Search found 31 matches

by Rachel Tat 3E
Sat Mar 12, 2016 10:28 pm
Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
Topic: 2013 Final Q3C
Replies: 2
Views: 476

2013 Final Q3C

Under what conditions would we use logQ instead of lnQ in the nernst equation? I was using ln for this problem, but in the answer key we use log.
by Rachel Tat 3E
Sat Mar 12, 2016 6:31 pm
Forum: *Cyclohexanes (Chair, Boat, Geometric Isomers)
Topic: Chair conformation and hydrogens
Replies: 1
Views: 319

Chair conformation and hydrogens

Will we get points deducted off if we do not draw all of the hydrogens in a chair structure?
by Rachel Tat 3E
Sat Mar 12, 2016 5:55 pm
Forum: *Cycloalkanes
Topic: 2012 Final Q6B
Replies: 2
Views: 438

2012 Final Q6B

The cycloalkane is named 1-isopropyl-3-neopentylcyclohexane. Would the IUPAC name for this be 1-(methyl-ethyl)-3-(2,2-dimethyl-propyl)-cyclohexane? Just to make sure, is the IUPAC naming always acceptable?
by Rachel Tat 3E
Fri Mar 11, 2016 3:45 pm
Forum: *Cyclohexanes (Chair, Boat, Geometric Isomers)
Topic: 2011 Final Q8C
Replies: 1
Views: 421

2011 Final Q8C

In this problem, we are asked to draw the most stable conformation for cis-1-ethyl-2-methylcyclohexane. Why is there a cis if the cyclo hexane does not have the -ene suffix indicating a double bond?
by Rachel Tat 3E
Thu Mar 10, 2016 9:27 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: pH and cell potential
Replies: 1
Views: 390

pH and cell potential

How does pH affect cell potential?
by Rachel Tat 3E
Tue Mar 01, 2016 12:52 am
Forum: *Cycloalkenes
Topic: Multiple substituents
Replies: 5
Views: 884

Re: Multiple substituents

Thank you for elaborating, I really appreciate it! But I still don't get why we only consider that 1<2 when 3 is also <5? Why is the 1 being less than 2 take precedence over the 3 being lower than 5?
by Rachel Tat 3E
Sun Feb 28, 2016 11:49 pm
Forum: *Cycloalkenes
Topic: Multiple substituents
Replies: 5
Views: 884

Re: Multiple substituents

I am referring more to cases such as this: https://scontent.xx.fbcdn.net/hphotos-xlf1/v/wl/t34.0-12/12804199_10204467686890886_1294557226_n.jpg?oh=5a80ab6849e637cc8c473d3f721be1a9&oe=56D6B04C , where is says that 1,5 is the correct number instead of 2,3 because 1 < 2, but 3 is less than 5, so wh...
by Rachel Tat 3E
Sun Feb 28, 2016 4:39 pm
Forum: *Cycloalkenes
Topic: Multiple substituents
Replies: 5
Views: 884

Multiple substituents

In the course reader, it is stated that for cycloalkanes with multiple substituents, the "first named group" gets the lower number, and in the organic chemistry textbook it says that the "first occurrence" of a substituent should get the lowest numbering. What exactly do they mea...
by Rachel Tat 3E
Tue Feb 16, 2016 2:08 am
Forum: Significant Figures
Topic: Winter 2015 Quiz 2 #8
Replies: 1
Views: 333

Winter 2015 Quiz 2 #8

The number with the least amount of significant figures in this problem is 0.35, so 2 significant figures, yet the final answer has 3 significant figures. Why is that?
by Rachel Tat 3E
Tue Feb 16, 2016 1:41 am
Forum: First Order Reactions
Topic: Winter 2015 Quiz 2 #3
Replies: 1
Views: 327

Winter 2015 Quiz 2 #3

We are given the reaction N2O --> N2 + O2 and rate = k[N2O] and asked to find the rate constant. In the answer key, however, the equation is balanced to become 2N2O --> 2N2 + O2. Is it necessary to balance the the reaction considering that it is not involved in our calculations?
by Rachel Tat 3E
Wed Feb 10, 2016 12:36 am
Forum: Significant Figures
Topic: 2015 Midterm Q4&5
Replies: 3
Views: 702

