## Search found 50 matches

Wed Mar 14, 2018 8:53 pm
Forum: Arrhenius Equation, Activation Energies, Catalysts
Topic: Arrhenius when Temperature Changes
Replies: 3
Views: 235

### Re: Arrhenius when Temperature Changes

As long as your k1 matches up with your T1 and your k2 matches up with your T2 then you should be fine
Wed Mar 14, 2018 8:50 pm
Forum: Reaction Mechanisms, Reaction Profiles
Topic: Finding the slow step
Replies: 5
Views: 430

### Re: Finding the slow step

If you are given the rate law, then you can look at the steps of the reaction in order to determine which step is the slow step
Wed Mar 14, 2018 8:49 pm
Forum: Reaction Mechanisms, Reaction Profiles
Topic: Elementary reactions
Replies: 6
Views: 392

### Re: Elementary reactions

Elementary reactions are simply just the steps that add up to form the overall reaction
Wed Mar 07, 2018 12:20 am
Forum: General Rate Laws
Topic: Writing rate laws
Replies: 4
Views: 261

### Re: Writing rate laws

It's not necessary to write the 1 in first order reactions, the one is just implied if you write out the reactant with no exponent
Wed Mar 07, 2018 12:14 am
Forum: First Order Reactions
Topic: 15.23C
Replies: 6
Views: 410

### Re: 15.23C

The coefficient is not always indicative of the reaction order, the problem may give the order or values the concentration of reactant and rate constant will be given and you must determine order by observing changes in these values
Wed Mar 07, 2018 12:09 am
Forum: First Order Reactions
Topic: k
Replies: 16
Views: 799

### Re: k

It isn't always necessary to change the units of k to s^-1, but just make sure that units always cancel
Sat Mar 03, 2018 5:17 pm
Forum: First Order Reactions
Topic: First Order Graph
Replies: 11
Views: 616

### Re: First Order Graph

The graph of just concentration vs time will have a curve, but if you graph the natural log of concentration vs time you will have a linear graph
Sat Mar 03, 2018 5:15 pm
Forum: Zero Order Reactions
Topic: Zero Order Reactions and Rate of Reaction
Replies: 5
Views: 340

### Re: Zero Order Reactions and Rate of Reaction

It basically means that concentration does not affect reaction rate
Sat Mar 03, 2018 5:13 pm
Forum: General Rate Laws
Topic: rate law
Replies: 3
Views: 200

### Re: rate law

You would be given a table typically and have to use the data in the table to determine how changes in concentration of reactant would affect the reaction rate, which would give you the order of each of the reactants
Thu Feb 22, 2018 11:51 pm
Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
Topic: 14.27
Replies: 6
Views: 398

### Re: 14.27

If you add the deltaG values together, then you can use the formula deltaG=-nFE to calculate the cell potential
Thu Feb 22, 2018 11:48 pm
Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
Topic: 14.31
Replies: 6
Views: 373

### Re: 14.31

Also if K>1, meaning that E>1 as well, then the reaction would be spontaneous in the forward direction
Thu Feb 22, 2018 11:47 pm
Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
Topic: Nernst Equation to find pH
Replies: 6
Views: 2836

### Re: Nernst Equation to find pH

Yeah, if you solve for the concentration of H+ ions, you can then calculate the pH using the equation pH=log[H+]
Sat Feb 17, 2018 11:57 pm
Forum: Balancing Redox Reactions
Topic: Oxidizing & Reducing Agents
Replies: 6
Views: 422

### Re: Oxidizing & Reducing Agents

The reducing agent is the molecule that causes the other molecule to be reduced, meaning that it is oxidized, and the oxidizing agent is the molecule that causes the other molecule to be oxidized, meaning that is reduced
Sat Feb 17, 2018 11:54 pm
Forum: Van't Hoff Equation
Topic: Van't Hoff equation
Replies: 4
Views: 552

### Re: Van't Hoff equation

Yes you can do this, but you can always just derive the Van't Hoff equation from deltaG=deltaH -t*deltaS
Sat Feb 17, 2018 11:52 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: reversible system
Replies: 9
Views: 583

### Re: reversible system

DeltaS total would be zero, which means that deltaS system=-(deltaS surroundings)
Sun Feb 11, 2018 1:37 am
Forum: Concepts & Calculations Using Second Law of Thermodynamics
Topic: conceptual entropy questions
Replies: 5
Views: 333

### Re: conceptual entropy questions

Since there are more electrons in bromine, there are more possible microstates, contributing to the higher entropy
Sun Feb 11, 2018 1:34 am
Forum: Gibbs Free Energy Concepts and Calculations
Topic: Stability in Gibbs standard free energy of formation
Replies: 2
Views: 533

