Search found 50 matches

by Julie Steklof 1A
Wed Mar 14, 2018 8:57 pm
Forum: Entropy Changes Due to Changes in Volume and Temperature
Topic: Midterm Question 6A
Replies: 2
Views: 206

Re: Midterm Question 6A

Both A and B were correct. A is right because bigger, more complex molecules have larger molar entropies than smaller molecules.
by Julie Steklof 1A
Wed Mar 14, 2018 8:46 pm
Forum: Entropy Changes Due to Changes in Volume and Temperature
Topic: Positive or Negative Entropy
Replies: 2
Views: 214

Re: Positive or Negative Entropy

Although the moles of gas of products and reactants are equivalent, the reaction produces 6 moles of liquid which is more "disordered" or "chaotic" than the solid that reacts so entropy increases in the reaction (is positive).
by Julie Steklof 1A
Wed Mar 14, 2018 8:42 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Oxidation Power
Replies: 3
Views: 134

Re: Oxidation Power

A large number for oxidation power means that the compound is readily reduced and so will have a more positive reduction potential.
by Julie Steklof 1A
Thu Mar 08, 2018 2:34 pm
Forum: Second Order Reactions
Topic: 15.35
Replies: 3
Views: 254

Re: 15.35

The half lives of second order reactions depend upon the initial concentration of reactants whereas the half lives of first order reactions do not.
by Julie Steklof 1A
Thu Mar 08, 2018 2:33 pm
Forum: Reaction Mechanisms, Reaction Profiles
Topic: 15.47
Replies: 4
Views: 199

Re: 15.47

Yes, an intermediate must be formed and consumed in a proposed reaction mechanism.
by Julie Steklof 1A
Mon Mar 05, 2018 9:59 pm
Forum: Reaction Mechanisms, Reaction Profiles
Topic: Molecularity and the Coefficient of an Elementary Step
Replies: 2
Views: 94

Re: Molecularity and the Coefficient of an Elementary Step

Molecularity is the number of species involved in an elementary step. So yes, for example a termolecular elementary step would have to have three reactants colliding which is seen in a reaction in which the stoichiometric coefficients add up to three.
by Julie Steklof 1A
Wed Feb 28, 2018 1:42 pm
Forum: Method of Initial Rates (To Determine n and k)
Topic: Value of k
Replies: 4
Views: 161

Re: Value of k

Yes, temperature will cause a change in k because an increase in temperature will increase the force of the collisions between molecules which gives more molecules enough energy to overcome the energy barrier and therefore speed up the rate of production of products. k can never be negative.
by Julie Steklof 1A
Wed Feb 28, 2018 1:39 pm
Forum: First Order Reactions
Topic: Direct Proportions and First Order
Replies: 5
Views: 181

Re: Direct Proportions and First Order

John Huang 1G wrote:Then what would it mean for a reaction to have a second order or zero order?


The rate of a zero order reaction does not depend on the concentration of reactant.
by Julie Steklof 1A
Wed Feb 28, 2018 1:36 pm
Forum: First Order Reactions
Topic: Deriving these Equations
Replies: 7
Views: 260

Re: Deriving these Equations

It would need to have the 0 subscript to be [A] initial.
by Julie Steklof 1A
Thu Feb 22, 2018 9:55 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Homework 14.13 part c
Replies: 1
Views: 90

Re: Homework 14.13 part c

The chlorine in Cl2 has an oxidation state of 0 and -1 in HCl. The hydrogen has an oxidation state of 0 in H2 and +1 in HCl.
by Julie Steklof 1A
Thu Feb 22, 2018 9:52 pm
Forum: General Rate Laws
Topic: 15.17
Replies: 1
Views: 125

Re: 15.17

The order of a reaction is given by adding the exponents of the concentrations in the rate law.
by Julie Steklof 1A
Thu Feb 22, 2018 12:08 pm
Forum: General Rate Laws
Topic: NO2 Example from Lecture
Replies: 2
Views: 122

Re: NO2 Example from Lecture

The O2 concentration increases half as fast as the NO2 concentration decreases. For these rates to be equal, d[O2]/dt must be multiplied by two so it equals -d[NO2]/dt.
by Julie Steklof 1A
Thu Feb 15, 2018 11:58 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Salt Bridge
Replies: 7
Views: 231

Re: Salt Bridge

A salt bridge keeps the solutions in each cell neutral and allows the redox reaction to continue.
by Julie Steklof 1A
Thu Feb 15, 2018 11:54 pm
Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
Topic: Delta G= Wmax
Replies: 8
Views: 463

Re: Delta G= Wmax

melissa carey 1f wrote:Whats the relationship between free energy and max work - are they equal?


