CHEMISTRY COMMUNITY

Cynthia Tsang

Q = [concentration of products] / [concentration of reactants]

Because the molarities/partial pressures of all of the components in the Q equation are given, you simply plug and chug. I believe we may have a different test version so I did not get the same answer as you.

Cynthia Tsang

There are two ways to calculate E(cell) with the E(knot) values of the half reactions. Method 1: 1. Reverse the anode half-reaction. 2. Keep the E(knot) value the same. 3. Use E(cathode) - E(anode) without changing the sign for the anode reaction, but using the reverse reaction. Method 2: 1. Reverse...

Cynthia Tsang

I got something different, but that k value would correspond to a spontaneous reaction.

Cynthia Tsang

The unique rate is just the basic rate of reaction. When you multiply a coefficient of a reactant by the unique rate, you get the rate of reaction of that compound.

Cynthia Tsang

The first law and the conservation of energy are the same. The first law just specifies for isolated systems because it is in discussion of thermodynamics.

Cynthia Tsang

In addition, the universe does not exchange heat or matter with anything beyond it, as there is nothing to do this with. So it is isolated.

Cynthia Tsang

Lavelle said third and fourth reactions won't be tested on, but we might cover them a little. He has intimated them a bit in our lectures.

Cynthia Tsang

If there are multiple reactants, you add up the exponents to find the total order of the reaction.

Cynthia Tsang

Since the question is asking for the rate at which O2 reacts, the negative is implied with the question.

Cynthia Tsang

Nope, as long as you separate the same phases with commas and the different phases with a single line.

Cynthia Tsang

No they work interchangeably.

Cynthia Tsang

Cynthia Tsang

No, the order doesn't matter.

Cynthia Tsang

Gases are also included in equilibrium solutions.

Cynthia Tsang

I think the current stops because there is no longer a need for transfer of electrons, but I'm not sure.

Cynthia Tsang

Then you have to make sure you balance the charges as well with electrons!

Cynthia Tsang

yep, i think so.

Cynthia Tsang

Some are liquid particles and loosely bound together and others are gaseous and flowing throughout the mixture.

Cynthia Tsang

Since the textbook said to specifically use the table, I would use the value from there. On the test, you would use the 40 kJ value and that would be fine.

Cynthia Tsang

No you won't ever use q(irrev) to calculate the deltaS, but you can use the fact that entropy is a state function to find the amount of energy needed for an irreversible reaction.

Cynthia Tsang

Like mentioned above, since the entropy of the products is higher, the total entropy would be a positive value.

Cynthia Tsang

deltaG = 0 at equilibrium, so that might be an indicator, but I'm not sure if that would be given.

Cynthia Tsang

The calorimeter can also be apart of the surroundings, as some calorimeters absorb some of the heat released in the reaction. In general though, the water is the surrounding and whatever you're adding is the system.

Cynthia Tsang

There is actually an equation stating deltaS = -(deltaH)/T. Because of this, we can infer that deltaS is smaller in this situation.

Cynthia Tsang

What chapter of homework do we need to do for this week? My TA said we should submit chapter 9 homework, but I have discussion Wednesday morning and we have barely touched on Chapter 9 topics.

Cynthia Tsang

Work is negative when the system does work. Work is positive when work is done on the system.

Cynthia Tsang

For the second question, the 800g comes from the 800 mL of water. Recall that water has a density of 1g/mL so this is used to change the volume to mass. Densities for other substances will be provided, but that's a good one to remember.

Cynthia Tsang

For the first question, standard energy of formations are 0 when a compound is in its most stable, standard state. The definition of standard enthalpy of formation is the amount of energy required to create a 1 mole of a substance from its original standard state. Examples include O2, H2, I2. Br2, h...

Cynthia Tsang

q = C (delta T) is also an equation that works, although I'm not sure when each is applied.

Cynthia Tsang

In general though, I think they're graded for correctness.

Cynthia Tsang

He said in class today that all values will be given!

Cynthia Tsang

Because the pressure is not changing, none of the heat being released is going into the surroundings. This would make the change a closed system and all of the heat released in a reaction would equal the enthalpy of the reaction.

