Search found 62 matches
- Fri Mar 16, 2018 7:26 am
- Forum: Method of Initial Rates (To Determine n and k)
- Topic: Test 3 question 5
- Replies: 3
- Views: 570
Re: Test 3 question 5
Given the instantaneous rate of the reaction. 2.7 x 10^2 andninitial mass of 1.8g confined to a 750ml vessel, what is the rate constant of this reaction. From the previous questions we have they the rate equation is rate=k[h2o][o2]^2
- Thu Mar 15, 2018 4:08 pm
- Forum: Method of Initial Rates (To Determine n and k)
- Topic: Test 3 question 5
- Replies: 3
- Views: 570
Test 3 question 5
Hey could anyone help me work through question 5 on test 3 i got the n, and the standard e correct but not the last question where you have to find the rate constant
- Wed Mar 14, 2018 1:42 pm
- Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
- Topic: Is enthalpy a state function?
- Replies: 12
- Views: 2178
Re: Is enthalpy a state function?
Yes enthaply is a state function!
- Wed Mar 14, 2018 1:40 pm
- Forum: Reaction Mechanisms, Reaction Profiles
- Topic: Slow steps and intermediates
- Replies: 2
- Views: 325
Re: Slow steps and intermediates
I agree with the above answer the slow step is the one with the matching rate law
- Wed Mar 14, 2018 1:37 pm
- Forum: Administrative Questions and Class Announcements
- Topic: Minimum for a B-?
- Replies: 3
- Views: 553
Re: Minimum for a B-?
I believe that everything between a 50-79% is a C and then regular percentages above that for B and C
- Tue Mar 06, 2018 9:32 am
- Forum: Kinetics vs. Thermodynamics Controlling a Reaction
- Topic: Kinetics Test
- Replies: 2
- Views: 535
Re: Kinetics Test
My TA said the same thing about hw problemss I believe it’s material until last Friday’s lecture
- Tue Mar 06, 2018 9:25 am
- Forum: Method of Initial Rates (To Determine n and k)
- Topic: Rate Constant Calculations [ENDORSED]
- Replies: 3
- Views: 592
Re: Rate Constant Calculations [ENDORSED]
You also need time!
- Tue Mar 06, 2018 9:23 am
- Forum: General Rate Laws
- Topic: Average vs. Unique Average Reaction Rate
- Replies: 1
- Views: 238
Re: Average vs. Unique Average Reaction Rate
I think the best explanation for this is the endorses chem_mod post that you can access in the announcements page!
- Tue Mar 06, 2018 9:10 am
- Forum: First Order Reactions
- Topic: 15.25
- Replies: 4
- Views: 601
Re: 15.25
Got it this makes sense now!
- Sun Mar 04, 2018 5:25 pm
- Forum: First Order Reactions
- Topic: 15.25
- Replies: 4
- Views: 601
15.25
Can someone explain where we get the reaction A= e^-kt * ao
- Wed Feb 28, 2018 1:28 pm
- Forum: Kinetics vs. Thermodynamics Controlling a Reaction
- Topic: Hw 15.1 [ENDORSED]
- Replies: 7
- Views: 1061
Re: Hw 15.1 [ENDORSED]
Yes I also agree! You use the coefficients and divide or multiply accordingly
- Wed Feb 28, 2018 1:25 pm
- Forum: First Order Reactions
- Topic: Deriving these Equations
- Replies: 7
- Views: 743
Re: Deriving these Equations
I believe it needs to explicitly show [A]o or else we are unsure what order concentration is given
- Wed Feb 28, 2018 1:13 pm
- Forum: Kinetics vs. Thermodynamics Controlling a Reaction
- Topic: Test 3
- Replies: 2
- Views: 368
Test 3
Does anyone know how much of kinetics (ch 15) will be on the test week 9?
- Tue Feb 20, 2018 8:56 pm
- Forum: Balancing Redox Reactions
- Topic: 3A Determining reduction vs oxidation
- Replies: 4
- Views: 576
3A Determining reduction vs oxidation
I am having trouble identifying the reducing and oxidizing agent in equations such as 3a in the homework?
- Tue Feb 20, 2018 8:54 pm
- Forum: Balancing Redox Reactions
- Topic: 14.3 (a)
- Replies: 3
- Views: 503
Re: 14.3 (a)
No there is a -2 charge on both sides of the equation.
reactants: 2- from s2o3
products: 4- from so4, 10+ from h, 8e-
reactants: 2- from s2o3
products: 4- from so4, 10+ from h, 8e-
- Tue Feb 20, 2018 8:50 pm
- Forum: Balancing Redox Reactions
- Topic: 14.1 D
- Replies: 3
- Views: 552
Re: 14.1 D
This is because we multiply the half reactions with a coefficient in order to cancel out the electrons on both sides.
