Search found 63 matches
- Wed Mar 14, 2018 10:34 pm
- Forum: Reaction Mechanisms, Reaction Profiles
- Topic: Finding the slow step
- Replies: 5
- Views: 1155
Re: Finding the slow step
even if the steps of the reaction mechanism aren't explicitly labeled as slow and fast, you should just try writing the rate law for each of the steps and seeing which one matches the experimentally determined rate law for the overall reaction. if the rate law for a step in the mechanism matches the...
- Wed Mar 14, 2018 10:31 pm
- Forum: Reaction Mechanisms, Reaction Profiles
- Topic: Catalyst and Intermediate
- Replies: 5
- Views: 750
Re: Catalyst and Intermediate
catalysts are not used up in the reaction, so you will see the catalyst in BOTH the product and reactant sides of the chemical equations. intermediates, on the other hand, so not appear in the chemical reaction equation.
- Wed Mar 14, 2018 10:30 pm
- Forum: First Order Reactions
- Topic: Determining Reaction Order
- Replies: 5
- Views: 891
Re: Determining Reaction Order
in general, the only way to determine the reaction order is experimentally or via the reaction mechanism.
- Wed Mar 07, 2018 9:13 pm
- Forum: General Rate Laws
- Topic: Rate Laws
- Replies: 3
- Views: 455
Re: Rate Laws
yeah i think for this class we do not need to consider the products' effects on the overall rate law for a reaction. however, if a product DOES have an effect on the overall reaction, then the reaction order for the product concentration would be a negative value in the overall rate law equation.
- Wed Mar 07, 2018 9:10 pm
- Forum: Reaction Mechanisms, Reaction Profiles
- Topic: Finding the intermediate(s)
- Replies: 5
- Views: 675
Re: Finding the intermediate(s)
you should be able to add all of the reaction mechanism (step) reactions together in a Hess's law type manner in order to get the final chemical equation.
- Wed Mar 07, 2018 9:08 pm
- Forum: General Rate Laws
- Topic: Units
- Replies: 11
- Views: 1424
Re: Units
since the unit for rate is mol/(liters*seconds), you'd want to ideally use those units for the calculations.
- Thu Mar 01, 2018 3:40 pm
- Forum: General Rate Laws
- Topic: Finding reaction rate [ENDORSED]
- Replies: 5
- Views: 751
Re: Finding reaction rate [ENDORSED]
use mols. in the book, some problems give amounts of a substance in terms of mmol (millimol), but you should try to convert this amount to mols by multiplying this value by 10^3.
- Thu Mar 01, 2018 3:32 pm
- Forum: First Order Reactions
- Topic: Fractional Order Reactions [ENDORSED]
- Replies: 3
- Views: 1207
Re: Fractional Order Reactions [ENDORSED]
for the purposes of chemistry 14b, only worry about zero order, first order, and second order reactions.
- Thu Mar 01, 2018 3:31 pm
- Forum: General Rate Laws
- Topic: Unique Rate [ENDORSED]
- Replies: 5
- Views: 805
Re: Unique Rate [ENDORSED]
the rate of reduction/formation of a reactant/product divided by its respective stoichiometric coefficient. every single species in a chemical reaction should have the same unique rate.
- Fri Feb 23, 2018 6:49 pm
- Forum: Kinetics vs. Thermodynamics Controlling a Reaction
- Topic: The rate of a reaction
- Replies: 5
- Views: 737
Re: The rate of a reaction
in general, remember that the rate constant k is dependent on temperature and the activation energy of the reaction.
- Fri Feb 23, 2018 6:48 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: Cell Diagrams [ENDORSED]
- Replies: 7
- Views: 839
Re: Cell Diagrams [ENDORSED]
electrodes have to be solid, and if none of the species in a reduction or oxidation reaction are solid (such as when two Fe species have different oxidation numbers but are both in aqueous form), then there must be an inert conductor to relay electrons.