Re: 2015 Midterm Q4&5

But what about in the case of, say ln(5.7/3.3)? The number you get is 0.546543706... continuing on, and is not a set number. The equation that is used is .150*8.314*ln(5.7/3.3) which equals .682, but from the original problem's numbers there should be 2 significant figures, yet there are 3.
by Rachel Tat 3E
Tue Feb 09, 2016 3:32 pm
Forum: Significant Figures
Topic: 2015 Midterm Q4&5
Replies: 3
Views: 702

2015 Midterm Q4&5

In part A, we are given 0.150 moles, 3.3 L and 5.7 L. What significant figure rules (I believe it has something to do with the ln?) makes the final answer for the problem have 3 significant figures? I have the same question with part B, where the final answer ends with 3 significant figures even tho...
by Rachel Tat 3E
Tue Feb 09, 2016 3:10 pm
Forum: Calculating Standard Reaction Entropies (e.g. , Using Standard Molar Entropies)
Topic: 2015 Midterm Q2&3B and C
Replies: 1
Views: 358

2015 Midterm Q2&3B and C

For part B, we are asked to find the enthalpy of reaction for 1 mole of H2O. If we are finding the enthalpy of reaction for one mole of H2O, isn't it the enthalpy of formation? Continuing on from that, why do use this enthalpy of reaction in part C to find the standard enthalpy of formation for HI? ...
by Rachel Tat 3E
Mon Feb 08, 2016 1:05 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: 2011 Midterm Q5B
Replies: 1
Views: 333

2011 Midterm Q5B

Why is it that, in the problem we are given standard enthalpy of combustion for glucose with the units kJ/mol, but in part b, when asked to find the free energy, our delta H's units become kJ. Why is that?
by Rachel Tat 3E
Sun Feb 07, 2016 8:11 pm
Forum: Phase Changes & Related Calculations
Topic: 2011 Midterm Q1A
Replies: 1
Views: 395

2011 Midterm Q1A

Why are we using the equation q = C cal *deltaT? I know that since this is a phase change we are going to replace the q with q = n*deltaH combustion , but where did the q = C cal *deltaT come from? Are we disregarding the mass/moles of the calorimeter because it was not included (as you would usuall...
by Rachel Tat 3E
Wed Feb 03, 2016 4:38 pm
Forum: Student Social/Study Group
Topic: Post All Chemistry Jokes Here
Replies: 8223
Views: 1435336

Re: Chemistry Jokes

Image
by Rachel Tat 3E
Tue Jan 26, 2016 1:08 am
Forum: Calculating Work of Expansion
Topic: When to use which work equation
Replies: 1
Views: 303

When to use which work equation

How do we know when to use w = -PdeltaV or w = -nRTln(V2/V1)? Do we only use the 2nd equation when told that it is an isothermal and reversible expansion/compression?
by Rachel Tat 3E
Sat Jan 23, 2016 3:26 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: Heat Capacity
Replies: 6
Views: 849

Heat Capacity

The definition of heat capacity is the heat required to raise the temperature of 1g (specific heat) or 1 mol (molar heat) of a substance by 1 degree C. Does the phase a substance is in affect it's heat capacity (for example, whether water is in as solid or liquid form)?
by Rachel Tat 3E
Wed Jan 20, 2016 6:26 pm
Forum: Thermodynamic Definitions (isochoric/isometric, isothermal, isobaric)
Topic: Reversible and irreversible
Replies: 1
Views: 354

Reversible and irreversible

What does it mean when a system is reversible or irreversible and how does this affect our calculations in regards to entropy/energy?
by Rachel Tat 3E
Mon Jan 11, 2016 11:30 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Problem 8.45
Replies: 1
Views: 1692

Problem 8.45

8.45 Carbon disulfide can be prepared from coke and elemental sulfur: 4 C (s) + S 8 (s) --> 4CS 2 (l) Standard reaction enthalpy = +358.8 kJ How much heat is absorbed in the reaction of 1.25 mol S 8 at constant pressure? B. Calculate the heat absorbed in the reaction of 197 g of carbon with an exce...
by Rachel Tat 3E
Sun Jan 10, 2016 8:42 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: When to use each method
Replies: 3
Views: 405