- Thu Feb 15, 2018 3:14 pm
- Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
- Topic: What does E stand for?
- Replies: 3
- Views: 1945
Re: What does E stand for?
E is cell potential which will not be covered on the midterm.
- Thu Feb 15, 2018 3:13 pm
- Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
- Topic: Hess's Law
- Replies: 5
- Views: 687
Re: Hess's Law
Yes you can! You don't call it hesss law but the same theory is used to make similar calculations
- Thu Feb 15, 2018 3:11 pm
- Forum: Calculating Work of Expansion
- Topic: Calculating work for winter 2013 midterm 4.B.
- Replies: 4
- Views: 611
Re: Calculating work for winter 2013 midterm 4.B.
What equation we use is based on if the equation is reversible or not. If it is reversible we use the equation with R in it and if it is irreversible we use the equation with w=-pextdeltaV
- Wed Feb 14, 2018 12:53 pm
- Forum: Administrative Questions and Class Announcements
- Topic: Midterm format
- Replies: 2
- Views: 405
Re: Midterm format
Yes, all of dr. lavelles tests follow the same format, except the midterm is longer than the tests and the final is even longer than that.
- Mon Feb 12, 2018 9:56 pm
- Forum: Concepts & Calculations Using First Law of Thermodynamics
- Topic: Test #7
- Replies: 7
- Views: 884
Re: Test #7
Can someone please show me their work with the numbers for this no matter what I do i keep getting the wrong answer?
- Wed Feb 07, 2018 1:25 pm
- Forum: Gibbs Free Energy Concepts and Calculations
- Topic: 11.19
- Replies: 1
- Views: 291
Re: 11.19
I believe we the question usually specifies if it is not calcite. (like they do with diamond when carbon is in the question).
- Wed Feb 07, 2018 1:21 pm
- Forum: Phase Changes & Related Calculations
- Topic: Endothermic/exothermic
- Replies: 4
- Views: 1180
Endothermic/exothermic
On the first quiz there was a question regarding heat exchange and release I had trouble understanding if you use endothermic/exothermic to answer these or just common knowledge such as the sun heats up water during evaporation therefore there is heat exchange.
- Wed Feb 07, 2018 1:19 pm
- Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
- Topic: quiz question #7
- Replies: 1
- Views: 311
quiz question #7
Can someone help me work through #7 on quiz 1 the one with five steps of enthalpies we must calculate.
- Wed Jan 31, 2018 2:57 pm
- Forum: Gibbs Free Energy Concepts and Calculations
- Topic: Class Example
- Replies: 6
- Views: 567
Re: Class Example
Dr. Lavelle continued to explain that the final answer is anything higher than 333k will result in a spontaneous reaction in the forward direction.
- Wed Jan 31, 2018 2:52 pm
- Forum: Thermodynamic Systems (Open, Closed, Isolated)
- Topic: Can a system exchange matter but not energy?
- Replies: 4
- Views: 454
Re: Can a system exchange matter but not energy?
I also think this is not possible because if a system exchanges matter the energy will also exchange. Therefore if a system is exchanging matter I think it always classified as a open system.
- Wed Jan 31, 2018 2:50 pm
- Forum: Administrative Questions and Class Announcements
- Topic: Midterm topics
- Replies: 1
- Views: 316
Midterm topics
Does anyone know what the last chapter on the midterm will be?
- Tue Jan 23, 2018 3:53 pm
- Forum: Administrative Questions and Class Announcements
- Topic: Homework Turn In for Week 3
- Replies: 2
- Views: 227
Re: Homework Turn In for Week 3
My TA asked us to move on to chapter 9 he said if you can't do all chapter 9 do half chapter 8 and half chapter 9
- Tue Jan 23, 2018 3:48 pm
- Forum: Administrative Questions and Class Announcements
- Topic: Week 3 Test Topic is endorsed
- Replies: 37
- Views: 4769
Re: Week 3 Test Topic is endorsed
After going through the homework I noticed numbers 3-13,25-31, and 47-49 all have to do with calculating work or internal energy. I would suggest studying all the other homework problems specifically for this upcoming test. Can anyone else confirm that these problems aren't going to be tested on? I...
- Tue Jan 23, 2018 3:33 pm
- Forum: Phase Changes & Related Calculations
- Topic: HW 8.1
- Replies: 2
- Views: 275
HW 8.1
Can someone explain to me how coffee in a thermos is an isolated system? Doesn't heat still escape?
- Thu Jan 18, 2018 11:00 am
- Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
- Topic: Specific Heat Capacity
- Replies: 5
- Views: 2030
Re: Specific Heat Capacity
I agree with the responses above that this is just a convention to allow us to do the calculations for solutions.
