Search found 28 matches

by Zoe Robertson 2H
Sun Mar 19, 2017 8:51 pm
Forum: Student Social/Study Group
Topic: Post All Chemistry Jokes Here
Replies: 7951
Views: 1362137

Re: Post All Chemistry Jokes Here

relatable
by Zoe Robertson 2H
Tue Mar 14, 2017 12:12 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: HW 8.73 (Bond Enthalpies
Replies: 5
Views: 815

Re: HW 8.73 (Bond Enthalpies

Why don't we include the C-H bonds? Is it because there are 3 moles of 2 C-H bonds broken and 6 C-H formed in the benzene ring, so they cancel out?
by Zoe Robertson 2H
Mon Mar 13, 2017 5:54 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: q=mc∆t vs q=c∆t? (chapter 8)
Replies: 2
Views: 11992

q=mc∆t vs q=c∆t? (chapter 8)

Hi! Could anyone clarify when to use q=mc∆t vs q=c∆t? I was working on question 8.53 and I was going to use q=mc∆t but the 'm' wasn't included in the solution. Thank you!!
by Zoe Robertson 2H
Sun Mar 12, 2017 4:05 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: HW Ch.8 question 8.25
Replies: 4
Views: 550

Re: HW Ch.8 question 8.25

Alex Uy 2D wrote:In the solutions manual to this, they say that q reaction + q calorimeter = 0. Is that something you just have to know? or where in the problem does it suggest that the change in internal energy is 0?


also wondering about this!
by Zoe Robertson 2H
Wed Mar 08, 2017 2:39 pm
Forum: *Alkanes
Topic: Self-Test 1.4A (condensed structural formula and names)
Replies: 1
Views: 479

Self-Test 1.4A (condensed structural formula and names)

Hi! I'm having trouble understanding how to get the answers to self test 1.4A on page 11 of the organic chem book. If anyone could explain how they solved/approached either problem I would really appreciate it! (a) Write the condensed structural formula for 2-methylpentane (b) Give the IUPAC names (...
by Zoe Robertson 2H
Sat Mar 04, 2017 9:28 pm
Forum: Student Social/Study Group
Topic: Post All Chemistry Jokes Here
Replies: 7951
Views: 1362137

Re: Post All Chemistry Jokes Here

Why did Carbon marry Hydrogen?
They bonded well from the moment they met!
<3
by Zoe Robertson 2H
Wed Feb 22, 2017 11:23 pm
Forum: Reaction Mechanisms, Reaction Profiles
Topic: K=...? (pg 73 course reader pre-equilibrium ex)
Replies: 1
Views: 292

K=...? (pg 73 course reader pre-equilibrium ex)

Hi!
For the pre-equilibrium example on page 73, the fast step is: NO + NO <==> N2O2. Then K is written as: K=[N2O2]/[NO]^2
I'm confused why N2O2 is in the numerator, because of the formula K1=k1/k1*. Isn't the reverse equilibrium reaction k1*?
I thought it would be flipped. Thanks!
by Zoe Robertson 2H
Sun Feb 19, 2017 2:56 pm
Forum: Zero Order Reactions
Topic: Homework Question
Replies: 4
Views: 579

Re: Homework Question

Hi! For this question, I'm confused as to why we don't square H 2 when it asks for the reaction rate with doubling the concentration of H 2 . Doesn't the equation for the rate law involve k[H 2 ] a , in which a= the coefficient, which would be 2 since we doubled it? Or am I mixing up concepts? Thanks!
by Zoe Robertson 2H
Sun Feb 12, 2017 9:17 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Homework help 14.11 [ENDORSED]
Replies: 5
Views: 784

Re: Homework help 14.11 [ENDORSED]

Is the the cathode in this example not given as an oxidation instead of reduction? Don't you read the diagram inside out?
by Zoe Robertson 2H
Sun Feb 12, 2017 7:41 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Homework 14.9b
Replies: 1
Views: 256

