CHEMISTRY COMMUNITY

Ava Kjos 1D

Definitely not for the overall rate law. As for the rate law for an elementary step, that's a really good question. My guess is no because I think that the only things in the rate law are supposed to be the reactants in the overall equation.

Ava Kjos 1D

K tells you the ratio of products to reactants. When more products are being formed, the forward rate constant is going to greater than the reverse constant. This means that k/k' is going to be greater than one, which aligns with what we would expect from K since there are more products than reactan...

Ava Kjos 1D

I noticed that for a lot of the Nernst equation problems, the solution manual combines partial pressures and concentrations in the expression for Q. For example, in problem 6N.3 Q is written as (.075M)^2(1 atm)/(1.0M)^2(1 atm) Does this mean that in general we don't have to convert the partial press...

Ava Kjos 1D

I'm also confused about this. Is there ever a case where we have to use the differential rate law or will we always be able to use the integrated form?

Ava Kjos 1D

the equation of half life is always t(1/2)=ln2/kr.

The proof for this is given in 7B.2 in the 7th edition textbook.

Ava Kjos 1D

I think it might be zero because it doesn't depend on the concentration of any reactants.

Ava Kjos 1D

I was confused about this too. Is it possible that there's a typo in the book? I feel like it should be this:
cl2---> HCLO+2Cl-

It seems weird to have cl2 on both sides of the equation.

Ava Kjos 1D

For the seventh edition you should look at the following chapters:
Gibbs Free Energy: 4J, 5G, 5J
Electrochem: 6K, 6L, 6M

Ava Kjos 1D

What do you do if there's a liquid? I think someone mentioned that Hg(l) is some exception, is that true?

Ava Kjos 1D

Did anyone find any practice problems specifically related to Van't Hoff's equation? Is there every a case where you have to use this relationship instead of just calculated the different G values at each temperature and dividing those by RT?

Ava Kjos 1D

Why does the free energy depend on pressure?

Ava Kjos 1D

What's the relationship between free energy and work?

Ava Kjos 1D

Yes. You first assume constant temperature and calculate the change in entropy due to change in volume. Next, assume constant volume and calculate the change in entropy due the change in temperature. Just add these together to find the total change in entropy. (You could also do this the other way a...

Ava Kjos 1D

Enthalpy is defined as the heat transferred or gained under constant pressure. Therefore, it must be equal to qp.

Ava Kjos 1D

Are reversible reactions always isothermal? Can we assume that delta U = 0 for any reversible or isothermal reaction?

Ava Kjos 1D

This question states "Calculate the final temperature and the change in enthalpy when 1.15 kJ of energy is transferred as heat to 0.820 mol Kr(g) at 298 K and 1.00 atm (a) at constant pressure; (b) at constant volume. Treat the gas as ideal." I understand how to calculate the final tempera...

Ava Kjos 1D

Internal energy is energy stored as kinetic energy and potential energy that can move in different ways, including translational energy, rotational energy, and vibrational energy. The translational energy is equivalent to 3/2RT and the rotational energy of a nonlinear molecule is also 3/2RT. Both of...

Ava Kjos 1D

Convert celsius to kelvin and use the equation deltaS=q/T.

Part a: 65J/298K = .22 J/K
Part b: 65J/373K = .17 J/K

Part b is smaller because the temperature is greater, resulting in a smaller change in entropy (as you can observe from the equation).

Ava Kjos 1D

When the volume is constant, you should use 3R/2. When the pressure is constant, you should use 5R/2.

Ava Kjos 1D

Yes exactly. The total heat will be the heat required to raise the copper temperature to 100 degrees Celsius (q(copper)) + the heat required to raise the water to 100 degrees Celsius (q(water)), using the formula you listed for both. For the second part you will just do q(water)/total heat *100% to ...

Ava Kjos 1D

Gases will probably be in a lot of the examples where work is being done because the work done by liquid and solids in a system is generally insignificant. However, they could definitely ask questions about solids and liquids in a closed system where the energy of the system is changed by heating/co...

Ava Kjos 1D

It depends on the what's happening in the problem. U=w+q is always true and can always be used. It just means that the change in the energy of the system is going to depend on the work done by or on the system and the heat released/absorbed. However, in some problems there is no work being done. If ...

Ava Kjos 1D

I believe that's possible. Could you list the problem you are working on?

Ava Kjos 1D

This has to be a mistake with the question. Adding water would not change the equilibrium concentration.