- Fri Feb 23, 2018 6:46 pm
- Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
- Topic: Standard State with Nernst Equation
- Replies: 4
- Views: 567
Re: Standard State with Nernst Equation
only assume that the reaction is not at standard conditions when the prompt itself gives some conditions (such as varying concentrations of reactant/product).
- Fri Feb 23, 2018 6:45 pm
- Forum: Kinetics vs. Thermodynamics Controlling a Reaction
- Topic: signs
- Replies: 6
- Views: 1103
Re: signs
yes, over time, if a reactant is decreasing, then the sign on the rate expression would be negative. however, if a reactant is increasing over time, then the sign on the rate expression would be positive.
- Fri Feb 23, 2018 6:44 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: Galvanic Cells
- Replies: 5
- Views: 653
Re: Galvanic Cells
if we calculate a cell potential and it comes out negative, then we know that the forward process is nonspontaneous while the reverse process IS spontaneous. therefore, the cell can be a galvanic cell going in the reverse (spontaneous) direction. a cell can be considered galvanic if there is some sp...
- Fri Feb 16, 2018 3:22 pm
- Forum: Gibbs Free Energy Concepts and Calculations
- Topic: reversible system
- Replies: 9
- Views: 1160
Re: reversible system
in a nonreversible process, S(system) is most likely not equal to S(surroundings), so S(total) would not be equal to zero.
- Fri Feb 16, 2018 3:21 pm
- Forum: Balancing Redox Reactions
- Topic: Oxidized vs oxidizing agent
- Replies: 5
- Views: 682
Re: Oxidized vs oxidizing agent
Oxidizing agents oxidize the species that it is reacting with, and reducing agents reduce the species it is reacting with
- Fri Feb 16, 2018 2:50 pm
- Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
- Topic: Delta G standard
- Replies: 4
- Views: 654
Re: Delta G standard
I think it's fine to leave it either way.
- Tue Feb 06, 2018 12:36 am
- Forum: Balancing Redox Reactions
- Topic: Salt Bridges?
- Replies: 6
- Views: 619
Re: Salt Bridges?
A common material for salt bridges is KCl. The K+ ions dissociate into the cation tub, and the Cl- ions dissociate into the anion tub to counter charge buildup and allow ion transfer.
- Tue Feb 06, 2018 12:31 am
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: salt bridge
- Replies: 3
- Views: 357
Re: salt bridge
Yes, the salt bridge essentially counters charge buildup as it allows ion transfer. A common salt bridge is a KCl bridge.
- Tue Feb 06, 2018 12:28 am
- Forum: Concepts & Calculations Using Second Law of Thermodynamics
- Topic: Reaction Enthalpy/Entropy vs Enthalpy/Entropy of Formation
- Replies: 2
- Views: 286
Re: Reaction Enthalpy/Entropy vs Enthalpy/Entropy of Formation
Yes, you are correct. Enthalpy of reaction can also be the enthalpy of formation if the reaction is simply the compound being formed from its constituent elements.
- Wed Jan 31, 2018 9:25 pm
- Forum: Entropy Changes Due to Changes in Volume and Temperature
- Topic: The value of Cp
- Replies: 8
- Views: 1510
Re: The value of Cp
Cp for ideal gases is 4R. Cv for ideal gases is 3R. When in doubt, remember that Cp = Cv + R
- Wed Jan 31, 2018 9:24 pm
- Forum: Gibbs Free Energy Concepts and Calculations
- Topic: State functions [ENDORSED]
- Replies: 7
- Views: 732
Re: State functions [ENDORSED]
Heat and work are not state functions; they are considered "path-dependent" functions
- Wed Jan 31, 2018 9:22 pm
- Forum: Concepts & Calculations Using Second Law of Thermodynamics
- Topic: Residual Entropy
- Replies: 1
- Views: 225
Re: Residual Entropy
residual entropy is the entropy of a sample at T=0 (absolute zero) arising from positional disorder surviving at that temperature. Gases tend to have higher residual entropy than solids and liquids because they have smaller dipole moments (leading to less orderly arrangements).
