Jan 20, 2020 12:13 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: Hw 6C.1
Replies: 2
Views: 16

Re: Hw 6C.1

Write (a) the chemical equation for the proton transfer equilibrium in water and the corresponding expression for Ka and (b) the chemical equation for the proton transfer equilibrium of the conjugate base and the corresponding expression for Kb for each of the following weak acids: (iii) C6H5OH For...
by sarahforman_Dis2I
Mon Jan 13, 2020 10:43 am
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: When does the partial pressure of a gas change?
Replies: 2
Views: 26

Re: When does the partial pressure of a gas change?

Hi, From my understanding, the reason that a change in pressure from adding inert gas (to a constant volume) doesn't cause the reaction to shift is because the addition of inert gas changes the total pressure but not the partial pressures of the reactants and products. However, I was wondering how ...
by sarahforman_Dis2I
Mon Jan 13, 2020 10:38 am
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: Change in Pressure
Replies: 6
Views: 15

Re: Change in Pressure

How does a reaction shift when the pressure of a system is decreased? As someone states above, if an inert gas is added to the mixture, the equilibrium will not shift. This is extremely important to understand because adding an inert gas will change the pressure of the system, but it will not chang...
by sarahforman_Dis2I
Mon Jan 13, 2020 10:35 am
Forum: Non-Equilibrium Conditions & The Reaction Quotient
Topic: "quick" way?
Replies: 4
Views: 26

Re: "quick" way?

What did Dr. Lavelle mean by the "quick way" of using Le Chatelier's Principle and what is the long way? The "quick way" is remembering that if the volume decreases, the reaction will shift to the side that has the fewest moles of gas. If the volume increases, the reaction will ...
by sarahforman_Dis2I
Mon Jan 13, 2020 10:32 am
Forum: Non-Equilibrium Conditions & The Reaction Quotient
Topic: PV=nRT
Replies: 9
Views: 24

Re: PV=nRT

When do we use the equation PV=nRT? And how would we use it? You would use this equation when you are trying to convert between partial pressure and concentration. Let's say, for example, you were given the Kc of a reaction and the partial pressure of some of the reactants. Since you were given the...
by sarahforman_Dis2I
Mon Jan 13, 2020 10:29 am
Forum: Ideal Gases
Topic: Variables
Replies: 3
Views: 28

Re: Variables

What does each variable/letter represent in the equation PV = nRT? P is pressure, V is volume, n is the number of moles, R is the gas constant (the values should be given to us), and T is temperature in K. It is important to note that the units on P will determine what value of R is used (whether t...
by sarahforman_Dis2I
Thu Jan 09, 2020 9:12 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Units for K
Replies: 10
Views: 45

Re: Units for K

In addition, because the activity is equal to a constant multiplied by the concentration, and often times that constant is equal to one under ideal conditions, we can assume that the concentration values are values of the activity. As someone stated above, activity values do not have units.
by sarahforman_Dis2I
Thu Jan 09, 2020 9:10 pm
Forum: Ideal Gases
Topic: Reaction Quotient (Q)
Replies: 8
Views: 30

Re: Reaction Quotient (Q)

Can someone explain the concept behind Q? When is it essential? Like someone else said above, Q is basically a way for you to determine whether the reaction is at equilibrium. You calculate Q the same way that you calculate K. The only difference, is the concentration or pressure values you put in ...
by sarahforman_Dis2I
Mon Jan 06, 2020 5:57 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Calculating Kc
Replies: 4
Views: 44

Re: Calculating Kc

Why do we not include solids or liquids in the equilibrium concentration calculations? It is important to note that solvents (eg. liquid water) are not included in the equilibrium expression because only a minimal amount of the solvent is taken away in the reaction. Because of this, we can assume t...
by sarahforman_Dis2I
Mon Jan 06, 2020 5:51 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: H3O and OH
Replies: 5
Views: 46

