CHEMISTRY COMMUNITY

Lia Inadomi 1I

This is because it is ln([A]0/[A]t) instead of ln([A]t/[A]0) which is when it would be -kt. This is just because of log rules so ln([A]t/[A]0)=-ln([A]0/[A]t) because coefficient of a log can be seen as the exponent inside the log function

Lia Inadomi 1I

The linear graphs help to determine what order a reaction is. It is linear because the k is a constant and it is the slope.

Lia Inadomi 1I

This can also be when there is a catalyst present or when there is an excess (so rate doesn't depend on concentration of reactant)

Lia Inadomi 1I

It depends on what information you're given in the problem. If they give you initial concentrations and initial rate values often you are able to determine how concentration effects rate to find out that way. If they only give you time and initial concentration then you can use the linear plots to d...

Lia Inadomi 1I

Examples of zero order reactions often have saturated enzymes that make the rate independent of reactant concentrations

Lia Inadomi 1I

A general formula can be M^(1-p)*s^-1, where p is the overall order of the reaction.

Lia Inadomi 1I

A negative delta G value shows that a reaction is spontaneous. The forward reaction in this case is melting so if delta G is negative then that is favored.

Lia Inadomi 1I

Salt bridges allow for a circuit so that the cathode doesn't become too saturated with electrons and thus reject electrons. The salt bridge allows a transfer of electrons back to the anode so that the transfer of electrons is continuous.

Lia Inadomi 1I

You can try to remember this like the oxidizing agent is the thing that does the oxidizing (accepting an electron) and in turn gets reduced. Basically just think of it as the action it is doing.

Lia Inadomi 1I

If a solution becomes too negatively charged, it will repel electrons so the addition of a salt bridge or a porous disk is to allow flow of electrons back to the reducing agent so that the solutions remain neutral and can continue to transfer electrons. It essentially makes the flow of electrons int...

Lia Inadomi 1I

The porous disk is between the two beakers and allows flow of electrons so that the solution that is reduced can still gain electrons and won't repel the electrons

Lia Inadomi 1I

We set deltaG equal to 0 because we need to determine at what temperature deltaG switches from positive to negative. Positive deltaG means it is not spontaneous and negative deltaG means it is spontaneous so we are looking for when deltaG=0 to find when it becomes spontaneous.

Lia Inadomi 1I

Cp is for when there is constant pressure whereas Cv is when there is constant volume. Hope this helps!

Lia Inadomi 1I

Really strong acids that dissociate completely do not have a Ka value. However we classify really weak acids with a Ka value of less than 10^(-3)

Lia Inadomi 1I

I believe all reversible reactions are isothermal but all isothermal reactions may not be reversible

Lia Inadomi 1I

You only need to know it to understand the derivation of the 2nd law of thermodynamics. The actual equations used do not include the integral.

Lia Inadomi 1I

Can someone explain how you know when it is reversible vs irreversible?

Lia Inadomi 1I

This is because you are finding the change in volume and the container is a cylinder. The pump being depressed is the depth you need to calculate changed volume and the equation gives you the diameter so you can find the area of the face of the cylinder.

Lia Inadomi 1I

Enthalpy is the change in heat from the two stages of a reaction. The energy required for the reaction to take place is generally greater than the enthalpy, even for endothermic reactions.

Lia Inadomi 1I

I beleive standard enthalpy is just when a pure element is under standard conditions of pressure and temperature, so it would just the phase of the element when it is under 1 atm and at 25 degrees C

Lia Inadomi 1I

I think this relates to the strength of the bonds. So when CO2 is formed, it releases more heat because two double bonds are stronger than four single bonds like in CH4.

Lia Inadomi 1I

Why does H2O attach to the aluminum when H2O is uncharged?

Lia Inadomi 1I

In the textbook the only polyprotic strong acid listed is sulfuric acid which dissociates completely.

Lia Inadomi 1I

This is when approximating x while using the ICE table. For instance, if the equation becomes (x^2)/(.10-x)=K then you can approximate it to (x^2)/.10=K so you have to do easier calculations.

Lia Inadomi 1I

The question is does a temperature increase shift equilibria towards products or reactants for X2<-->2X?
Why is X2-->2X endothermic? Isn't it a catabolic reaction and therefore exothermic?

Lia Inadomi 1I

Solving for Q is the same as solving for K in regards to setting up the problem. The only difference is that K is when the reaction is at equilibrium whereas Q is at any arbitrary stage in the reaction.

Lia Inadomi 1I

Homogenous vs heterogenous reactions just refers to the phases of the reactants and the products. So if all the reactants and products are the same phase then it will be a homogenous reaction. Hope this helps!

