Search found 32 matches

by Gevork 2E
Sat Mar 17, 2018 12:33 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: 9.55 vs 9.57
Replies: 1
Views: 229

Re: 9.55 vs 9.57

Hi, So it really depends on the question. If the question is asking for the entire reaction, then you should be aware of all the coefficients and make sure that you are using them. Typically we divide when it asks for a specific molecule. Here is an example: 2A + B --> C If the question asks for the...
by Gevork 2E
Sat Mar 17, 2018 12:29 pm
Forum: Balancing Redox Reactions
Topic: Eletro chem Test
Replies: 4
Views: 239

Re: Eletro chem Test

Hi, You have to see which molecule in the pair is being reduced/oxidized and then go from there. I don't entirely understand the example you wrote so sorry if the question was specific to that example. If you are going from O2 to OH-, then your oxygen goes from a charge of 0 to a charge of -2. It is...
by Gevork 2E
Thu Mar 15, 2018 11:36 pm
Forum: *Alkanes
Topic: Organic chemistry [ENDORSED]
Replies: 3
Views: 331

Re: Organic chemistry [ENDORSED]

Hi, It might also be worthwhile to note that you should be able to identify the functional groups both in the line structure AND if you were just given something like: CH2CHCOOH. Dr. Lavelle did stress multiple times in class to know how to identify the groups visually (which I think is relating to ...
by Gevork 2E
Sun Mar 11, 2018 12:43 am
Forum: General Rate Laws
Topic: 15.101(a) Overall Reaction
Replies: 2
Views: 118

Re: 15.101(a) Overall Reaction

Hello,

I personally think that the solutions manual is correct. There is nothing to cancel out that Cl so it should be there as a product as far as I know. Maybe it was just an error?
by Gevork 2E
Sun Mar 11, 2018 12:37 am
Forum: Second Order Reactions
Topic: Half life of second order reactions
Replies: 8
Views: 529

Re: Half life of second order reactions

Hello, I remember reading this as well and I am pretty much going to ignore what it says. We have the equations and understand how a second order reaction occurs so I wouldn't stress about what the book says. Maybe it had to do with the publisher or authors not including them? Hard to tell for the r...
by Gevork 2E
Sun Mar 11, 2018 12:31 am
Forum: Arrhenius Equation, Activation Energies, Catalysts
Topic: Michelis-Menten Mechanism?
Replies: 2
Views: 109

Re: Michelis-Menten Mechanism?

Hi,

I believe that this is a model that is used to describe changes in concentration of enzymes over time. It helps us to understand the interactions between enzyme and substrate, which is useful when trying to understand biological processes and their rates.

Hope this was helpful
by Gevork 2E
Wed Mar 07, 2018 9:28 pm
Forum: Student Social/Study Group
Topic: Post All Chemistry Jokes Here
Replies: 7348
Views: 887436

Re: Post All Chemistry Jokes Here

Chemistry??...more like cheMYSTERY because I don't know what's going on.

(JK... maybe)
by Gevork 2E
Mon Feb 26, 2018 10:57 am
Forum: Zero Order Reactions
Topic: Homework question
Replies: 2
Views: 133

Re: Homework question

Hi, I think it would also be better to know where the units are coming from with the use of the equation that we used in class. rate = k[A]^n Using this, let's see what happens when we are in a third order reaction (just an example, you can use this for anything): k = rate/[A]^3 = mol x L^-1 x s^-1/...
by Gevork 2E
Mon Feb 26, 2018 10:47 am
Forum: Reaction Mechanisms, Reaction Profiles
Topic: Steady State Approximation [ENDORSED]
Replies: 2
Views: 109

Re: Steady State Approximation [ENDORSED]

Hi, So steady state is referring to a portion of the reaction or multiple portions that are occurring at a constant rate. Knowing that these constant rates, we can calculate for a rate of the reaction. For example, we have three reactions that are occurring: A + B --> C C + D --> E E + F --> G In st...
by Gevork 2E
Mon Feb 26, 2018 10:38 am
Forum: Arrhenius Equation, Activation Energies, Catalysts
Topic: Homework 14.41
Replies: 2
Views: 109

Re: Homework 14.41

Hi,

I also think that it might have to do with it being E*cell of the reaction. As we know, this is related to K and so when there is equilibrium we would have a voltage of 0.

Hope this was helpful.
by Gevork 2E
Mon Feb 26, 2018 10:30 am
Forum: Arrhenius Equation, Activation Energies, Catalysts
Topic: Activation Energy???
Replies: 7
Views: 254

Re: Activation Energy???