Re: H3O and OH

Regarding the Chemical Equilibrium Pt 1B Pre-Assessment, for reactions that involve liquid water as a product and H3O+(aq) or OH-(aq) as a product, are the H3O/OH included in the K calculation? Yes, as these solutions are aqueous they would. Water (H2O(l)) would not be included because it is the so...
by sarahforman_Dis2I
Mon Jan 06, 2020 5:48 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: The Significance of K
Replies: 5
Views: 40

Re: The Significance of K

Typically, molarity/concentration units are given when the products and reactants are in aqueous solution whereas partial pressure is given when the reactants and products are all in the gas phase. Ultimately, however, Kc and Kp give you the same information about a reaction.
by sarahforman_Dis2I
Mon Jan 06, 2020 5:45 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Writing Equilibrium Constant Labels
Replies: 4
Views: 34

Re: Writing Equilibrium Constant Labels

When writing the products and reactants for the equilibrium constant, why do we add P before the formula that is part of the chemical equation? Does this represent the partial pressure? I believe that you are correct. If all of the substances in the equilibrium reaction are in the gas phase, that m...
by sarahforman_Dis2I
Mon Jan 06, 2020 5:42 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Equilibrium Constant
Replies: 3
Views: 28

Re: Equilibrium Constant

Dr. Lavelle mentioned today in lecture that a more stabilized molecule would have more concentration and a higher k value as a result. Can anyone please explain this to me? Thank you Hi! The value of K is equal to the concentration of the products (raised to the stoichiometric coefficient) divided ...
by sarahforman_Dis2I
Thu Dec 05, 2019 8:47 pm
Forum: Naming
Topic: Using bis-, tris-, tetrakis-, pentakis-
Replies: 2
Views: 33

Re: Using bis-, tris-, tetrakis-, pentakis-

Can someone give examples of how we would change the naming of a ligand that has di, tri, and tetra- or is a polydentate to its name that has bis-, tris-, tetrakis-, or pentakis-? You would do this when the ligand is a polydentate. For example, Na3[Co(C2H4)3] would be named sodium tris(oxalato)coba...
by sarahforman_Dis2I
Thu Dec 05, 2019 8:46 pm
Forum: Naming
Topic: Using bis-, tris-, tetrakis-, pentakis-
Replies: 2
Views: 33

Re: Using bis-, tris-, tetrakis-, pentakis-

Can someone give examples of how we would change the naming of a ligand that has di, tri, and tetra- or is a polydentate to its name that has bis-, tris-, tetrakis-, or pentakis-? You would do this when the ligand is a polydentate. For example, Na3[Co(C2H4)3] would be named sodium tris(oxalato)coba...
by sarahforman_Dis2I
Mon Dec 02, 2019 10:39 am
Forum: Biological Examples
Topic: How Cisplatin Works?
Replies: 2
Views: 35

Re: How Cisplatin Works?

In class, Dr. Lavelle talked about how cisplatin works as a chemotherapy drug while translation does not. Why is this, and could someone explain how cisplatin interacts with DNA? Cisplatin binds to two sites in the DNA because the two Cl atoms are on the same side of the atom. Cisplatin can bind to...
by sarahforman_Dis2I
Mon Dec 02, 2019 10:29 am
Forum: Properties & Structures of Inorganic & Organic Acids
Topic: neutralization
Replies: 4
Views: 24

Re: neutralization

Sophia Dinh 1D wrote:what does neutralization form?