I wrote in my notes from 2/9 that maximum cell potential is directly related to the free energy difference between reactants and products in the cell/ redox reaction.
by Julie Steklof 1A
Thu Feb 15, 2018 11:52 pm
Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
Topic: Delta G=-nFE
Replies: 5
Views: 965

Re: Delta G=-nFE

After writing balanced half reactions, you will be able to see the moles of electrons involved in the redox reaction. This is the number you use for n.
by Julie Steklof 1A
Sat Feb 10, 2018 3:51 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Anode and cathode
Replies: 9
Views: 265

Re: Anode and cathode

Does the anode always have to be drawn on the left and cathode on the right? Or is it necessary to know the solutions in order to tell which cell is which?
by Julie Steklof 1A
Sat Feb 10, 2018 3:38 pm
Forum: Calculating Work of Expansion
Topic: irreversible reactions
Replies: 4
Views: 308

Re: irreversible reactions

In an irreversible reaction, infinitely small changes occur that allow the reaction to end at equilibrium. In a reversible reaction, finite changes occur, usually quickly, that result in no equilibrium within the system.
by Julie Steklof 1A
Sat Feb 10, 2018 3:30 pm
Forum: Balancing Redox Reactions
Topic: Salt Bridges
Replies: 14
Views: 373

Re: Salt Bridges

A salt bridge serves to keep the charges between the two solutions to remain neutral and for the redox reaction to continue.
by Julie Steklof 1A
Fri Feb 02, 2018 10:00 am
Forum: Concepts & Calculations Using Second Law of Thermodynamics
Topic: Trouton's Rule
Replies: 1
Views: 86

Re: Trouton's Rule

Based on this website, there may be some correlation but no definitive consistency can be found for solids.

https://chem.libretexts.org/Core/Physic ... eqn-approx
by Julie Steklof 1A
Fri Feb 02, 2018 9:54 am
Forum: Gibbs Free Energy Concepts and Calculations
Topic: Spontaneous
Replies: 14
Views: 417

Re: Spontaneous

Reactions are considered spontaneous when the products are favored over the reactants.
by Julie Steklof 1A
Fri Feb 02, 2018 9:53 am
Forum: Gibbs Free Energy Concepts and Calculations
Topic: Endergonic vs Endothermic
Replies: 2
Views: 120

Re: Endergonic vs Endothermic

Endergonic means that energy is absorbed from the surroundings (in terms of Gibbs Free Energy) so deltaG is positive and exothermic means a negative deltaH. I think it's possible for this to occur only when the entropy change is negative and the temperature is high.
by Julie Steklof 1A
Fri Jan 26, 2018 8:59 am
Forum: Entropy Changes Due to Changes in Volume and Temperature
Topic: Monatomic Gas
Replies: 5
Views: 221

Re: Monatomic Gas

Does this mean that the specific heat for all ideal monatomic gases is equal?
by Julie Steklof 1A
Fri Jan 26, 2018 8:56 am
Forum: Concepts & Calculations Using Second Law of Thermodynamics
Topic: Degeneracy
Replies: 3
Views: 122

Re: Degeneracy

I think one of the main points made was that like a "boulder on a hill" (in the enthalpy diagram) you would not expect it to start rolling up the hill without work being put in, naturally it would go to the lowest point. This is in contrast to entropy where you would not expect a system to...
by Julie Steklof 1A
Wed Jan 24, 2018 7:27 pm
Forum: Concepts & Calculations Using Second Law of Thermodynamics
Topic: Relating Degeneracy and Volume
Replies: 2
Views: 92

Relating Degeneracy and Volume

In the example that Dr. Lavelle gave today during lecture he said that when V2=2V1, each gas molecule has 2x positions available to it and that because of this the ratio of W2 to W1 was equal to 2. How do we know that each gas molecule has 2x positions available to it?
by Julie Steklof 1A
Sat Jan 20, 2018 1:20 pm
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: Reversible Processes
Replies: 2
Views: 140

Reversible Processes

Why does a system being at equilibrium mean that it is a reversible process?
by Julie Steklof 1A
Sat Jan 20, 2018 1:14 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: Diathermic walls
Replies: 3
Views: 214

Re: Diathermic walls

AlyssaPeckham1A wrote:Would adiabatic walls be almost the opposite of diathermic walls?


