Search found 60 matches
- Sat Mar 16, 2019 8:19 pm
- Forum: Student Social/Study Group
- Topic: Post All Chemistry Jokes Here
- Replies: 9651
- Views: 3998493
Re: Post All Chemistry Jokes Here
What would you do with a dead scientist? Just Barium.
- Sat Mar 16, 2019 8:17 pm
- Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
- Topic: Calculating E*
- Replies: 1
- Views: 450
Re: Calculating E*
You can add them when it is a completed redox reaction where all of the electrons cancel out, but in that problem, the equations were not equivalent, so we could not add the E*'s together.
- Sat Mar 16, 2019 8:15 pm
- Forum: Zero Order Reactions
- Topic: Graphs
- Replies: 13
- Views: 1412
Re: Graphs
You might have to label the axes of the graphs and the slope if given the reaction order.
- Sat Mar 16, 2019 8:12 pm
- Forum: Phase Changes & Related Calculations
- Topic: heat capacity of an object
- Replies: 3
- Views: 631
Re: heat capacity of an object
I believe that is the units for specific heat capacity because it has grams in it.
- Sat Mar 16, 2019 8:09 pm
- Forum: Reaction Mechanisms, Reaction Profiles
- Topic: Approaches to mechanisms
- Replies: 2
- Views: 346
Re: Approaches to mechanisms
They are both just different ways to reach an associated reaction mechanism or rate, but he said not to worry about steady-state, so I would just focus on pre-equilibrium problems. You will get the same answer both ways.
- Sat Mar 16, 2019 1:28 pm
- Forum: First Order Reactions
- Topic: Pseudo 1st order rate laws
- Replies: 2
- Views: 531
Pseudo 1st order rate laws
After you have identified the reactant(s) in large excess, making them negligible in terms of the rate law. Are there any fundamental differences when composing a pseudo-first-order rate law vs. a normal first-order rate law?
- Sat Mar 16, 2019 1:23 pm
- Forum: Gibbs Free Energy Concepts and Calculations
- Topic: Test 2 Q 7 [ENDORSED]
- Replies: 5
- Views: 1016
Re: Test 2 Q 7 [ENDORSED]
Because the outside environment is providing that heat directly, making this a naturally occurring reaction, no extra energy must be put in to make this reaction occur, so it is spontaneous.
- Sat Mar 16, 2019 1:19 pm
- Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
- Topic: applying Le Chatelier's Principle
- Replies: 4
- Views: 803
Re: applying Le Chatelier's Principle
If your determined Q is less than K, then the reaction shifts forward.
- Sat Mar 16, 2019 12:05 pm
- Forum: Reaction Mechanisms, Reaction Profiles
- Topic: Rate constants at equilibrium
- Replies: 5
- Views: 646
Re: Rate constants at equilibrium
The actual rates would be equal, but not the rate constants
- Sat Mar 16, 2019 12:04 pm
- Forum: Arrhenius Equation, Activation Energies, Catalysts
- Topic: Catalysts
- Replies: 4
- Views: 673
Re: Catalysts
I would assume no because catalysts increase a rate, so including it in the rate would not make sense
- Fri Mar 15, 2019 3:07 pm
- Forum: Second Order Reactions
- Topic: 7th edition 7B.13
- Replies: 3
- Views: 768
Re: 7th edition 7B.13
First, you find k using the second order half-life equation, then you isolate t in the integrated rate law to solve for it. Because we already have the ratio of initial to final concentrations, you can use that to relate the two fractions together, making [A]t the same as [A]0. You can then subtract...
- Fri Mar 15, 2019 12:08 pm
- Forum: First Order Reactions
- Topic: Half-life Formulas
- Replies: 2
- Views: 579
Half-life Formulas
I know we have to know how to derive the integrated rate laws, but will we have to solve for the half-life formulas as well? or will we just have to recognize which half-life formula is for which order?
- Fri Mar 15, 2019 12:05 pm
- Forum: General Rate Laws
- Topic: Determining the order
- Replies: 3
- Views: 558
Re: Determining the order
You would have to be given enough information to calculate it, specific units that go along with a specific order, or data to graph.
