CHEMISTRY COMMUNITY

Jason Liu 1C

Yes, you can just write all the reactants into the rate law. If there are two of the same molecule in the reactants, then you will know it's second order.

Jason Liu 1C

From what I got on my test, it seems like the more positive the reduction half reaction was, the greater the oxidation power.

Jason Liu 1C

For a multistep reaction, you just multiply the rate constants of each forward reaction and divide it by the product of the rate constants of each reverse reaction. So K = (k1 x k2)/(k'1 x k'2)

Jason Liu 1C

The larger the value of k is, the faster the rate. If Ea is large, more energy is required for the reaction to occur, which means the rate will be slower. If the rate is slower, k will be smaller.

Jason Liu 1C

I would still study the half life of second order reactions and understand how they work because it was on the homework and was on my test as well. I think it'd be a good idea to study it in case it's on the final.

Jason Liu 1C

I'm assuming you're talking about a problem asking for the entropy of vaporization at a temperature lower than the boiling point. Since you can't directly find the entropy of vaporization when the temperature is lower than the boiling point, you need to find the entropy of vaporization at the boilin...

Jason Liu 1C

The slowest step determines the rate of the overall reaction because other intermediate steps need the products of the slowest step to continue on with the reaction. These other steps may be faster, but they can only go as fast as the slowest step, which is why the rate of the overall reaction is de...

Jason Liu 1C

I think half lives are just a convenient way of comparing the speed of reaction between reactions. You can just refer to the half lives of different reactions to see which occurs at a faster rate.

Jason Liu 1C

Yes, the equation at the bottom of page 613 takes into account the coefficients and signs (positive or negative) of reactants and products in each reaction, so you should be getting the same unique rate whether you use reactant or product.

Jason Liu 1C

We are looking to find the rate of reaction immediately after the reaction starts. This means that none of the reactants have turned into product yet, which is why we can focus only on the forward reaction. Once there is product causing the reverse reaction, it is hard to find the rate of reaction. ...

Jason Liu 1C

Usually the cathode is on the right in a cell diagram, but you should find the standard potentials of each half reaction to make sure. The reaction with the more positive standard potential will be the cathode.

Jason Liu 1C

Pt is only used in cell diagrams when a solid is needed to for the transfer of electrons from the anode to the cathode. If there is already a solid transferring the electrons, there is no need for Pt.

Jason Liu 1C

There are 2 electrons on the product side of the oxidation half reaction. There are 6 electrons on the reactant side of the reduction half reaction. When you combine the two half reactions, you need to multiply everything in the oxidation half reaction by 3 to cancel out the electrons.

Jason Liu 1C

I think you need an inert conductor when the reactants and products of the half reaction are both gases or solids because you need a solid to transfer the electrons to make the half reaction occur.

Jason Liu 1C

The atoms being oxidized and reduced actually aren't both present in the same molecule in the products. The oxidation half reaction is O3 --> O2 and the reduction half reaction is Br- --> BrO3-

Jason Liu 1C

ΔS isn't 0 for diatomic molecules because there is always entropy. S is only 0 when T = 0K.

Jason Liu 1C

I think it might be because the coefficients in the chemical equations only have one sigfig

Jason Liu 1C

We are looking for K, which can be found with the equation ΔG = -RTlnK. So first we need to find ΔG. We can do that by using the equation ΔG = ΔH - TΔS. We are given the temperature, but we still need to find ΔH and ΔS in order to find ΔG.

Jason Liu 1C

I don't think cooling a vapor down to under its boiling point takes away enough kinetic energy from the molecules to cause them to condense. For example, at room temperature, there is still water vapor in the air. However, a cold bottle in the room will cause the water vapor to condense on the bottle.

Jason Liu 1C

I agree. Gas has a much greater entropy than liquid, so just the fact that there is no gas on the product side should be enough to show that entropy has decreased.

Jason Liu 1C

For problems with ΔT, you can use either Celsius or Kelvin because the difference between the temperatures will be the same. However, for problems with just T, you should generally use Kelvin because that is the SI unit.

Jason Liu 1C

For homework problem 9.1, the solutions manual says to use the temperature in Kelvin instead of Celsius, but it was given in Celsius in the problem. How do I know when to use Kelvin and when to use Celsius?

Jason Liu 1C

Are irreversible reactions isothermal as well? Does a change in temperature make a reaction not reversible?

Jason Liu 1C

The universe is an isolated system because energy cannot be created or destroyed. Likewise, matter cannot be added or taken away from the universe.

Jason Liu 1C

Since the intermediate steps in Hess's Law are only used to find the enthalpy of the overall reaction, the intermediate steps do not necessarily have to be able to be carried out. Therefore, it is OK to use fractions because all you need are values to calculate the overall reaction's enthalpy.

