CHEMISTRY COMMUNITY

Nicole Lee 4E

I would match the units with whatever is given in the problem. This is what the solutions manual seems to do as well.

Nicole Lee 4E

When you integrate 1/[A], you get a negative sign so the slope of k switches from negative to positive.

Nicole Lee 4E

The half life equations are all on the equation sheet.

Nicole Lee 4E

I think kinetics since that is what we have been covering for the past week. Also since our final is coming up, practicing kinetics will probably be useful. Though I think questions on the Nernst equation would also be acceptable since it wasn't covered in Test 2.

Nicole Lee 4E

The x-intercept would tell you the time at which all of your reactant A runs out.

Nicole Lee 4E

I found the Kw2 value using the Van't Hoff equation. I square rooted the Kw2 value to find the H3O+ concentration at the new "neutral" pH value. I used -log[H3O+] to find the pH value and compared it with the pH value given in the question. My new pH value ended up being 7.27 and 7.0 is le...

Nicole Lee 4E

I usually balance out the half reactions. If the redox rxn that is given is balanced, you only need to balance one of the half reactions to see how many moles of electrons you need.

Nicole Lee 4E

In basic redox reactions, you don't balance with H+. You balance with OH-

Nicole Lee 4E

You separate the two reactions. Br2(l) -> BrO3(^-1) (aq) and Br2(l) -> Br(^-1) (aq) and balance each separately.

Nicole Lee 4E

Isothermal, reversible reactions. The area under the curve of a Pressure v. Volume graph of a reversible reaction is greater than that of an irreversible reaction.

Nicole Lee 4E

It shouldn't matter. However almost all of the answers in the textbook are given in kJ.

Nicole Lee 4E

Some elements have too many possible oxidation states to memorize. They should be calculable from the reaction.

Nicole Lee 4E

Delta U is equal to 0 for reversible processes.

Nicole Lee 4E

ΔS=ΔH/T at constant pressure and temperature.

Nicole Lee 4E

I haven't really come across any problems using this equation.

Nicole Lee 4E

Isothermal systems have a net energy change of zero so the work must be equal to the opposite of the amount of heat.

Nicole Lee 4E

Another example of an isolated system would be a thermos.

Nicole Lee 4E

The equation Cp = Cv + R shows us that the heat capacity at constant pressure is higher than the heat capacity at constant volume.

Nicole Lee 4E

An open system can exchange matter and energy. A closed system can exchange energy (e.g. heat) but not matter. An isolated system cannot exchange energy or matter.

Nicole Lee 4E

I think we would be expected to know them. We covered the material in 14A.

Nicole Lee 4E

Exergonic means that no work needs to be done for the reaction to occur. So the reaction is spontaneous.

Nicole Lee 4E

For Kp we use bar or atm and for Kc we use mol/L for gases.

Nicole Lee 4E

It is called the ideal gas law and it relates the pressure, volume, mols, and temperature of a gas.

Nicole Lee 4E

pH tells us the acidity or basicity of a solution by measuring the concentration of hydrogen ions. We calculate it by taking the negative log of the concentration of hydronium ions. (pH = -log[H3O+])

Nicole Lee 4E

It is a tool to make calculations easier. The concentration of the reactant is not significantly changed by subtracting the small x. Dr. Lavelle gave an example in class about a millionaire. If a millionaire gives $1000 to someone, it does not really affect the total amount of money the millionaire ...

Nicole Lee 4E

I solve all of the homework problems before tests because this helped me last quarter in 14A. I am also going to redo the video module problems.

Nicole Lee 4E

I believe it is by the end of the week on Sunday.

Nicole Lee 4E

The R constant's units are in Kelvin, so Kelvin should be used for temperature.

Nicole Lee 4E

It depends on the state of the molecules in the equation. If they are gases then use P for partial pressure.

Nicole Lee 4E

Dr. Lavelle told us to use the phrases "favor the products" and "favor the reactants."

Nicole Lee 4E

You use cobaltate and ferrate if the complex is an anion and cobalt and iron if the complex is a cation.

Nicole Lee 4E

The molecule is polar regardless of the location of the Cl atoms because the molecule is tetrahedral-shaped. The position of Cl would matter and affect polarity if the shape was square planar.

Nicole Lee 4E

I believe it is ammine.