- Tue Jan 23, 2018 11:42 pm
- Forum: Phase Changes & Related Calculations
- Topic: Phase Changes Equations
- Replies: 4
- Views: 580
Re: Phase Changes Equations
Hm refers to the molar enthalpy of the solid or liquid. and yes, i think we need to know to use these delta H for phase change problems.
- Tue Jan 23, 2018 11:40 pm
- Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
- Topic: calorie and Calorie
- Replies: 2
- Views: 239
Re: calorie and Calorie
one Calorie is just 1000 calories!
- Tue Jan 23, 2018 11:40 pm
- Forum: Phase Changes & Related Calculations
- Topic: Names of phase changes
- Replies: 4
- Views: 462
Re: Names of phase changes
condensation, freezing, deposition!
- Tue Jan 23, 2018 12:09 am
- Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
- Topic: Reaction Enthalpy
- Replies: 2
- Views: 326
Re: Reaction Enthalpy
The standard enthalpy of formation is defined as the change in enthalpy when one mole of a substance in the standard state (1 atm of pressure and 298.15 K) is formed from its pure elements under the same conditions.
- Mon Jan 22, 2018 11:56 pm
- Forum: Concepts & Calculations Using First Law of Thermodynamics
- Topic: Work, reversible and irreversible
- Replies: 2
- Views: 249
Re: Work, reversible and irreversible
in reversible expansion, the maximum amount of work is being done by the system because external pressure remains equal to the internal pressure as the gas expands. in irreversible expansion, the external pressure is constant and work is not maximized.
- Mon Jan 22, 2018 11:55 pm
- Forum: Phase Changes & Related Calculations
- Topic: Specific heat capacity
- Replies: 3
- Views: 437
Re: Specific heat capacity
if substance 1 has a smaller specific heat capacity than substance 2, then one gram of substance 1 needs less heat than substance 2 to increase its temperature by 1 degree Celsius.
- Fri Jan 19, 2018 9:19 pm
- Forum: Phase Changes & Related Calculations
- Topic: Closed Systems [ENDORSED]
- Replies: 8
- Views: 1171
Re: Closed Systems [ENDORSED]
Yes the above reply is correct. Recall that in a closed system, energy can be transferred by the system to the surroundings, but matter cannot be transferred by the system to the surroundings. Therefore, the internal energy of the system can be changed by work and heat applied to or by the system to...
- Fri Jan 19, 2018 9:14 pm
- Forum: Concepts & Calculations Using First Law of Thermodynamics
- Topic: Q 8.25
- Replies: 1
- Views: 196
Re: Q 8.25
the qreaction is equal to the qcalorimeter, as related by the equation qreaction = -qcalorimeter. all the heat released from the reaction would be absorbed by the calorimeter.
- Fri Jan 19, 2018 9:12 pm
- Forum: Calculating Work of Expansion
- Topic: What exactly is reversible expansion?
- Replies: 2
- Views: 356
Re: What exactly is reversible expansion?
isothermal reversible expansion describes gas expansion whose direction can be reversed by inducing infinitesimal changes in the internal or external pressure. the pressure on the inside has to be a LITTLE bit more than the pressure on the outside, because the gas would not expand if the pressures w...
- Tue Jan 09, 2018 9:50 pm
- Forum: Concepts & Calculations Using First Law of Thermodynamics
- Topic: Delta U
- Replies: 3
- Views: 506
Re: Delta U
Delta U represents a system's internal energy, or total store of energy in a system. If delta U is zero, then there has been no energy transfer (work or heat) between the system and surroundings.