- Fri Mar 15, 2019 12:03 pm
- Forum: Arrhenius Equation, Activation Energies, Catalysts
- Topic: calculating A in Arrhenius equation
- Replies: 2
- Views: 408
Re: calculating A in Arrhenius equation
From the practice problems and textbook, I think it is safe to assume they will give us A in a chart or just in the question of the problem.
- Wed Feb 27, 2019 10:06 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: Water in Cell Diagrams
- Replies: 2
- Views: 426
Water in Cell Diagrams
Should water be included in cell diagrams? If not, y?
- Mon Feb 25, 2019 10:48 pm
- Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
- Topic: Redox Reaction Oxidizing Agent
- Replies: 1
- Views: 303
Redox Reaction Oxidizing Agent
Is the oxidizing agent in a redox reaction always the couple that has a higher standard cell potential (being that it is more positive on the table)?
- Mon Feb 25, 2019 8:23 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: Cell Diagrams Example 14.4 in 6th Edition Book
- Replies: 2
- Views: 826
Cell Diagrams Example 14.4 in 6th Edition Book
Can anyone explain to me how they came up with the reduction and oxidation half-reactions for the cell diagram Pt(s)|H2(g)|HCl(aq)|Hg2Cl2(aq)|Hg(l)? I am confused at how they got Cl- as a separate component when it is not in the cell diagram and why the coefficient for H2(g) becomes 1/2 in the oxida...
- Mon Feb 25, 2019 7:53 pm
- Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
- Topic: Gibbs Units
- Replies: 2
- Views: 434
Gibbs Units
When calculating Gibbs free energy with the Delta G = -nFE equation and you are canceling units, is it necessary to change volts to J.C^-1 or can we keep the final answer in C.V?
- Mon Feb 25, 2019 7:52 pm
- Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
- Topic: Gibbs At Equilibrium
- Replies: 3
- Views: 545
Gibbs At Equilibrium
What will Gibbs free energy be when the reaction is at equilibrium?
- Mon Feb 25, 2019 7:51 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: Salt Bridge
- Replies: 2
- Views: 328
Salt Bridge
Do galvanic cells have to have a salt bridge?
- Mon Feb 25, 2019 7:51 pm
- Forum: Balancing Redox Reactions
- Topic: Balancing Oxygens vs. Hydrogens
- Replies: 1
- Views: 340
Balancing Oxygens vs. Hydrogens
*When balancing redox reactions, is it necessary to balance the oxygen atoms before the hydrogen ones?
- Mon Feb 11, 2019 7:54 pm
- Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
- Topic: 7th Edition 4.7
- Replies: 1
- Views: 234
7th Edition 4.7
For part c, the internal energy change of formation is the change in enthalpy of formation plus work. Why is this? I'm just confused on if the enthalpy of formation is replacing heat in this equation?
- Sun Feb 10, 2019 4:42 pm
- Forum: Thermodynamic Definitions (isochoric/isometric, isothermal, isobaric)
- Topic: Constant Pressue
- Replies: 3
- Views: 530
Constant Pressue
If the problem does not note a pressure change can we assume that no change in pressure was made?
- Sun Jan 20, 2019 1:59 pm
- Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
- Topic: 7th Edition 6B #9
- Replies: 1
- Views: 329
7th Edition 6B #9
When I fill in the table to find the [OH-] using the already given [H3O+] I keep getting 6.7x10^-14, but the solutions manual says the answer is 1.5x10^-14. I am just dividing 10^-14 by the given molarity (1.5). This is for the i part of the table. Can anyone explain what I am doing wrong?
- Sat Jan 19, 2019 3:01 pm
- Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
- Topic: Changes in K
- Replies: 4
- Views: 478
Changes in K
Does anyone know what actually changes K? I know changing the reaction and the temperature changes it, but does anything else change it?
- Sat Jan 19, 2019 2:52 pm
- Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
- Topic: Partial Pressure and Moles
- Replies: 3
- Views: 472
Partial Pressure and Moles
When increasing and decreasing partial pressure and concentration in a chemical equilibrium reaction, does the number of moles matter? or do they only matter when considering increasing or decreasing pressure on the whole system?
