Search found 28 matches
- Sun Mar 19, 2017 8:51 pm
- Forum: Student Social/Study Group
- Topic: Post All Chemistry Jokes Here
- Replies: 9651
- Views: 3642252
Re: Post All Chemistry Jokes Here
relatable
- 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: 1324
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?
- 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: 35455
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!!
- Sun Mar 12, 2017 4:05 pm
- Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
- Topic: HW Ch.8 question 8.25
- Replies: 4
- Views: 907
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!
- Wed Mar 08, 2017 2:39 pm
- Forum: *Alkanes
- Topic: Self-Test 1.4A (condensed structural formula and names)
- Replies: 1
- Views: 896
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 (...
- Sat Mar 04, 2017 9:28 pm
- Forum: Student Social/Study Group
- Topic: Post All Chemistry Jokes Here
- Replies: 9651
- Views: 3642252
Re: Post All Chemistry Jokes Here
Why did Carbon marry Hydrogen?
They bonded well from the moment they met!
<3
They bonded well from the moment they met!
<3
- Wed Feb 22, 2017 11:23 pm
- Forum: Reaction Mechanisms, Reaction Profiles
- Topic: K=...? (pg 73 course reader pre-equilibrium ex)
- Replies: 1
- Views: 532
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!
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!
- Sun Feb 19, 2017 2:56 pm
- Forum: Zero Order Reactions
- Topic: Homework Question
- Replies: 4
- Views: 992
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!
- 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: 1235
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?
- Sun Feb 12, 2017 7:41 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: Homework 14.9b
- Replies: 1
- Views: 435
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...
- Sat Feb 11, 2017 9:11 pm
- Forum: Balancing Redox Reactions
- Topic: Homework 14.1
- Replies: 3
- Views: 714
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...
- Sat Feb 11, 2017 8:35 pm
- Forum: Balancing Redox Reactions
- Topic: Homework 14.1
- Replies: 3
- Views: 714
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...
- Thu Feb 02, 2017 12:21 am
- Forum: Administrative Questions and Class Announcements
- Topic: Quiz 1 Preparation Answers
- Replies: 130
- Views: 25699
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...
- Wed Feb 01, 2017 4:48 pm
- Forum: Calculating Work of Expansion
- Topic: Sign of Work
- Replies: 4
- Views: 1072
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 ...
- Wed Feb 01, 2017 4:42 pm
- Forum: Concepts & Calculations Using First Law of Thermodynamics
- Topic: units for heat capacity
- Replies: 5
- Views: 1456
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?
- Sun Jan 29, 2017 4:40 pm
- Forum: Student Social/Study Group
- Topic: Post All Chemistry Jokes Here
- Replies: 9651
- Views: 3642252
Re: Post All Chemistry Jokes Here
You can freeze yourself at -273°C and still be 0K
:)
:)
- Sat Jan 21, 2017 9:09 pm
- Forum: Student Social/Study Group
- Topic: Post All Chemistry Jokes Here
- Replies: 9651
- Views: 3642252
Re: Post All Chemistry Jokes Here
Q: What do you get when you mix sulfur, tungsten, and silver?
A: SWAG
8-)
A: SWAG
8-)
- Sun Jan 15, 2017 8:17 pm
- Forum: Student Social/Study Group
- Topic: Post All Chemistry Jokes Here
- Replies: 9651
- Views: 3642252
Re: Post All Chemistry Jokes Here
Organic chemistry is difficult. Those who study it have alkynes of trouble.
:/
:/
- 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: 1842
Re: Difference between KA and PKA
This equation might help:
pKa= -log(Ka)
pKa= -log(Ka)
- Mon Jul 25, 2016 5:26 pm
- Forum: Conjugate Acids & Bases
- Topic: Equilibrium sign or not [ENDORSED]
- Replies: 4
- Views: 1182
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?
- Sun Jul 24, 2016 9:33 pm
- Forum: Formal Charge and Oxidation Numbers
- Topic: Formal charge in Q4.21 [ENDORSED]
- Replies: 1
- Views: 702
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...
- Sun Jul 24, 2016 7:31 pm
- Forum: Determining Molecular Shape (VSEPR)
- Topic: Shape of I3- (Q 4.13a)
- Replies: 1
- Views: 527
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!!
- Sat Jul 23, 2016 10:39 pm
- Forum: Administrative Questions and Class Announcements
- Topic: Chemistry Community Points
- Replies: 11
- Views: 1975
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...
- Wed Jul 20, 2016 7:08 pm
- Forum: Determining Molecular Shape (VSEPR)
- Topic: H2O Shape [ENDORSED]
- Replies: 3
- Views: 1304
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!
- Wed Jul 13, 2016 4:11 pm
- Forum: *Molecular Orbital Theory (Bond Order, Diamagnetism, Paramagnetism)
- Topic: Bond Order and Bond Length
- Replies: 6
- Views: 1695
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...
- Tue Jul 05, 2016 9:55 pm
- Forum: Dipole Moments
- Topic: How do you find the "largest dipole moment"?
- Replies: 6
- Views: 91937
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...
- Wed Jun 29, 2016 7:02 pm
- Forum: Limiting Reactant Calculations
- Topic: Fundamentals M5 [ENDORSED]
- Replies: 4
- Views: 1025
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 ...
- Sat Jun 25, 2016 10:45 am
- Forum: Accuracy, Precision, Mole, Other Definitions
- Topic: Self-Test E.1B [ENDORSED]
- Replies: 2
- Views: 1201
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...