- Tue Jan 09, 2018 9:47 pm
- Forum: Calculating Work of Expansion
- Topic: Work for reversible vs irreversible process
- Replies: 3
- Views: 405
Re: Work for reversible vs irreversible process
The book quotes, "If the external pressure were to be increased even infinitesimally at any stage of the (ideal gas) expansion, the piston would move in instead of out. Therefore, the work done during a reversible expansion of a gas is the maximum expansion work possible."
- Mon Jan 08, 2018 6:05 pm
- Forum: Administrative Questions and Class Announcements
- Topic: Having the textbook in discussion
- Replies: 2
- Views: 316
Re: Having the textbook in discussion
a PDF is fine for discussion!
- Mon Jan 08, 2018 6:05 pm
- Forum: Phase Changes & Related Calculations
- Topic: Endothermic Reaction
- Replies: 10
- Views: 9436
Re: Endothermic Reaction
imagine the ice cube as the system, and its immediate surroundings as the surroundings. in order for the ice cube to melt, it needs to absorb heat from its surroundings in order to reach its melting point. thus, the phase change is endothermic because the system takes heat from its surroundings (del...
- Tue Dec 05, 2017 5:18 pm
- Forum: Acidity & Basicity Constants and The Conjugate Seesaw
- Topic: Reason for not including water
- Replies: 6
- Views: 727
Re: Reason for not including water
for K (acid/base) constants, we only use concentrations of aqueous or gaseous substances, and leave out pure substances (solid and liquid).
- Tue Dec 05, 2017 5:17 pm
- Forum: Properties & Structures of Inorganic & Organic Bases
- Topic: HCOOH to HCO2^-
- Replies: 1
- Views: 1187
Re: HCOOH to HCO2^-
i think either way is fine, but if you write the formula as HCOO-, you emphasize the point that the carboxyl group in HCOOH has lost a H+ ion.
- Tue Dec 05, 2017 5:15 pm
- Forum: Conjugate Acids & Bases
- Topic: Example 12.1 b
- Replies: 1
- Views: 190
Re: Example 12.1 b
the reaction is O2 + H20 --> 2(OH-), so the book is just saying that OH- is the conjugate acid of O2 without specifying that there are two of them per reaction.
- Wed Nov 29, 2017 12:36 am
- Forum: Hybridization
- Topic: Ch 4 Question 95
- Replies: 1
- Views: 225
Re: Ch 4 Question 95
All "central" atoms (atoms that are bonded to more than one atom) have hybridized orbitals. All "non-central" atoms (only bonded to one atom) do not have hybridized orbitals.
- Wed Nov 29, 2017 12:34 am
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: 11.37
- Replies: 2
- Views: 531
Re: 11.37
You wrote the question wrong. I think you combined portions of 11.37 and 11.38.
Re: 17.29d
I think that was a book typo. The ligands should always be in alphabetical order.
- Wed Nov 29, 2017 12:30 am
- Forum: *Molecular Orbital Theory (Bond Order, Diamagnetism, Paramagnetism)
- Topic: Heteronuclear diatomic species
- Replies: 1
- Views: 376
Re: Heteronuclear diatomic species
We'd just need to label the bonds using the atoms' respective orbitals. For example, for the four single bonds in CCl4, the bond notation would be (C2sp3, Cl3p)
- Tue Nov 21, 2017 11:14 pm
- Forum: *Crystal Field Theory
- Topic: Coordination Complex
- Replies: 3
- Views: 1480
Re: Coordination Complex
ligands definitely impact a change in magnetic properties and color of the transition metal in an aqueous solution. CFT qualitatively describes the strength of metal-ligand bonds and describes how the presence of ligands contributes to the breaking of orbital degeneracy in transition metal complexes
- Tue Nov 21, 2017 11:08 pm
- Forum: Biological Examples
- Topic: Coordination Compound
- Replies: 2
- Views: 501
Re: Coordination Compound
a coordination compound is a neutrally charged compound where one of its ions is a coordination complex, which in turn consists of a central transition metal and a set of attached ligands (bonded by coordinate covalent bonds). these do not relate to hybridization, but we would sometimes need to know...