### Re: Stability in Gibbs standard free energy of formation

Yes, if the Gibbs standard free energy of one compound is more negative than another it is more stable because when it is in the form of its constituent elements it is less stable, meaning that when the reaction is spontaneous the formation of the product, which is more stable, is favored
Sun Feb 11, 2018 1:33 am
Forum: Gibbs Free Energy Concepts and Calculations
Topic: Delta G
Replies: 4
Views: 225

### Re: Delta G

Delta G refers to the spontaneity of a reaction, so if delta G is positive, then the reaction is not spontaneous and the reactants are favored, but when it is negative, the reaction is spontaneous and the products are favored. So, when delta G is 0 neither the products nor reactants are favored thus...
Sat Feb 03, 2018 6:00 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: What does it mean for a reaction to be "thermodynamically favored?"
Replies: 6
Views: 14405

### Re: What does it mean for a reaction to be "thermodynamically favored?"

A reaction if thermodynamically favorable if delta G is negative, which means that the reaction is spontaneous and thus doesn't require energy to occur
Sat Feb 03, 2018 5:56 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: Spontaneous
Replies: 14
Views: 821

### Re: Spontaneous

Reactions are spontaneous when delta G is negative, meaning that the free energy of the products is less than the free energy of the reactants. If you look at a graph of free energy, this makes sense because it does not require energy to go down a hill, meaning that this process is spontaneous, howe...
Sat Feb 03, 2018 5:54 pm
Forum: Calculating Standard Reaction Entropies (e.g. , Using Standard Molar Entropies)
Topic: How to tell what happens to entropy by seeing a reaction?
Replies: 6
Views: 461

### Re: How to tell what happens to entropy by seeing a reaction?

The phase of the reactants and products are the best way of looking at a reaction and determining how entropy changes, and entropy increases from solid to liquid to gas
Wed Jan 24, 2018 12:18 am
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Exothermic
Replies: 7
Views: 367

### Re: Exothermic

The release of heat in an endothermic reaction causes the temperature of the surroundings to increase, whereas an endothermic reaction absorbs heat, thus decreasing the temperature
Wed Jan 24, 2018 12:14 am
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: 8.65
Replies: 6
Views: 323

### Re: 8.65

They put fractions in the reaction because they wanted to display the reaction that only produces one mole of N2O5, which would result in their being fractional coefficients for some of the reactants
Wed Jan 24, 2018 12:13 am
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Hess's Law
Replies: 5
Views: 376

### Re: Hess's Law

If the two molecules are on opposite sides of the equation in equal amounts, then they can be canceled out because nothing is changing from reactants to products
Thu Jan 18, 2018 1:21 am
Forum: Phase Changes & Related Calculations
Topic: Open/Closed/Isolated
Replies: 11
Views: 590

### Re: Open/Closed/Isolated

It would be a closed system with the lid on because mass cannot be transferred from the tank if there is a lid on top, although energy can be transferred
Thu Jan 18, 2018 1:15 am
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: 8.1 systems
Replies: 4
Views: 283

### Re: 8.1 systems

Both heat and mass are released from the system, therefore the system is open
Thu Jan 18, 2018 1:09 am
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: Cm
Replies: 3
Views: 215

### Re: Cm

You would use Cs when calculating heat using the equation q=(g)(Cs)(delta t)
Wed Jan 10, 2018 9:14 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Hess's Law
Replies: 8
Views: 560

### Re: Hess's Law

If you choose to reverse the reaction or multiply by coefficients then you would have to change the enthalpy of the reaction as well. If the reaction is reversed, you multiply the enthalpy by -1 or by the coefficient that you multiplied the equation by.
Wed Jan 10, 2018 9:11 pm
Forum: Phase Changes & Related Calculations
Topic: Enthalpy is a state property
Replies: 13
Views: 741

### Re: Enthalpy is a state property

Enthalpy being a state property means that the path that it takes to get to the value is not important, unlike work which is not a state property
Wed Jan 10, 2018 9:09 pm
Forum: Phase Changes & Related Calculations
Replies: 5
Views: 617

### Re: Reaction in a Flask

Endothermic reactions involve the absorption of heat, so whatever is in the flask will take the heat from the flask, making the flask cold
Fri Dec 08, 2017 9:24 am
Forum: Lewis Acids & Bases
Topic: HF
Replies: 4
Views: 322

### Re: HF

Fluorine has a very small atomic radius so in turn it also has a very short bond length, resulting in a very strong bond, and the fluorine is less likely to give up a hydrogen
Fri Dec 08, 2017 9:12 am
Forum: Conjugate Acids & Bases
Topic: HW 12.45
Replies: 4
Views: 449

### Re: HW 12.45

If an acid has a low pKa, that means that it is a strong acid, and thus it has a weak conjugate base, and thus acids with high pKa's have strong conjugate bases
Thu Nov 30, 2017 2:52 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: 11.1
Replies: 4
Views: 345

### Re: 11.1

In order to re-establish equilibrium, the reaction will convert some of these new reactants into products, which is why the addition of reactants will result in the formation of more products.
Thu Nov 30, 2017 2:48 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: Changes in K
Replies: 4
Views: 234