- Thu Jan 18, 2018 10:58 am
- Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
- Topic: Bond Enthalpies
- Replies: 5
- Views: 502
Re: Bond Enthalpies
This makes sense now, thank you all for the responses! I was having trouble grasping the concept earlier.
- Thu Jan 18, 2018 10:57 am
- Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
- Topic: 8.29 heat capacity
- Replies: 3
- Views: 364
8.29 heat capacity
Can someone explain to me why heat capacity increases as molecular complexity increases?
- Wed Jan 10, 2018 2:50 pm
- Forum: Phase Changes & Related Calculations
- Topic: Heat and Phase Transition
- Replies: 3
- Views: 384
Heat and Phase Transition
Can someone explain how a sample's temp remains constant during phase transitions?
- Wed Jan 10, 2018 2:49 pm
- Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
- Topic: Bond Enthalpies
- Replies: 5
- Views: 502
Bond Enthalpies
Can someone help me figure out for the bond enthalpies method why the reactants have positive enthalpies and the products negative?
- Wed Jan 10, 2018 2:43 pm
- Forum: Phase Changes & Related Calculations
- Topic: Endo and Exothermic Ways to Remember
- Replies: 28
- Views: 11428
Re: Endo and Exothermic Ways to Remember
I use the prefixes, Ex->exiting heat, en-> entering heat or needing heat.
- Fri Dec 08, 2017 10:42 pm
- Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
- Topic: Le chateliers principle
- Replies: 3
- Views: 538
Le chateliers principle
Can someone please explain this principle to me and how we are supposed to apply it?
Re: Naming
Could someone help me name and draw the Lewis structure for the test problem [HgF2(OH2)2]+
- Mon Dec 04, 2017 11:12 am
- Forum: Properties & Structures of Inorganic & Organic Acids
- Topic: Using The Equilibrium Arrow
- Replies: 5
- Views: 3262
Re: Using The Equilibrium Arrow
Yes I agree with the post above! Only use the equilibrium arrow when you are working with weak acids and bases.
- Mon Dec 04, 2017 11:11 am
- Forum: Non-Equilibrium Conditions & The Reaction Quotient
- Topic: ICE table question
- Replies: 5
- Views: 11776
Re: ICE table question
Always remember to keep it consistent! If one reactant is decreasing by X then all of them should be decreasing and visa versa!
- Mon Dec 04, 2017 11:07 am
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Question 11.7
- Replies: 4
- Views: 572
Re: Question 11.7
Thank you so much! I just wasn't understanding why we originally count out of 17 but now I get it!
- Thu Nov 30, 2017 12:07 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Question 11.7
- Replies: 4
- Views: 572
Re: Question 11.7
Can someone help me out with part C of 11.7, I don’t really understand why the answer book is out of 17?
- Tue Nov 28, 2017 6:30 pm
- Forum: Sigma & Pi Bonds
- Topic: Sigma and pi
- Replies: 12
- Views: 1558
Re: Sigma and pi
Is the single sigma bond always the "center" bond?
- Tue Nov 28, 2017 5:53 pm
- Forum: Naming
- Topic: Naming polydentates
- Replies: 1
- Views: 202
Re: Naming polydentates
I believe you name it based on the exact type that the ligand is acting as in the specific polydentate.
- Mon Nov 20, 2017 10:21 am
- Forum: Electronegativity
- Topic: Electroegativity
- Replies: 9
- Views: 1255
Re: Electroegativity
In my opinion knowing the trend is the easiest way to remember the electronegativity of different elements. An easy trick for that is just learning the atomic radius trend and knowing that everything else is the opposite! The only exception there is for the last group of elements because their valen...
- Mon Nov 20, 2017 10:04 am
- Forum: Determining Molecular Shape (VSEPR)
- Topic: Are moleculary geometry and shape different? [ENDORSED]
- Replies: 3
- Views: 582
Re: Are moleculary geometry and shape different? [ENDORSED]
I believe they are different things. Molecular shape is the 3D structure of a molecule which includes the bond angles and the orientation of the different atoms. On the other hand molecular geometry is the name of the shape for example trigonal planar or tetrahedral.
- Mon Nov 13, 2017 10:47 am
- Forum: Determining Molecular Shape (VSEPR)
- Topic: Homework week 7
- Replies: 1
- Views: 193
Homework week 7
Does anyone know if the homework from week 7 is from chapter 4 or chapter 17?
- Mon Nov 13, 2017 10:44 am
- Forum: Determining Molecular Shape (VSEPR)
- Topic: Memorization
- Replies: 5
- Views: 590
Re: Memorization
Personally, I️ think memorizing what type of shape a certain number atom molecule is and the angles associated with that is the quickest way to learn! But once you know it for a single 3 atom molecule you know it for all 3 atom molecules!
