Search found 49 matches

by Annalise Eder 2L
Fri Mar 16, 2018 11:05 pm
Forum: Arrhenius Equation, Activation Energies, Catalysts
Topic: Transition States
Replies: 1
Views: 101

Re: Transition States

Transition states have partial bonds and are not defined as individual molecules.
by Annalise Eder 2L
Fri Mar 16, 2018 11:02 pm
Forum: Reaction Mechanisms, Reaction Profiles
Topic: Slow Step Vs. Steady State Approximation
Replies: 3
Views: 174

Re: Slow Step Vs. Steady State Approximation

Using the steady step method will get you the same result as using the pre-equilibrium approach. Either way you will need to identify the slow step of the reaction as it is the rate determining step.
by Annalise Eder 2L
Fri Mar 16, 2018 11:00 pm
Forum: Arrhenius Equation, Activation Energies, Catalysts
Topic: Catalysts
Replies: 2
Views: 122

Re: Catalysts

A catalyst provides an alternate pathway and that pathway has a lower activation energy than the original. It increases the number of successful collisions.
by Annalise Eder 2L
Sun Mar 11, 2018 4:21 pm
Forum: Student Social/Study Group
Topic: Post All Chemistry Jokes Here
Replies: 7606
Views: 1019126

Re: Post All Chemistry Jokes Here

What do chemists call a benzene ring with iron atoms replacing the carbon atoms?

A ferrous wheel.
by Annalise Eder 2L
Sun Mar 11, 2018 4:17 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Heat Required to Heat a Substance
Replies: 5
Views: 237

Re: Heat Required to Heat a Substance

More complex molecules generally have high heat capacities because they have more degrees of freedom and more ways to store energy. Materials with more atoms per unit volume will generally have higher heat capacities.
by Annalise Eder 2L
Sun Mar 11, 2018 4:11 pm
Forum: Reaction Mechanisms, Reaction Profiles
Topic: Using pre-equilibrium approach
Replies: 3
Views: 120

Re: Using pre-equilibrium approach

The pre-equilibrium approach should be used on problems where the slow step is not the first step in the reaction and the reaction rate of the later step contains and intermediate. You could also try using the steady state approach, but this is much more complicated and difficult.
by Annalise Eder 2L
Sun Mar 04, 2018 2:27 pm
Forum: Student Social/Study Group
Topic: Post All Chemistry Jokes Here
Replies: 7606
Views: 1019126

Re: Post All Chemistry Jokes Here

A photon checks into a hotel and is asked if he needs any help with his luggage. He says, "No, I'm traveling light."
by Annalise Eder 2L
Sun Mar 04, 2018 2:24 pm
Forum: First Order Reactions
Topic: Integrated rate law for first order reaction
Replies: 3
Views: 170

Re: Integrated rate law for first order reaction

The integrated rate law for a first order reaction is ln[A]=ln[A]initial-kt. I am unsure what the other equation is that you are referring to.
by Annalise Eder 2L
Sun Mar 04, 2018 2:21 pm
Forum: Second Order Reactions
Topic: Slope of second order reaction
Replies: 3
Views: 198

Re: Slope of second order reaction

The variable for a second order reaction that create a linear graph are 1/[A] over time while for a first order reaction it is ln[A] over time and for a zero order reaction it is [A] over time. The 1/[A] creates a positive slope because as the concentration of A decreases 1/[A] increases.
by Annalise Eder 2L
Sun Feb 25, 2018 7:20 pm
Forum: Student Social/Study Group
Topic: Post All Chemistry Jokes Here
Replies: 7606
Views: 1019126

Re: Post All Chemistry Jokes Here

If you're not part of the solution, you're part of the precipitate.
by Annalise Eder 2L
Sun Feb 25, 2018 7:16 pm
Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
Topic: Dissolving metal in a solution
Replies: 3
Views: 162

Re: Dissolving metal in a solution

You will want to balance the equation with the solid metal on the reactants side and the aqueous dissociated ions on the product side. If the formation of the ions is favorable, the metal will dissolve in the solution.
by Annalise Eder 2L
Sun Feb 25, 2018 7:10 pm
Forum: Kinetics vs. Thermodynamics Controlling a Reaction
Topic: Kinetics vs. Thermodynamics
Replies: 2
Views: 164

Re: Kinetics vs. Thermodynamics

The rate constant k, associated with kinetics, is related to the activation energy required for a reaction to occur and can tell you about the speed of a reaction and how quickly is reaches equilibrium. Thermodynamics is related to the free energy, ΔG, given off by a reaction and tells you about a r...
by Annalise Eder 2L
Sun Feb 18, 2018 11:14 pm
Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
Topic: Cell Diagram
Replies: 3
Views: 443

