CHEMISTRY COMMUNITY

Meredith Steinberg 2E

I do not believe we will have to draw the functional groups, I think we will just have to recognize one given a structure or chemical formula of a molecule.

Meredith Steinberg 2E

Elementary reactions are the specifics of an overall reaction. They're elementary in that there may be species seen, such as intermediates and catalysts, that are not seen in the net reaction that takes place.

Meredith Steinberg 2E

Intermediates are produced in one of the elementary steps, and consumed in another, thereby cancelling it out. Catalysts, however, are not produced in between and are at the beginning of the reaction and are at the end of the elementary steps to cancel out.

Meredith Steinberg 2E

If the slope were to be positive for the first order reaction, we would have to look at -ln(concentration) on the y axis, which doesn't conceptually make sense, so I don't think we would have to calculate a positive slope for equations that are given with a slope w a -k value.

Meredith Steinberg 2E

In the equation, rate=K[reactants], K is directly related to the rate. Keep in mind, however, that K depends ONLY on the reaction and the temperature and will not change if the reactant concentrations change.

Meredith Steinberg 2E

I wouldn't worry too much about deriving the half life of a second order process. If we ever needed to use the equation, we would need 2 of the 3 unknowns: k, initial concentration, or the half life.

Meredith Steinberg 2E

I wouldn't worry too much about it when you're studying, since we will only be tested on 1st, 2nd and zeroth order.

Meredith Steinberg 2E

Today in class we derived that t1/2= 1/(k[A]sub0)

Meredith Steinberg 2E

We will use gas constant, R, when we talk more about activation energy and its relationship to k and A.

Meredith Steinberg 2E

They are both just different ways to write the Nernst Equation, but they should yield the same answer

Meredith Steinberg 2E

You only use commas when they are in the same phase, such as when they're both aqueous. All other times a single line should be used.

Meredith Steinberg 2E

Redox reactions are spontaneous when standard potential is positive. This makes sense if you think about the equation G=-nFE. If E is positive, G will be negative, indicating a spontaneous process.

Meredith Steinberg 2E

There isn't an overall difference, because both maintain neutrality in the solutions

Meredith Steinberg 2E

Salt bridges keep both solutions neutral as reduction and oxidation are occurring

Meredith Steinberg 2E

Usually the anode is on the left and the cathode is on the right, and we see the electrons flow from left to right. If this isn't the case, though, just remember that oxidation (loss of elections) occurs at the anode and reduction (gain of electrons) occurs at the cathode.

Meredith Steinberg 2E

It should be two sig figs, but I wouldn't worry too much about it since we won't be penalized for improper sig figs on tests.

Meredith Steinberg 2E

The forward reaction is favored when there doesn't need to be an outside source, such as increasing temperature, to catalyze the reaction. If the forward reaction is favored, then the reverse reaction is not favored (and vice versa).

Meredith Steinberg 2E

Ideal gas behavior assumes that the ideal gas has a quantity of 1 mol.

Meredith Steinberg 2E

When heat is leaving a system, it's energy sign is negative. When it is entering a system, its energy sign is positive. This can also be applied when you're doing problem 9.5 when heat is being transferred from one reservoir to another.

Meredith Steinberg 2E

Heat is being given off in the 800K reservoir, which makes the energy sign negative, and it's being absorbed in the 200K reservoir, which makes its energy sign positive.

Meredith Steinberg 2E

Heat is leaving the large reservoir at 800K, which explains why the entropy is negative.

Meredith Steinberg 2E

In combustion reactions, the products normally come in the form of gaseous CO2 and liquid H20, unless otherwise specified.

Meredith Steinberg 2E

It ends up not mattering which side gets the negative. What's important to know (as seen in the solutions manual) is that
heat lost=-(heat gained).

Meredith Steinberg 2E

I think it depends on how far we get into the Second & Third Laws and if we move on to Electrochemistry before the midterm. We'll probably learn more about it as the midterm gets closer.

Meredith Steinberg 2E

Yes because there is a transfer of heat from the water to the ice

Meredith Steinberg 2E

The solutions manual explains that as more atoms are present in the molecule, there are more possible bond vibrations that can absorb added energy

Meredith Steinberg 2E

The R value depends on the units you're working with

Meredith Steinberg 2E

An ideal gas means the gas follows the properties of gases "ideally." For example, an ideal gas contains random particle motion, and each particle collision is completely elastic (no energy is lost during the collision). An ideal gas follows the ideal gas law PV=nRT.

Meredith Steinberg 2E

O2 is the most stable form of oxygen and therefore has an enthalpy equal to zero. This is the same for other diatomic elements, such as nitrogen (N2), chlorine (Cl2), etc.

