CHEMISTRY COMMUNITY

Iris Bai 2K

When the half reaction doesn't include a conductive metal, you add Pt to that side of the cell diagram.

Iris Bai 2K

The anode is on the right and the cathode is on the left. So in this case, you would right it so that the Ni losing electrons and the Ag is gaining electrons.

Iris Bai 2K

Iris Bai 2K

For the first half reaction, you don't need H2O. Adding it would just make it end up getting canceled from both sides. For the second half reaction adding 12 to one side and 24 to the other is the same as adding just 12 to one side.

Iris Bai 2K

Since you can see that an increase concentrations of both species also increase the rate by the same factor, you can tell that this reaction is first order for both reactants.

Iris Bai 2K

It's determined experimentally, but I don't think we have to know how. Also, rate law is determined by the slow step.

Iris Bai 2K

Reaction intermediates appear and disappear within the course of the reaction, so they don't appear reactants on the first step or the products of the last step.

Iris Bai 2K

it should be 1/[A] vs time

Iris Bai 2K

There always needs to be a conducting solid so that there is a path for the electrons to move across. The solid is only Pt (s) when none of the species in the half reaction are a solid conducting metal.

Iris Bai 2K

Yes i think because there needs to be an actual metal electrode.

Iris Bai 2K

to maintain the charge in the cell because otherwise electrons would only be moving in one direction.

Iris Bai 2K

Isothermal, reversible reactions allow for the maximum amount of work to be done.

Iris Bai 2K

There are two values for delta S (one for hot and one for cold), and delta S total is just the sum of the two delta S values.

Iris Bai 2K

I'm taking LS 7B, a cluster, Chem 14B and BL this quarter and I don't think it's that bad. BL is mostly busy work so you don't have to spend a lot of time studying. I usually spend about 3 hours a week outside of class on the labs.

Iris Bai 2K

Standard usually means at 1mol, 1 atm, and 298 K, and molar only requires 1 mol I think.

Iris Bai 2K

If the specific heat capacity is the same as water, it shouldn't be negative. The constant is on the formula sheet. Usually, a problem will tell you that one reactant is in excess; if it doesn't, you probably need to find the limiting reactant.

Iris Bai 2K

Yes, but you can also just add the moles of helium and krypton together before calculating anything. The answer wont change.

Iris Bai 2K

You use q=nC(delta)T when you are given the amount of moles, and q=mCdeltaT when you are given the mass, I don't think q=C(delta)T should really be used.

Iris Bai 2K

I don't think so unless you know the structures in your head.

Iris Bai 2K

Dr. Lavelle said in lecture that double bonds have to break completely in order to form a single bond between the same two atoms. It's probably because a single bond isn't actually half the energy of a double bond, so you can't just break one of the bonds in a double bond.

Iris Bai 2K

C is just heat capacity, and Cp molar heat capacity at constant pressure while Cv is molar heat capacity at constant volume.

Iris Bai 2K

Both changes in energy are acting on the gas, so the change in energy of the gas is just the addition of the two values.

Iris Bai 2K

The standard enthalpy of formation of O2 is 0, not the standard enthalpy (idk if that's even a thing). It's because oxygen is found naturally as a diatomic molecule, so it doesn't take energy to "form" it the way it's found in nature.

Iris Bai 2K

Because diatomic molecules are not bonded to anything else, the bond enthalpies measured for those bonds are the most accurate. If that same bond occurs in a larger molecule, the bond enthalpy for the same bond in the larger molecule may be slightly different.

Iris Bai 2K

We'll probably be given all the values we need to do the problems

Iris Bai 2K

X is just a variable used to find the value you are looking for. I would set X as whatever concentration the question is asking you to find.

Iris Bai 2K

Solids have no concentration and liquids only have concentration if they are in a solvent (if the solvent is water it's aqueous not liquid). I'm not sure what you mean by water and gas. Concentration is usually found in moles of solute/liters of solvent.

Iris Bai 2K

I would complete the ICE table using partial pressures and convert your answer to molar concentrations afterwards.

Iris Bai 2K

If Q is less than K, that means there is a higher concentration of reactants than products compared to the respective concentrations at equilibrium. Since all systems want to be at equilibrium, this scenario would favor the forward reaction in order to decrease the reactant concentration, making the...

Iris Bai 2K

The K expression includes anything thats aqueous or gaseous.

Iris Bai 2K

I'm pretty sure we just need to know how to calculate pH given an H+ concentration or how to calculate H+ concentration given a pH.

