Search found 67 matches
- Thu Mar 14, 2019 6:25 pm
- Forum: General Rate Laws
- Topic: rate laws
- Replies: 6
- Views: 601
Re: rate laws
no the only way to find the rate law is with experimental data, not the equation on its own
- Thu Mar 14, 2019 6:20 pm
- Forum: First Order Reactions
- Topic: Doubling Concentrations
- Replies: 3
- Views: 378
Re: Doubling Concentrations
You can only find orders based on experimental data so this depends on the reaction. If you double the concentration and nothing happens to the rate, this is a zero order reaction. If you double the concentration and the rate also doubles, this is a first order reaction. If you double the concentrat...
- Thu Mar 14, 2019 6:18 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: OH-(aq) in cell diagram
- Replies: 3
- Views: 638
Re: OH-(aq) in cell diagram
I believe you include H+ and OH- but exclude H2O
- Tue Mar 12, 2019 9:45 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: Test #2 4b
- Replies: 2
- Views: 305
Re: Test #2 4b
In cell diagrams it is standard to leave out water but put H+
- Mon Mar 11, 2019 6:39 pm
- Forum: Kinetics vs. Thermodynamics Controlling a Reaction
- Topic: Problem 7A17
- Replies: 2
- Views: 534
Problem 7A17
I am confused in part c of this problem. When I solved for k i used the values from the first row of the table and got 2.85 however the answer is 2.85x10^12. I don't understand the solution for this and why everything is multiplied by .457 when that is nowhere in the problem. Is this because of units?
- Mon Mar 11, 2019 2:36 pm
- Forum: First Order Reactions
- Topic: Integration
- Replies: 3
- Views: 493
Re: Integration
we should probably be familiar with it but it would be very unlikely for him to ask you to do it
- Mon Mar 11, 2019 2:35 pm
- Forum: Zero Order Reactions
- Topic: Zero Order Units
- Replies: 3
- Views: 421
Re: Zero Order Units
it may be easier to understand where the units come from by solving for it rather than memorizing them
- Mon Mar 11, 2019 2:33 pm
- Forum: Zero Order Reactions
- Topic: Graphs
- Replies: 8
- Views: 2141
Re: Graphs
all graphs are linear but the slopes and axis vary
- Mon Mar 11, 2019 2:31 pm
- Forum: General Rate Laws
- Topic: Rate Laws
- Replies: 8
- Views: 833
Re: Rate Laws
One Ta said that we should be familiar with the derivation but it would be very unlikely for it to be asked on the exam
- Sun Feb 24, 2019 7:52 pm
- Forum: Balancing Redox Reactions
- Topic: Oxidation and Reduction?
- Replies: 6
- Views: 802
Re: Oxidation and Reduction?
Reduction means gaining an electron
- Sun Feb 24, 2019 7:51 pm
- Forum: Balancing Redox Reactions
- Topic: Oxidation and Reduction?
- Replies: 6
- Views: 802
- Wed Feb 20, 2019 6:02 pm
- Forum: Non-Equilibrium Conditions & The Reaction Quotient
- Topic: Midterm Question
- Replies: 5
- Views: 838
Midterm Question
One of the questions asks you to comment on the relative stability of reactants and products. How were you suppose to go about solving this problem?
- Wed Feb 20, 2019 5:57 pm
- Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
- Topic: Max Work
- Replies: 5
- Views: 541
Re: Max Work
isothermal reversible reactions
- Wed Feb 20, 2019 5:56 pm
- Forum: Gibbs Free Energy Concepts and Calculations
- Topic: Delta G a state function?
- Replies: 23
- Views: 2736
Re: Delta G a state function?
yes it is a state function, and can be added like enthalpy and calculated in very similar ways
- Wed Feb 20, 2019 5:55 pm
- Forum: General Science Questions
- Topic: Midterm
- Replies: 5
- Views: 847
Re: Midterm
Ka2 is the second deprotonation, when an acid is polyprotic and can give away multiple hydrogens
- Wed Feb 20, 2019 5:54 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: Porous disc explanation?
- Replies: 6
- Views: 595
Re: Porous disc explanation?
