CHEMISTRY COMMUNITY

Sarah Fatkin 4I

Hi! Will the Vant Hoff equation be on the formula sheet? It was for test 2, but is not on the "constants and equations" sheet from Dr. Lavelle's website.

Sarah Fatkin 4I

The species with the most positive reduction potential will be reduced. The species with the most negative reduction potential will be oxidized.

Sarah Fatkin 4I

They'll tell us. If the balanced redox reaction has H+ in it, it's acidic. If it has OH- in it, it's basic.

Sarah Fatkin 4I

You should try using an ICE chart using the initial concentrations given as well as the concentration of NH3 at equilibrium. Hope this helps!

Sarah Fatkin 4I

You usually won't need to include liquids (because H2O is the most common liquid in our equations, and because aqueous implies in solution, including H2O would be redundant), but if you did, it would be solid|liquid|aqueous||aqueous|liquid|solid.

Sarah Fatkin 4I

Adiabatic systems have constant temperature. Isochoric systems have constant volume.

Sarah Fatkin 4I

Yes, k' is the reverse reaction.

Sarah Fatkin 4I

A bomb calorimeter is a closed system, meaning that matter cannot be exchanged with surroundings, but heat can. A coffee cup calorimeter is an isolated system, which means that no matter and no heat is exchanged with surroundings. Hope this helps!

Sarah Fatkin 4I

Every reaction has a unique k. Also, you should know how to find the units of k based on the fact that rate = M/s.

Sarah Fatkin 4I

They're given on the formula sheet, but they won't be labelled, so you should be familiar with them.

Sarah Fatkin 4I

We can determine if a reaction is first or second order using the equation rate = k[A]^n[B]^m. If n and m add up to one, it is a first order reaction. If n and m add to two, it is a second order reaction. Also, if a reaction is first order, then the graph of ln[A] vs t will have a slope of -k. If a ...

Sarah Fatkin 4I

I don't think you should mix partial pressures and concentrations -- Kc is when using concentrations and Kp is when using partial pressures. Hope this helps!

Sarah Fatkin 4I

Makenzie is right, don't include H2O but do include H+ and OH-, because their aqueous state implies that they are in water.

Sarah Fatkin 4I

They serve the same purpose, except salt bridges are represented by double bars and porous disks are represented by single bars in cell diagrams.

Sarah Fatkin 4I

If something has a high reducing power then it will act as a reducing agent.

Sarah Fatkin 4I

"n" is the number of electrons transferred in a balanced redox reaction. For example, in the reduction of Ce4+ to Ce3+ with I-, there are 2 electrons being transferred, so n = 2.

Sarah Fatkin 4I

They basically serve the same purpose except that that with the salt bridge, there are two beakers connected with a tube filled with gel that allows the salts to move, whereas with the porous disk, the salts can transport to either side of the disk because it's porous. Salt bridges are represented w...

Sarah Fatkin 4I

The change in internal energy is equal to zero when the system is isothermal.

Sarah Fatkin 4I

You can assume that the work of the system is zero when the system is at constant pressure and is not changing volume.

Sarah Fatkin 4I

The change in internal energy (delta U) is equal to q + w, and when the system is at constant pressure, then q = delta H, which is enthalpy.

Sarah Fatkin 4I

Delta S total is equal to Ssys + Ssurr, and delta S equals zero when the system is undergoing reversible expansion or is at equilibrium.

Sarah Fatkin 4I

Delta S of the system equals zero when there is no heat entering the system, because detla S = q(reversible)/T.

Sarah Fatkin 4I

Delta S equals zero when there is no heat entering the system, because delta S = q(reversible)/T. Hope this helps!

Sarah Fatkin 4I

Isothermal reversible reactions do more work than irreversible reactions, because isothermal reactions have to work against more external pressure than irreversible reactions. Dr. Lavelle gave the example of a boulder at the top of a hill; work has to be done for the boulder to go up the hill, while...

Sarah Fatkin 4I

Yep! For example, if a system has constant pressure, we know that delta(V) = 0, so the work is zero.

Sarah Fatkin 4I

Most of the problems we do require enthalpy in joules, because delta(H) = detla(U) + pV, where detla(U) is in joules and pV can easily be converted into joules with the constant 101.325 J/(atm*L). Also, delta(H) is just H[final] - H[initial], both of which are in joules. Hope this helps!