Hi, So the rate of the reaction can depend on the activation energy. I think a good example would be enzymes. They decrease the total activation energy required to start a reaction and are well known for catalyzing a reaction. Thinking about it, I suppose if each molecule required less energy to rea...
by Gevork 2E
Sun Feb 18, 2018 8:11 pm
Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
Topic: 14.116
Replies: 1
Views: 126

14.116

Hi, What did you guys get for part B of this question? A fuel cell in which hydrogen reacts with nitrogen instead of oxygen is proposed. (a) Write the chemical equation for the reaction in water, which produces aqueous ammonia. (b) What would be the maximum free energy output of the cell for the con...
by Gevork 2E
Sun Feb 18, 2018 8:07 pm
Forum: Balancing Redox Reactions
Topic: 14.5d
Replies: 2
Views: 116

Re: 14.5d

Hi,

can you maybe be a bit more specific about your question? Are you asking for how this reaction occurs or how the process is to get the products? I think the main idea here is that P4 is acting as both the oxidizing AND the reducing agent. Was that the part that was confusing?
by Gevork 2E
Sun Feb 18, 2018 8:04 pm
Forum: Balancing Redox Reactions
Topic: Exercise 14.17
Replies: 6
Views: 191

Re: Exercise 14.17

Hi,

This question has to do with half reactions and balancing for the cell. There are a lot of other similar questions, so was there something specific about this one that was confusing? Are you maybe confused about the cell diagram?

Hope this was helpful
by Gevork 2E
Sun Feb 11, 2018 7:19 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: 8.49
Replies: 3
Views: 135

Re: 8.49

Hi, So usually we are told that a reaction is occurring under constant pressure, which makes it viable to have delta H = q. However, if the reaction is not occurring at a constant pressure, then you need to account for this and hence your delta H is not going to equal q. I have not seen a question l...
by Gevork 2E
Sun Feb 11, 2018 7:12 pm
Forum: Balancing Redox Reactions
Topic: Reduction and Oxidation
Replies: 4
Views: 110

Re: Reduction and Oxidation

KayleeMcCord1F wrote:Is it necessary to memorize the oxidation numbers for some elements?


I think that is useful to know the most common elements that we are going to be seeing. I think it will help in general with the material, and might help to solve problems faster. I wouldn't worry too much about it though.
by Gevork 2E
Sat Feb 10, 2018 2:21 pm
Forum: Calculating Standard Reaction Entropies (e.g. , Using Standard Molar Entropies)
Topic: Question related to previous midterm
Replies: 1
Views: 115

Question related to previous midterm

Hello, This post is in reference to the 2013 Midterm question 5B. the question is: Arrange the following substances in order of increasing standard molar entropy: CHF3,CF4,CH3F, CH2F2 I had initially thought the order was CF4,CH3F,CH2F2, then CH3F, but the answer key is the opposite. Additionally, I...
by Gevork 2E
Sun Feb 04, 2018 3:13 pm
Forum: Entropy Changes Due to Changes in Volume and Temperature
Topic: Problem 9.19 about Standard Entropy
Replies: 6
Views: 173

Re: Problem 9.19 about Standard Entropy

Hi, So I was also really confused about this, and I found an article on it.

https://chemistry.stackexchange.com/que ... t-of-water

I found this to be really useful.

Hope this is helpful.
by Gevork 2E
Sun Feb 04, 2018 10:44 am
Forum: Concepts & Calculations Using Second Law of Thermodynamics
Topic: Clausius inequality
Replies: 1
Views: 88

Re: Clausius inequality

Hi, From my understanding, the theorem is referencing to the idea that in reality, systems in the world are not completely ideal as we see many times in questions. For instance, work or other factors may be taking part on the system we are looking at, which are going to be altering the value that we...
by Gevork 2E
Sat Feb 03, 2018 7:24 pm
Forum: Concepts & Calculations Using Second Law of Thermodynamics
Topic: 9.47 [ENDORSED]
Replies: 2
Views: 107

Re: 9.47 [ENDORSED]

Hi,

So just because the system is isothermal does not mean that no heat is moving in or out of the system (if it was I wouldn't have missed that on the test :( ). I think the main idea is that its a "free expansion".

Hope this is helpful.
by Gevork 2E
Sat Feb 03, 2018 7:15 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: Using Appropriate Equation
Replies: 2
Views: 79

Re: Using Appropriate Equation

Hi,

If the Delta G values were given at a specific temp then it would be okay as long as they are all at the same temperature. I believe that the same applies to the other conditions like pressure.