Meredith Steinberg 2E

Because heat is needed for a phase change, the temperature of the sample will remain the same even though heat is being supplied because the heat is being used to break bonds.

Meredith Steinberg 2E

In an acid-base equilibrium reaction, a proton is transferred (bronsted), or another way to thing about it is that an electron is donated (Lewis).

Meredith Steinberg 2E

I think it's important just to know the trends on the periodic table, which will help you determine which acids/bases are strong. For example, group 1 and group 2 hydroxides are generally strong bases. In addition, we learned that as the atomic radius increases (weaker bonds), it's easier for acids ...

Meredith Steinberg 2E

-ate is added when the overall complex has a negative charge. Remember for iron instead of it becoming ironate it becomes ferrate.

Meredith Steinberg 2E

TM cations in solution form complexes with H2O. Some ligands, however, bind more easily than others. Adding NH3 or KCN (electron rich species) will replace H20 ligands because it's an easier way to make coordination compounds.

Meredith Steinberg 2E

T shape structures have the VSEPR formula AX3E2, which means there are 2 lone pairs on the central atom. Trigonal pyramidal structures have the VSEPR formula AX3E, which means there's one lone pair on the central atom.

Meredith Steinberg 2E

Yes, the electron arrangement takes into account the lone pairs (same as looking at the amount of regions of electron density). For example, NH3 has 4 regions of electron density (tetrahedral arrangement), but has a molecular shape of trigonal pyramid.

Meredith Steinberg 2E

A lone pair (like a single, double, or triple bond) counts as a region of electron density when determining hybridization. For example, oxygen in a water molecule has two single bonds and two lone pairs. 2+2=4 regions of electron density, creating the sp3 hybrid.

Meredith Steinberg 2E

Diaqua means there are two water molecules (H2O) in the coordination complex

Meredith Steinberg 2E

We definitely need to know the shapes we learned in class, and also the shapes of molecules based on the regions of electron density before lone pairs are taken into account. Even though we didn't go over T-shaped, we had homework problems assigned that incorporated that shape, so I would definitely...

Meredith Steinberg 2E

It's most favorable for the central atom to have a formal charge of zero. This is why an expanded octet on the central atom can be more stable than a regular octet. For example, SF6 has an expanded octet on the sulfur atom, but that is the most stable lewis structure.

Meredith Steinberg 2E

If you think about trends on the periodic table, ionization energy decreases to the left, as does electronegativity (so you can think about it both ways). For SCN-, the overall trend for ionization energy is that it decreases down and to the left of the periodic table (carbon is further left, and th...

Meredith Steinberg 2E

Formal charge changes depending on the way in which you draw the lewis structure of the compound. If the compound is not drawn in its most stable structure, I don't think the formal charge will always accurately display the most electronegative atom. When constructing the dipole moment, the arrow is...

Meredith Steinberg 2E

A shell corresponds to the principal quantum number (n). Inside each shell are subshells, which are the angular momentum quantum numbers (l). Depending on the subshell, there is a specific amount of orbitals. For example, in the subshell l=1 (p-orbital) there are 3 orbitals where 6 electrons can occ...

Meredith Steinberg 2E

You write the electron configuration in order of increasing energy. Since n=3 is lower energy than n=4, 3d is written before 4s even though 4s comes first in the periodic table.

Meredith Steinberg 2E

Writing the electron configuration for an excited atom IS different than writing it in its ground state. When electron is in an excited state, it's in a higher energy level than its normal ground state. Therefore, when writing the electron configuration, you can put electrons in higher energy levels...

Meredith Steinberg 2E

If given n=6 on our test the correct answer for the possible l values are 0 to n-1. Even though we don't go beyond the f-orbital, there are levels of angular momentum beyond l=3.

Meredith Steinberg 2E

Electrons can move up and down energy levels and the changes in energy are modeled by the difference in En for the hydrogen atom. Make sure that when you're finding Efinal-Einitial, the negative sign in the equation for En doesn't get lost.

Meredith Steinberg 2E

I used the one given in Hz or s^-1 for question 1.13, and I think all of them should use the number in those units. When you're working on 1.13, don't forget the negative sign in the equation (this helped me realize a mistake I made in that problem).

Meredith Steinberg 2E

Since speed of light is constant (3.00 x 10^8 m/s) and therefore cannot change, if wavelength increases, frequency must decrease to keep their product equal to speed of light.

Meredith Steinberg 2E

I took chemistry in high school too and I still feel behind in some topics we're going to be learning soon. I found that the best way to learn the material was to do as many practice problems as possible and to find random youtube videos that describe processes in a creative way to make it help stic...

Search found 50 matches