- Sun Nov 19, 2017 2:37 pm
- Forum: Naming
- Topic: Terminology
- Replies: 4
- Views: 402
Re: Terminology
A ligand is a Lewis base (donates electrons) that forms a coordinate covalent bond with the central transition metal of a coordination complex. They can be either ions or molecules. The number of ligands that can be bonded to a particular transition (d-block) metal is determined by the metal's coord...
- Sun Nov 19, 2017 2:33 pm
- Forum: Coordinate Covalent Bonds
- Topic: coordination compounds
- Replies: 2
- Views: 586
Re: coordination compounds
A coordination complex is a potentially charged complex consisting of a central transition (d-block) metal and its attached ligands, which are Lewis bases that can be either ions or molecules. A coordination compound is a neutral compound in which one of the ions is the coordination complex. A coord...
- Thu Nov 16, 2017 12:24 am
- Forum: Shape, Structure, Coordination Number, Ligands
- Topic: Ligands
- Replies: 2
- Views: 271
Re: Ligands
i think the coordination number just depends on the specific transition metal used, but know that the number of coordinate metal-ligand bonds generally increases as the positive charge on the metal ion becomes larger
- Thu Nov 16, 2017 12:20 am
- Forum: Determining Molecular Shape (VSEPR)
- Topic: VSEPR and Electrons
- Replies: 3
- Views: 524
Re: VSEPR and Electrons
yes we should!
- Fri Nov 10, 2017 11:01 pm
- Forum: Ionic & Covalent Bonds
- Topic: Polar vs. Non-polar
- Replies: 11
- Views: 1001
Re: Polar vs. Non-polar
Only diatomic molecules (ex. H2) have a truly nonpolar bond. If the two elements involved in the bond are different, there's going to be at least a little bit of electronegative difference, which results in a slightly polar covalent bond. Polarity of an entire molecule is different than when we are ...
- Fri Nov 10, 2017 10:58 pm
- Forum: Ionic & Covalent Bonds
- Topic: Ionic & Nonpolar/polar
- Replies: 3
- Views: 1055
Re: Ionic & Nonpolar/polar
Adding on to the previous reply:
Truly nonpolar covalent bonds arise only when the two elements bonded are identical (ex. diatomic molecules). If the two elements are different, then there's always going to be a little bit of electronegativity difference that results in a polar covalent bond.
Truly nonpolar covalent bonds arise only when the two elements bonded are identical (ex. diatomic molecules). If the two elements are different, then there's always going to be a little bit of electronegativity difference that results in a polar covalent bond.
- Thu Nov 02, 2017 12:04 am
- Forum: Trends in The Periodic Table
- Topic: 2.67
- Replies: 5
- Views: 699
Re: 2.67
Electron affinity generally follows the same trend as ionization energy (with some exceptions, such as how carbon has a higher electron affinity than nitrogen).
- Wed Nov 01, 2017 11:55 pm
- Forum: Quantum Numbers and The H-Atom
- Topic: Which Quantum Number Represents What?
- Replies: 3
- Views: 774
Re: Which Quantum Number Represents What?
think of the quantum numbers as a progression of specificity with regards to identifying a particular electron of an atom. n -> l -> ml -> ms energy level of electron -> subshell within the energy level (n) where the electron is located -> the specific orbital within the subshell (l) in which the el...
- Wed Nov 01, 2017 11:51 pm
- Forum: Electron Configurations for Multi-Electron Atoms
- Topic: **HW: 2.55
- Replies: 1
- Views: 319
Re: **HW: 2.55
Hi, I think there's a typo in the book! Or, the book meant the 5th group OF transition metals (group 7 on the periodic table). If we are talking about group 5 on the periodic table however, you are right. Transition metals in group 5 (such as Vanadium) should have the electron configuration (n-1)d^3...