- Mon Nov 13, 2017 10:43 am
- Forum: Formal Charge and Oxidation Numbers
- Topic: A tip for calculating formal charge [ENDORSED]
- Replies: 2
- Views: 3208
Re: A tip for calculating formal charge [ENDORSED]
I️ agree with this tip! It helps to prevent errors in calculation which can ruin your Lewis structure
- Mon Nov 06, 2017 11:10 am
- Forum: Administrative Questions and Class Announcements
- Topic: Homework for this week [ENDORSED]
- Replies: 2
- Views: 325
Re: Homework for this week [ENDORSED]
The homework for this week is ch 4! However I’m not sure how the discussions on Friday turn in the homework!
- Mon Nov 06, 2017 11:07 am
- Forum: Electron Configurations for Multi-Electron Atoms
- Topic: unpaired electrons [ENDORSED]
- Replies: 3
- Views: 400
Re: unpaired electrons [ENDORSED]
Determining whether or not electrons are paired can be done using an Aufbau diagram if every electron has a pair for example 2 arrows on every line than all electrons are paired! An easy trick is if the number of electrons in each sub shell is at the maximum then all electrons are paired.
- Mon Nov 06, 2017 11:05 am
- Forum: Wave Functions and s-, p-, d-, f- Orbitals
- Topic: Energy of subshells
- Replies: 2
- Views: 349
Re: Energy of subshells
5s has a lower energy until there are 2 electrons in that orbital. Once there are 2 electrics 4d has a lower energy!
- Mon Oct 30, 2017 8:26 pm
- Forum: Electron Configurations for Multi-Electron Atoms
- Topic: 2.63
- Replies: 2
- Views: 308
2.63
Can someone help me work through chapter 2 section 63?
- Mon Oct 30, 2017 8:22 pm
- Forum: Octet Exceptions
- Topic: lewis structures
- Replies: 2
- Views: 445
Re: lewis structures
Can anyone explain how we determine the bonding when it comes to exceptions to the octet rule ad drawing lewis structures.
- Mon Oct 23, 2017 11:31 am
- Forum: Electron Configurations for Multi-Electron Atoms
- Topic: Electron orbital filling order [ENDORSED]
- Replies: 1
- Views: 373
Re: Electron orbital filling order [ENDORSED]
There is no scientific reason why we fill the px orbital first. Theoretically, it could fill any on of them however we start with px for simplicity.
- Mon Oct 23, 2017 11:28 am
- Forum: Electron Configurations for Multi-Electron Atoms
- Topic: Chromium and Copper Electron Configuration Exceptions [ENDORSED]
- Replies: 5
- Views: 1325
Re: Chromium and Copper Electron Configuration Exceptions [ENDORSED]
Is there a reason for this exception? (the difference in stability)
- Mon Oct 16, 2017 11:33 am
- Forum: Empirical & Molecular Formulas
- Topic: Test 1 Compound X [ENDORSED]
- Replies: 5
- Views: 877
Re: Test 1 Compound X [ENDORSED]
This helps so much! Thank you, Is there any combustion where we know the oxygen because in the homework there were sceniors where we did not approach the problem this way.
- Mon Oct 16, 2017 11:23 am
- Forum: DeBroglie Equation
- Topic: De Broglie Wavelength
- Replies: 23
- Views: 3332
Re: De Broglie Wavelength
What is the smallest wavelength that can be detected?
- Fri Oct 13, 2017 8:58 am
- Forum: Photoelectric Effect
- Topic: Problem 1.7 HW
- Replies: 4
- Views: 538
Re: Problem 1.7 HW
I also solved the problem and got 150 pm, I think the back of the book is a typo as the solutions manual agrees with our answer.
- Fri Oct 13, 2017 8:57 am
- Forum: Empirical & Molecular Formulas
- Topic: Test 1 Compound X [ENDORSED]
- Replies: 5
- Views: 877
Test 1 Compound X [ENDORSED]
Can someone help me work through the compound X question on Test 1. It was the second to last question on the test?
- Fri Oct 06, 2017 5:31 pm
- Forum: Molarity, Solutions, Dilutions
- Topic: E9 [ENDORSED]
- Replies: 5
- Views: 4767
Re: E9 [ENDORSED]
Can someone explain step by step how to do step B
- Thu Oct 05, 2017 7:53 pm
- Forum: SI Units, Unit Conversions
- Topic: Sig Figs [ENDORSED]
- Replies: 16
- Views: 3190
Re: Sig Figs [ENDORSED]
Hello!
I just wanted to ask if the 0 after the number 0.0450 counts as a significant figure? Is this 5 or 4 sig figs?
I just wanted to ask if the 0 after the number 0.0450 counts as a significant figure? Is this 5 or 4 sig figs?