I believe that the porous disk serves the same function as the salt bridge
- Wed Feb 13, 2019 4:07 pm
- Forum: Administrative Questions and Class Announcements
- Topic: midterm location
- Replies: 3
- Views: 354
Re: midterm location
yes on his website under midterm information
- Tue Feb 12, 2019 9:42 am
- Forum: Concepts & Calculations Using Second Law of Thermodynamics
- Topic: Entropy Equations
- Replies: 2
- Views: 387
Re: Entropy Equations
Also generally when you use the boltzmann equation it will ask you for either residual or positional entropy rather than just entropy.
- Tue Feb 12, 2019 9:40 am
- Forum: Entropy Changes Due to Changes in Volume and Temperature
- Topic: entropy change
- Replies: 2
- Views: 266
Re: entropy change
You can answer this question by looking at the equation delta s = q/T. If the temperature is higher than the delta s will go down, and vise versa
- Tue Feb 12, 2019 9:39 am
- Forum: Entropy Changes Due to Changes in Volume and Temperature
- Topic: Delta S = nC In (T2/T1)
- Replies: 2
- Views: 360
Re: Delta S = nC In (T2/T1)
You should use the equation that has the n in it. The other one is assuming that if you have an amount other than 1 mole you will account for this and multiply by that as well
- Tue Feb 12, 2019 9:36 am
- Forum: Calculating Work of Expansion
- Topic: 0 work vs no work
- Replies: 4
- Views: 475
Re: 0 work vs no work
I believe no work and 0 work are interchangeable
- Mon Feb 04, 2019 5:37 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Midterm
- Replies: 12
- Views: 2108
Re: Midterm
I also like to redo the tests we have done before the midterm to test myself again and make sure I've learned from my mistakes
- Mon Feb 04, 2019 5:36 pm
- Forum: Thermodynamic Systems (Open, Closed, Isolated)
- Topic: Cup of Tea
- Replies: 17
- Views: 2432
Re: Cup of Tea
you can both change the matter within it (the tea) and transfer energy by holding it and making it warmer or cooler
- Mon Feb 04, 2019 5:33 pm
- Forum: Calculating Work of Expansion
- Topic: Units for Work
- Replies: 2
- Views: 293
Re: Units for Work
I think those are the only units for Joules that you should know about
- Sun Feb 03, 2019 4:46 pm
- Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
- Topic: When to use Quadratic equation
- Replies: 10
- Views: 6423
Re: When to use Quadratic equation
you need to use the quadratic equation when you can not estimate the x in the denominator and must solve it fully by hand
- Sun Feb 03, 2019 4:43 pm
- Forum: Phase Changes & Related Calculations
- Topic: Drawing a heating curve
- Replies: 6
- Views: 1081
Re: Drawing a heating curve
I dont think it matters in terms of units, however it could matter in relativity to other transitions
- Sun Feb 03, 2019 4:41 pm
- Forum: Calculating Work of Expansion
- Topic: What is Work?
- Replies: 5
- Views: 485
Re: What is Work?
work is the process of achieving motion against an opposing force
- Sun Feb 03, 2019 4:40 pm
- Forum: Thermodynamic Systems (Open, Closed, Isolated)
- Topic: open system
- Replies: 8
- Views: 1307
Re: open system
This is the same idea as adding a drop of water into the ocean. A drop of water compared to the volume of the ocean is so small that it will not affect it just like how the whole universe is tiny compared to the beaker
- Wed Jan 23, 2019 9:10 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: 5% Rule
- Replies: 5
- Views: 482
Re: 5% Rule
the 5 percent rule can be used in any calculation of K
- Wed Jan 23, 2019 9:08 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: HW Problem 6D. 15
- Replies: 1
- Views: 212
Re: HW Problem 6D. 15
In the homework problems they sometimes do not put the Ka value in the question but they instead expect you to refer to a chart in the reading that lists many of the Ka values.