Ava Kjos 1D

Pretty much all of the formulas and conversions are given. You should know the following relationships:

pOH + pH = pKw
[OH][H30] = Kw
(Ka)(Kb) = Kw
pKa + pKb = pKw
PV = nRT

If you know these then you should be good.

Ava Kjos 1D

It's important to keep in mind that when counting the number of moles on each side, you are only counting the moles of gas. For example, if the reactant side has 2 moles of gas and 1 mole of a solid while the product side has 3 moles of gas, then the reaction will shift left because the reactants ha...

Ava Kjos 1D

If you think about it, gases such as oxygen and nitrogen typically exist as 02 and N2 because that is there lowest energy state. Therefore, in order to break this low energy state, energy has to be put into this system, therefore making it endothermic.

Ava Kjos 1D

Convert each concentration to a partial pressure using PV=nRT. You are given n/V, R and T so you just need to solve for P.

Ava Kjos 1D

Going off of what what previously said, the inert gas will change the pressure of the system. However, since this pressure isn't as a result of compression (which would decrease the volume and change the concentrations), it won't affect the calculations. Because of this, adding an inert gas will not...

Ava Kjos 1D

The partial pressure is different than the overall pressure. Basically, treat partial pressure kind of like concentration. For gases, often you are given the partial pressure instead of the concentration but as far as our calculations go you can treat them almost the same. The overall pressure is wh...

Ava Kjos 1D

I believe that the question is asking which flask shows when the reaction reached equilibrium. So even though the third flask and the fourth flask are both at equilibrium, the third flask better shows when the reaction first reached equilibrium. You can tell that it's at equilibrium at this point be...

Ava Kjos 1D

Amphoteric means that a compound can behave as both an acid and a base. In general any of the metalloid oxides can be amphoteric. However, the most important example that you need to know is water... Water as a base: HCl(aq) + H2O(l) --> Cl-(aq) + H3O (aq) Water behaves as a base in this case becaus...

Ava Kjos 1D

What were the other equations for the cause of acid rain besides the one with carbon dioxide (CO2 + H2O --> H2CO3)? What are some possible options to reduce acid rain?

Ava Kjos 1D

I'm having trouble with this question:
"Which is the stronger base, the hypobromite ion, BrO-, or morphine, C17H19O3N? Justify your answer."

From the solutions manual I saw that they used the pKb values of the base, but how are you supposed to know the pKb value?

Ava Kjos 1D

There is a total of 3 p-orbitals. In an sp hybridized orbital, one of those p orbitals is combined with the s orbital while the other two remain true p-orbitals. In an sp^2 hybridization, two p orbitals are hybridized with the s orbital, leaving one p-orbital unhybridized. In sp^3, all p orbitals ar...

Ava Kjos 1D

Hybrid orbitals will point in the directions of the different VSEPR models we have learned so just figure out which VSEPR model each hybrid orbital corresponds to.

Ava Kjos 1D

Are the intermolecular forces part of 2D? Should we expect to see this on the test?

Ava Kjos 1D

That is correct, since there are only two single bonds with oxygen you can assume that there are two lone pairs that are not shown to finish the octet around oxygen. Therefore, the shape must be bent with an angle of 109 degrees.

Ava Kjos 1D

In the second example, the dipole moments are pointed away from each other so some of that pull will be cancelled if the vectors are added together. However, if the two dipole vectors are added in the first example, they are pointed in almost the same direction so the magnitude will be larger.

Ava Kjos 1D

It's easier to understand why it's linear if you imagine a bipyramidal structure. Since there are three lone pairs in the I3- ion, imagine that the three central atoms of the bipyramidal structure are removed, leaving only the top, middle, and bottom atoms in a linear formation.

Ava Kjos 1D

We haven't been given a way to actually calculate the bond angles. However, it's easier to remember the angles if you remember the bond angles associated with each number of electron densities. For example, when there are two areas of electron density the angle will always be 180 degrees, when there...

Ava Kjos 1D

Polarizing power is the power of a cation to distort the shape of an anion by pulling its electrons over. In general, the smaller the ion, the more polarizing power it will have. This means that ions that are towards the top left side of the periodic table and with a greater charge will have a great...

Ava Kjos 1D

On the outline it says we should know the following: • Explain how covalent bond dissociation energy is related to covalent bond multiplicity, atomic radius, and the presence of unpaired electrons. I understand that covalent bond dissociation is the energy required to break the bond. From my underst...

