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: 458
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: 1155
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: 859
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: 582
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: 796
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: 1565
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: 1875
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: 786
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: 459
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: 751
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: 709
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: 10062
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: 1150
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: 953
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: 1156
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: 773
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: 1402
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: 533
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: 31405
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: 1931
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: 988
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: 853
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: 680
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: 866
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: 1119
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: 502
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: 361
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: 1393
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: 1838
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
- Topic: Reaction in a Flask
- Replies: 5
- Views: 2124
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: 577
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: 1190
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: 595
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: 348
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: 1034
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: 328
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: 2630
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: 383
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: 8205
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: 733
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: 417
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: 390
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: 1087
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: 757
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: 2107
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: 462
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
- Topic: Wavelengths of Electromagnetic Radiation
- Replies: 4
- Views: 2259
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: 1460
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: 3227
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: 1308
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?