Homework 14.9b

I'm having trouble with finding n in delta G = -nFE. I understand that you have to balance each half reaction first, and then n is the number of transferred electrons-- however, do you balance these half-reactions the same way you do for redox equations? If so, how do you know to assume basic or aci...
by Zoe Robertson 2H
Sat Feb 11, 2017 9:11 pm
Forum: Balancing Redox Reactions
Topic: Homework 14.1
Replies: 3
Views: 388

Re: Homework 14.1

How do you go about getting the answer for part d? It asks to combine the half reactions to produce a balanced redox equation, and the answer is: 8H+Cr 2 O 7 2- +3C 2 H 5 OH-->2Cr 3+ +3C 2 H 4 O+7H 2 O I understand how to get to the individual half-reactions, I'm just a bit confused about how to co...
by Zoe Robertson 2H
Sat Feb 11, 2017 8:35 pm
Forum: Balancing Redox Reactions
Topic: Homework 14.1
Replies: 3
Views: 388

Re: Homework 14.1

How do you go about getting the answer for part d? It asks to combine the half reactions to produce a balanced redox equation, and the answer is: 8H+Cr 2 O 7 2- +3C 2 H 5 OH-->2Cr 3+ +3C 2 H 4 O+7H 2 O I understand how to get to the individual half-reactions, I'm just a bit confused about how to com...
by Zoe Robertson 2H
Thu Feb 02, 2017 12:21 am
Forum: Administrative Questions and Class Announcements
Topic: Quiz 1 Preparation Answers
Replies: 130
Views: 16881

Re: Quiz 1 Preparation Answers

You would use ΔG^o=ΔH^o−TΔS^o after you find ΔH^o (rxn) and ΔS^o (rxn) values from the tables provided. Make sure your units match. You will need to convert ΔS^o to KJ for the final answer. That is the equation I am using. And I remembered to convert J to kJ. Still got the wrong answer. I also do n...
by Zoe Robertson 2H
Wed Feb 01, 2017 4:48 pm
Forum: Calculating Work of Expansion
Topic: Sign of Work
Replies: 4
Views: 614

Re: Sign of Work

When the system is doing work, it's negative. When work is done on the system, it's positive. If it helps, you can think of it like a person doing work... if they do it, they're exerting energy and will become tired (negative), and if someone does work on them, they're gaining energy so it would be ...
by Zoe Robertson 2H
Wed Feb 01, 2017 4:42 pm
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: units for heat capacity
Replies: 5
Views: 946

Re: units for heat capacity

If in doubt, is it a good idea to use Kelvin instead of Celsius (in general, for all kinds of problems) unless specified otherwise?
by Zoe Robertson 2H
Sun Jan 29, 2017 4:40 pm
Forum: Student Social/Study Group
Topic: Post All Chemistry Jokes Here
Replies: 7951
Views: 1362137

Re: Post All Chemistry Jokes Here

You can freeze yourself at -273°C and still be 0K
:)
by Zoe Robertson 2H
Sat Jan 21, 2017 9:09 pm
Forum: Student Social/Study Group
Topic: Post All Chemistry Jokes Here
Replies: 7951
Views: 1362137

Re: Post All Chemistry Jokes Here

Q: What do you get when you mix sulfur, tungsten, and silver?

A: SWAG

8-)
by Zoe Robertson 2H
Sun Jan 15, 2017 8:17 pm
Forum: Student Social/Study Group
Topic: Post All Chemistry Jokes Here
Replies: 7951
Views: 1362137

Re: Post All Chemistry Jokes Here

Organic chemistry is difficult. Those who study it have alkynes of trouble.
:/
by Zoe Robertson 2H
Mon Jul 25, 2016 5:32 pm
Forum: Calculating pH or pOH for Strong & Weak Acids & Bases
Topic: Difference between KA and PKA
Replies: 4
Views: 1061

Re: Difference between KA and PKA

This equation might help:
pKa= -log(Ka)
by Zoe Robertson 2H
Mon Jul 25, 2016 5:26 pm
Forum: Conjugate Acids & Bases
Topic: Equilibrium sign or not [ENDORSED]
Replies: 4
Views: 673

Re: Equilibrium sign or not [ENDORSED]

