CHEMISTRY COMMUNITY

Dimitri Speron 1C

You can use the pseudo especially when your rate law is dependent on multiple reactants. If the reaction is first order with respect to any of them it can be rewritten as pseudo-first order.

Dimitri Speron 1C

No, the order of the reaction is unchanging, but the rate is dependent on the initial concentrations of the reactant. Therefore by doubling the concentration (doubling the physical amount of it, not adding a two to the chemical equation) will double the initial rate.

Dimitri Speron 1C

According to the textbook the average rate isn't very important. As far as I know, instantaneous rates are all that is relevant for all of the types of problems we are going to be doing. (unless the problem is "find the average rate")

Dimitri Speron 1C

This can be for a number of reasons. The one that Lavelle specifically mentioned in class is that the reaction is dependent on an enzyme or catalyst rather than on the concentration of reactants.

Dimitri Speron 1C

The final is pretty evenly everything that we have covered. I wouldn't expect anything to be more common than other stuff.

Dimitri Speron 1C

Yes, that's exactly correct.

Dimitri Speron 1C

What he meant is that despite the fact that the compound is technically thermodynamically unstable, its kinetic stability trumps that, and the reaction either does not proceed or does so exceedingly slowly.

Dimitri Speron 1C

Yes, generally. This is because the reaction will require a greater buildup of heat in order to reach the energy of its transition state.

Dimitri Speron 1C

straight lines indicate that they are in the same phase in the same beaker. A straight line indicates that they are in different phases. (when used to show the different between oxidized and reduced states)

Dimitri Speron 1C

The potential of the reverse reaction is negative, therefore it is not spontaneous and will require a supply of energy to occur.

Dimitri Speron 1C

it depends, the half reactions ought to be balanced, otherwise your standard reaction potential will not really make sense/be the right number.

Dimitri Speron 1C

No, n is the number of moles of electrons being transferred.

Dimitri Speron 1C

Statistical entropy is the total amount of entropy for the given amount of micro states, whereas residual entropy is a specific entropy that is left after most of the thermal energy of the system is gone. (i.e. the temp approaches 0K)

Dimitri Speron 1C

The actual derivation for Boltzmann's equation is quite complicated and involves a lot of multivariable calc, so I would just take it for granted.

Dimitri Speron 1C

You have to balance the chemical equation to see if the number of moles of gas will change. For the temperature the problem will tell you.

Dimitri Speron 1C

The density of water is 1g/mL and the question states that there are 800mL of solution. You can assume the contribution to density from dissolved solids is negligible and therefore that the weight of the water in question is 800g.

Dimitri Speron 1C

This equation is derived from the equipartition theorem. This is the form that is for the translational energy of a monatomic gas, and the form can change as you change the molecular structure of the gas in question. (i.e. you have diatomic or polyatomic gases) The equipartition theorem gives us the...

Dimitri Speron 1C

How do we convert between (units of pressure x liters) to joules? I know that for (atm x liters) you multiply by 101.325, but I am not sure about other units of pressure, or conceptually why this works.

Dimitri Speron 1C

Change in volume is (pi)(r^2)(change in d) because r is a constant and does not change in between the final and initial volumes. (at least in this example, it could potentially change but that would be a rather more complicated) So in order to calculate change in volume you just need to replace the ...

Dimitri Speron 1C

An isolated system does not necessarily have constant volume, but it could. Isolated just means that there is no exchange of heat or matter with the surroundings.

Dimitri Speron 1C

Heat and work both contribute to change in internal energy by the equation (delta)U = heat + work. When you have heat exiting the system you subtract from internal energy. Heat into a system adds to internal energy. Work done on a system adds to internal energy, work done by a system subtracts inter...

Dimitri Speron 1C

Fusion is an endothermic process because you put in heat to the system to change the phase, but the temp of the substance does not change. Solidification, or the reverse reaction, is exothermic because the heat that was input to liquify the substance (the enthalpy of fusion) is being released in ord...

Dimitri Speron 1C

For bonds that are not from diatomic molecules, (molecules with 2 atoms) it is practically impossible to get a constant value for a bond that is found in many different molecules. For example, the carbon-carbon double bond is present in tons of different molecules and has a very slightly different b...