It forms water and a salt. For example, NaOH(aq) + HCl(aw) ---> NaCl(aq) + H2O

Since the NaCl is aqueous, it consists of Na+ and Cl- ions in the water solution. I hope that this helps!
by sarahforman_Dis2I
Mon Dec 02, 2019 10:26 am
Forum: Properties & Structures of Inorganic & Organic Acids
Topic: Weak acids & pH
Replies: 4
Views: 50

Re: Weak acids & pH

How does the solvent play a role in the pH of a weak acid solution? The pH is a measure of the concentration of H+ ions in solution. Some solvents may allow for the dissociation of a weak acid more than water, meaning that more H+ ions will dissociate. This means that the pH of the solution will be...
by sarahforman_Dis2I
Mon Dec 02, 2019 10:18 am
Forum: Calculating pH or pOH for Strong & Weak Acids & Bases
Topic: pH vs pOH
Replies: 4
Views: 37

Re: pH vs pOH

After your calculation, how would you determine which value is your pH and your pOH? For example in 6B. 5D how would you determine that 3.15 is your pOH and 10.85 is your pH? Remember that the pH added to the pOH equals 14. This is because the sum of the OH- ion and H+ ion concentration must equal ...
by sarahforman_Dis2I
Mon Dec 02, 2019 10:12 am
Forum: Properties & Structures of Inorganic & Organic Acids
Topic: Electronegativity and acid strength
Replies: 5
Views: 29

Re: Electronegativity and acid strength

Why would an acid such as HClO be stronger than, say, HBrO? HClO would be a stronger acid because Cl is more electronegative than Br. Because of this, the Cl atom pulls electrons away from the hydrogen and towards the Cl. This means that it will be easier for the H+ ion to be released from the comp...
by sarahforman_Dis2I
Mon Nov 25, 2019 12:51 pm
Forum: Sigma & Pi Bonds
Topic: Molecular Shape
Replies: 11
Views: 58

Re: Molecular Shape

No, sigma and pi bonds do not influence a molecule's shape (in other words, the type of bond doesn't affect the shape). It is important to note, however, that pi bonds cannot rotate. This means that having pi bonds (double and triple bonds), can prevent the molecule from rotating which can impact h...
by sarahforman_Dis2I
Mon Nov 25, 2019 12:48 pm
Forum: Bond Lengths & Energies
Topic: Hydrogen Bonding and Dispersion
Replies: 5
Views: 52

Re: Hydrogen Bonding and Dispersion

I'm a bit confused between the concepts of hydrogen bonding and dispersion. Can someone clarify the difference between the two? Hydrogen bonding occurs between H and either N,F, or O (three very electronegative attractions). This means that H-bonding is an extremely strong dipole dipole interaction...
by sarahforman_Dis2I
Mon Nov 25, 2019 12:45 pm
Forum: Bronsted Acids & Bases
Topic: Bronsted vs Lewis Acid/Base
Replies: 5
Views: 27

Re: Bronsted vs Lewis Acid/Base

Thanks everyone. The other thing that's confusing to me is how does an atom donate a proton? I thought interactions between atoms were all through electrons. Maybe an example will help. Let's say that we have a reaction that is between hydrochloric acid and water. HCl(aq) + H2O (l) --> H3O+ (aq) + ...
by sarahforman_Dis2I
Mon Nov 25, 2019 12:38 pm
Forum: Photoelectric Effect
Topic: Midterm Question
Replies: 4
Views: 58

Re: Midterm Question

Hi, I still don't understand why the correct answer for the graph on the midterm isn't just linear. The reason that the graph is a horizontal is that the question states that the intensity of the light is kept constant. This is extremely important because a constant intensity means that there are t...
by sarahforman_Dis2I
Mon Nov 25, 2019 12:33 pm
Forum: Bronsted Acids & Bases
Topic: Definition
Replies: 5
Views: 43

Re: Definition

What is the difference between a Bronsted acid and a Lewis acid? A Bronsted acid gives away a proton. A Lewis acid accepts a pair of electrons. If you think of a H+ ion, the H+ ion is a proton and therefore can donate a proton (Bronsted acid). Since it has a positive charge, it can accept electron ...
by sarahforman_Dis2I
Wed Nov 20, 2019 12:48 pm
Forum: Sigma & Pi Bonds
Topic: Why are sigma bonds stronger than pi bonds?
Replies: 6
Views: 63

Re: Why are sigma bonds stronger than pi bonds?