- Sun Jan 13, 2019 3:00 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Module Part 2 Question
- Replies: 2
- Views: 260
Module Part 2 Question
Can anyone explain what I am doing wrong on this question: 29. A researcher fills a 1.00 L reaction vessel with 1.84 x 10-4 mol of BrCl gas and heats it to 500 K. At equilibrium, only 18.3 % of the BrCl gas remains. Calculate the equilibrium constant, assuming the following reaction is taking place....
- Wed Jan 09, 2019 10:10 am
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: 7th edition 5G.5
- Replies: 3
- Views: 253
Re: 7th edition 5G.5
Here's what I could gather from looking at the solutions manual. We first have to recognize that the decomposition of X2 has an equilibrium equation of X2 <-> 2X, making the partial pressure ratio 1:2. Since the initial pressure is 0.10 bar, we must multiply it by the fraction of molecules that have...
- Wed Jan 09, 2019 9:50 am
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: 5G 1c 7th Edition
- Replies: 1
- Views: 290
5G 1c 7th Edition
Clarity on how pressure vs. temperature affects the K value?
- Wed Jan 09, 2019 9:24 am
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Kc vs. Kp
- Replies: 7
- Views: 695
Re: Kc vs. Kp
Just for further clarification, when there are all gases, so you use Kp and partial pressure, the format for K would be Kp = and then use parenthesis with P and the molecule as the subscript, but for Kc and concentrations, the format for K would be Kc= and then use brackets?
- Sat Dec 08, 2018 1:45 pm
- Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
- Topic: Energy Levels
- Replies: 2
- Views: 713
Energy Levels
When an electron jumps from a lower energy level to a higher energy level does it gain or lose energy?
- Sat Dec 08, 2018 1:43 pm
- Forum: Properties & Structures of Inorganic & Organic Acids
- Topic: Ligands
- Replies: 6
- Views: 1058
Ligands
I'm not sure where to put this so I'm putting it here.
Can anyone explain to me what a porpfyrin ligand is? Might be spelled wrong, but still confusing!
Can anyone explain to me what a porpfyrin ligand is? Might be spelled wrong, but still confusing!
- Sat Dec 08, 2018 1:40 pm
- Forum: DeBroglie Equation
- Topic: Calculating Wavelength of Ejected Electron
- Replies: 1
- Views: 503
Calculating Wavelength of Ejected Electron
If anyone has the same test #2 as me, I am confused on question 4c. It says to calculate the wavelength of the ejected electron, which I assumed would just be de Broglie (wavelength = h/mv). However, when I did that, I got the answer 3.64 x 10-10 m, but my TA wrote the 7.09 x 10-7 m as the write ans...
- Sat Dec 08, 2018 1:29 pm
- Forum: Quantum Numbers and The H-Atom
- Topic: Determining Amount of Electrons From Quantum Numbers
- Replies: 4
- Views: 6147
Re: Determining Amount of Electrons From Quantum Numbers
A really simple way to think about this is just knowing that the angular quantum number (l) specifies the subshells. If only n is given you can just use the formula 2(n)^2 to determine the number of electrons. If l is given it can mean multiple things. If l = 0, it is the s orbital, which has 1 subs...
- Fri Dec 07, 2018 10:17 am
- Forum: Interionic and Intermolecular Forces (Ion-Ion, Ion-Dipole, Dipole-Dipole, Dipole-Induced Dipole, Dispersion/Induced Dipole-Induced Dipole/London Forces, Hydrogen Bonding)
- Topic: Boiling Point
- Replies: 6
- Views: 2628
Re: Boiling Point
Does H2Se have dipole-dipole forces as well as London dispersion forces?
- Thu Dec 06, 2018 10:08 pm
- Forum: Amphoteric Compounds
- Topic: Amphoteric vs Amphiprotic
- Replies: 4
- Views: 870
Re: Amphoteric vs Amphiprotic
Can someone provide examples of compounds that are both amphoteric and amphiprotic and some that are one or the other? I understand what they are as defined terms, but some examples would be very helpful.
