CHEMISTRY COMMUNITY

Kelly Sun 3E

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.

Kelly Sun 3E

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.

Kelly Sun 3E

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...

Kelly Sun 3E

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.

Kelly Sun 3E

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!

Kelly Sun 3E

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...

Kelly Sun 3E

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

Kelly Sun 3E

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

Kelly Sun 3E

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.

Kelly Sun 3E

How do you know when you are supposed to balance equations with whole numbers vs fractions?

Kelly Sun 3E

Kelly Sun 3E

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.

Kelly Sun 3E

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.

Kelly Sun 3E

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!

Kelly Sun 3E

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...

Kelly Sun 3E

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...

Kelly Sun 3E

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).

Kelly Sun 3E

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"

Kelly Sun 3E

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.

Kelly Sun 3E

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?

Kelly Sun 3E

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%

Kelly Sun 3E

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.

Kelly Sun 3E

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?

Kelly Sun 3E

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.

Kelly Sun 3E

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?

Kelly Sun 3E

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.

Kelly Sun 3E

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?

Kelly Sun 3E

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

CHEMISTRY COMMUNITY

Search found 28 matches

Re: Substituents vs. Functional Groups

Ethane vs Ethene

Re: Practice quiz 1: #6 tert-butyl

Re: Quiz 3 Preparation 1 Problem #5

Remembering the Prefixes for Organic Molecules

Re: reaction coefficients relation to exponent in rate law

Re: Chapter 15 question 3c.

Re: Pre Equilibrium Approach

Re: Balancing Equations

Balancing Equations

Re: Chemistry Jokes- Electrochemistry

Re: Finding change in entropy with no numbers

Re: w=-PdeltaV Equation

Re: Isothermal Processes

ΔG=0 #9 Practice Quiz 2

Re: Maximum work

Easy way to remember state functions

Re: Course Reader Page 19 and 20

Re: Why is BF3 an acid?

Deprotonation Calculation

Re: percentage ionization

Re: Ignoring x in Chemical Equilibrium

Gibbs Free Energy Equation (11.29 HW)

Re: Bonding Orbitals versus Anti-Bonding Orbitals

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

Re: Determining Difference in Electronegativity

Determining the Bond Angles

Online Assessments