Yes, adiabatic walls do not allow heat transfer between a system and its surroundings.
by Julie Steklof 1A
Sat Jan 20, 2018 1:09 pm
Forum: Phase Changes & Related Calculations
Topic: 8.13
Replies: 3
Views: 139

Re: 8.13

Yes, the surroundings (the cooling system) gain 947 kJ as heat meaning that the system must lose 947 kJ.
by Julie Steklof 1A
Fri Jan 12, 2018 9:21 am
Forum: Phase Changes & Related Calculations
Topic: Constant Temperature
Replies: 4
Views: 201

Constant Temperature

During a phase change, why does the temperature of a sample remain constant even when heat is being supplied?
by Julie Steklof 1A
Fri Jan 12, 2018 9:14 am
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Standard Enthalpies of Formation of Diatomic Molecules
Replies: 6
Views: 1252

Re: Standard Enthalpies of Formation of Diatomic Molecules

All elements in their natural states have an enthalpy equal to zero because there is no change involved in their formation.
by Julie Steklof 1A
Fri Jan 12, 2018 9:04 am
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Enthalpy Change Signs
Replies: 5
Views: 201

Re: Enthalpy Change Signs

Yes, reversing a reaction will result in a enthalpy of opposite sign. This is because enthalpy is a state function/property.
by Julie Steklof 1A
Thu Dec 07, 2017 9:48 am
Forum: Conjugate Acids & Bases
Topic: HW: 12.17
Replies: 4
Views: 504

Re: HW: 12.17

Helen Shi 1B wrote:Can someone explain why BaO is basic and As2O3 and Bi2O3 amphoteric?


As and Bi are metalloids and can act as either acids or bases.
by Julie Steklof 1A
Thu Dec 07, 2017 9:39 am
Forum: Acidity & Basicity Constants and The Conjugate Seesaw
Topic: Percent ionization
Replies: 3
Views: 214

Re: Percent ionization

Yes they are the same thing. When an acid is deprotonated it is the same thing as being ionized.
by Julie Steklof 1A
Thu Nov 30, 2017 10:03 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: 11.1
Replies: 4
Views: 253

Re: 11.1

Because the only thing changed in the problem is concentration and k is constant regardless of initial concentrations, more product must be formed in order to make the ratio of concentration of products to concentration of reactants (k) the same.
by Julie Steklof 1A
Thu Nov 30, 2017 9:57 pm
Forum: Lewis Acids & Bases
Topic: How to tell when a molecule is an acid or base
Replies: 2
Views: 343

Re: How to tell when a molecule is an acid or base

You could draw Lewis structures and see if a molecule has an element with an open octet (for example Boron in BF3). This tells you that the molecule is a Lewis acid. Similarly, if you draw a Lewis structure and see that an element has an unshared pair of electrons to be able to donate. This would be...
by Julie Steklof 1A
Mon Nov 20, 2017 9:00 pm
Forum: Naming
Topic: Cations
Replies: 1
Views: 113

Cations

I know that when naming coordination compounds if the overall charge is negative we add -ate to the end of the transition metal name. Is there any rule for when the overall charge is positive?
by Julie Steklof 1A
Mon Nov 20, 2017 6:54 pm
Forum: Naming
Topic: Homework #17.31
Replies: 1
Views: 138

Re: Homework #17.31

When naming coordination complexes, the ligands are listed alphabetically. I don't think the order when writing the chemical formula is significant because everything within the square brackets is directly bonded to the transition metal.
by Julie Steklof 1A
Thu Nov 16, 2017 2:21 pm
Forum: *Molecular Orbital Theory (Bond Order, Diamagnetism, Paramagnetism)
Topic: Bond Angles
Replies: 8
Views: 428

Re: Bond Angles

Yes putting less than 109.5 degrees for bond angles will be fine because molecules with lone electron pairs have bond angles that are determined experimentally and differ from molecule to molecule even if both have the same VSEPR shape.
by Julie Steklof 1A
Thu Nov 16, 2017 1:58 pm
Forum: Hybridization
Topic: the number of pi bonds
Replies: 3
Views: 177

Re: the number of pi bonds

The unhybridized 2p electrons are the ones forming the 3 pi bonds.
by Julie Steklof 1A
Mon Nov 06, 2017 2:41 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: trigonal pyramidal
Replies: 3
Views: 167

Re: trigonal pyramidal

Yes, three bonds and a lone pair of electrons on the central atom results in a trigonal pyramidal shape. However, in response to the above comment, three bonding pairs with no lone pair is trigonal planar, not trigonal pyramidal.
by Julie Steklof 1A
Mon Nov 06, 2017 2:36 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: VSEPR Formula?
Replies: 3
Views: 189

Re: VSEPR Formula?

