Search found 27 matches

by Samiksha Chopra 2I
Sat Mar 12, 2016 2:19 am
Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
Topic: Winter Final Exam 2013 4A
Replies: 4
Views: 635

Re: Winter Final Exam 2013 4A

For that I understand that two electrons are being transferred, but how come it needs to be multiplied by 2? There are 2 molecules of Fe(OH)2 by there are also 2 of Fe, so shouldn't it be a one to one ratio?
by Samiksha Chopra 2I
Fri Mar 11, 2016 12:26 pm
Forum: *Cyclopropanes and Cyclobutanes
Topic: strain
Replies: 1
Views: 505

Re: strain

If all the C are in the plane then torsional strain would occur because all the hydrogens are eclipsed. There is no steric strain because the H atoms are not large enough to actually occupy each others space. However, cyclobutane typically adopts the butterfly conformation which relieves steric stra...
by Samiksha Chopra 2I
Fri Mar 11, 2016 12:22 pm
Forum: *Cyclopropanes and Cyclobutanes
Topic: Bond Angles and Energies
Replies: 1
Views: 488

Re: Bond Angles and Energies

I do not think we need to memorize the exact total strain values for the cycloalkanes; we would probably need to know trends within it like which one releases torsional strain or steric strain and which ones are higher. I do think we need to know bond angles however so I would understand/memorize th...
by Samiksha Chopra 2I
Fri Mar 11, 2016 12:19 pm
Forum: *Alkanes
Topic: Drawing compound-Winter Q #3, 2016
Replies: 1
Views: 228

Drawing compound-Winter Q #3, 2016

Just curious as to how one would draw the line structure for: 3-ethyl-2,4-dimethylheptane If you draw it straightforward as its named with a straight chain like ( \/\/\/ ) and then add the substituents, there is another chain that is made with 7 C's and it does not make the same molecule. Any clue a...
by Samiksha Chopra 2I
Mon Feb 15, 2016 4:35 pm
Forum: General Rate Laws
Topic: Rate Concentrations
Replies: 1
Views: 248

Re: Rate Concentrations

As long as it is consistent through the entire problem it should not make a difference. Be careful to notice that M (molarity) is typically in mol/L not mmol/L.
by Samiksha Chopra 2I
Mon Feb 15, 2016 4:34 pm
Forum: Second Order Reactions
Topic: Quiz 2 Prep Winter 2014 #9 Reaction Order
Replies: 1
Views: 225

Re: Quiz 2 Prep Winter 2014 #9 Reaction Order

We know the order of the reaction by looking at the units for K. The only way to end up with the rate of the reaction as M/s would be to multiple [concentration]^2 to the K to cancel out the units properly.
by Samiksha Chopra 2I
Mon Feb 15, 2016 4:32 pm
Forum: Reaction Mechanisms, Reaction Profiles
Topic: Reaction Intermediates
Replies: 1
Views: 224

Re: Reaction Intermediates

It is not that we specifically eliminate them, its more that they are eliminated on their own. Over the course of the whole reaction they are made and then aid in the subsequent steps to get the final desired product. They are not in the rate law because while they may show up in a single step, they...
by Samiksha Chopra 2I
Mon Feb 15, 2016 4:27 pm
Forum: General Rate Laws
Topic: Units
Replies: 1
Views: 200

Re: Units

Yes, the units for rate will always be concentration/time. Typically we see M/s although it can be per minute or per hour. Only K varies question per question with respect to the overall order.
by Samiksha Chopra 2I
Mon Feb 15, 2016 4:25 pm
Forum: Arrhenius Equation, Activation Energies, Catalysts
Topic: Winter Quiz 2, Preparation 2 (w/answers) #11
Replies: 3
Views: 331

Winter Quiz 2, Preparation 2 (w/answers) #11

11. The rate constant for the reaction A -> B is 25 1/min at 298 K and 35 1/min at 350 K. Calculate the value of the rate constant at 770 K. Give your answer in 1/min.