Cynthia Tsang

They are similar but amphiprotic is more specific. Amphiprotic is when something can donate or receive a proton. Amphoteric is when something can act as an acid or a base.

Cynthia Tsang

In trigonal bi-pyramidal, there is no dipole moment because the five atoms around the central atom are evenly spread and symmetrical. For square pyramidal though, where there is a lone pair and 5 bonds to other atoms, this would form a dipole moment.

Cynthia Tsang

When can you assume that, in your ICE table, x is negligible and can be removed from your equilibrium constant equation?

Cynthia Tsang

If given the reaction 2 NO2(g) + F2(g) <-> 2 FNO2(g) are the following equilibrium constants the same? If not, what are the differences and what units or information do you input into each one? K = \frac{[FNO_{2}]^{2}}{[F^{2}][NO_{2}]^{2}} vs. K = \frac{[P_{FNO_{2})}]^2}{[P_{F_{2}}][P_{NO_{2}}]^...

Cynthia Tsang

Sigma bonds are always the first bonds that form. Pi bonds are all the bonds after that. So the second and triple bond are pi bonds and the first bond is still a sigma bond.

Cynthia Tsang

Yup! -ate is only used when the transition metal forms an anion.

Cynthia Tsang

The central atom is always the one with the lowest electronegativity. Be is lower than C so it is in between the two carbons

Cynthia Tsang

Lone pairs provide more repulsion than other atoms with electrons attached. Therefore the angles between the lone pairs and the atoms will be bigger than expected for the shape, and the angles between the atoms will be smaller because the lone pair pushes them closer together.

Cynthia Tsang

I think it was SO2. KCl was ionic. SO2 was polar and N2 was nonpolar.

Cynthia Tsang

So you find that the indeterminacy of the position of the gutter ball is an extremely small number -- about 2.42 x 10^-34 m. This is less than a single millimeter, so you cannot blame the Heisenberg Principle for a gutter ball because the principle would only shift your bowling ball an extremely sma...

Cynthia Tsang

So when you draw molecules, such as CO2, there are a total of 16 electrons present. Carbon has 4 valence electrons and oxygen has 6. So you draw the structure and find that Carbon is in the center and has the oxygens on the side. They are connected with double bonds. Carbon has used all of its valen...

Cynthia Tsang

Well electron affinity and ionization are fundamentally different things. Electron affinity is the change in energy of an atom for adding an electron. When observed in reactions, it's shown that adding an electron is actually exothermic, meaning it releases energy, instead of needing energy to add e...

Cynthia Tsang

I'm pretty sure he'll enter it all in at once or else it would be such a hassle. Someone should ask him in class or ask their TA though.

Cynthia Tsang

So l is the momentum of the electron rotating around the nucleus. Ml on the other hand, is the angle at which the electron is rotating around the nucleus. If you look at orbitals and their different shapes, you'll see that each ml has a different orbital shape and this ml number determines exactly w...

Cynthia Tsang

Hund's Rule basically states that every orbital shell is to be occupied by an electron before any orbital is occupied with two electrons. Usually this means that one spin direction is occupied for all the orbital shells before the opposite spin direction occupies the orbital to fill the shells.

Cynthia Tsang

Frequency can't be negative, but I've noticed that when you switch the two original n-values, one will result in a negative frequency and one will result in the same positive frequency. So whatever value you get, just take the positive form of it and continue.

Cynthia Tsang

So you are given the mass of CO2 and H2O. You convert these both to moles. We can start with CO2. 7.48 grams of CO2 is 0.16996 moles of CO2. You multiple this value by (1 mol of C/1 mol of CO2) to isolate the moles of C. This will give you 0.16996 moles of C. You do the same for oxygen, multiplying ...

Cynthia Tsang

This equation is for kinetic energy. The total energy of a photon is composed of two energies: threshold and kinetic. The threshold energy is the energy needed to free or move an electron. The kinetic energy is the remaining energy, assuming the energy of the photon is greater than the threshold ene...

Cynthia Tsang

If they give you the mass of the compound, you convert it to moles, with the molar mass, and then multiple it by Avogadro's number! That's the amount of atoms that are in each mole of anything.

Cynthia Tsang

I think all of the appendixes are just for reference in the future. It doesn't necessarily mean we'll be tested on them!

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