### Re: Changes in K

K is a constant, so if concentrations of molecules in the reaction are changed, the reaction quotient eventually go back to whatever K was, unless temperature is changed as well
Fri Nov 24, 2017 4:41 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: K and Kc
Replies: 7
Views: 471

### Re: K and Kc

Kc is just more specific than K, K covers both Kc and Kp
Fri Nov 24, 2017 4:40 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Equilibrium constant
Replies: 4
Views: 192

### Re: Equilibrium constant

You should always disregard solids and liquids when calculating the value of K
Fri Nov 17, 2017 9:16 am
Forum: Hybridization
Topic: Polar/nonpolar [ENDORSED]
Replies: 14
Views: 1660

### Re: Polar/nonpolar[ENDORSED]

Also, nonpolar molecules are symmetrical while polar molecules are not symmetrical
Fri Nov 17, 2017 9:09 am
Forum: Hybridization
Topic: Lone pairs effect hybridization
Replies: 3
Views: 196

### Re: Lone pairs effect hybridization

When counting regions of electron density around an atom to determine hybridization, you would include the lone pairs
Tue Nov 07, 2017 10:47 pm
Forum: Formal Charge and Oxidation Numbers
Topic: Formal Charge and stability [ENDORSED]
Replies: 7
Views: 4110

### Re: Formal Charge and stability[ENDORSED]

Depending on the arrangement of single/double/triple bonds in a structure, there may be a difference in the formal charges of the atoms in the molecule, and the closer formal charges are to zero, the more stable the molecule is
Tue Nov 07, 2017 10:31 pm
Forum: Polarisability of Anions, The Polarizing Power of Cations
Topic: Highly Polarizable
Replies: 4
Views: 421

### Re: Highly Polarizable

Yes, small cations have high polarizing power while large anions have large polarizability.
Fri Nov 03, 2017 9:36 am
Forum: Electron Configurations for Multi-Electron Atoms
Topic: Drawing the configuration
Replies: 4
Views: 268

### Re: Drawing the configuration

According to Hund's Rule, electrons in the same subshell occupy different orbitals with parallel spin, but when electrons are initially added, it doesn't matter whether the spin is up or down, as long as they are all parallel.
Fri Nov 03, 2017 9:33 am
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: Orbitals
Replies: 2
Views: 235

### Orbitals

When asked what orbital an electron belongs to, would you answer, with just just s, p, d, or f, or would you have to specify the subshell as well? (for example, 4s, 3p, etc.)
Wed Oct 25, 2017 9:19 pm
Forum: Ionic & Covalent Bonds
Topic: covalent bond
Replies: 7
Views: 668

### Re: covalent bond

Yes, this is true, and ionic bonds are between a metal and a nonmetal
Wed Oct 25, 2017 9:16 pm
Forum: Ionic & Covalent Bonds
Topic: Ionization Energy [ENDORSED]
Replies: 5
Views: 390

### Re: Ionization Energy[ENDORSED]

Also, ionization energy increases going from left to right on the periodic table because there is a greater effective nuclear charge and the electrons are more attracted to the nucleus of the atom, thus it requires more energy to remove the electrons.
Wed Oct 18, 2017 9:11 pm
Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
Topic: Rydberg Equation! [ENDORSED]
Replies: 8
Views: 914

### Re: Rydberg Equation![ENDORSED]

Is it possible to end up with a negative frequency or will the answer always end up being positive?
Mon Oct 16, 2017 10:49 pm
Forum: DeBroglie Equation
Topic: Homework Problems
Replies: 3
Views: 283

### Homework Problems

What set of problems are we supposed to choose from for this Friday's homework?
Thu Oct 12, 2017 12:54 pm
Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
Replies: 4
Views: 558

### Re: Wavelengths of Electromagnetic Radiation

Should we be expected to memorize the range of wavelengths for each of the types of electromagnetic radiation?
Thu Oct 12, 2017 12:42 pm
Forum: Properties of Light
Topic: Planck Constant [ENDORSED]
Replies: 8
Views: 676

### Re: Planck Constant[ENDORSED]

It's probably better to use 6.626x10^-34 just so that your final answer is more accurate and precise, but to be safe, use whatever is given on the formula sheet
Wed Oct 04, 2017 9:15 pm
Forum: SI Units, Unit Conversions
Topic: Sig Figs
Replies: 12
Views: 1226

### Re: Sig Figs

The period at the end would have significance if the number ended in zeroes. For example, the number 100 has only one sig fig, while the number 100. has three sig figs because those two zeroes are now captive.
Mon Oct 02, 2017 9:22 pm
Forum: SI Units, Unit Conversions
Topic: Formula Units [ENDORSED]
Replies: 9
Views: 741

### Formula Units[ENDORSED]

Problem E9 asks how many formula units of the compound are present and I was wondering what is a formula unit? Is it the just asking how many molecules there are?