I am not sure where to even begin or what relationship to use. Anything helps!
by Samiksha Chopra 2I
Mon Feb 15, 2016 4:19 pm
Forum: Administrative Questions and Class Announcements
Topic: Quiz 2 Winter 2016
Replies: 18
Views: 6923

Re: Quiz 2 Winter 2016

If anyone has already gone through the problem set for Chapter 15, would he/she please post the questions that are going to be covered on this quiz?

Thanks in advance!
by Samiksha Chopra 2I
Mon Feb 08, 2016 11:03 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: HW Question 14.91
Replies: 1
Views: 220

HW Question 14.91

A voltaic cell functions only when the electrical circuit is complete. In the external circuit, the current is carried by the flow of electrons through a metal wire. Explain how the current is carried through the cell itself. The answer key sates that a negatively charged electrolyte flows from the ...
by Samiksha Chopra 2I
Sun Jan 24, 2016 11:12 pm
Forum: Third Law of Thermodynamics (For a Unique Ground State (W=1): S -> 0 as T -> 0) and Calculations Using Boltzmann Equation for Entropy
Topic: Residual Entropy
Replies: 2
Views: 477

Residual Entropy

Can someone outline or explain in more detail how the S=nRln2 comes about?
And, is it always ln2 no matter the number of moles of a molecule or the size of a molecule?
by Samiksha Chopra 2I
Sun Jan 24, 2016 11:09 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: General delta H question
Replies: 1
Views: 151

General delta H question

Because combustion reactions are meant to provide energy, can we know that all combustion reactions have a negative change in enthalpy? There is a question on the unanswered problems for Quiz 1 that gives a given deltaH for a combustion reaction as + 777 J/mol and I was wondering if that was possibl...
by Samiksha Chopra 2I
Sun Jan 24, 2016 11:05 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Standard Reaction Entropy
Replies: 1
Views: 207

Standard Reaction Entropy

This question is part of Quiz One without the answers. I am not looking for the answer in the end just a more general question about it. The question reads: Calculate the standard reaction entropy for the following combustion reaction using standard molar entropies. (Then it follows with an equation...
by Samiksha Chopra 2I
Wed Dec 02, 2015 10:34 pm
Forum: Calculating pH or pOH for Strong & Weak Acids & Bases
Topic: 12.55 pH of CCl3COOH
Replies: 1
Views: 442

Re: 12.55 pH of CCl3COOH

It is not a strong acid, it is stronger than CH3COOH, but relative to the wider spread of acids its considered weak. The strong acids are the ones that are separately listed and include HCl HBr and a few others.
by Samiksha Chopra 2I
Tue Dec 01, 2015 12:07 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: Is Le Chatelier's Principle Quantifiable? 200 Final Q6C
Replies: 1
Views: 340

Re: Is Le Chatelier's Principle Quantifiable? 200 Final Q6C

Yes we could calculate it if it specified how much it increased. If it said some was "just added" we would not be able to use the ICE chart to calculate anything. But if it said it was doubled, we know by how much since there was an original concentration that was given.
by Samiksha Chopra 2I
Fri Nov 27, 2015 11:16 am
Forum: Ideal Gases
Topic: gas constant R
Replies: 3
Views: 502

Re: gas constant R

There have been a couple of questions that do not specify the units for pressure. I believe that you can use whichever value for R that is easiest for you, just make sure you are clear that your final answer or numbers chosen corresponds directly to the value of R that you used.
by Samiksha Chopra 2I
Fri Nov 27, 2015 11:06 am
Forum: Ideal Gases
Topic: Using the Ideal Gas Law
Replies: 1
Views: 367

Re: Using the Ideal Gas Law

You divide by the 1.0732L because when you use the ICE chart you should be comparing molarities. However you will notice that both terms are divided by that number so it cancels out. In case you were wondering where the number came from, it used PV=nRT to solve for V. If you were wondering about the...
by Samiksha Chopra 2I
Wed Nov 18, 2015 11:21 pm
Forum: Calculating pH or pOH for Strong & Weak Acids & Bases
Topic: Question about problem in course reader
Replies: 1
Views: 299

