Search found 28 matches

by Kelly Sun 3E
Sun Mar 13, 2016 11:53 am
Forum: *Alkanes
Topic: Substituents vs. Functional Groups
Replies: 2
Views: 549

Re: Substituents vs. Functional Groups

substituents only contain carbon and hydrogen, while functional groups contain atoms other than carbon, such as oxygen or nitrogen. Functional groups are always given priority over substituents when naming. So methyl, ethyl, propyl, etc. are all substituents because they are hydrocarbons.
by Kelly Sun 3E
Thu Mar 10, 2016 4:13 pm
Forum: Phase Changes & Related Calculations
Topic: Ethane vs Ethene
Replies: 2
Views: 5393

Ethane vs Ethene

In the 2011 final, question 1c, it says ethane has a higher boiling point than ethene. Why is this the case? I thought more emphasis would be placed on the double bonds because they require more energy to break.
by Kelly Sun 3E
Wed Mar 02, 2016 10:25 am
Forum: *Identifying Primary, Secondary, Tertiary, Quaternary Carbons, Hydrogens, Nitrogens
Topic: Practice quiz 1: #6 tert-butyl
Replies: 1
Views: 426

Re: Practice quiz 1: #6 tert-butyl

When looking at that substituent, don't include the parent chain in your substituent. A neo- shape would be a cross, while a tert- shape is a T. So the shape is tert, and you count the number of carbons to be 4, so tert-butyl. I think you counted the parent chain in your naming, so in order for it t...
by Kelly Sun 3E
Mon Feb 29, 2016 4:30 pm
Forum: *Cycloalkanes
Topic: Quiz 3 Preparation 1 Problem #5
Replies: 1
Views: 411

Re: Quiz 3 Preparation 1 Problem #5

The correct name is 3-bromo-1-iodocyclohexane. Because there are two halogens attached to the ring structure, you prioritize the atomic number, not whichever comes first in the alphabet. Since iodine has a larger atomic number than bromine, iodine must have the smallest number, which would be 1.
by Kelly Sun 3E
Mon Feb 22, 2016 4:09 pm
Forum: *Alkanes
Topic: Remembering the Prefixes for Organic Molecules
Replies: 2
Views: 619

Remembering the Prefixes for Organic Molecules

In high school, I was taught to remember the mnemonic "Mom Eats Peanut Butter" to remember the order of the prefixes.
M=meth
E=eth-
P=prop-
B=But-

Hope this helps!
by Kelly Sun 3E
Wed Feb 17, 2016 11:31 am
Forum: General Rate Laws
Topic: reaction coefficients relation to exponent in rate law
Replies: 1
Views: 2789

Re: reaction coefficients relation to exponent in rate law

For elementary reactions, you can write the rate law with coefficients as exponents. This is because at the elementary level, the molecularity describes exactly what is happening. However, for the overall reaction, you cannot directly state that the coefficients are the exponents of each reactant. T...
by Kelly Sun 3E
Wed Feb 17, 2016 11:26 am
Forum: Kinetics vs. Thermodynamics Controlling a Reaction
Topic: Chapter 15 question 3c.
Replies: 2
Views: 543

Re: Chapter 15 question 3c.

The unique rate of a reaction is the same as reaction rate, which is the rate of change of any reactant divided by its stoichiometric coefficient. The sign is always negative for reactants and positive for products. -(1/a)dA/dt=(1/b)dB/dt
by Kelly Sun 3E
Mon Feb 15, 2016 11:34 pm
Forum: Reaction Mechanisms, Reaction Profiles
Topic: Pre Equilibrium Approach
Replies: 1
Views: 350

Re: Pre Equilibrium Approach

Because the rate= (-1/a)(d[A]/dt), which is on page 60 in the course reader, "a" was determined to be 2 because that is the coefficient for NO2 in the overall reaction
by Kelly Sun 3E
Sat Feb 06, 2016 9:03 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Balancing Equations
Replies: 3
Views: 330

Re: Balancing Equations

For problem #5 in the midterm, I balanced the equation like 2C6H6(l) + 15O2(g) --> 12CO2(g) + 6H2O(l), but the solution contained the equation C6H6(l) + (15/2)O2(g)-->6CO2(g) + 3H2O(l). The correct net moles would be -1.5 moles instead of -3 moles.
by Kelly Sun 3E
Fri Feb 05, 2016 10:55 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Balancing Equations
Replies: 3
Views: 330

Balancing Equations

How do you know when you are supposed to balance equations with whole numbers vs fractions?
by Kelly Sun 3E
Tue Jan 26, 2016 10:03 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: Finding change in entropy with no numbers
Replies: 1
Views: 254

Re: Finding change in entropy with no numbers

In the case of Cl2--> 2Cl, since the number of moles increase, the entropy increases. This is because more moles creates more random possible molecular positions and collisions and the "disorder", or entropy increases.
by Kelly Sun 3E
Tue Jan 26, 2016 9:40 pm
Forum: Calculating Work of Expansion
Topic: w=-PdeltaV Equation
Replies: 2
Views: 5409

Re: w=-PdeltaV Equation

Yes this refers to the work of the system because of the negative sign. Whenever the volume increases, the system is doing work on the surroundings, and the work is negative. When there is work being done on a system, the work of the system is positive.
by Kelly Sun 3E
Tue Jan 26, 2016 9:36 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: Isothermal Processes
Replies: 4
Views: 650

Re: Isothermal Processes

This is from the equation deltaU=3/2RdeltaT. So when temperature is constant, deltaT=0, which makes deltaU=0. It's on page 33 of the course reader!
by Kelly Sun 3E
Mon Jan 25, 2016 8:26 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: ΔG=0 #9 Practice Quiz 2
Replies: 1
Views: 348