- Wed Jan 23, 2019 9:06 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: ICE boxes
- Replies: 5
- Views: 469
Re: ICE boxes
yes, ice boxes work with pressures, molarity, and moles
- Tue Jan 15, 2019 6:24 pm
- Forum: Ideal Gases
- Topic: Homework for week 2 [ENDORSED]
- Replies: 10
- Views: 2946
Re: Homework for week 2 [ENDORSED]
you can always do homework from any relevant section, or whichever section you think will help you the most to practice at the level you are at
- Tue Jan 15, 2019 6:21 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: ICE table
- Replies: 4
- Views: 437
Re: ICE table
Whenever you are dealing with equilibrium and have unknown values, setting up an ice table can be helpful in order to know which parts you are missing as well as how to solve for them
- Tue Jan 15, 2019 6:19 pm
- Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
- Topic: Exothermic vs. Endothermic Reaction
- Replies: 9
- Views: 3162
Re: Exothermic vs. Endothermic Reaction
Yes you should be given delta h in order to determine whether the action is endo( taking in heat) or exo(giving off heat)thermic
- Mon Jan 14, 2019 4:01 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Solids and Liquids in K
- Replies: 4
- Views: 417
Solids and Liquids in K
I understand that solids and liquids should not be included in the calculation of K values, but could someone explain why this is? Why are they insignificant?
- Mon Jan 14, 2019 3:57 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: K changing with temperature [ENDORSED]
- Replies: 3
- Views: 287
K changing with temperature [ENDORSED]
Could someone please explain why Kp changes when temperature is changed but not when the pressure is changed. Thanks
- Mon Jan 14, 2019 3:55 pm
- Forum: Ideal Gases
- Topic: Using Kc or Kp
- Replies: 13
- Views: 930
Re: Using Kc or Kp
both of them always work, you just have to see which information you are given to work with. If you are given moles and liters molarity can be found so Kc can be used but if pressures are given use Kp. Kp is also most commonly with gases
- Fri Dec 07, 2018 10:50 pm
- Forum: Calculating pH or pOH for Strong & Weak Acids & Bases
- Topic: molarity and acid base calcs
- Replies: 1
- Views: 252
molarity and acid base calcs
#6B3 in the textbook edition seven asks about calculating the difference between 200 ml of 0.025M HCL solution and accidentally using a 250 ml flask to make this solution. I know that HCl completely dissociates so calculations with ph can be calculated with the 0.025M. However, i dont understand the...
- Thu Dec 06, 2018 9:20 pm
- Forum: Calculating pH or pOH for Strong & Weak Acids & Bases
- Topic: Ka&Final
- Replies: 1
- Views: 274
Re: Ka&Final
It was mentioned in the lectures briefly and it is also in the assigned reading so I think it would be best to know how to calculate it and what it represents, however in one of the review sessions a TA said he didn't think we would be tested on that so im not sure.
- Thu Dec 06, 2018 9:13 pm
- Forum: Lewis Acids & Bases
- Topic: Strong Acids
- Replies: 6
- Views: 613
Re: Strong Acids
HF is weaker than HI because Iodine is a larger atom and thus it is going to have a weaker bond with hydrogen. Because of this it can give away the hydrogen very easily making it a stronger acid.
- Tue Nov 27, 2018 3:28 pm
- Forum: Lewis Structures
- Topic: Complicated Lewis Structures
- Replies: 3
- Views: 334
Complicated Lewis Structures
I'm having a hard time knowing where to put each element with more complicated Lewis structures. For example, in question 2E19. in the seventh edition it asks for the shape and bond angles of (CH3)2Be. I drew the Lewis structure and it seemed correct. I drew it as H-C-C-Be with two more hydrogens on...
- Mon Nov 26, 2018 7:48 pm
- Forum: Hybridization
- Topic: s-character and bond angle, question 2F15 7th edition
- Replies: 1
- Views: 353
Re: s-character and bond angle, question 2F15 7th edition
This question also states that the bond angle for sp3 is 109.5 and bond angle for sp2 is 120. You can think of it as sp3 being 25 percent s characteristics and 75 percent p characteristics (1:3 ratio), and for sp2 this would be 33.3 percent s characteristic and 66.6 percent p characteristic (1:2 rat...
- Mon Nov 26, 2018 7:41 pm
- Forum: Interionic and Intermolecular Forces (Ion-Ion, Ion-Dipole, Dipole-Dipole, Dipole-Induced Dipole, Dispersion/Induced Dipole-Induced Dipole/London Forces, Hydrogen Bonding)
- Topic: London Forces
- Replies: 2
- Views: 272
Re: London Forces
London dispersion forces are present between all molecules, including polar molecules
- Mon Nov 26, 2018 7:15 pm
- Forum: Administrative Questions and Class Announcements
- Topic: Dipole Moment
- Replies: 3
- Views: 412
Re: Dipole Moment
I believe the arrow should point towards the more electronegative element or you can write the greek letter (not sure what its called) with the positive and negative signifying that it is partially negative or partially positive on each element in the molecule
- Mon Nov 26, 2018 7:11 pm
- Forum: Determining Molecular Shape (VSEPR)
- Topic: Location of Lone Pairs
- Replies: 2
- Views: 208
Re: Location of Lone Pairs
Someone asked this question in my lecture, and Dr. Lavelle showed that because octahedral is completely symmetrical no matter where you put a lone pair is is exactly the same. There is no "top" or "bottom." It was easier to visualize when he showed us with his 3D props, but octah...