Sarah Fatkin 4I

Bomb calorimeters (which a lot of problems include) are considered isolated, because no matter can be added and external heat does not have an effect on the internal system. Hope this helps!

Sarah Fatkin 4I

A really good thermos that does not let any heat in or out is considered an isolated system, because neither matter nor energy can be inputted into the system. Hope this helps!

Sarah Fatkin 4I

Closed systems can exchange heat but not matter, while isolated systems can exchange neither matter nor heat. An example of a closed system is a water bottle, and an example of an isolated system is a bomb calorimeter. Hope this helps!

Sarah Fatkin 4I

Qv is heat at constant volume, while Qp is heat at constant pressure. At constant volume, delta(U) = Qv, because no work is being done on the system. At constant pressure, delta(U) = delta(H) - p(delta(V)). Hope this helps!

Sarah Fatkin 4I

Hi! I don't think so, but it is helpful to remember that when pH is lower, Ka is smaller and when pOH is lower, Kb is smaller.

Sarah Fatkin 4I

Hi! Another thing to think about is that exothermic reactions heat up their surrounding areas, while endothermic reactions cool down surrounding areas.

Sarah Fatkin 4I

Some more examples of state properties are energy, pressure, volume, temperature, density, and heat capacity. An example of something that is not state properties is work done. Hope this helps!

Sarah Fatkin 4I

It shouldn't give you a different answer for K, but typically concentrations are used to find the K of solutions and partial pressures are used to find the K of gases. You can calculate partial pressure by using concentrations and the formula PV = nRT. Hope this helps!

Sarah Fatkin 4I

You should get the same K value regardless of which notation you use; however, partial pressure is usually used for gases and concentration is usually used for solutions. Hope this helps!

Sarah Fatkin 4I

Yes, OH- and H3O+ do indicate whether something is an acid or a base. This is because OH- is formed when bases are combined with water and H3O+ is formed when acids are combined with water. It might be helpful to draw out the lewis structures of these reactions so that you can visualize the proton d...

Sarah Fatkin 4I

Condensation is exothermic. For example, like Dr. Lavelle said in lecture, when steam condenses from vapor to liquid, it releases heat. This is why steam burns are worse than burns from liquid water.

Sarah Fatkin 4I

You're right! Because pKa is the -log of Ka, when Ka is larger and the acid is stronger, pKa is decreased.

Sarah Fatkin 4I

I think this might have to do with how water bonds in a certain pattern when it forms ice (hexagon shapes)

Sarah Fatkin 4I

Hi! To find the concentration of OH- you need to take the -log[H30+] then take the difference between that and 14 to find pOH. Then raise 10^(-pOH) to find [OH-]. This gives you 1.50*10^-14. Hope this helps!

Sarah Fatkin 4I

Hi! The coordination numbers of the TMs are 4, 2, 6, 6. The oxidation state is the charge of the TM, while the coordination number is the number of bonds that the TM has to ligands. Hope this helps!

Sarah Fatkin 4I

Water is amphoteric, meaning that it can act as both an acid and a base. It's useful to look at the other reactant in order to determine whether water is acting as an acid or as a base. For example combining water and hydrochloric acid (HCl), water acts as a base by accepting protons. Hope this helps!

Sarah Fatkin 4I

Hi! This link might be helpful: viewtopic.php?f=38&t=37731&p=127151&hilit=ch2cl2&sid=21ba50c54756d8bcf2b3d98b852255fa#p127151

Sarah Fatkin 4I

Hi! IF5 would not have trigonal pyramidal shape because that would mean it would be AX3E (three bonds, one lone pair).

Sarah Fatkin 4I

I think that the lone pairs are further away from everything if they are in the t-shaped position -- if you had a trigonal planar molecule with two lone pairs at axial positions then it would look kinda like trigonal bipyramidal, but because lone pairs repel more than bonds, it wouldn't work out to ...

Sarah Fatkin 4I

Yes, it does!

Sarah Fatkin 4I

Hi Chemistry Community! Is I3- bent or linear shape? It seems like it should be bent, because one side has 2 lone pairs, whereas the other only has one; however, it could be like tetrahedral. Thanks!