Hope this was helpful
by Gevork 2E
Sat Jan 27, 2018 6:51 pm
Forum: Calculating Work of Expansion
Topic: equation
Replies: 2
Views: 109

Re: equation

Hello, The differences are also seen in the type of question asked, I rewrote this to piggy back off the previous answer since she beat me to it! The ideal gas questions are seen in chapter 9 vs when in chapter 8 we were just using PdeltaV (at least from what I saw). The latter seems to be used in m...
by Gevork 2E
Sat Jan 27, 2018 6:33 pm
Forum: Phase Changes & Related Calculations
Topic: 8.40
Replies: 4
Views: 155

8.40

Hello, Has anyone attempted this question? I got 709.97 kJ (ignoring sig figs) and I wanted to see what others might have ended up with for this question. For your convenience, here is the question: 0 If we start with 276 g of water at 25. C, how much heat must we add to convert all the liquid into ...
by Gevork 2E
Sat Jan 27, 2018 6:26 pm
Forum: Concepts & Calculations Using Second Law of Thermodynamics
Topic: Sign of ΔS
Replies: 3
Views: 159

Re: Sign of ΔS

Hi, so the idea here is what you are looking at, either your system or your surroundings. So for the questions with the negative, note: "At what rate does your body heat generate entropy in your surroundings , taken to be at 20. C? I believe that this is the case. Same with question 9.5. You ne...
by Gevork 2E
Mon Jan 15, 2018 7:19 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Constant Pressure Enthalpy
Replies: 1
Views: 88

Re: Constant Pressure Enthalpy

reactions typically take place in a place that is open to the atmosphere so there is a constant pressure. The heat that is released or absorbed by that reaction is then equal to the change in enthalpy for that said system.

Check page 279 of the textbook.

Hope this was helpful.
by Gevork 2E
Mon Jan 15, 2018 7:14 pm
Forum: Phase Changes & Related Calculations
Topic: work, heat, and internal energy
Replies: 2
Views: 131

Re: work, heat, and internal energy

Internal energy is a state function because it does not matter how the system gets to that particular state. Work on the other hand, is proportional to distance traveled, so it matters how you got to your endpoint/ what path you took. Heat is similar.

Hope this was helpful.
by Gevork 2E
Mon Jan 15, 2018 7:09 pm
Forum: Phase Changes & Related Calculations
Topic: reversible, isothermal expansion of a gas
Replies: 2
Views: 120

Re: reversible, isothermal expansion of a gas

I think that the main idea behind that box in the book is for us to understand where work comes from. I do not see there being a specific question about it on a test. It also gives you a good idea about the relationship between pressure and volume and how work ties into that.

Hope this was helpful.
by Gevork 2E
Sun Jan 14, 2018 8:43 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: Discussion Calorimetry Question
Replies: 1
Views: 106

Re: Discussion Calorimetry Question

So from your post it seems the question is asking for the delta H of the whole solution. In this case, the NaOH is dissolving into the water, so when we calculate for the delta H, we are really only factoring in the mass/volume of the water, which is not really changing due to the sodium hydroxide b...
by Gevork 2E
Sun Jan 14, 2018 8:30 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: Molar Heat Capacity
Replies: 1
Views: 69

Re: Molar Heat Capacity

I think this might have to do with rotations and vibrations that are occurring within those particular molecules. With simple molecules, there are typically less ways in which atoms in that molecule can vibrate or rotate. Having complex molecules means so many different ways to rotate and vibrate du...
by Gevork 2E
Thu Jan 11, 2018 10:33 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Ch 8 #57
Replies: 2
Views: 116

Re: Ch 8 #57

I think it might have to do with it being a reaction, so it is probably referring to the idea that you would react one mol of reactants in that theoretical reaction. This might not be the case, but that's how I had understood it. As far as what units needs to be used, it would depend on the context ...
by Gevork 2E
Thu Jan 11, 2018 5:39 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: 8.59
Replies: 2
Views: 105

Re: 8.59

From my understanding, Nitrogen has its value as 0 because in standard conditions it will be diatomic. It would not require any energy loss or gain to be in that state, so therefore its value is 0.
by Gevork 2E
Thu Jan 11, 2018 5:34 pm
Forum: Phase Changes & Related Calculations
Topic: Intensive vs. Extensive
Replies: 5
Views: 278

Re: Intensive vs. Extensive

Extensive: Dependent on the amount of the substance that you have.
Example: Mass, volume, etc.

Intensive: Not dependent on the amount of the substance.
Examples: Density, maybe something like color, conductance.

Hope this helps.

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