So if we are dealing with any strong acid, we use ----> instead of <----> ? Does the same apply for strong bases?
by Zoe Robertson 2H
Sun Jul 24, 2016 9:33 pm
Forum: Formal Charge and Oxidation Numbers
Topic: Formal charge in Q4.21 [ENDORSED]
Replies: 1
Views: 384

Formal charge in Q4.21 [ENDORSED]

Chapter 4 question 21b asks to draw the Lewis structure for ClCN. In the solutions manual, the Lewis structure has a triple bond between N and C, one lone pair on N, a single bond between C and Cl, and 3 lone pairs on Cl. After calculating the formal charge of that Lewis structure, it comes out to b...
by Zoe Robertson 2H
Sun Jul 24, 2016 7:31 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Shape of I3- (Q 4.13a)
Replies: 1
Views: 364

Shape of I3- (Q 4.13a)

I don't understand why I3- is linear. I assumed that the two lone pairs on the central I atom would repel each other, and cause the shape to be bent. Could someone please explain why this isn't the case? Thanks!!
by Zoe Robertson 2H
Sat Jul 23, 2016 10:39 pm
Forum: Administrative Questions and Class Announcements
Topic: Chemistry Community Points
Replies: 11
Views: 1209

Re: Chemistry Community Points

I believe it's one post per week to ensure that you're getting discussion credit for that week, although I'm sure it doesn't hurt to post more than that! I was also wondering, though, if the posts must be made during the week days, or if we still get credit as long as the post is made before the ne...
by Zoe Robertson 2H
Wed Jul 20, 2016 7:08 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: H2O Shape [ENDORSED]
Replies: 3
Views: 825

H2O Shape [ENDORSED]

I'm confused about why H2O is bent and not linear. I understand that the two lone pairs on the oxygen atom cause the H atom bonds to be repelled and form a bent shape, but what I don't understand is, why can't the lone pairs go on opposite sides of the oxygen atom, making it linear? Thanks!
by Zoe Robertson 2H
Wed Jul 13, 2016 4:11 pm
Forum: *Molecular Orbital Theory (Bond Order, Diamagnetism, Paramagnetism)
Topic: Bond Order and Bond Length
Replies: 6
Views: 1163

Re: Bond Order and Bond Length

What happens if the bond order is a non integer such as 2.5? Do we round the number up? I believe that it doesn't matter whether or not the Bond Order is an integer. My TA told us that the greater the BO, the more stable it is. If it is zero or negative, it is unstable. For example, if you were com...
by Zoe Robertson 2H
Tue Jul 05, 2016 9:55 pm
Forum: Dipole Moments
Topic: How do you find the "largest dipole moment"?
Replies: 6
Views: 61845

Re: How do you find the "largest dipole moment"?

HBr would have a larger dipole moment than HI since as Jamlah said, there's a greater electronegativity difference between H and Br than between H and I. In other words HBr is more polar and Bromine will attract electrons to itself more. I'm not understanding why HBr has a larger dipole moment than...
by Zoe Robertson 2H
Wed Jun 29, 2016 7:02 pm
Forum: Limiting Reactant Calculations
Topic: Fundamentals M5 [ENDORSED]
Replies: 4
Views: 697

Fundamentals M5 [ENDORSED]

In the textbook, question m5 asks: The reaction 6ClO2(g)+2BrF3(l)-->6ClO2F(s)+Br2(l) is carried out with 12 mol ClO2 and 5 mol BrF3. a) Identify the excess reactant Since the solutions manual doesn't have this answer worked out, I thought I'd explain why the answer is BrF3, in case anyone is having ...
by Zoe Robertson 2H
Sat Jun 25, 2016 10:45 am
Forum: Accuracy, Precision, Mole, Other Definitions
Topic: Self-Test E.1B [ENDORSED]
Replies: 2
Views: 722

Self-Test E.1B [ENDORSED]

The question asks: A small cup of coffee contains 3.14 mol H2O. What is the number of H atoms present in the coffee? The answer isn't given, so I'm not sure if I'm going about solving the problem correctly. Since it gives the moles of H2O but asks for the number of H atoms, I'm not sure if I have to...

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