- Thu Dec 06, 2018 6:18 pm
- Forum: Naming
- Topic: Knowing oxidation states
- Replies: 11
- Views: 969
Re: Knowing oxidation states
Is the oxidation state the same as an oxidation number? or do the oxidation numbers of each element determine the compound's state?
- Thu Dec 06, 2018 4:43 pm
- Forum: Bronsted Acids & Bases
- Topic: Electronegativity and Acidity
- Replies: 1
- Views: 364
Electronegativity and Acidity
The book says the greater the electronegativity of A, the stronger the acid HA is, however, F if the most electronegative element, but the book also says that HF is the weakest acid. Can someone explain why?
- Thu Dec 06, 2018 4:39 pm
- Forum: Bronsted Acids & Bases
- Topic: Zinc Nitrate
- Replies: 2
- Views: 435
Zinc Nitrate
If I am making zinc nitrate what base do I use?
- Thu Dec 06, 2018 3:41 pm
- Forum: Identifying Acidic & Basic Salts
- Topic: Acids and Bases
- Replies: 4
- Views: 789
Re: Acids and Bases
Can someone differentiate when to use the Lewis acid definition of an acid vs. the Bronsted Lowry definition?
- Mon Dec 03, 2018 11:57 pm
- Forum: Bronsted Acids & Bases
- Topic: Comparing pH levels
- Replies: 3
- Views: 295
Re: Comparing pH levels
I think there is a good probability of that showing up on the final mostly because he explicitly mentioned it in class. Also, it is really good information to know for checking your answer and comparing relative acidity.
- Mon Dec 03, 2018 11:53 pm
- Forum: Bronsted Acids & Bases
- Topic: Strong Acids
- Replies: 4
- Views: 347
Re: Strong Acids
That helps! my only issue is if we are unsure of the Ka. Should we just go off of electronegativity and size of the atom? This still confuses me a little bit.
- Mon Dec 03, 2018 11:51 pm
- Forum: SI Units, Unit Conversions
- Topic: bond angles
- Replies: 5
- Views: 1203
Re: bond angles
Does anyone know if there are ways to figure out if the bond angles are not the standard 90, 109.5, 120, 180 and how we would denote on the final if they were more or less than that?
- Sun Nov 25, 2018 3:52 pm
- Forum: Determining Molecular Shape (VSEPR)
- Topic: 2.45
- Replies: 2
- Views: 232
2.45
Can anyone explain 2.45 to me? I understand how to get the lewis structure and what is a sigma and pi bond, but why is the C hybridization 2sp2 for a sigma bond and 2p for a pi bond?
- Sun Nov 25, 2018 2:43 pm
- Forum: Hybridization
- Topic: Hybridization and Hybrid Orbitals
- Replies: 4
- Views: 560
Hybridization and Hybrid Orbitals
Can someone please explain to me the difference between hybridization of the central atom and the hybrid orbitals used by the central atom? (If there is a difference?)
- Sun Nov 25, 2018 2:42 pm
- Forum: Hybridization
- Topic: SeF3+
- Replies: 5
- Views: 8469
SeF3+
Does anyone know the lewis structure and geometric shape for SeF3+?
- Sun Nov 25, 2018 2:40 pm
- Forum: Determining Molecular Shape (VSEPR)
- Topic: Sigma and Pi bonds
- Replies: 6
- Views: 688
Re: Sigma and Pi bonds
When determining the number of sigma and pi bonds in a molecule, do you have to put them only for the most common resonance structure? (Referring to homework problem 2F #3 for the SO2 lewis structures)
- Sun Nov 25, 2018 2:39 pm
- Forum: Hybridization
- Topic: Hybridization Orbitals
- Replies: 2
- Views: 443
Re: Hybridization Orbitals
When describing how a hybrid orbital is oriented on the test, would it be necessary to put the degrees? (Ex: 120 degrees for trigonal planar)
- Sun Nov 04, 2018 5:47 pm
- Forum: Octet Exceptions
- Topic: What are the octet exceptions?
- Replies: 9
- Views: 1156
Re: What are the octet exceptions?