- Mon Nov 26, 2018 7:08 pm
- Forum: Hybridization
- Topic: Electron Density and Hybridization
- Replies: 1
- Views: 360
Electron Density and Hybridization
Do the regions of electron density surrounding the atom always match up with the hybridization state? So far I have been doing this and it has been working ex: if there are two regions of electron density it is sp hybridization,3 is sp2 and so on. However in the solution manual for 2F13. (seventh ed...
- Fri Nov 16, 2018 6:06 pm
- Forum: Determining Molecular Shape (VSEPR)
- Topic: dash and wedge diagram
- Replies: 3
- Views: 210
Re: dash and wedge diagram
the dash shows that the atom is farther away from you and the wedge shows that the atom is coming towards you. We do not need to draw the Lewis structures this way it is just helpful to visualize the 3d nature of molecules on a 2d surface. However, if you were to draw them this way, where the dashes...
- Fri Nov 16, 2018 6:01 pm
- Forum: Electron Configurations for Multi-Electron Atoms
- Topic: Bromine Electron Configuration
- Replies: 2
- Views: 2572
Re: Bromine Electron Configuration
I believe the reason you would have received half credit for this answer is because it asked for the full electron configuration. You gave the short hand noble gas version. Your configuration was correct it just should have started at 1s2 etc.
- Fri Nov 16, 2018 5:59 pm
- Forum: Resonance Structures
- Topic: Bond Lengths
- Replies: 2
- Views: 199
Re: Bond Lengths
yes, in this question you were suppose to take the average of the bond lengths. This is because of resonance and how electrons are delocalized and double and single bonds are just used as visual representations for Lewis structures.
- Thu Nov 01, 2018 10:56 pm
- Forum: Lewis Structures
- Topic: central atoms
- Replies: 8
- Views: 737
Re: central atoms
ionization energy and electronegativity do follow the same trends so technically you could use either. Using electronegativity makes more sense to me because if something was extremely electronegative it is not likely to want to share a lot of electrons therefore will not be in the middle
- Mon Oct 29, 2018 10:35 pm
- Forum: Lewis Structures
- Topic: D block valence electrons
- Replies: 2
- Views: 120
D block valence electrons
How do you count valence electrons when an element is in the d block? Do you only count the s block or the d block as well up until that element? If you don't include the d block why is this?
- Mon Oct 29, 2018 10:29 pm
- Forum: Resonance Structures
- Topic: Bond lengths
- Replies: 6
- Views: 400
Re: Bond lengths
you will not need to calculate bond lengths. Professor Lavelle just included this in order to show that Lewis structures have a limitation, and this is why we need to show resonance
- Mon Oct 29, 2018 10:27 pm
- Forum: Lewis Structures
- Topic: Number of Electrons
- Replies: 2
- Views: 98
Re: Number of Electrons
to find the number of valence electrons you count across the period the s and p elements including the element you are looking at. You cant only look at the column numbers because for example carbon is in the 14th column but only has 4 valence electrons
- Sun Oct 28, 2018 11:12 pm
- Forum: Ionic & Covalent Bonds
- Topic: Roman numerals next to element
- Replies: 8
- Views: 6037
Roman numerals next to element
What do roman numerals next to an elements name mean? Ex: in 2A.23 indium(III) sulfide
- Sun Oct 28, 2018 9:36 pm
- Forum: Electronegativity
- Topic: Electronegativity vs Electron Affinity
- Replies: 4
- Views: 36712
Electronegativity vs Electron Affinity
Could someone please explain what the difference is between electronegativity and electron affinity. In lecture they seemed like the same thing and they seem to have the same trends on the periodic table. Can these terms be used interchangeably?