Iris Bai 2K

Ka is the equilibrium constant for acids, and Ka is the equilibrium constant for bases. For an acid that is ionized, you would fine Ka, not Kb.

Iris Bai 2K

I'm not sure about the justification equation, but to determine whether a compound is acidic or basic, you look at the conjugate acid/base in each salt. For example, in NH4Br is made of NH4+ and Br-. The conjugate base would be NH3 (weak base), and the conjugate acid would be HBr (strong acid). Ther...

Iris Bai 2K

The oxidation number of the metal will be the same as the charge of the complex.

Iris Bai 2K

I remember in lecture Dr. Lavelle said that CN- ions are more attractive to central ions than H2O, so they replace the water. I'm pretty sure it's because CN- has a full charge, so it will be more attracted to the cation in the center. Water is a neutral molecule, so the first coordination complex h...

Iris Bai 2K

Double and triple bonds would cause more repulsion between itself and other bonded or lone electrons in the molecule. I wouldn't really say it takes up more space, but it will cause other electrons to be further away.

Iris Bai 2K

I think they will just ask us to identify how many sigma or pi bonds there are in a molecule.

Iris Bai 2K

The number of bonded pairs in the molecule is the same as the number of orbitals in the hybridized orbital. For example, if there are 3 bonded pairs, then the hybridization is sp2. If there are 4, then it's sp3, and so on.

Iris Bai 2K

Electron density includes both lone pairs and bonding electrons. Accounting for all the areas of electron density gives you the molecular orbital geometry. VSEPR geometry only accounts for the bonded electrons.

Iris Bai 2K

If a molecule is polarized, there is a positive and negative dipole. If not, there are no dipoles except instantaneous dipoles.

Iris Bai 2K

I don't think it matters in this question because they don't specify which isomer we need to draw. The orientation that you draw the molecule in doesn't matter because the molecule is always moving.

Iris Bai 2K

If there's a double bond you should still draw the double bond in the VSEPR model, but it would not change the shape.

Iris Bai 2K

Use the formula FC=V-(L+S) to determine the formal charge. The structure that has more atoms with a formal charge of 0 has lower energy.

Iris Bai 2K

Pentane is just a string of 5 carbon molecules bonded to hydrogen atoms with single bonds. 2,2-Dimethylpropane is a string of 3 carbon atoms with two methyl groups attached to the second carbon in the chain (it looks like a + sign) with hydrogens bonded to the outer carbon atoms. The have the same m...

Iris Bai 2K

yes. depending on how many lone pairs there are, the bond angles will change.

Iris Bai 2K

Iris Bai 2K

If it's the first electron to go in that orbital, the spin number is -1/2. If it's the second electron to go in that orbital, the spin number is +1/2. More simply, if the atom is in the first half of the block it's in, the electron will have a spin number of -1/2, and vice versa.

Iris Bai 2K

Since he doesn't require us to memorize the polyatomic ions, I'm pretty sure he'll give us the formulas on the tests.

Iris Bai 2K

All size ones generally increase to the bottom left, and all reactivity ones generally increase to the top right, but understanding the reasoning makes it a lot easier.

Iris Bai 2K

S-block metals have lower ionization energies, which makes it easier for them to give electrons and form compounds.

Iris Bai 2K

When the d orbital can be half filled or completely filled, the electrons will try to fill the orbital instead of going to the s orbital. It's similar to the Cr and Cu examples Dr. Lavelle gave in lecture.

Iris Bai 2K

You use E=hv when looking at light as a wave, and you use E=pc when looking at light as a particle.

Iris Bai 2K

Light travels faster than anything else, so it's not possible for anything to be faster than the speed of light.

Iris Bai 2K

A photon of light is a fixed amount for each electron in each element, so there is no change in intensity of a particular photon.

Iris Bai 2K

We're given a periodic table, so all the molar masses should be on there.

Iris Bai 2K

Constants will be given.

Iris Bai 2K

I think Dr. Lavelle mentioned during a lecture that O2 is sometimes left out of the reactants if it's an unbalanced equation, so you would have to add that in as a reactant. The balanced equation would then be 6FeBr2+ 6Na2CO3 + O2--> 12NaBr + 6CO2 +2Fe3O4.

Iris Bai 2K

I'm pretty sure you need to do both calculations.

Iris Bai 2K

You would multiply the 1.56 mol reactant by 4 mol product/5 mol reactant. This uses stoichiometry to convert the moles of reactant into moles of product.

Iris Bai 2K

Tin has different oxidation states, so the IV is needed to show that tin has a +4 charge and not a +2 charge.

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