Search found 21 matches

by Swan Ng 1L
Sat Mar 18, 2017 8:45 pm
Forum: *Alkanes and Substituted Alkanes (Staggered, Eclipsed, Gauche, Anti, Newman Projections)
Topic: A question about isomers
Replies: 1
Views: 502

A question about isomers

In class we learned about Cis and Trans isomers. I was wondering if it is possible for another isomer where the arrangement of substituents around one carbon can vary, for example, if we had a carbon atom and its substituents were arranged in an order such as Hydrogen, Chlorine, Iodine, and Bromine,...
by Swan Ng 1L
Sat Mar 11, 2017 10:26 pm
Forum: *Alkanes and Substituted Alkanes (Staggered, Eclipsed, Gauche, Anti, Newman Projections)
Topic: Ethane (H3C–CH3) conformation clarification [ENDORSED]
Replies: 2
Views: 445

Ethane (H3C–CH3) conformation clarification [ENDORSED]

The molecule of ethane is C2H6. I know it can exist in staggered and eclipsed conformations and is more slightly stable when it is in staggered conformation. It is easier to visualize it on the diagram that we are given in the course reader but is there an easier way to tell which conformation is mo...
by Swan Ng 1L
Sat Mar 04, 2017 11:20 pm
Forum: *Constitutional and Geometric Isomers (cis, Z and trans, E)
Topic: Constitutional isomers confusion on their properties
Replies: 1
Views: 385

Constitutional isomers confusion on their properties

I know that constitutional isomers are different ways of attaching same atoms. I also know that in order to determine that two molecules are constitutional isomers, you have to count each atom in both molecules and see how the atoms are arranged. From my understanding, I know that constitutional iso...
by Swan Ng 1L
Sat Feb 25, 2017 9:38 pm
Forum: *Cycloalkenes
Topic: Carbon binding preferences for HBr [ENDORSED]
Replies: 1
Views: 337

Carbon binding preferences for HBr [ENDORSED]

Why does the bromine atom bond to the tertiary carbon in the alkene of cholesterol in the reaction: cholesterol + HBr? Why does the hydrogen bond first?
by Swan Ng 1L
Sat Feb 18, 2017 7:51 pm
Forum: First Order Reactions
Topic: 2013 Quiz Preparation Question#5 for 1st Order Reactions [ENDORSED]
Replies: 3
Views: 480

2013 Quiz Preparation Question#5 for 1st Order Reactions [ENDORSED]

The question is: For the 1st order reaction cyclobutane(g) --> 2ethylene(g) at 800 K, the half-life is 0.43s. Calculate the time needed for the concentration of cyclobutane to fall to 1/64 of its initial value. I am not sure how to approach this problem. How should I approach this problem? Thank you!
by Swan Ng 1L
Sat Feb 11, 2017 9:09 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Midterm 2013 Question 7 Clarification with the cell diagram
Replies: 1
Views: 229

Midterm 2013 Question 7 Clarification with the cell diagram

I am confused by question number 7 because I'm not sure where the e knot values are coming from. I know that it is usually given, but if I look at the formula sheet, I'm not able to find e knot values. Will we be given e knot values during the exam? The question is: Calculate K and delta G at 298k f...
by Swan Ng 1L
Sat Feb 04, 2017 9:40 pm
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: Quiz 1 Preparation Practice Quiz from 2010
Replies: 2
Views: 267

Quiz 1 Preparation Practice Quiz from 2010

The question is: The internal energy of a system was decreased by 1763 kJ after performing 1357 kJ of work. Was heat transferred to or from the system? What percentage of the change in internal energy was used for the actual work?

How do I approach this problem? Thank you!
by Swan Ng 1L
Sat Jan 21, 2017 9:43 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Homework Question Ch.8 Problem 8.107
Replies: 1
Views: 285

Homework Question Ch.8 Problem 8.107

The question is: A person of average mass burns about 30. kJ*min^-1 playing tennis. Find the time you would have to spend playing tennis to burn up the energy in a 2.0-oz serving of cheese, which has a specific enthalpy of combustion of 17.0 kJ*g^-1. I am not sure how to approach this question. I wa...
by Swan Ng 1L
Sat Jan 14, 2017 9:42 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Enthalpy Clarification
Replies: 1
Views: 235

Enthalpy Clarification

Does enthalpy always change when the sample size differs or is this based on a special case? Is this also the reason why the enthalpy of the reaction scale is proportional to the moles used in the reaction? Thanks for the clarification.
by Swan Ng 1L
Sun Jul 24, 2016 8:20 pm
Forum: Calculating pH or pOH for Strong & Weak Acids & Bases
Topic: Homework Question 12.55 Clarification
Replies: 1
Views: 289

Homework Question 12.55 Clarification

I noticed that in the process for solving x in part a, the ka =(x^2)/(0.20-x)= (x^2)/(0.20); however for part b, the ka= (x^2)/(0.20-x) and leaves the x there. Why is it that x is completely ignored in the denominator for part a, but not for part b? Does it have something to do with ka being big or ...
by Swan Ng 1L
Tue Jul 19, 2016 4:27 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Determining Flask at Equilibrium Homework Question 11.7a
Replies: 1
Views: 250