- Sun Oct 28, 2018 9:34 pm
- Forum: Heisenberg Indeterminacy (Uncertainty) Equation
- Topic: Equation
- Replies: 2
- Views: 371
Re: Equation
Whatever is given in the prompt is what should be used because it is about uncertainty, not the same exact measurement each time. It will depend on the situation
- Sun Oct 28, 2018 9:30 pm
- Forum: Lewis Structures
- Topic: Dot's in the Lewis Structure
- Replies: 10
- Views: 2224
Re: Dot's in the Lewis Structure
Just make sure each side has one before pairing them. This applies to hund's rule from quantum mechanics. Same spin electrons should be put in different orbitals before pairing them.
- Sun Oct 21, 2018 2:10 pm
- Forum: Trends in The Periodic Table
- Topic: Homework
- Replies: 10
- Views: 692
Re: Homework
I think this is individual to the person. As long as you do 7 problems you should get full credit, however it may be more helpful to work on the sections you need the most help with
- Sun Oct 21, 2018 2:08 pm
- Forum: *Shrodinger Equation
- Topic: Application of Equation on test
- Replies: 5
- Views: 813
Re: Application of Equation on test
I think having an understanding of the equation and what it is used for will be helpful on the test, rather than knowing how to actually compute it
- Sun Oct 14, 2018 5:42 pm
- Forum: Properties of Electrons
- Topic: Energy emitted by electrons
- Replies: 6
- Views: 517
Re: Energy emitted by electrons
The energy is released as positive electromagnetic radiation (photons)
- Sun Oct 14, 2018 5:39 pm
- Forum: SI Units, Unit Conversions
- Topic: Unit Conversions
- Replies: 3
- Views: 484
Re: Unit Conversions
Personally I just have the very common units memorized such as kilo and milli. You generally memorize these just through using them so much. I would just memorize the units as they come up in the different topics of chem, because there are likely some that won't come up. However if you are intent on...
- Wed Oct 10, 2018 6:11 pm
- Forum: Significant Figures
- Topic: Repeating Decimal
- Replies: 3
- Views: 2472
Re: Repeating Decimal
Using the fraction is a good idea, or just keeping as many decimals as possible until the end result when you can round to the proper number of sig figs. As long as you keep a reasonable amount of decimal places, the end result shouldn't change
- Wed Oct 10, 2018 5:57 pm
- Forum: *Black Body Radiation
- Topic: Black Body
- Replies: 10
- Views: 1295
Re: Black Body
Professor Lavelle said a black body is a hypothetical material that can absorb all frequencies of light (it's not real).
- Mon Oct 08, 2018 11:33 pm
- Forum: Limiting Reactant Calculations
- Topic: How to find the limiting reactant easily and quickly
- Replies: 5
- Views: 13395
Re: How to find the limiting reactant easily and quickly
I've always found that the easiest way to find the LR(but maybe not the fastest) is converting both reactants into one product. You do this by taking the mass given to you of both products and using molar mass and molar ratios to convert into product. You can convert to either moles of grams, both w...
- Thu Oct 04, 2018 8:52 pm
- Forum: Limiting Reactant Calculations
- Topic: Actual yield [ENDORSED]
- Replies: 4
- Views: 391
Re: Actual yield [ENDORSED]
The actual yield is the amount that is produced within a lab setting. The theoretical yield is the amount produced assuming there are no errors, outside reactions etc. The actual yield will typically be given to you in a problem where you must find the percent yield. Here you would divide the actual...
- Thu Oct 04, 2018 8:45 pm
- Forum: Limiting Reactant Calculations
- Topic: Limiting Reactant vs. Reagent??? [ENDORSED]
- Replies: 6
- Views: 757
Re: Limiting Reactant vs. Reagent??? [ENDORSED]
In lecture, Dr. Lavelle said that reactant is used in the hypothetical sense when doing calculations but reagent is when you are referring to a lab setting and actually doing the experiment. For the purposes of the class, because there is no lab component they can be interpreted as the same thing.
- Thu Oct 04, 2018 8:44 pm
- Forum: Significant Figures
- Topic: Significant figures for molar mass
- Replies: 7
- Views: 5258
Re: Significant figures for molar mass
Both molar masses would be adequate and likely get you the same result because the difference is so small. In general the more accurate one would be preferable. You should keep as many sig figs as possible until the very end of the calculation when you have your answer