Re: Question about problem in course reader

The molar ratio is 2:1, so 2 OH- for every 1 Ba(OH)2...... (0.0030 mol Ba(OH)2 / L)*(2 mol OH-/ 1mol Ba(OH)2)= .0060 mol/L of the OH-.
by Samiksha Chopra 2I
Wed Nov 18, 2015 11:18 pm
Forum: Naming
Topic: Hydrate
Replies: 1
Views: 247

Re: Hydrate

IF the H2O is outside the coordination compound itself, it is referred to as a hydrate.
Ex. [Fe(H2O)6]2+, the H2O would be named as aqua....but in [Fe(CN)2(NH3)4] * H2O, the H2O would just be mentioned at the end as a hydrate
For reference, pg 104 in the course reader illustrates this.
by Samiksha Chopra 2I
Wed Nov 18, 2015 11:14 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Equilibrium Concentrations
Replies: 2
Views: 251

Re: Equilibrium Concentrations

Because their ratios are dependent on their moles, and their moles are used in the concentration. If the concentration is not changing then the ratio should not change also.
by Samiksha Chopra 2I
Wed Nov 18, 2015 11:11 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Aqueous Solutions v. Liquids for Equilibrium Constants
Replies: 1
Views: 217

Re: Aqueous Solutions v. Liquids for Equilibrium Constants

This is due to the activities of the reactants and products influencing the equilibrium constant. For solids and liquids, the activity is 1, so in an expression, dividing or multiplying by one does not change anything. The reason why the activity is 1, is because the concentrations are so large that...
by Samiksha Chopra 2I
Wed Nov 18, 2015 11:05 pm
Forum: Significant Figures
Topic: Temperature
Replies: 2
Views: 332

Re: Temperature

As a follow up, in the quiz book there is a problem that uses the temperature in the calculation and it is only one sig fig, yet the answers in the back have three sig figs, so if this problem comes up for you on a test I would just show the evidence of inconsistency and I am sure the TAs will be le...
by Samiksha Chopra 2I
Wed Nov 18, 2015 11:03 pm
Forum: Significant Figures
Topic: Temperature
Replies: 2
Views: 332

Re: Temperature

If the question is given at a certain temperature, and that temperature is not used in any calculations for the problem, I would not worry about it. However, if that number is used in the calculation, for example in PV=nRT, to find some partial pressure or concentration, it should be considered for ...
by Samiksha Chopra 2I
Wed Nov 18, 2015 10:59 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: I need help on 11.29
Replies: 1
Views: 187

Re: I need help on 11.29

Because 14A does not cover thermodynamics and concepts like Gibbs Free Energy constant, we can not solve the problem without doing outside reading. I would not worry about it for this class, but if you still want an explanation besides what is in the solutions manual I do not mind explaining now to ...
by Samiksha Chopra 2I
Tue Oct 13, 2015 11:31 pm
Forum: Balancing Chemical Reactions
Topic: Fall 2009 Q 1 A
Replies: 2
Views: 498

Re: Fall 2009 Q 1 A

Also, with what is physically reacting and we are observing, the H2O typically does not add or take away from our reaction. It is unnecessary to add it because it stays the same in the beginning and the end, it is not reacting or being produced.
by Samiksha Chopra 2I
Tue Oct 13, 2015 11:19 pm
Forum: Empirical & Molecular Formulas
Topic: Compounds burned in Air
Replies: 2
Views: 443

Compounds burned in Air

Between two questions like: A compound is burned in air and produces 5.0g CO2 and 7.20g of H2o, find the empirical formula. and 6.40 grams of a compound is burned in air and produces 5.0g CO2 and 7.20g of H2o, find the empirical formula. Do we make the assumption in both cases that the compound cons...

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