Ava Kjos 1D

Each different geometric shape has implied bond angles. For instance, trigonal planar will always be 120 degrees, linear will be 180 degrees, tetrahedral will 109.5 degrees and so on. You won't need to calculate any bond angles, you will just have to figure out the shape and then use the bond angles...

Ava Kjos 1D

The purpose of A is just to represent the central atom in the particular molecule that you are looking at.

Ava Kjos 1D

If you look at the diagram for an octahedral shape you can see that there are three atoms in the vertical direction that are in a straight line (or 180 degree angle). There's also 4 atoms located in the middle around this vertical line. These 4 atoms will repel each other and each form 90 degree ang...

Ava Kjos 1D

All we need to know is the trend of electronegativity. You should generally be able to tell which element is more electronegative when comparing between elements. However, you won't need to actually calculate the exact values. If there's a situation where the exact values are important a chart will ...

Ava Kjos 1D

To expand on that, if there is only one resonance structure, the bond lengths will be exactly the length of a single bond or a double bond, depending on what kind of bond it is. However, if there are multiple resonance structures, the bond length will be somewhere in between the length of a single b...

Ava Kjos 1D

The only elements that the octet always applies to is B, C, N, O, F. The max number of electrons they can have is 8 because there is no 2d orbital, meaning once they fill up the 2s and 2p orbitals there's no room left for any additional bonds. Once you reach period 3, the 3d orbital can be utilized ...

Ava Kjos 1D

On the Midterm information sheet posted on the website it says that the midterm will cover up to 2C in the 7th edition and 3.11 in the 6th edition. However, in class on Friday and in some of the review sessions we went into the properties of bonds (which is 2D in the 7th edition). Is it possible tha...

Ava Kjos 1D

How do you know when an element can have more than eight electrons? Do we just need to memorize the exceptions or is there some way of figuring it out?

Ava Kjos 1D

No resonance won't affect the shape in the Lewis structures at all. To show resonance, you will need to draw multiple diagrams to show the different possibilities.

Ava Kjos 1D

I think he said that with electron affinity there's less of a clear trend as with ionization energy and atomic radius. In general the elements in the upper right side will have the highest electron affinity, but that doesn't guarantee that elements right next to each other or above/below each other ...

Ava Kjos 1D

This will not be on the test. He wanted us to understand the factors that affect electrons in multi-electron atoms, but you won't be asked to solve any equations like this.

Ava Kjos 1D

Yes it would be a good idea to memorize the visible light and UV wavelengths, but don't worry too much about memorizing the wavelengths of radio waves, gamma rays, etc because it most likely won't be on the test

Ava Kjos 1D

There most likely will be conceptual questions. You should be able to explain the photoelectric affect, and the atomic spectra, and other things he has put emphasis on

Ava Kjos 1D

Yes, n stands for the principal quantum number, l stands for the orbital angular momentum, and m1 is the magnetic quantum number. n indicates the energy level, l indicates the rate at which the electron circulates around the nucleus, and m1 distinguishes the individual orbitals within a subshell.

Ava Kjos 1D

I believe that the average distance of electrons from the nucleus in the 2s orbital is greater than the average distance of electrons in the 1s orbital. Both orbitals are drawn in a sphere shape showing the potential locations of the electrons, so the 2s sphere will be larger than the 1s sphere.

Ava Kjos 1D

How do you figure out how many orbitals are subshells with l equal to a specific value?

Ava Kjos 1D

In general I think those statements are true. Most of the questions should clearly state what form they want the answer with, and I'm sure it will be very clear on the test.

Ava Kjos 1D

With what we are doing currently, the states of matter won't affect any calculations. My TA said that we should include the states whenever possible, and later on they will become more relevant to us.

Ava Kjos 1D

Reagent refers to an actual physical chemical, while reactant refers to the word or symbol in the equation. If you were doing a physical experiment with real materials, you could refer to those materials as reagents. However, if you are talking about the reaction, you should refer to them as reactan...

Ava Kjos 1D

You will start by converting the mass into the number of moles by dividing by the molecular mass of the compound. To convert to formula units from moles, just multiply by Avogadro's constant.

Ava Kjos 1D

Does anyone know how the 7 questions will be graded? Should I be showing every single step and make sure my work is super clear, or is it more based on completion?

Ava Kjos 1D

The molar ratio between the two reactants is essential for determining the limiting reactant. However, once you find the limiting reactant you do not need to use the molar ratio between the reactants to determine the theoretical yield. You will be using the molar ratio between the limiting reactant ...

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