Lia Inadomi 1I

Le Chatelier's principle essentially says that a reaction in equilibrium will adjust to minimize the stress of changing factors ie pressure or concentration. For example when more reactants are added to a reaction, the reaction will in turn produce more products to limit the stress.

Lia Inadomi 1I

1 bar = 0.987 atm, but both are just units of pressure. Hope this helps!

Lia Inadomi 1I

Stoichiometric coefficients are used as the exponent when calculating the equilibrium constant. So if it was 2CO2 then it will be [CO2]^2 in when finding K.

Lia Inadomi 1I

Conjugate acids and bases deal with the Bronsted definition of acids and bases so it is proton (H+) transfer

Lia Inadomi 1I

These are the only definitions of acids and bases that Lavelle has taught. Just remember that Bronsted deals with protons while Lewis deals with electrons! Hope this helps

Lia Inadomi 1I

For Part A, water is produced as OH- is taken from KOH and an H atom is taken from CH3COOH, thus leaving CH3CO2K as the salt produced

Lia Inadomi 1I

If you are unfamiliar with a ligand you can draw a Lewis structure to help you determine the number of lone pairs

Lia Inadomi 1I

The arrangement is just based on number of regions of electron density whereas the shape includes if the regions are lone pair vs bonds

Lia Inadomi 1I

I think hybridization depends on the number of regions of electron density, not the sigma or pi bonds, so it would be sp3

Lia Inadomi 1I

The question asks for the hybrid orbitals so you need to determine the regions of electron density. Tthe d-orbital is incorporated when there are too many regions of electron density for sp3

Lia Inadomi 1I

You will have to memorize the names of the molecular geometry but you can figure out the regions of electron density from the Lewis structure. Hope this helps!

Lia Inadomi 1I

Lavelle said we wouldn't need to draw them but it is probably recommended that you know the shapes

Lia Inadomi 1I

Yes because hybridization depends on the number of regions of electron density

Lia Inadomi 1I

My TA has mentioned that you do not necessarily have to do homework in the current sections as long as they are recent and applicable to what we're learning now. Hope that helps!

Lia Inadomi 1I

The electron geometry is tetrahedral whereas the molecular geometry is bent. This is because oxygen has two lone pairs and two covalent bonds.

Lia Inadomi 1I

I believe that for certain molecular shapes you will know the angles ie trigonal planar is 120 degree angles, but for the case of molecules with lone pair electrons those you will have to give a range because there is no way to calculate the actual bond angle just by looking at VSEPR. Hope that helps!

Lia Inadomi 1I

The bond lengths are equal despite that double and single bonds have different lengths. Somehow the actual bond length will fall between the length of single or double if those are the only bonds present.

Lia Inadomi 1I

Does only the net formal charge matter? Or do you also have to account for each atom as well?

Lia Inadomi 1I

Why can they have expanded shells?

Lia Inadomi 1I

How do you determine the average bond length when there are not just single bonds? When we did the problem in class, there was one bond 1.2 Angstrom and two 1.4 Angstrom but the actual length was 1.24 Angstrom. How do you find the actual bond length from those numbers?

Lia Inadomi 1I

For ionic compounds, how do you know which elements will become cations and which will be anions?

Lia Inadomi 1I

Lewis structures are meant to represent where the electrons are and how the molecule is bonded, not an accurate visual representation

Lia Inadomi 1I

Yesterday at office hours the TA said delta X should be in meters

Lia Inadomi 1I

2d cannot exist because the principle quantum number is 2 and the magnetic quantum number must be at least less than the quantum number so it can either be 1 or 0, but not 2

Lia Inadomi 1I

De Broglie's equation is only applicable to things that have rest mass

Lia Inadomi 1I

You should also know that it changes a probability into an observable value

Lia Inadomi 1I

My TA just said to do hw problems that are relevant to what we're learning so as long as they aren't super old problems then you can do them too

Lia Inadomi 1I

For b, wavelength and frequency are inversely related so they cannot both decrease at the same time due to c=lambda*nu

Lia Inadomi 1I

What does it mean when there is a period after a number but no decimals after the period? For example, 50. g of something. Is that still 2 sigfigs?

Lia Inadomi 1I

Avogadro's constant can be used as the number of particles per mole of a substance

Lia Inadomi 1I

I think in class he said you should convert to L when using a formula that uses L and then you can choose to convert again at the end of the problem depending on what the question is asking for.

Lia Inadomi 1I

My TA said that you should always include states of matter when writing out an equation

Lia Inadomi 1I

Is there a tip on how to find integers when you get a ratio that isn't whole numbers?

Lia Inadomi 1I

Is it possible that two reagents get used up at the same time so that an equation can have two limiting reactants?

Lia Inadomi 1I

Are you supposed to keep sigfigs the entire time while doing conversions or do you round to sigfigs only at the end of the problem?

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