Because in a sigma bond the orbitals can overlap to a greater extent where as with pie bonds they are overlapping indirectly which means they can't overlap as much as sigma bond. The more they over lap, the stronger the pull what do you mean by "overlap"? Sigma bonds overlap end to end wh...
by sarahforman_Dis2I
Wed Nov 20, 2019 12:44 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: 3F19 Part C
Replies: 2
Views: 22

Re: 3F19 Part C

The boiling point of pentane - CH3(CH2)3 CH3 is 36.1 C, whereas that of C(CH3)4 is 9.5C. The solutions say that pentane has a higher surface area and thus stronger London forces than C(CH3)4 because C(CH3)4 is spherical and more compact, but how do you draw the lewis structure of C(CH3)4 to determi...
by sarahforman_Dis2I
Mon Nov 18, 2019 11:24 am
Forum: Hybridization
Topic: 2.29
Replies: 1
Views: 14

Re: 2.29

Part b asks for the hybridization of the carbon-oxygen bond in the molecule CH4O. I understand why the carbon atom is sp3, but don't understand why the oxygen atom is also sp3 hybridized. Can someone provide an explanation? You are correct that the hybridization of the C atom is sp3. The oxygen ato...
by sarahforman_Dis2I
Mon Nov 18, 2019 11:13 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: 1/r^6
Replies: 3
Views: 32

Re: 1/r^6

What is this equation exactly and do we need it for the test this week? This equation is just saying that the strength of the intermolecular attraction between two molecules is related to how close the two molecules are from each other (r). r^6 means that the strength of the interaction greatly dep...
by sarahforman_Dis2I
Mon Nov 18, 2019 11:10 am
Forum: Electron Configurations for Multi-Electron Atoms
Topic: Midterm
Replies: 2
Views: 42

Re: Midterm

Why was the ground state of calcium given as Ca2+? I got this question wrong for the midterm even though I wrote the right electron configuration for Ca. In order to get this correct on the midterm, you needed to take away two electrons from the electron configuration of Ca. When you do this, you w...
by sarahforman_Dis2I
Mon Nov 18, 2019 11:07 am
Forum: Determining Molecular Shape (VSEPR)
Topic: Molecular Shape vs. Molecular Geometry
Replies: 3
Views: 31

Re: Molecular Shape vs. Molecular Geometry

What’s the difference between molecular shape and geometry? We talked a bit about it during discussion but I’m just confused on what extent we need to know for the exam. Thank you! I think that the molecular geometry is the amount of bonding and lone pairs around the atoms. Molecular shape is the a...
by sarahforman_Dis2I
Mon Nov 18, 2019 11:05 am
Forum: Student Social/Study Group
Topic: Test 2
Replies: 5
Views: 38

Re: Test 2

Cavalli_1E wrote:Does anyone know if material covered in today's (Monday) lecture will be covered on test 2?


I believe that sigma and pi bonding will be on the exam. Dr. Lavelle said that hybridization would not be on the test, however.
by sarahforman_Dis2I
Thu Nov 14, 2019 3:13 pm
Forum: Formal Charge and Oxidation Numbers
Topic: Best Formal Charge
Replies: 7
Views: 83

Re: Best Formal Charge

I'm a little confused about what ionization energy has to do with the fact that it is very unlikely for an extremely electronegative element (such as O, N, F, Cl) to have a positive charge? Ionization energy is the energy needed to remove an electron. Elements that have high ionization energies hav...
by sarahforman_Dis2I
Tue Nov 12, 2019 10:22 am
Forum: Dipole Moments
Topic: Melting point due to dipole-dipole interaction
Replies: 2
Views: 18

Re: Melting point due to dipole-dipole interaction

Why would C4H9OH have a higher melting point than C2H5OC2H5? Similar to what the other person said above, since C4H9OH has an OH group, it can form hydrogen bonds with other molecules, whereas C2H5OC3H5 cannot. It is important to remember that hydrogen bonds are strong dipole dipole interactions th...
by sarahforman_Dis2I
Tue Nov 12, 2019 10:16 am
Forum: Formal Charge and Oxidation Numbers
Topic: Best Formal Charge
Replies: 7
Views: 83