Dimitri Speron 1C

While I can't confirm what is on the test, you just take the negative log of both sides and then use the formula log(ab) = loga + logb to derive the final equation.

Dimitri Speron 1C

If you have a reaction with a polyprotic acid, (acid capable of donating more than one proton, of which H2SO4 is an example) then you can express it as two equilibrium reactions in which the second one the concentration of H3O+ is more than 0. For the vast majority of polyprotic acids the second or ...

Dimitri Speron 1C

The percentage protonated is just another way of indicating the power of a base. If the percent protonated was close to 100, that would mean that you have a strong base because all, or almost all, of the base has received a proton from water and become the conjugate acid. A low percent protonation i...

Dimitri Speron 1C

A strong acid dissociates completely in water, or at least so much that it is practically completely. Mathematically, this means that the Ka (acidity constant) is infinitely large. For weak acids the acidity constant will be less that 10^-3. This means that not all of the acid is dissociating in wat...

Dimitri Speron 1C

K is the general term for an equilibrium constant, which the textbook defines in terms of activities. (which Dr. Lavelle said was more accurate, but unnecessary for an undergraduate-level class) Kp is the equilibrium constant in terms of partial pressures, which applies only to homogenous gas reacti...

Dimitri Speron 1C

Why is it that we don't include pure solids and liquids in equilibrium constants?

Dimitri Speron 1C

Acidic and basic oxides are just that, oxides that act as acids or bases. Acidic oxides are usually covalent compounds whereas basic oxides are typically metal oxides. The ones that fall in between, the metalloids, (with a bit of overlap and exceptions) are the amphoteric oxides that can act as eith...

Dimitri Speron 1C

Lewis and Bronsted, Arrhenius is a pretty outdated definition that was superseded by the Lewis and Bronsted-Lowry theories.

Dimitri Speron 1C

Strong acids totally dissociate in water forming as many hydronium ions as there are acid molecules in the solution. (for monoprotic acids, for acids that donate more than one proton it can be two or three times as many) Weak acids will have incomplete dissociations.

Dimitri Speron 1C

An oxidation number is pretty much the positive charge on an element if it is positive, or the negative charge if it is negative. It represents the number of electrons lost (positive) or gained. (negative) An oxidation reaction in general refers to the loss of electrons, which is why positive oxidat...

Dimitri Speron 1C

We will have to be able to list the orbitals that are present in a hybrid orbital but I do not believe that he will have us actually draw the hybrid orbitals.

Dimitri Speron 1C

The reason for the tighter bond is because multiple coordinate bonds are formed due to the presence of several lone pairs on the chelate. This means that instead of a lone ligand which would only form one bond, the chelate compound can form several, increasing the overall strength.

Dimitri Speron 1C

If you memorize which molecules are the ones without lone pairs, then it is fairly easy to intuit which molecules are the ones with one less atom and a lone pair instead. (identical electron arrangement, different molecular shape) This is the method that I usually use.

Dimitri Speron 1C

Pi bonds are weaker because due to the parallel overlap, the total area of overlap is smaller. This can be derived from quantum mechanical representations of the bonding models.

Dimitri Speron 1C

Yes, this results in a t-shape molcule with a VSEPR configuration of AX4E1. If you were to change that to AX3E2, then the resultant geometry would be t-shaped, not see-saw.

Dimitri Speron 1C

He said that we definitely won't have to, but knowing the equation for the sake of conceptual questions is probably a good idea.

Dimitri Speron 1C

It is when you have one molecules that already has a dipole (polar) and you bring it into proximity of another non-charged molecule, particularly one that has lone pairs. When you bring them together, the dipole's net charge will distort the electrons of the otherwise uncharged molecule, thus induci...

Dimitri Speron 1C

The types of atoms do not affect it, rather the number of atoms and electrons. Indirectly the type of atom affects shape by determining the number of electrons available.

Dimitri Speron 1C

The reason that nitrogen has a higher ionization energy than oxygen is because oxygen has an orbital with 2 electrons in it, which results in some electron-electron repulsion. Whereas nitrogen has just one electron in each of its 2p orbitals and therefore lacks that same electron-electron repulsion.

