Search found 28 matches
- Sun Mar 13, 2016 11:53 am
- Forum: *Alkanes
- Topic: Substituents vs. Functional Groups
- Replies: 2
- Views: 917
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.
- Thu Mar 10, 2016 4:13 pm
- Forum: Phase Changes & Related Calculations
- Topic: Ethane vs Ethene
- Replies: 2
- Views: 9686
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.
- 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: 642
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...
- Mon Feb 29, 2016 4:30 pm
- Forum: *Cycloalkanes
- Topic: Quiz 3 Preparation 1 Problem #5
- Replies: 1
- Views: 613
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.
- Mon Feb 22, 2016 4:09 pm
- Forum: *Alkanes
- Topic: Remembering the Prefixes for Organic Molecules
- Replies: 2
- Views: 1519
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!
M=meth
E=eth-
P=prop-
B=But-
Hope this helps!
- Wed Feb 17, 2016 11:31 am
- Forum: General Rate Laws
- Topic: reaction coefficients relation to exponent in rate law
- Replies: 1
- Views: 4872
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...
- Wed Feb 17, 2016 11:26 am
- Forum: Kinetics vs. Thermodynamics Controlling a Reaction
- Topic: Chapter 15 question 3c.
- Replies: 2
- Views: 799
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
- Mon Feb 15, 2016 11:34 pm
- Forum: Reaction Mechanisms, Reaction Profiles
- Topic: Pre Equilibrium Approach
- Replies: 1
- Views: 522
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
- 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: 554
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.
- 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: 554
Balancing Equations
How do you know when you are supposed to balance equations with whole numbers vs fractions?
- Sat Jan 30, 2016 2:17 pm
- Forum: Student Social/Study Group
- Topic: Post All Chemistry Jokes Here
- Replies: 9651
- Views: 2983153
- 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: 381
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.
- Tue Jan 26, 2016 9:40 pm
- Forum: Calculating Work of Expansion
- Topic: w=-PdeltaV Equation
- Replies: 2
- Views: 6495
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.
- Tue Jan 26, 2016 9:36 pm
- Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
- Topic: Isothermal Processes
- Replies: 4
- Views: 963
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!
- Mon Jan 25, 2016 8:26 pm
- Forum: Gibbs Free Energy Concepts and Calculations
- Topic: ΔG=0 #9 Practice Quiz 2
- Replies: 1
- Views: 478
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...
- Sat Jan 23, 2016 4:12 pm
- Forum: Concepts & Calculations Using Second Law of Thermodynamics
- Topic: Maximum work
- Replies: 1
- Views: 412
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...
- Sat Jan 16, 2016 4:20 pm
- Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
- Topic: Easy way to remember state functions
- Replies: 1
- Views: 900
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).
- 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: 430
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"
- Mon Nov 30, 2015 11:24 am
- Forum: Properties & Structures of Inorganic & Organic Acids
- Topic: Why is BF3 an acid?
- Replies: 2
- Views: 2794
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.
- Thu Nov 26, 2015 8:45 pm
- Forum: Polyprotic Acids & Bases
- Topic: Deprotonation Calculation
- Replies: 1
- Views: 528
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?
- Thu Nov 26, 2015 8:37 pm
- Forum: Lewis Acids & Bases
- Topic: percentage ionization
- Replies: 1
- Views: 651
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%
[CH3COO-] / [CH3COOH]
(1.3x10^-3) / (.10) x 100%= 1.3%
- Thu Nov 19, 2015 10:31 am
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Ignoring x in Chemical Equilibrium
- Replies: 4
- Views: 1886
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.
- Mon Nov 09, 2015 10:30 am
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Gibbs Free Energy Equation (11.29 HW)
- Replies: 1
- Views: 502
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?
- Mon Nov 09, 2015 9:05 am
- Forum: Bond Lengths & Energies
- Topic: Bonding Orbitals versus Anti-Bonding Orbitals
- Replies: 2
- Views: 810
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.
- 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: 378
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?
- Wed Oct 28, 2015 9:09 am
- Forum: Electronegativity
- Topic: Determining Difference in Electronegativity
- Replies: 13
- Views: 919
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.
- Wed Oct 21, 2015 3:11 pm
- Forum: Determining Molecular Shape (VSEPR)
- Topic: Determining the Bond Angles
- Replies: 1
- Views: 322
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?
- Mon Oct 05, 2015 3:28 pm
- Forum: Administrative Questions and Class Announcements
- Topic: Online Assessments
- Replies: 1
- Views: 538
Online Assessments
Is there any way to view the results of our assessments and see the correct answers?