Re: Best Formal Charge

For the question right above this comment: Exactly. Atoms such as fluorine and oxygen are highly electronegative and are able to pull electrons closer to themselves. Putting a negative on them only makes sense because they have a natural tendency to be negative in a molecule. This is correct. Addit...
by sarahforman_Dis2I
Tue Nov 12, 2019 10:11 am
Forum: Determining Molecular Shape (VSEPR)
Topic: Molecular Shape
Replies: 3
Views: 30

Re: Molecular Shape

During lecture, how does a shape of a molecule contribute to the strength of an interaction? And by shape, do we mean spherical or log shapes, and how far apart they are from another atom/molecule? thanks Just to echo what other people have said on this thread, if a nonpolar molecule has a more fla...
by sarahforman_Dis2I
Tue Nov 12, 2019 10:05 am
Forum: Polarisability of Anions, The Polarizing Power of Cations
Topic: Polarizing Power
Replies: 6
Views: 40

Re: Polarizing Power

Can someone define polarizability and polarizing power please? I am still slightly confused and want to be sure I have it down for the upcoming quiz/final. Polarizability is the ease at which electrons can be moved away from the nucleus whereas polarizing power is how easily a cation can pull elect...
by sarahforman_Dis2I
Tue Nov 12, 2019 9:49 am
Forum: Bond Lengths & Energies
Topic: Shorter bond lengths
Replies: 12
Views: 69

Re: Shorter bond lengths

Why do more bonds lead to shorter bond lengths? Like why are double bonds shorter than single bonds? I am going to echo what other people are saying on this thread. According to Coloumb's law, which is the formula that determines the strength of the force between two charged particles, as the charg...
by sarahforman_Dis2I
Mon Nov 04, 2019 11:48 am
Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
Topic: HW Question 1A.15
Replies: 1
Views: 24

Re: HW Question 1A.15

Whenever I solve this equation out am getting the the energy of the photon is 1.936x10^-18 J but there is apparently this whole answer is supposed to be negative. Could someone please explain why this is; where does the negative sign come from? Your math is correct. The positive value that you calc...
by sarahforman_Dis2I
Mon Nov 04, 2019 11:41 am
Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
Topic: N initial and N final
Replies: 1
Views: 20

Re: N initial and N final

When trying to find energy level n initial or n final I know you use the equation delta E=(-hR/nf^2)-(-hR/ni^2) but when ever I try to isolate out the variable I am looking for I am off by 1 negative sign every time and I don't know what I am doing wrong. Could someone please show the work for this...
by sarahforman_Dis2I
Mon Nov 04, 2019 11:34 am
Forum: Lewis Structures
Topic: Exceptions to the Octet Rule
Replies: 2
Views: 14

Re: Exceptions to the Octet Rule

Can someone summarize/explain why certain elements can have incomplete octets and why some can have extended (overfilled) octets? I know there are exceptions, I am just unsure of which ones follow which exceptions and why. So if someone could summarize them, that would be AMAZING. Thank you! I can ...
by sarahforman_Dis2I
Mon Nov 04, 2019 11:26 am
Forum: Electron Configurations for Multi-Electron Atoms
Topic: Electron Configuration vs. Ground-state Electron Configuration
Replies: 2
Views: 24

Re: Electron Configuration vs. Ground-state Electron Configuration

Is there a difference between electron configuration and ground-state electron configuration? I thought ground-state referred to neutral atoms but the past-exam question in lecture today asked for the ground-state e- configuration of ions. The ground-state electron configuration is just asking for ...
by sarahforman_Dis2I
Mon Nov 04, 2019 11:22 am
Forum: *Shrodinger Equation
Topic: Explanation of Shrodinger Equation and Hamiltonian
Replies: 3
Views: 66