VSEPR formulas are generalized formulas describing the molecular shape of a compound. A represents the central atom, X represents the bonded atom(s), and E represents the lone pair(s) of a molecule. For example, a trigonal pyramidal molecule would have the VSEPR formula: AX3E, one central atom bonde...
by Julie Steklof 1A
Thu Nov 02, 2017 10:47 pm
Forum: Bond Lengths & Energies
Topic: Bond Length
Replies: 5
Views: 286

Re: Bond Length

I'm pretty sure bond length is determined experimentally.
by Julie Steklof 1A
Thu Nov 02, 2017 10:44 pm
Forum: Ionic & Covalent Bonds
Topic: Chemical bonds create lower energy?
Replies: 4
Views: 206

Re: Chemical bonds create lower energy?

To add to the above response, atoms that are bonded are more stable and therefore have less energy than the free atoms which are more unstable.
by Julie Steklof 1A
Thu Oct 26, 2017 7:10 pm
Forum: Trends in The Periodic Table
Topic: Conductors
Replies: 1
Views: 111

Conductors

Why is it that elements with low ionization energy conduct electricity in their solid states?
by Julie Steklof 1A
Thu Oct 26, 2017 7:03 pm
Forum: Trends in The Periodic Table
Topic: Isoelectronic ions
Replies: 2
Views: 955

Re: Isoelectronic ions

The above response is correct. Because each ion has the same amount of electrons, to determine size we need to look at the number of protons within the ion. Because Magnesium 2+ has the highest nuclear charge, and each ion in the series have the same number of electrons, it will have the smallest io...
by Julie Steklof 1A
Thu Oct 19, 2017 9:20 pm
Forum: Photoelectric Effect
Topic: Ionization in energy levels
Replies: 4
Views: 236

Re: Ionization in energy levels

The energy required to ionize an electron is the same as the energy required to remove an electron.
by Julie Steklof 1A
Thu Oct 19, 2017 9:15 pm
Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
Topic: Question about energy levels [ENDORSED]
Replies: 8
Views: 450

Re: Question about energy levels [ENDORSED]

I have not seen any energy levels higher than n=9.
by Julie Steklof 1A
Wed Oct 11, 2017 8:07 pm
Forum: Photoelectric Effect
Topic: Units Cancelling Out
Replies: 3
Views: 234

Re: Units Cancelling Out

In E=hv, the units for h are Joules*seconds and units of v are seconds^-1. Multiplying these gives you Joules which is an appropriate unit for energy. In E=1/2mv^2, mass is measured in kilograms and velocity in meters per second. Joules is technically "short" for units of kg*m^2/s^2 which ...
by Julie Steklof 1A
Wed Oct 11, 2017 8:00 pm
Forum: Einstein Equation
Topic: E=hv and ΔE=hv
Replies: 3
Views: 379

Re: E=hv and ΔE=hv

ΔE is the energy change that occurs when an atom absorbs or emits a photon (atomic spectra experiment) whereas E is used to calculate the energy per photon when completely removing electrons from an atom (photoelectric effect).
by Julie Steklof 1A
Thu Oct 05, 2017 1:39 pm
Forum: Accuracy, Precision, Mole, Other Definitions
Topic: Fundamentals E Question 35 [ENDORSED]
Replies: 2
Views: 281

Re: Fundamentals E Question 35 [ENDORSED]

I thought percent change was always (final-intial)/initial x100%? This would make the equation (504.3-502.31)/502.31 x100% which gives you .396% and rounds to .40%. However the solutions manual shows dividing by 504.3. Does anyone know why this is?
by Julie Steklof 1A
Tue Oct 03, 2017 8:31 pm
Forum: Empirical & Molecular Formulas
Topic: Self-Test M.4A (p.F114)
Replies: 3
Views: 362

Re: Self-Test M.4A (p.F114)

In class we were told that for rounding if the number ends in a 5 we should round to the nearest even number. So if the number was .065 we would simply round to .06 but if the number was .055 we would round up to .06.

Go to advanced search