Sarah Fatkin 4I

Hi Chemistry Community!

What's the difference between seesaw and tetrahedral bipyramidal molecular shape? Thanks!

Sarah Fatkin 4I

Yes, for example, NO2 and O3 both have one lone pair and have bent molecular shape.

Sarah Fatkin 4I

Hi Danya! You're right, it's because oxygen has two lone pairs, which means that the structure has tetrahedral shape and bond angles of 109.5 degrees.

Sarah Fatkin 4I

Hi Danya! You're right about elements with n=3 or higher can have an expanded octet because they have access to the d-orbital. I'm pretty sure that Silicon can have an expanded octet. As for Aluminum, while it can have an expanded octet, it often has a sextet. For example, Aluminum has a sextet in A...

Sarah Fatkin 4I

Hi Chemistry Community! I was wondering why N3+ has a higher polarizability than O2-? I thought that the ionic radius decreases across a period. Thanks!

Sarah Fatkin 4I

Oxygen is the most electronegative. O, N, and F are the most electronegative elements, which is why they tend to participate in London forces.

Sarah Fatkin 4I

Hi! Dipole moments occur when a molecule has partially negative and a partially positive end. For example, H2O molecules are polar and have dipole moments during which the positive H ends are attracted to the negative O ends of different particles.

Sarah Fatkin 4I

Hi! All elements above period 3 can have an expanded octet.

Sarah Fatkin 4I

Hi Chemistry Community! Why is the second ionization energy larger than the first ionization energy? Thanks!

Sarah Fatkin 4I

Hi Chemistry Community! Why are anions larger than their parent atoms? And why are cations smaller? Thanks!

Sarah Fatkin 4I

Hi chemistry community, why is the metal (M) M^3+ with the ground state [Ar]3d^6 Co^3+? How did you get that answer? Thanks!

Sarah Fatkin 4I

Hi chemistry community, I'm having some trouble understanding ground states. When is the f orbital part of an element's ground state (for example: 2A.5 part d) Why is the ground state of Ti^3+ is [Xe]4f^14 5d^10?) Is there a trick to know when f orbital is introduced? Thanks!

Sarah Fatkin 4I

Ionic bonds involve one atom losing an electron (cation) and another atom gaining one (anion), while covalent bonds are when two atoms share electrons to form molecules. Hope this helps!

Sarah Fatkin 4I

Hi Chemistry Community! I thought that the electrons closest to the nucleus (with lowest n-value / at ground state) had the lowest (most negative) energy, but I just saw this in the textbook: "...electron-electron repulsions cause the energy of a 2p-orbital to be higher than that of a 2s-orbita...

Sarah Fatkin 4I

Hi Chemistry Community! Will the radial distribution function (P) be on Test 2? Thanks!

Sarah Fatkin 4I

Yes! They just might not be detectable to us, so they basically don't exist from what we can tell

Sarah Fatkin 4I

I like taking notes by hand because that's how I remember things the best. To be honest though, it's a little annoying not being able to edit notes like on Google Docs and not being able to search things though.. so I guess it really depends on what is most important to you.

Sarah Fatkin 4I

I think that it has to with the fact that no one really knows what a particle looks like -- there will always be some amount of uncertainty

Sarah Fatkin 4I

I would write it just in case, but I don't think we're expected to know what the states would be unless they're given to us. Good luck!!

Sarah Fatkin 4I

It would probably be helpful if you had something like 250 mL (2.50 * 10^2 vs 2.5 * 10^2).

Sarah Fatkin 4I

Yes, they can! Just make sure you divide the given molar mass by the molar mass of the empirical formula to double check.

Sarah Fatkin 4I

I would re-do them just to be sure. You should be fine using 6.022 * 10^23.

Sarah Fatkin 4I

So I know that for this week we are turning in any seven of the "Fundamentals" problems in during Friday's lecture, but is there anywhere that the homework assignment (due dates, instructions) will be posted or will we always be choosing seven of the problems on the outline and turning the...

Sarah Fatkin 4I

I did one question from each section just in case, but I'm pretty sure any 7 will be fine! I think that we will usually turn homework in during the discussions.

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