Re: Cell Diagram

Don't forget to include phases for all of the elements. The Br ions would be (aq).
by Annalise Eder 2L
Sun Feb 18, 2018 10:58 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Electrochemical Series Definition
Replies: 4
Views: 173

Re: Electrochemical Series Definition

An electrochemical series is a list of reduction half reactions listed in order of increasing E°values.
by Annalise Eder 2L
Sun Feb 18, 2018 10:50 pm
Forum: Balancing Redox Reactions
Topic: Basic and Acidic conditions [ENDORSED]
Replies: 11
Views: 3382

Re: Basic and Acidic conditions [ENDORSED]

For acidic questions balance with H3O+ and water. For basic conditions use OH- and water.
by Annalise Eder 2L
Sun Feb 11, 2018 8:22 pm
Forum: Van't Hoff Equation
Topic: Free Energy, pressure, and equilibrium constant
Replies: 2
Views: 226

Re: Free Energy, pressure, and equilibrium constant

Gibbs free energy is an extensive property that depends on the amount and concentration of substances.
by Annalise Eder 2L
Sun Feb 11, 2018 8:20 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Positive cell potentials
Replies: 2
Views: 79

Re: Positive cell potentials

If you were to leave the + off of your answer on a test I am sure you would get full credit.
by Annalise Eder 2L
Sun Feb 11, 2018 8:15 pm
Forum: Balancing Redox Reactions
Topic: Nature
Replies: 5
Views: 177

Re: Nature

Reduction and oxidation occur together. This is why they are called redox reactions.
by Annalise Eder 2L
Sun Feb 04, 2018 10:28 pm
Forum: Thermodynamic Systems (Open, Closed, Isolated)
Topic: Open, closed, or isolated test 1 question
Replies: 10
Views: 590

Re: Open, closed, or isolated test 1 question

This is an open system because it can freely exchange energy and matter with its surroundings.
by Annalise Eder 2L
Sun Feb 04, 2018 10:27 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: Heat Transfer Test 1 Concept Question
Replies: 2
Views: 145

Re: Heat Transfer Test 1 Concept Question

Heat is a measure of thermal energy being transferred and does not necessarily result in a change of temperature.
by Annalise Eder 2L
Sun Feb 04, 2018 4:08 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: Periodic Trends
Replies: 4
Views: 187

Re: Periodic Trends

Heat capacity is an extensive property and therefore depends on the amount of a substance. Specific heat capacities of elements are different depending on what state they are in. Therefore, it is difficult to measure the periodic trends.
by Annalise Eder 2L
Sun Jan 28, 2018 7:55 pm
Forum: Entropy Changes Due to Changes in Volume and Temperature
Topic: Entropy Change equation
Replies: 1
Views: 77

Re: Entropy Change equation

The heat capacity equation is Q = ncΔ T
Change in entropy can be calculated using different equations depending on the situation
Boltzmann' equation: S = kB ln W
for an isothermal process ∆S = qREV/T
for a reversible process: ∆S = nR lnV2/V1
at constant volume: ∆ST1 ---> T2= nC ln(T2/T1)
by Annalise Eder 2L
Sun Jan 28, 2018 7:39 pm
Forum: Thermodynamic Definitions (isochoric/isometric, isothermal, isobaric)
Topic: work definition
Replies: 5
Views: 216

Re: work definition

Both have to do with a transfer of energy. Work is defined as the amount of energy transferred by a force acting through a distance. Heat is defined as the energy stored as random motion of molecules or atoms.
by Annalise Eder 2L
Sun Jan 28, 2018 7:32 pm
Forum: Thermodynamic Systems (Open, Closed, Isolated)
Topic: Adiabatic vs. Isolated
Replies: 3
Views: 187

Re: Adiabatic vs. Isolated

In an adiabatic system there is no transfer of heat while in an isolated system there is no contact with the surroundings and therefore no exchange of energy or matter.
by Annalise Eder 2L
Sun Jan 21, 2018 3:15 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: Change in temperature,volume and pressure for different equations
Replies: 2
Views: 107

Re: Change in temperature,volume and pressure for different equations

For enthalpy, delta H, pressure is constant. For change in internal energy, delta U, volume is constant.
by Annalise Eder 2L
Sun Jan 21, 2018 3:01 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: 8.31? Molar heat capacity of a monatomic idea gas at constant pressure?
Replies: 1
Views: 98

Re: 8.31? Molar heat capacity of a monatomic idea gas at constant pressure?