I understand why H is an exception to the octet rule, but can someone explain why Hi, Le, and Be are as well?
- Sat Nov 03, 2018 8:45 pm
- Forum: Electron Configurations for Multi-Electron Atoms
- Topic: S-orbital and D-orbital
- Replies: 2
- Views: 450
Re: S-orbital and D-orbital
Would the configuration of Ni as [Ar]3d84s2 be considered wrong on a test? Is it always preferred to fill the shell in order to make it more stable?
- Fri Nov 02, 2018 2:38 pm
- Forum: Electron Configurations for Multi-Electron Atoms
- Topic: Valence Electrons
- Replies: 3
- Views: 15417
Re: Valence Electrons
This really cleared things up for me! Does this mean that zinc has 12 valence electrons?
- Fri Nov 02, 2018 2:29 pm
- Forum: Ionic & Covalent Bonds
- Topic: Valence electron
- Replies: 4
- Views: 343
Re: Valence electron
I'm still slightly confused. The solutions manual says that Mn has 7 valence electrons, but it is in the 7th group, so you're saying that it would have 9?
- Fri Nov 02, 2018 2:26 pm
- Forum: Lewis Structures
- Topic: Drawing Lewis Structures
- Replies: 14
- Views: 2114
Re: Drawing Lewis Structures
Can anyone confirm my understanding of ionic and covalent bonding in regards to lewis structures? I believe that when you have an ion you use ionic bonding with the brackets and if the atoms are a neutral charge you use covalent bonding? Is there anything more specific to drawing these diagrams?
- Sun Oct 28, 2018 8:35 pm
- Forum: SI Units, Unit Conversions
- Topic: formula units [ENDORSED]
- Replies: 69
- Views: 33204
Re: formula units [ENDORSED]
I was confused about this as well. Thank you so much for the clarification! Does anyone know in what depth we need to know these bonds for the test? (just in terms of specific elements or molecules or even just sketching them out)
- Thu Oct 25, 2018 10:39 am
- Forum: Heisenberg Indeterminacy (Uncertainty) Equation
- Topic: Everyday objects and Heisenberg's uncertainty
- Replies: 3
- Views: 1641
Re: Everyday objects and Heisenberg's uncertainty
So, based on this response, it would be No because the uncertainties of a large moving object are small?
- Sat Oct 20, 2018 4:36 pm
- Forum: Properties of Light
- Topic: energy required to remove an electron [ENDORSED]
- Replies: 7
- Views: 3933
Re: energy required to remove an electron [ENDORSED]
Yeah if you do the full problem out (by dividing Avogadro's number) you end up with 2.501 x 10^-19 J of energy as the work function, which after plugging it in to get the frequency of incident light gets you 6.78 x 10^14 Hz!
- Sat Oct 20, 2018 3:55 pm
- Forum: Properties of Light
- Topic: Planck's constant
- Replies: 5
- Views: 530
Re: Planck's constant
Will I ever have a need to convert Hertz to Joules? or would they stay separate?
- Sun Oct 07, 2018 3:26 pm
- Forum: Empirical & Molecular Formulas
- Topic: When to double moles
- Replies: 13
- Views: 1077
Re: When to double moles
Just double checking that if I had 1.1 of something rounding to 1 would be ok, even though it is more than 0.05?
- Sun Oct 07, 2018 3:21 pm
- Forum: Significant Figures
- Topic: All students read this sig fig post [ENDORSED]
- Replies: 170
- Views: 37595
Re: All students read this sig fig post [ENDORSED]
Can someone help me with a quick review of zeros in sig figs? I always get confused as to which zeros count as significant and which ones do not.
- Sun Oct 07, 2018 3:17 pm
- Forum: General Science Questions
- Topic: Rusty on High School Chem [ENDORSED]
- Replies: 347
- Views: 483346
Re: Rusty on High School Chem [ENDORSED]
Hi Guys!!
I definitely recommend making quizlets with basic SI units, conversions, and terms so that you can drill yourself on basic stuff before it gets too confusing!
I definitely recommend making quizlets with basic SI units, conversions, and terms so that you can drill yourself on basic stuff before it gets too confusing!