Jason Liu 1C

At a constant pressure, if volume increases, it means that the system is expanding and energy is leaving the system as work. This leaves the system with a lower internal energy. The negative sign means that when a system expand, it is losing energy as work.

Jason Liu 1C

I think it has more to do with how many atoms are in each molecule

Jason Liu 1C

The water is not undergoing a phase change between the melting and boiling phases. It is in its liquid state, so adding heat will increase the temperature of the water.

Jason Liu 1C

I think the amount of energy is what damages the skin. And since steam has so much more energy than water at 100 degrees Celsius, that damages the skin a lot more.

Jason Liu 1C

Something is in its standard state when one mole of it is being produced. You can put something into its standard state by dividing both sides of the chemical equation by however much you need to make the product one mole.

Jason Liu 1C

The locations are separated by lecture time and last name

Jason Liu 1C

Ka is the equilibrium constant for the reaction, so a small Ka means there are few products, indicating a weaker acid. I think of pKa and Ka as inversely related; the smaller the Ka, the larger the pKa. So weak acid would have a small Ka and a large pKa.

Jason Liu 1C

If there are different ligands around the metal, does it matter where I put each ligand?

Jason Liu 1C

Since hybridization relies only on areas of electron density, lone pairs count, but keep in mind that double and triple bonds only count as one area of electron density

Jason Liu 1C

Yes, I think that's part of the test topics

Jason Liu 1C

I think s-character refers to how much of the hybrid orbital is from the s orbital. So for example, the sp hybrid orbital would be 50% s-character, while the sp^3 hybrid orbital would have 25% s-character.

Jason Liu 1C

I personally prefer drawing 1 bond between the central atom and each of the other atoms and then figuring out how many more bonds or lone pairs I need in order to have the right number of electrons

Jason Liu 1C

On problem 4.11 part d, the Xe atom has 7 pairs of electrons. I was wondering how you figure out how many pairs of electrons should be assigned to an atom that can have an expanded octet.

Jason Liu 1C

I don't quite understand the distinction between molecular shape and electron arrangement. What is the difference and how are they related?

Jason Liu 1C

I think the molecular structure has to do with the atoms that make up the molecule and how the bonds and lone pairs of electrons will interact. The shape would be influenced by the structure and be based on the attractions and repulsion caused by the electrons.

Jason Liu 1C

I think the molecular structure has to do with the atoms that make up the molecule and how the bonds and lone pairs of electrons will interact. The shape would be influenced by the structure and be based on the attractions and repulsion caused by the electrons.

Jason Liu 1C

Yes. If you refer to figure 2.20, on page 51 you can see that the atomic radius of Ba is 217 pm. In figure 2.22 on page 52, it shows that Cs+1 has an atomic radius of 167 pm.

Jason Liu 1C

Biradicals have two unpaired electrons, meaning each electron is in a different orbital. An atom with a lone pair has two electrons in the same orbital.

Jason Liu 1C

The correct answer for 16 is C. Since Heisenberg's Indeterminacy Equation is (uncertainty of momentum) x (uncertainty of position) = h/4*pi, this means that uncertainty of momentum and uncertainty of position are inversely related. h/4*pi is a constant value, so if uncertainty of momentum is high, u...

Jason Liu 1C

Ionization energy refers to how hard it is to remove an electron from an atom. Atoms are more stable with a full shell, and metals in groups 1 and 2 have 1 or 2 extra electrons outside of their full shell. Since atoms are more stable with just the full shell, it's easier to remove the 1 or 2 extra e...

Jason Liu 1C

I think the material we've covered is up to 2.7, but it's always good to read ahead!

Jason Liu 1C

My TA said that the Lyman series comes to rest at n=1 and the Balmer series comes to rest at n=2, so I'm not quite sure what they're actually supposed to be.

Jason Liu 1C

My TA said that the Lyman series comes to rest at n=1 and the Balmer series comes to rest at n=2, so I'm not quite sure what they're actually supposed to be.

Jason Liu 1C

I don't see the Rydberg formula on the constants and equations sheet. Does that mean we will have to memorize it? I also don't quite understand why there is a negative sign in the formula En=-hR/n^2

Jason Liu 1C

What relationship do these series have with the elements? Do all elements have these series? Are the different series only referring to the electrons?

Jason Liu 1C

I think you need to first need to subtract the mass of the (OH)2 from the original mass to find what element "M" is. You'll find that the molar mass of "M" matches the molar mass of Calcium. The sulfide of this metal is calcium sulfide (CaS), and you can just calculate the molar ...

Jason Liu 1C

When I'm balancing equations, in what order should I balance the elements?

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