These numbers have to do with the equipartition of energy theorem which involves molecules' degrees of freedom. It depends on translational and rotational degrees of freedom. R is the gas constant.
by Annalise Eder 2L
Sun Jan 21, 2018 2:37 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: State Functions and Bond Enthalpies
Replies: 2
Views: 92

Re: State Functions and Bond Enthalpies

On the other hand, path functions do depend on the path taken from initial to final state. One way to think about state functions is if you had a bank account with $1,000 in it and you took out $100 at once or $25 on four separate occasions, you would have $900 left in your bank account either way a...
by Annalise Eder 2L
Sun Jan 14, 2018 11:30 am
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: Why isn't heat a state function?
Replies: 2
Views: 240

Re: Why isn't heat a state function?

Enthalpy is a state function meaning it does not matter what path was taken. It depends only on the initial and final states. Enthalpy requires constant pressure and measures the heat given off or taken up by a reaction. On the other hand, heat is a path function meaning it does depend on the path t...
by Annalise Eder 2L
Sun Jan 14, 2018 11:21 am
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: Extensive vs Intensive Property
Replies: 3
Views: 122

Re: Extensive vs Intensive Property

This relates to calorimetry because heat capacity is an extensive property that depends on the amount of the substance while specific heat is an intensive property that does not change based on the amount of the substance.
by Annalise Eder 2L
Sun Jan 14, 2018 11:12 am
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Reaction Enthalpy vs. Enthalpy of Formation
Replies: 2
Views: 112

Re: Reaction Enthalpy vs. Enthalpy of Formation

The reaction enthalpy is the heat taken up or given off during a reaction which is the difference in enthalpies between the products and the reactants. The enthalpy of formation is the change in enthalpy between elements in their standard states to the compound they form.
by Annalise Eder 2L
Tue Dec 05, 2017 4:17 pm
Forum: Acidity & Basicity Constants and The Conjugate Seesaw
Topic: High pKa
Replies: 1
Views: 162

Re: High pKa

pH tells you the concentration of hydronium while pKa tells you the substance's ability to give up protons. For both, a lower number means a stronger acid. However, the pH scale is not the same as pKa values. If a substance has a Pka value over 7 it does not mean it is a base.
by Annalise Eder 2L
Tue Dec 05, 2017 4:04 pm
Forum: Acidity & Basicity Constants and The Conjugate Seesaw
Topic: HCOOH vs CH3COOH
Replies: 2
Views: 171

Re: HCOOH vs CH3COOH

HCOOH is a slightly stronger acid than CH3COOH because H is slightly more electronegative than the CH3 group. A stronger acid forms a more stable anion when it dissociates and HCOO is more stable than CH3COO.
by Annalise Eder 2L
Sun Dec 03, 2017 12:00 pm
Forum: Lewis Acids & Bases
Topic: HW12.13
Replies: 2
Views: 172

Re: HW12.13

The definition of a Lewis acid is a substance than can accept a pair of electrons while a Lewis base is a substance that donates a pair of electrons. Cations, atoms with an incomplete octet, or molecules where the central atom can have an expanded octet can act as Lewis acids. An atom, ion, or molec...
by Annalise Eder 2L
Wed Nov 29, 2017 4:56 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: 4.13 d
Replies: 1
Views: 126

Re: 4.13 d

You use the least electronegative atom as the central atom. Nitrogen is less electronegative than oxygen.
by Annalise Eder 2L
Sun Nov 26, 2017 2:40 pm
Forum: Sigma & Pi Bonds
Topic: Sigma and Pi Bonds
Replies: 5
Views: 416

Re: Sigma and Pi Bonds

A single bond is always a sigma bond. In a a double or triple bond the first bond is always a sigma bond, but any following bonds must be pi bonds.
by Annalise Eder 2L
Sun Nov 26, 2017 2:37 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: S Character Influencing Bond Angles
Replies: 2
Views: 156

Re: S Character Influencing Bond Angles

You can determine the bond angle based on the hybridization. SP has 180 degree bond angle, SP2 has 120 degree bond angle, and SP3 has 109.5 degree bond angle usually. As the number of p orbitals increases the s character decreases as does the bond angle as seen with the given numbers.
by Annalise Eder 2L
Sun Nov 26, 2017 2:31 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: partial pressure
Replies: 3
Views: 159

Re: partial pressure

If all of the species given are gases then partial pressure can be used to calculate the equilibrium constant. If you are given Kp you would also use partial pressure. If you are given Kc you would use concentration.
by Annalise Eder 2L
Sun Nov 19, 2017 10:44 am
Forum: Electron Configurations for Multi-Electron Atoms
Topic: Valence Shell Electron Configuration
Replies: 2
Views: 480