Re: Explanation of Shrodinger Equation and Hamiltonian

What do we need to understand conceptually about the Shrodinger equation and the Hamiltonian? How do these concepts interact, and do we need to know the equation/how to solve the Hamiltonian? I believe that for the midterm we just need to know what the Hamiltonian is. The Hamiltonian is a double de...
by sarahforman_Dis2I
Mon Oct 28, 2019 4:48 pm
Forum: Trends in The Periodic Table
Topic: Ionization Energy
Replies: 3
Views: 23

Re: Ionization Energy

Is it possible that the first ionization energy of any atom could be more than the second? I'm just wanting to clarify for my notes. No, the First Ionization Energy is always smaller than the second. This is because of the decreased electron-electron repulsion with the same positive charge. Because...
by sarahforman_Dis2I
Mon Oct 28, 2019 4:46 pm
Forum: Lewis Structures
Topic: valence electron counting
Replies: 2
Views: 25

Re: valence electron counting

In class, Lavelle told us to count the valence electrons before making our Lewis structures. I don't really think this is necessary but I was going through and checking some of my drawings and for BrF3, Br has 7 valence electrons and so does F so there should be 28 electrons drawn. I drew single bo...
by sarahforman_Dis2I
Mon Oct 28, 2019 4:41 pm
Forum: Ionic & Covalent Bonds
Topic: Roman numerals
Replies: 2
Views: 9

Re: Roman numerals

If a problem says: Indium(III) sulfide Does the (III) just give the charge for Indium or is it telling us how many atoms of Indium there will be? I'm assuming charge since the formula is Ir2S3. It is telling you the charge of In. Since In is a metal, it forms a cation. The roman numerals are just t...
by sarahforman_Dis2I
Mon Oct 28, 2019 4:38 pm
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: HW Question 2A5
Replies: 3
Views: 35

Re: HW Question 2A5

The reason for this is because Cu has only one unpaired electron in the d block, it turns out that it is at a lower energy state to take an electron from the s orbital and put it in the d orbital. This is one of the exceptions that Lavelle talked about in class. It is also important to note that Cu,...
by sarahforman_Dis2I
Mon Oct 28, 2019 4:36 pm
Forum: Electron Configurations for Multi-Electron Atoms
Topic: Lanthanides and Actinides
Replies: 2
Views: 19

Re: Lanthanides and Actinides

No, I believe that in class, the Professor specified that we do not need to know the electron configurations of the lanthanides and actinides. Just focus on the top part of the d block.
by sarahforman_Dis2I
Mon Oct 21, 2019 11:33 am
Forum: Properties of Electrons
Topic: QM Description of Atoms - Electron standing wave
Replies: 2
Views: 38

Re: QM Description of Atoms - Electron standing wave

Last week, when explaining why electrons have quantized energy states, Dr. Lavelle talked about how electrons are comparable to a "circular standing wave" around the nucleus, and that the two "ends" must be in phase in order for the energy levels to be stable. I can understand t...
by sarahforman_Dis2I
Mon Oct 21, 2019 11:24 am
Forum: Heisenberg Indeterminacy (Uncertainty) Equation
Topic: 1B. 25
Replies: 2
Views: 34

Re: 1B. 25

This is the question: What is the minimum uncertainty in the speed of an electron confined within a lead atom of diameter 350. pm? Model the atom as a one-dimensional box with a length equal to the diameter of the actual atom. For this problem, I am trying to use the uncertainty equation but am unc...
by sarahforman_Dis2I
Mon Oct 21, 2019 11:22 am
Forum: DeBroglie Equation
Topic: 1B. 19
Replies: 4
Views: 35

Re: 1B. 19

Protons and neutrons have nearly the same mass. How different are their wavelengths? Calculate the wavelength of each particle when traveling at 2.75 x 10^5 m/s in a particle accelerator and report the difference as a percentage of the wavelength of the neutron. Since protons and neutrons have appr...
by sarahforman_Dis2I
Mon Oct 21, 2019 11:18 am
Forum: Photoelectric Effect
Topic: 0KE electron?
Replies: 2
Views: 30

Re: 0KE electron?