Determining Flask at Equilibrium Homework Question 11.7a

Homework question 11.7a asks "Which flask represents the point in time at which the reaction has reached equilibrium?" The homework questions shows four flasks, and the answer is the 3rd flask. But is there an explanation or reason why the 3rd flask has reached equilibrium? The last three ...
by Swan Ng 1L
Sun Jul 17, 2016 4:17 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Shortcut to determine VSEPR without drawing Lewis Structure
Replies: 1
Views: 778

Shortcut to determine VSEPR without drawing Lewis Structure

I was wondering if there is a shortcut to determine the molecular shape without fully drawing out the lewis structures. I saw that in some of the practice midterms, there were questions asking to determine the VSEPR and didn't require us to draw out the lewis structures. From looking at it, it seems...
by Swan Ng 1L
Sat Jul 16, 2016 2:12 pm
Forum: Shape, Structure, Coordination Number, Ligands
Topic: 3-D Structure Question about the Solid Dash Wedge [ENDORSED]
Replies: 1
Views: 304

3-D Structure Question about the Solid Dash Wedge [ENDORSED]

The course reader shows examples of 3-D structures by using the solid dash wedge model. If we were to draw lewis structures and name their shape on the exam, are we require to use the solid dash model, or can we just draw it out like we usually do? The homework uses the solid dash model for referenc...
by Swan Ng 1L
Fri Jul 15, 2016 11:25 pm
Forum: Shape, Structure, Coordination Number, Ligands
Topic: Coordination Compound Question
Replies: 1
Views: 291

Coordination Compound Question

What is one easy shortcut to tell the coordination number of a lewis structure? I thought it would be easy to tell by just looking at the number of elements in a compound. i.e. [Fe(Cl)4(en)]^2- : By just looking at this at first glance, the obvious answer may seem like 5, but why is it 6? I know for...
by Swan Ng 1L
Fri Jul 08, 2016 11:11 pm
Forum: Lewis Structures
Topic: Determining Lowest Lewis Structure
Replies: 1
Views: 3628

Determining Lowest Lewis Structure

Is there a quick way to determine the lowest energy lewis structure? It takes me a few tries to draw out different lewis structures for the same formulas, and I was wondering if there is a quick way or short cut to know when to draw a single, double or triple bond. I know that the element with the l...
by Swan Ng 1L
Fri Jul 01, 2016 9:42 pm
Forum: Empirical & Molecular Formulas
Topic: Empirical Formula Question about non-whole numbers [ENDORSED]
Replies: 2
Views: 4457

Empirical Formula Question about non-whole numbers [ENDORSED]

I have a question about writing an empirical formula with non-whole numbers. For example, if the empirical formula was C2H1.4C3, am I allowed to multiply the whole empirical formula by 5 in order to make 1.4 from H a whole number? Would that change or effect the answer at all? I know empirical formu...
by Swan Ng 1L
Fri Jun 24, 2016 5:14 pm
Forum: Properties of Light
Topic: Frequency Question [ENDORSED]
Replies: 2
Views: 701

Re: Frequency Question [ENDORSED]

Hi Jennifer, From what I know, in order to calculate the wavelength, you have to convert the nanometers to meters. One nanometer is 10^-9. All you have to do is multiply 580X10^-9 to convert the wavelength from nanometer to meter. Since we want to solve for the frequency and already know the wavelen...
by Swan Ng 1L
Thu Nov 26, 2015 12:35 am
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: Video: Molecular Orbital
Replies: 4
Views: 13146

Re: Video: Molecular Orbital

Hello!

We made a video on Molecular Orbitals! Hopefully, it helps you understand it better!
I made this video with Jasmine and Vivian!
This video is our version of "Hotline Bling" by Drake.
If you need clarification, you can always ask us!
I uploaded this video in mp4 format.

-Swan Ng
by Swan Ng 1L
Sun Nov 08, 2015 10:49 am
Forum: Lewis Acids & Bases
Topic: How do you determine if an element is an Acid or Base?
Replies: 2
Views: 467

How do you determine if an element is an Acid or Base?

Hi, I was wondering if there was a way to tell if an element is an Acid or Base in a Lewis Structure. Thanks!
by Swan Ng 1L
Sat Oct 31, 2015 11:46 pm
Forum: *Molecular Orbital Theory (Bond Order, Diamagnetism, Paramagnetism)
Topic: (2013) Practice Quiz#2 Problem #10
Replies: 1
Views: 365

(2013) Practice Quiz#2 Problem #10

Hello there, I have trouble with question #10: Give the ground state electron configuration and bond order of O2 and predict it's magnetic properties. I know how to solve the bond order and draw the lewis structure of O2, however, I'm not sure what steps I should take next to solve for the magnetic ...
by Swan Ng 1L
Sat Oct 10, 2015 11:30 pm
Forum: Empirical & Molecular Formulas
Topic: Quiz #1 Practice Question
Replies: 1
Views: 408

Quiz #1 Practice Question

Hello, I need help on this question, as it's a bit confusing to me. Do I use a mole conversion formula? Thanks!
How many molecules of water are present in a 7.45g sample?

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