Re: Valence Shell Electron Configuration

Copper is also an exception because its electron configuration is [Ar]3d10 4s1 not [Ar] 3d9 4s2. This is because a half-filled or full d subshell is more stable.
by Annalise Eder 2L
Sun Nov 19, 2017 10:41 am
Forum: Electron Configurations for Multi-Electron Atoms
Topic: 3.5 Give the ground state configuration expected for each of the following ions:
Replies: 3
Views: 516

Re: 3.5 Give the ground state configuration expected for each of the following ions:

You always remove electrons from the outmost shell first. This is because the electrons in front of them are essentially blocking them from the pull of the nucleus.
by Annalise Eder 2L
Sun Nov 12, 2017 10:19 am
Forum: Trends in The Periodic Table
Topic: Hydrogen Electronegativity
Replies: 4
Views: 1011

Re: Hydrogen Electronegativity

Hydrogen does not take a full octet. It has a half filled 1s orbital and only wants one more electron. Therefore it has high electronegativity.
by Annalise Eder 2L
Sun Nov 12, 2017 10:06 am
Forum: Properties of Light
Topic: Atomic Spectra
Replies: 2
Views: 182

Re: Atomic Spectra

Knowing the series may also be helpful. The Balmer series is associated with energy changes where n=2 and exists in the visible light spectrum. The Lyman series is associated with energy changes where n=1and exists in the UV spectrum. These series are for Hydrogen only.
by Annalise Eder 2L
Sun Nov 05, 2017 6:24 pm
Forum: Trends in The Periodic Table
Topic: electron affinities
Replies: 2
Views: 182

Re: electron affinities

The electron affinities are close to zero. Noble gases have complete octets and do not want any more electrons. The Alkaline metals also have very low electron affinity as they often form cations and prefer to give up electrons than gain them.
by Annalise Eder 2L
Sun Nov 05, 2017 6:14 pm
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: Lower in Energy? [ENDORSED]
Replies: 6
Views: 289

Re: Lower in Energy? [ENDORSED]

The quantum number n gives the energy level while the angular momentum quantum number tells you the subshell of the electron. So use n as l does not give you information about the energy level. For potassium and Calcium 4s has lower energy than 3d which may seem counterintuitive, but for Scandium th...
by Annalise Eder 2L
Sun Oct 29, 2017 9:34 pm
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: 4s and 3d orbitals
Replies: 5
Views: 437

Re: 4s and 3d orbitals

The electrons in the 3d orbitals essentially shield electrons in the 4s orbital from the nucleus, so electrons in the 4s orbital are lost first during ionization.
by Annalise Eder 2L
Sun Oct 29, 2017 6:48 pm
Forum: Lewis Structures
Topic: Sulfate Ion
Replies: 4
Views: 205

Re: Sulfate Ion

Sulfur can have an expanded octet by using the empty 3d orbitals to accommodate "extra" electrons.
by Annalise Eder 2L
Sun Oct 22, 2017 5:59 pm
Forum: Heisenberg Indeterminacy (Uncertainty) Equation
Topic: heisenberg post-module question 21
Replies: 1
Views: 180

Re: heisenberg post-module question 21

I would just choose the answer choice that best fits the question and repeat the calculations without worrying about them being included in the given answers.
by Annalise Eder 2L
Sat Oct 21, 2017 6:54 pm
Forum: Electron Configurations for Multi-Electron Atoms
Topic: 3d and 4s
Replies: 3
Views: 189

Re: 3d and 4s

For Potassium and Calcium, 4s is lower in energy than 3d. From Scandium on 3d is lower in energy
by Annalise Eder 2L
Sat Oct 14, 2017 9:07 pm
Forum: Properties of Light
Topic: 1.15 [ENDORSED]
Replies: 2
Views: 209

Re: 1.15 [ENDORSED]

The wavelength of the emitted photon is 102.6 nm which is in the ultraviolet spectrum. This section of the emission spectra for Hydrogen is know as the Lyman series which always corresponds to n=1 as one of the principle energy levels.
by Annalise Eder 2L
Tue Oct 10, 2017 8:08 pm
Forum: Properties of Light
Topic: Calculating the wavelength of light [ENDORSED]
Replies: 5
Views: 344

Re: Calculating the wavelength of light [ENDORSED]

This equation is used to calculate the energy of a photon when you are given the wavelength of the light. For example, you could use this equation on homework question 1.9 where you are given the wavelength 2.5 nm and asked for the frequency and energy of the photon.

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