Nicole Lee 4E

Polarizability is usually used to describe anions and polarizing power is usually used for cations.

Nicole Lee 4E

You consider one of the iodine atoms the central atom and the VSEPR formula predicts the shape around the central atom. For I3-, the VSEPR formula is AX2E3.

Nicole Lee 4E

Its bond angles are less than 109.5 because of the presence of lone pairs.

Nicole Lee 4E

Dr. Lavelle's examples in class were H2O and H2S. H2O has a higher melting point at 0°C and higher boiling point at 100°C compared to H2S which has a melting point of -80°C and boiling point of -60°C. Since H2O has hydrogen bonds, the melting point and boiling point increase.

Nicole Lee 4E

I believe Dr. Lavelle said we only need to know how to draw Lewis structures, which would mean we don't need to draw the wedges. He said we would need to be able to name their shapes instead.

Nicole Lee 4E

Like said above, most of the homework problems and examples we covered in class don't have any major calculation elements, so I don't think Test 3 will.

Nicole Lee 4E

Here is a visual of an example of a molecule with a see-saw shape.

Nicole Lee 4E

You arrange the bonding pairs and lone pairs around the central atom in a way that minimizes electron pair repulsion. For molecules where there is no lone pair around the central atom, the bond angles are 180 degrees for molecules with 2 bonding pairs around the central atom, 120 degrees for 3 bondi...

Nicole Lee 4E

It's the model we use to predict shapes of molecules and polyatomic ions.

Nicole Lee 4E

You can find the shape by drawing a Lewis structure to determine the number of bonding pairs around the central atom.

Nicole Lee 4E

Exact lengths have to be given, but you can figure out comparatively which bond lengths are longer or shorter. For example, a single bond would have a longer bond length than a triple bond.

Nicole Lee 4E

They depend on both the bonding pairs and the lone pairs.

Nicole Lee 4E

Electrons are removed from the 4s orbital before 3d electrons are removed, so you get [Ar]3d^8 instead of [Ar]3d^6 4s^2.

Nicole Lee 4E

Electrons are filled in this order: 1s 2s 2p 3s 3p 4s 3d 4p 5s 4d 5p 6s 4f 5d 6p 7s 5f 6d 7p. This order can be figured out looking at the periodic table.

Nicole Lee 4E

We didn't discuss this in class and there weren't any homework questions related to this topic, so I would assume no.

Nicole Lee 4E

I think the second question refers to whether the calculated results will match the experimentally observed results. Since they do confirm the experimentally observed results, the answer would be yes.

Nicole Lee 4E

Dr. Lavelle said that we don't have the ability to measure such small wavelengths, so a number as small as 6.94 x 10^-38m can be ignored.

Nicole Lee 4E

Multiply your answer by 6.022x10^23 because there are 6.022x10^23 electrons in 1 mol of electrons.

Nicole Lee 4E

@Veronica Thanksgiving break is Thursday-Friday, November 22-23 during Week 8. We have a 4-day weekend.

Nicole Lee 4E

Dr. Lavelle's Quantum World Lecture Outline on his website specifies which equations we need to know.

Nicole Lee 4E

It's more practical to use kilograms to measure things. Though we measure the weight of small things like electrons in chemistry, kilograms is more useful in measuring everyday objects.

Nicole Lee 4E

The threshold energy is the work required to remove an electron from a metal surface. The energy of the photon must be greater or equal to the threshold energy in order to remove an electron from the surface. E(photon) - Threshold Energy = Kinetic Energy of Electron

Nicole Lee 4E

I usually just test all of the reactants to see how much I get of one specific product. Whichever reactant gives me the least product (mol or grams) is the limiting reactant. It is sometimes inefficient when you're only asked to find the limiting reactant, but most problems I've run into end up aski...

Nicole Lee 4E

Light acts as both, but we use the quantum model for specific topics and the wave model for others. Dr. Lavelle emphasized on Monday that the wave model does not apply to the photoelectric effect.

Nicole Lee 4E

I try to balance all other elements before balancing oxygen and hydrogen. If there are polyatomic ions within the problem, I balance those first, treating them as one unit.

Nicole Lee 4E

400. or 4.00x10^2 would both work.

Nicole Lee 4E

You get the most accurate answer if you use the true value while you are calculating. Apply significant figures only to your final answer so you don't have rounding error.

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