ΔG=0 #9 Practice Quiz 2

Under what conditions would ΔG=0? In #9, what calculations would you need to do to get ΔG and ΔSsys equal to 0? The question is: A sample of 1 mol of gas initially at 1 atm and 298 K is heated at constant pressure to 350K, then the gas is compressed isothermally to its initial volume and finally coo...
by Kelly Sun 3E
Sat Jan 23, 2016 4:12 pm
Forum: Concepts & Calculations Using Second Law of Thermodynamics
Topic: Maximum work
Replies: 1
Views: 268

Re: Maximum work

When a process occurs reversibly, it happens slowly (infinitely slow) so that less heat is loss to its surroundings. Processes that are done irreversibly usually are quick, but inefficient because they lose heat to the surroundings by friction and turbulence. This is why there are no biological proc...
by Kelly Sun 3E
Sat Jan 16, 2016 4:20 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: Easy way to remember state functions
Replies: 1
Views: 480

Easy way to remember state functions

In case you have a hard time remembering which properties are state functions, my teacher in high school told me that they are usually represented by an uppercase letter (T, P, V, H) and the rest are lower case letters (work).
by Kelly Sun 3E
Fri Jan 08, 2016 7:11 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Course Reader Page 19 and 20
Replies: 1
Views: 259

Re: Course Reader Page 19 and 20

Yes, oxygen in its most stable form is O2, so it requires no enthalpy of formation. Other diatomic molecules are N2, Br2, Cl2, F2, I2, and H2. An easy way to remember these is with the acronym "BrINClHOF"
by Kelly Sun 3E
Mon Nov 30, 2015 11:24 am
Forum: Properties & Structures of Inorganic & Organic Acids
Topic: Why is BF3 an acid?
Replies: 2
Views: 1804

Re: Why is BF3 an acid?

BF3 acts as a lewis acid because it has an empty 2p orbital that can accept a lone pair. It is stable with 3 bonding pairs but it has the ability to accept another electron pair.
by Kelly Sun 3E
Thu Nov 26, 2015 8:45 pm
Forum: Polyprotic Acids & Bases
Topic: Deprotonation Calculation
Replies: 1
Views: 377

Deprotonation Calculation

For number 12.81, why is it that we can ignore the 2nd deprotonation calculations when Ka2<Ka1? Isn't this the case for most acids except for sulfuric acid?
by Kelly Sun 3E
Thu Nov 26, 2015 8:37 pm
Forum: Lewis Acids & Bases
Topic: percentage ionization
Replies: 1
Views: 477

Re: percentage ionization

To find percent ionization, you divide (the concentration of the conjugate base)/(the original concentration). So using the concentration you found-->1.3x10^-3 M

[CH3COO-] / [CH3COOH]
(1.3x10^-3) / (.10) x 100%= 1.3%
by Kelly Sun 3E
Thu Nov 19, 2015 10:31 am
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Ignoring x in Chemical Equilibrium
Replies: 4
Views: 1273

Re: Ignoring x in Chemical Equilibrium

You can assume x makes a negligible difference when k<10^-3. Anything less than this indicates that the reaction strongly favors the reactants, so you can assume the change in concentration for the reactants is minuscule.
by Kelly Sun 3E
Mon Nov 09, 2015 10:30 am
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Gibbs Free Energy Equation (11.29 HW)
Replies: 1
Views: 369

Gibbs Free Energy Equation (11.29 HW)

For number 29 in the homework, we are supposed to find the K value for N2+O2-->2NO. They did this using the Gibbs energy of formation in appendix 2A. I didn't see anything about this in the course reader, so are we expected to learn it on our own?
by Kelly Sun 3E
Mon Nov 09, 2015 9:05 am
Forum: Bond Lengths & Energies
Topic: Bonding Orbitals versus Anti-Bonding Orbitals
Replies: 2
Views: 610

Re: Bonding Orbitals versus Anti-Bonding Orbitals

Antibonding orbitals are higher in energy because the electrons are placed outside the two nuclei, whereas the bonding electrons are found in between the two nuclei. Electrons in the antibonding orbitals will be less stable because of this, and so they are higher in energy.
by Kelly Sun 3E
Thu Nov 05, 2015 6:25 pm
Forum: Shape, Structure, Coordination Number, Ligands
Topic: Coordination Number [PrCl2(en)2]^2 (17.37 in book)
Replies: 1
Views: 257

Coordination Number [PrCl2(en)2]^2 (17.37 in book)

For the molecule [PrCl2(en)2]^2, I said that the coordination number is 4 since ethylenediamine is bidentate. According to the solutions manual, the coordination number is 6 because (en) is bidentate. Why would the coordination number not just be 2x2=4?
by Kelly Sun 3E
Wed Oct 28, 2015 9:09 am
Forum: Electronegativity
Topic: Determining Difference in Electronegativity
Replies: 1
Views: 374

Re: Determining Difference in Electronegativity

Electronegativity values were experimentally calculated, which we do not need to do. You should be given a table of electronegativity values for each atom and you can calculate the difference from that.
by Kelly Sun 3E
Wed Oct 21, 2015 3:11 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Determining the Bond Angles
Replies: 1
Views: 221

Determining the Bond Angles

For a molecule such as SOCl2, will the bond angles will all be equal and less than 109.5, regardless of the fact that one of the atoms is O and the other two are Cl? Should we only look at the regions of electron density and not take into account the pull of each atom?
by Kelly Sun 3E
Mon Oct 05, 2015 3:28 pm
Forum: Administrative Questions and Class Announcements
Topic: Online Assessments
Replies: 1
Views: 381

Online Assessments

Is there any way to view the results of our assessments and see the correct answers?

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