We learned that if you remove an electron using exactly the work function amount of energy that the electron will have 0KE. While mathematically this makes sense, how is the electron "removed" if it is not moving? If you give it the threshold energy then it will escape the atom, but then ...
by sarahforman_Dis2I
Mon Oct 21, 2019 11:16 am
Forum: *Shrodinger Equation
Topic: Parts of the Schrodinger Equation
Replies: 1
Views: 29

Parts of the Schrodinger Equation

Hi all! I understand that we will not need to calculate the equation itself, but I am still confused on how the equation works. I understand that the hamiltonian is the double derivative, but what is it the double derivative of? Can someone please explain the parts of this equation?
by sarahforman_Dis2I
Mon Oct 14, 2019 4:37 pm
Forum: *Shrodinger Equation
Topic: Shrodinger Equation
Replies: 1
Views: 25

Shrodinger Equation

I am still a little bit confused on the difference between psi and psi squared and how they relate to the sine model. For example, why does psi squared equal the distribution of electrons? Could someone please help me understand the difference between psi and psi squared? Thank you!!
by sarahforman_Dis2I
Mon Oct 14, 2019 4:32 pm
Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
Topic: Postive or Negative Frequency
Replies: 2
Views: 35

Re: Postive or Negative Frequency

Question on the Atomic Spectra Module asks: Calculate the frequency of a photon emitted by a hydrogen atom when an electron makes a transition from the fourth to the second principal quantum level. I did the calculations and got A. -6.17 x 10^14 Hz However, it said my answer was wrong. Are frequenc...
by sarahforman_Dis2I
Mon Oct 14, 2019 3:57 pm
Forum: Heisenberg Indeterminacy (Uncertainty) Equation
Topic: Problem 1B.27
Replies: 3
Views: 31

Re: Problem 1B.27

A bowling ball of mass 8.00 kg is rolled down a bowling alley lane at 5.00 +/- 5.0 m/s. What is the minimum uncertainty in its position? In the answer key, they used 5.00 m/s as the uncertainty in velocity (delta v). Why wouldn't the uncertainty be 10.00 m/s? I thought it would be that because 10.0...
by sarahforman_Dis2I
Mon Oct 14, 2019 1:25 pm
Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
Topic: Question about 1A.15
Replies: 2
Views: 35

Re: Question about 1A.15

While I was working through this problem, I wasn't sure how I was supposed to already know that n 1 =1. The problem reads: In the ultraviolet spectrum of atomic hydrogen, a line is observed at 102.6 nm. Determine the values of n for the initial and final energy levels of the electron during the emi...
by sarahforman_Dis2I
Mon Oct 14, 2019 1:10 pm
Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
Topic: Bohr Frequency Condition??
Replies: 3
Views: 31

Re: Bohr Frequency Condition??

Just for clarification, it is only used regarding a DROP of an electron from one energy level to another (releasing a photon), not when it goes from a lower to higher energy level (absorbing a photon), right? Will we ever need calculate the latter? What the Bohr Frequency Condition means is the ene...
by sarahforman_Dis2I
Mon Oct 07, 2019 12:48 pm
Forum: Limiting Reactant Calculations
Topic: thereotical yield
Replies: 5
Views: 56

Re: thereotical yield

Normally theoretical yield is in grams, but if the number is extremely small or large you may want to convert the grams to milligrams or kilograms in order to make the answer easier to understand. In other words, yes, theoretical yield is typically in grams, but it can be any SI mass unit (g, kg, mg...
by sarahforman_Dis2I
Mon Oct 07, 2019 12:45 pm
Forum: Properties of Light
Topic: 1A- Electromagnetic Radiation
Replies: 4
Views: 39