Re: When to use each method

Essentially, yes; for example, if the equation gives two different equations with the enthalpy for each one, use hess' law, or if standard enthalpy of formations (Hf) are given, use the method for that and so on. Other methods can be used to solve for reaction enthalpies, but one will typically be m...
by Rachel Tat 3E
Sat Dec 05, 2015 11:36 pm
Forum: *Molecular Orbital Theory (Bond Order, Diamagnetism, Paramagnetism)
Topic: LUMO and HOMO
Replies: 2
Views: 1725

Re: LUMO and HOMO

I believe it would be the next level of orbitals, (pi*2p) because technically pi2px and pi2py are still the same orbital, pi2p
by Rachel Tat 3E
Sun Nov 29, 2015 7:35 pm
Forum: Calculating pH or pOH for Strong & Weak Acids & Bases
Topic: Rounding off
Replies: 2
Views: 491

Rounding off

When we were doing equilibrium, we disregarded subtracting x or adding x when doing our ICE chart if our equilibrium constant was extremely small. However, in chapter 12, the answer key in the book usually disregards the subtracting/adding x even when the acidity or basicity constant is not extremel...
by Rachel Tat 3E
Sun Nov 29, 2015 7:32 pm
Forum: Significant Figures
Topic: Significant figures in Ch.12
Replies: 1
Views: 361

Significant figures in Ch.12

In many of the homework problems in chapter 12, the numbers given in the homework will have 2 significant figures, but the answer key to the textbook usually has 4 or 3 significant figures when solving for pH or molar concentrations and not 2 significant figures, which has made rounding during my ca...
by Rachel Tat 3E
Wed Nov 18, 2015 10:25 pm
Forum: Significant Figures
Topic: Temperature
Replies: 2
Views: 422

Temperature

Do we include temperature when considering significant figures or does temperature act as a constant? I've been wondering this as I have been doing equilibrium problems, and sometimes the temperature is given with a decimal and sometimes without. The answer key to the book is also inconsistent about...
by Rachel Tat 3E
Wed Oct 28, 2015 12:25 am
Forum: *Molecular Orbital Theory (Bond Order, Diamagnetism, Paramagnetism)
Topic: Valence electron configuration
Replies: 1
Views: 431

Valence electron configuration

I'm very confused about how to write valence electron configuration. For example, with B2, the solutions manual (\sigma 2s)^2 (\sigma ^*2s)^2 (\Pi 2p)^2 but with F2, the solution manual says (\sigma 2s)^2 (\sigma ^*2s)^2 (\sigma 2p)^2 (\pi 2p)^...
by Rachel Tat 3E
Tue Oct 27, 2015 6:31 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Homework Problem 4.23c Lewis Structure
Replies: 2
Views: 372

Re: Homework Problem 4.23c

It shouldn't matter because regardless of where you place the O and F, since they are around the central atom I their formal charges will be the same no matter the order.
by Rachel Tat 3E
Tue Oct 27, 2015 6:14 pm
Forum: Formal Charge and Oxidation Numbers
Topic: Formal charge and resonance structures
Replies: 2
Views: 580

Formal charge and resonance structures

If a question asks us to draw the lewis structure for a molecule that has resonance structures, are we expected to find the formal charges to find the best structure, even if the question doesn't specifically ask for it?
by Rachel Tat 3E
Wed Oct 14, 2015 5:59 pm
Forum: Empirical & Molecular Formulas
Topic: Using mass percent
Replies: 1
Views: 457

Using mass percent

What is the empirical formula of a hydrocarbon which produces 2.703 g CO2 and 1.108 g H2O when combusted? Part of finding empirical formulas involve finding the mass percent of a compound's individual elements, but for a question like the one quoted above, why is it unnecessary to find the mass per...
by Rachel Tat 3E
Sat Sep 26, 2015 8:09 pm
Forum: Administrative Questions and Class Announcements
Topic: Class Pacing
Replies: 1
Views: 416

Class Pacing

Is there an approximate schedule for when we will be covering which subjects? I want to be able to plan ahead my study schedule for future chapters.

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