- Mon Oct 23, 2017 10:47 pm
- Forum: Electron Configurations for Multi-Electron Atoms
- Topic: 2.55
- Replies: 2
- Views: 208
Re: 2.55
In lecture, Lavelle covered only the Copper (Cu) and Chromium (Cr) exceptions to the standard electron configuration rules. I don't think you'd need to know any of the other exceptions.
- Mon Oct 23, 2017 10:45 pm
- Forum: Quantum Numbers and The H-Atom
- Topic: The 4 Quantum Numbers [ENDORSED]
- Replies: 5
- Views: 3188
Re: The 4 Quantum Numbers [ENDORSED]
Lets say that we are describing a valence electron in Aluminum. The principle quantum number (n) would be 3, the angular momentum quantum number (l) would be 1 (because 1 signifies the p orbital), the magnetic quantum number (m sub l) would be -1 (because the ml numbers -1 0 and 1 represent the px, ...
- Mon Oct 23, 2017 10:35 pm
- Forum: Administrative Questions and Class Announcements
- Topic: Test 3
- Replies: 2
- Views: 325
Re: Test 3
I'm pretty sure Test 3 will include only 1.6, 1.7, and Chapter 2.
- Tue Oct 17, 2017 1:48 am
- Forum: *Shrodinger Equation
- Topic: Upcoming Test
- Replies: 4
- Views: 619
Re: Upcoming Test
Nope! For this week's test, you just need to know the equations introduced in 1.1-1.5 in the textbook. You do not need to know the Heisenberg uncertainty or Schrodinger equations for the test, but you do need to know the De Broglie equation, atomic spectra equations (such as [v=R((1/nf^2)-(1/ni^2))]...
- Tue Oct 17, 2017 1:43 am
- Forum: Einstein Equation
- Topic: Chapter 1 Question 25 [ENDORSED]
- Replies: 4
- Views: 710
Re: Chapter 1 Question 25 [ENDORSED]
For part B you would need to convert the 5.00 mg of sodium atoms into mols of sodium, convert that mol value into the number of atoms (using Avogradro's number), and then multiply the number of atoms by the energy (J) value you found in part A. For part C you basically do the same thing except you k...
- Wed Oct 11, 2017 9:26 am
- Forum: *Shrodinger Equation
- Topic: Schrodinger Equation and Wave Functions
- Replies: 2
- Views: 549
Re: Schrodinger Equation and Wave Functions
I too was a bit confused with that section, but I think the main idea is the idea of Heisenberg uncertainty and that both the position and momentum of a small object cannot be known at the same time. You're right about everything you mentioned in your post also (the stuff about probability density, ...
- Wed Oct 11, 2017 9:20 am
- Forum: Properties of Light
- Topic: Chapter 1 #3
- Replies: 9
- Views: 982
Re: Chapter 1 #3
λν=c
Just think of this formula when answering questions related to wavelength (λ) and frequency (v). The product of the two must always equal c (3.00 x 10^8), so if either the wavelength or frequency decreases, then the other must increase.
Just think of this formula when answering questions related to wavelength (λ) and frequency (v). The product of the two must always equal c (3.00 x 10^8), so if either the wavelength or frequency decreases, then the other must increase.
- Wed Oct 04, 2017 5:17 pm
- Forum: Empirical & Molecular Formulas
- Topic: Trouble in finding the Molecular Formula
- Replies: 6
- Views: 2334
Re: Trouble in finding the Molecular Formula
Sometimes, when the molar ratios aren't as clean as 1:1:1.33, you're going to have to guess and check and see what coefficient you need to multiply the molar values by.
- Wed Oct 04, 2017 5:04 pm
- Forum: Student Social/Study Group
- Topic: Post All Chemistry Jokes Here
- Replies: 9651
- Views: 3009556
Re: Post All Chemistry Jokes Here
Q: What's a show that cesium and iodine love watching together?
A: CSI
A: CSI