Dimitri Speron 1C

There are also exceptions based on what the central atom is and such. For example, if resonance is possible, then the structure will always have resonance because resonance structures are lower energy than non-resonance structures.

Dimitri Speron 1C

8.5 to 8 is a pretty big jump. I would check your calculations up to that point, its possible that you rounded too early. The rule, according to my TA, for empirical formulas, is that you can round up or down if the value is within 5% of that rounded value.

Dimitri Speron 1C

In lecture Dr. Lavelle said that we can pretty much always use the abbreviated form unless specifically stated to do otherwise.

Dimitri Speron 1C

This is because it is more stable for the entire 3d subshell to be filled than to have the 4s subshell with 2 and the 3d with 9. This is pretty much just how the math happens to work out and what is experimentally observed. A parallel to this is the electronic structure of Chromium, from the same su...

Dimitri Speron 1C

It is usually on a case-by-case basis. For example, CuCl2 is more stable than CuCl, but CuI is more stable than CuI2. This is due to the specific physics of the electrons in the 3d subshell.

Dimitri Speron 1C

I assume you meant photons, not protons. (because protons do indeed have mass) The reason that photons have momentum is related to the equation E = mc^2. Since c is the velocity of a photon, this equation can also be written as E = mv^2. Since momentum is equal to mv, this can be rewritten as E = pc...

Dimitri Speron 1C

Spectral lines are the patterns created from the light absorbed or emitted by a hydrogen atom. Diffraction patterns are the patterns created when two light waves interact with each other creating patterns of constructive or destructive interference. These are not necessarily related in the context o...

Dimitri Speron 1C

The names of each of the orbitals correspond to one of the axes of the three-dimensional cartesian coordinate plane. For example, the Px orbital lies along the x-axis of the plane, whereas the Py orbital lies along the y-axis of the plane and the Pz along the z-axis. This is the way to differentiate...

Dimitri Speron 1C

Will there be audio-visual focus modules available for the other topics in the quantum world section? Right now I can only seem to find ones up to Heisenberg's uncertainty principle.

Dimitri Speron 1C

They have extremely similar masses. Given the number of significant figures in the problem they have identical wavelengths, and this is the answer that they are looking for. However, if you hypothetically had more sig figs, you could indeed find a percent difference (tiny) between the two wavelengths.

Dimitri Speron 1C

If you want to use the Rydberg Equation, use the final energy level = n1, the initial energy level is =n2. Then you simply plug in to a calculator and solve. As mentioned in lecture though, the other method is somewhat less susceptible to errors.

Dimitri Speron 1C

The question asks us to find the minimum uncertainty in a bowling ball. In lecture Dr. Lavelle said when you are given a velocity + or - a certain value you use the entire range of values as your uncertainty. (i.e. the velocity is 1 m/s +/- 3 m/s, therefore your uncertainty is 6 m/s) The solution ma...

Dimitri Speron 1C

It is meant to draw notice to the fact that numbers in quantum equations cannot be "anything" like in a lot of classical mechanics situations. In lecture he used the example F= ma can have pretty much any number for each of those values, whereas in a quantum equation some variables will on...

Dimitri Speron 1C

I believe you are supposed to do the ones from the unit on the syllabus that we are in right now. So for this week it would be anything from the "Quantum World" section

Dimitri Speron 1C

Extent of change is just a weird way to refer to the slope of the wave. The wave's amplitude is the electric field, so the changes to the slop would represent the extent of change to the electric field.

Dimitri Speron 1C

If you have .3 moles of a substance (and you have verified that this is your limiting reactant) and the equation states that there is a 1:3 ratio between that particular reactant and the product in question, then you will produce .9 moles of the product. (1 mole of the reactant becomes 3 moles of th...

Dimitri Speron 1C

Is it acceptable to write the number 1 as a stoichiometric coefficient in a balanced chemical equation instead of just leaving the reactant/product with nothing in front of it? I ask only because I keep doing this out of habit and am not sure whether or not this is the proper notation.

Dimitri Speron 1C

He did mention that he wants us to use the proper states of atoms. I would recommend memorizing some of the basic ones and looking for the trends in the periodic table. (i.e. the diatomic elements are usually gasses, etc.)

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