CHEMISTRY COMMUNITY

Daria MacAuslan 1H

no you always use h20 to balance out the o's, then you use oh's later on, in basic solutions to balance the charge (not in acidic solutions though).

Daria MacAuslan 1H

Delta S total is equal to delta s or the surroundings plus delta s of the system. When the reaction is reversible then delta s total is equal to zero because the work done on the surroundings and on the system is equal

Daria MacAuslan 1H

It can be used on any reaction order because it has to do with changes in the rate constant rather than changes regarding the reaction order.

Daria MacAuslan 1H

Rate laws can be used in this question because for bimolecular reactions like the one in part a, the rate is simply equal to k[NO}^2, because there are two molecules of NO reacting and colliding with each other. This makes the coefficient for NO 2, and thus that becomes the exponent in the rate law ...

Daria MacAuslan 1H

I think the units for a zero order reaction are molarity per second (or M/second). In a zero order reaction, the reactant is just pretty much colliding with the walls of the space it is within, not with any other reactant.

Daria MacAuslan 1H

Although this isn't on the equation sheet itself, you should know how to derive it. It basically draws a relationship between temperatures and K values that are changing/ different.

Daria MacAuslan 1H

Pt is a solid used to conduct the actual processes happening, so it should be added to the side of a cell in which there is only aq solutions, or aq and gas.

Daria MacAuslan 1H

Leave H2O out of all cell diagrams, it should not be there

Daria MacAuslan 1H

You usually use ln, just because it is more direct and it is also given to us on our equation sheets. If you want to use log however, just multiply by the conversion factor, it shouldn't really matter in the end

Daria MacAuslan 1H

you can definitely simplify at the end, it won't change the potentials at all. Still, usually after balancing half reactions the final one will already be in its most simplified form

Daria MacAuslan 1H

In a battery, if ions were to flow freely to their corresponding sides, there would eventually be a buildup of charge. The cathode side would get extremely negative because of the electrons flowing to it, and the anode side would get very positive. The salt bridge neutralizes this and prevents it fr...

Daria MacAuslan 1H

A general rule of thumb my TA said was that the anode is usually on the left and the cathode is on the right.

Daria MacAuslan 1H

I think that the only way we have been learning and the only way they do it in the textbook is in terms of reduction potentials, so that's probably what we should pay attention to

Daria MacAuslan 1H

I don't think the order matters at all. Sometimes, it is written in the order of reactants then products, but this isn't a rule and you shouldn't assume it will be that way in a question.

Daria MacAuslan 1H

If you are talking about acidic solutions (which I assume you are since you asked about H+ ions), you can just add H20 first to balance out the number of oxygens in the reaction, and then add however many H+ ions you need to balance out the hydrogens as well.

Daria MacAuslan 1H

When the change in Gibbs Free Energy value is negative, then we can know that the reaction is spontaneous and proceeding towards the products. If it is a positive change, then the reaction is not favorable or spontaneous and proceeds towards reactants.

Daria MacAuslan 1H

So for this question, you have to look at what system will have the smallest volume and the greatest amount of substance that is concentrated in it. My TA explained it in the way that a smaller volume will allow for a greater concentration of substrate to interact, and a higher concentration will al...

Daria MacAuslan 1H

an oxidized species will have lost electrons (in other words, its oxidation number will increase), and a reduced one will have gained electrons (so the oxidation number decreases and becomes more negative from the negative charge of the electrons)

Daria MacAuslan 1H

yes the values will be given or you can look them up I believe

Daria MacAuslan 1H

In an irreversible reaction, the total change in entropy will be equal to the change in entropy of the system. In a reversible expansion, the total will be equal to zero, which can also be interpretted as the entropy change of the system is equal to the entropy change of the system but in negative f...

Daria MacAuslan 1H

If delta g, gibbs free energy, is a negative value, then the reaction in question can be determined to be spontaneous

Daria MacAuslan 1H

Irreversible usually means there is a sudden change that happens very quickly, and the surroundings/ system entropies are not equal. Reversible means that there are a series of little partial changes during which the entropy change of the system is equal to the negative entropy change of the surroun...

Daria MacAuslan 1H

At equilibrium, we know that both the forward and reverse reactions are occurring at roughly the same rate, and with roughly the same favorability. This means that neither one is specifically favored or spontaneous, so delta g is 0

Daria MacAuslan 1H

This equation is a way of calculating the entropy of a system of molecules entirely based on their position and the number of ways they can be arranged

Daria MacAuslan 1H

when looking at work in an irreversible expansion, it is equal to external pressure times change in volume. In a vacuum, there is no external pressure so there is no work done

Daria MacAuslan 1H

The delta sign just smbolizes that there is a change in that specific value. Both entropy and enthalpy are state functions, and both of them can have calculated changes in their values.