Re: 1A- Electromagnetic Radiation

Like another student said, A is not correct because the speed of constant. Because the speed of light is constant, and lambda(frequency)=the speed of light, if the frequency decreases, the wavelength must increase, so therefore B is incorrect as well. D is incorrect because as the frequency and ener...
by sarahforman_Dis2I
Mon Oct 07, 2019 12:36 pm
Forum: Limiting Reactant Calculations
Topic: Question about Calculating Limiting Reactants
Replies: 5
Views: 48

Re: Question about Calculating Limiting Reactants

Yes, as long as you make sure that you are taking the stoichiometric coefficients in the balanced chemical equation into account.
by sarahforman_Dis2I
Mon Oct 07, 2019 12:34 pm
Forum: Photoelectric Effect
Topic: light intensity and kinetic energy
Replies: 3
Views: 33

Re: light intensity and kinetic energy

I believe that increasing the light intensity would not affect the kinetic energy in the photoelectric effect. It would just cause more electrons to be ejected from the surface. Only increasing the frequency/energy (or decreasing the wavelength) of the light source would have an effect on the kineti...
by sarahforman_Dis2I
Mon Oct 07, 2019 12:25 pm
Forum: Properties of Light
Topic: Photoelectric Effect
Replies: 4
Views: 29

Re: Photoelectric Effect

Yes, that is correct. Before the experiment was done, it was predicted that regardless of the energy (or frequency) of the light, increasing the intensity (amplitude) of even low energy lights would cause an electron to be ejected. This was not the case. In reality, only high energy lights (high fre...
by sarahforman_Dis2I
Sat Sep 28, 2019 5:08 pm
Forum: SI Units, Unit Conversions
Topic: Question E1, visualization
Replies: 2
Views: 83

Re: Question E1, visualization

Yep! That's exactly what it means. The nuclear distance (or the distance from one nucleus to the other), will be 2(144), so 288. You would want to use the 288 pm value in your dimensional analysis to solve this problem.
by sarahforman_Dis2I
Sat Sep 28, 2019 5:00 pm
Forum: Molarity, Solutions, Dilutions
Topic: mass of solute
Replies: 3
Views: 39

Re: mass of solute

Maybe another example will make this more clear. For example, if you have one mole of water molecules (H2O), you will have ONE mole of O (because there is one O in every molecule of H2O) and TWO moles of H (because there are 2 molecules on H in every molecule on H2O). When thinking about CuSO4(5H2O)...
by sarahforman_Dis2I
Sat Sep 28, 2019 4:51 pm
Forum: Molarity, Solutions, Dilutions
Topic: HW Question: G5 (Part A)
Replies: 3
Views: 58

Re: HW Question: G5 (Part A)

The first thing that you have to do in this problem is find the molarity of the solution you are making. You do this by dividing the number of grams of Na2CO3 (2.11g) by the molar mass to find the moles of Na2CO3. Then you divide that number of moles by the volume of solution in L (.2500L). Now you ...
by sarahforman_Dis2I
Sat Sep 28, 2019 4:42 pm
Forum: Accuracy, Precision, Mole, Other Definitions
Topic: Avogradro's Number [ENDORSED]
Replies: 5
Views: 169

Re: Avogradro's Number [ENDORSED]

I think what this question is getting at is just how large the unit of a "mole" is. Even though it seems strange to think that the world does not even have close to one mole of people, this unit is useful when used in the context of atoms, as a mole of atoms can be held in your hand. Since...
by sarahforman_Dis2I
Sat Sep 28, 2019 4:10 pm
Forum: Limiting Reactant Calculations
Topic: moles of reagant
Replies: 4
Views: 332

Re: moles of reagant

What you need to do is first find the limiting reagent. You would do this by converting mass of both reagents to moles, and then using the stoichiometric coefficients to analyze which reagent will run out first. In short, you would need to use the coefficient in the equation in your conversions in o...

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