Daria MacAuslan 1H

Yes, because both types of molecules have different amount of orientations and states

Daria MacAuslan 1H

I dont think we covered this in class so I am unsure if it is necessary for the exam, especially since we focused more on changes in internal energy, rather than fixed amounts...

Daria MacAuslan 1H

the question will often let you know whether the pressure, volume, or temperature is going to be held constant. Sometimes, too, the question will say that the reaction is isobaric or isochoric, which tells you which value is being held constant in the system.

Daria MacAuslan 1H

degeneracy can be thought of as having more than one state for a molecule or system. it has to do with entropy and disorder.

Daria MacAuslan 1H

In an exothermic reaction, heat is exuded once the reaction runs. It is emitted from the reaction proceeding, so you can almost consider it a product of the reaction itself. Thus, if we want to maintain equilibrium in a system, adding more of this product (adding heat/ increasing the temperature) wi...

Daria MacAuslan 1H

Pretty much all gases are not ideal. an "ideal gas" is just a concept to help us be able to solve problems and equations assuming that the gas does not take up any volume or have any intermolecular forces (which non-ideal gases obviously do).

Daria MacAuslan 1H

inert and noble gases are the same thing. They are in the very last column of the periodic table and are not reactive and very stable.

Daria MacAuslan 1H

Salts usually only affect pH if they are weak rather than strong. Strong acids and bases can disassociate totally, and they wont affect the pH, while a weak one will only disassociate partially, meaning that the concentration of H30+ or OH- molecules will increase or decrease depending on the compou...

Daria MacAuslan 1H

most equations in chemistry tend to use Kelvin instead of Celcius or Farenheit. This is important for these calculations because without conversion, the answers to some questions may come out incorrectly. Usually, if the question does not want you to use Kelvin, it will let you know.

Daria MacAuslan 1H

Today we only covered three methods, but I imagine we will get to the fourth in the next lecture.

Daria MacAuslan 1H

Steam at 100 degrees celcius is clearly extremely hot, and when it touches skin, there is a huge difference in temperatures. The steam then undergoes a phase change extremely rapidly, going from a gas form to a liquid water form. This releases a lot of energy and thus ends up creating a much more in...

Daria MacAuslan 1H

The forward reaction is favored because of the fact that changing the amount of reactants by increasing it will allow for more reactions to take place, ultimately increasing the amount of products and favoring this forward reaction.

Daria MacAuslan 1H

The enthalpy of bonds is calculated by taking the averages of many different molecules, so you cant get a perfectly accurate and specific value for this. For diatomic molecules, however, it is accurate.

Daria MacAuslan 1H

Delta G refers to Gibbs free energy, the amount of energy available to do work in a system. Delta H, however, refers to enthalpy, or internal energy plus pressure and volume.

Daria MacAuslan 1H

If you are asked for the molar concentration, answer in mols/L, rather than pH or pOH. If you are asked for either of those, though, then you would need to take the negative log of the molar concentration and answer in that way.

Daria MacAuslan 1H

the ice box should pretty much always be used because it can help get rid of mistakes and organize our thoughts. x is only negligible when the k value is ver, very small. it has to be less than 1x10^-3 in order to just ignore x, otherwise you can't simply get rid of it.

Daria MacAuslan 1H

An inert gas is one that will not react or really have any effect on an ongoing reaction. For Le Chatlier's principle, adding an inert gas won't change the reaction. These are really stable, non-reactive gases: the noble gases in other words.

Daria MacAuslan 1H

From Chemistry 14A, we were advised to simply memorize the list of strong acids and bases. There is a comprehensive list in the textbook. Contextually speaking, though, strong acids and bases are basically the ones that dissociate completely in reactions, while weak ones are the ones that only parti...

Daria MacAuslan 1H

Cl2 is more thermodynamically stable than F2 because of its smaller K vale, or equilibrium constant. This also means that it is going to dissociate less totally than F2 into singular atoms, which in turn makes it more stable (since it wants to stay in its original state of a diatomic molecule).

Daria MacAuslan 1H

The activity of pure substances is equal to 1, which means that in a reaction their concentration will not ever change. Because of this, liquids are not included in the calculations.

Daria MacAuslan 1H

There can never be negative concentration values, so the only answers you would want to use for your answers are the ones that come out positive after solving the quadratic formula.

Daria MacAuslan 1H

Yes, partial pressure is only used for gases. Basically, a sum of all the partial pressures of different gases or compounds is equal to the total pressure of the system.

Daria MacAuslan 1H

R is the Universal Gas Constant. It is described in the textbook as well. The values can be in different units of pressure. It is 8.314 J/molK, 0.082L-atm/ molK, or 62.36L-torr/molK.

Daria MacAuslan 1H

Definitely outline 1 and maybe a little of outline 2

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