CHEMISTRY COMMUNITY

anjali41

In an electrolytic cell, the set up is similar to the galvanic cell. However, the anode is not directly connected to the cathode. Instead, it is connected to an external power supply that drives the reaction.

anjali41

A couple of the TA's discussion reviews posted on Chemistry Community also review problems like this for additional assistance.

anjali41

I think the equations also appear on our formula sheet. It's always good to know how they are derived though, just in case.

anjali41

When the K value is less than 10-3, it is generally safe to estimate without the x. However, make sure to only exclude variables that are being added or subtracted. To make sure estimation was appropriate, make sure the percent dissociation is under 5%.

anjali41

N is the moles of electrons transferred. This is variable depending on the reaction, and can range from 1 and above.

anjali41

It is important to know that O has an oxidation number of 2- and H has an oxidation number of 1+. You are usually given the overall charge of a molecule. All the individual charges should add up to the overall charge. Thus, you can then solve for the unknown oxidation number.

anjali41

I believe there are some Khan Academy videos on how to balance redox reactions as well where he works through an example.

anjali41

While it could come up on the final, I don't think Dr. Lavelle has asked us in either 14A or 14B to derive any equations. I think they are provided on the formula sheet too.

anjali41

The states of matter hint at the answer, as all the products and reactants in answer choice a are solids.

anjali41

Electrochemical series are redox couples arranged in order of oxidizing and reducing strengths. They are usually arranged with strong oxidizing agents at the top of the list and strong reducing agents at the bottom.

anjali41

I think he meant to say nonmetal, as the electrode must be both solid and metal.

anjali41

A TA mentioned that the cell diagrams could be written in the form s|g|aq||aq|g|s. So, I'm not sure why the textbook chose to write it otherwise. I think the TAs will not take off points if we stick to this structure on the exams.

anjali41

The instantaneous rate is used because it refers to the rate at one specific time. In contrast, the average rate occurs over a longer time period, so it is not as precise.

anjali41

Reaction order is the power to which the concentration of a single substance is raised in a rate law.

anjali41

In an electrolytic cell, the set up is pretty similar to the galvanic cell. However, the anode is not directly connected to the cathode. Instead, it is connected to an external power supply that drives the reaction.

anjali41

We mainly discussed the Nernst equation, which is covered in section 6N of the textbook I think.

anjali41

Yes, I believe that the Van't Hoff equation could be on Test 2.

anjali41

Trans is the opposite of cis in this case. While trans will be on different sides, cis will both be on the same side.

anjali41

Yes, I believe that Gibbs free energy will be covered on Test 2. More specifically, the second set of problems on the Thermodyamics outline will be covered on Test 2.

anjali41

G naught is used for elements in their standard states under normal conditions. G is used for nonstandard conditions.

anjali41

Although this is not a set list, the outlines for each topic sometimes mention specific biological examples to know. However, it is good to be familiar with anything that Dr. Lavelle mentions.

anjali41

Oxidizing agents are a species that removes electrons from a species being oxidized (and is itself reduced) in a redox reaction. On the other hand, reducing agents are species that supplies electrons to a substance being reduced (and is itself being oxidized) in a redox reaction.

anjali41

W is referring to the degeneracy. W can be calculated by raising the number of different orientations/states by the number of atoms/molecules.

anjali41

When G=0, the reaction is at equilibrium.

anjali41

I believe that the answer would be 7 kJ. To find the change in internal energy, use the equation delta U = q +w. You know that q = -15 kJ because q = delta H. If work is being done on a system, the work is positive. If work is done by a system, then work is negative. So, the equation would be delta ...

anjali41

I think my TA from last quarter mentioned that each problem is graded by one TA, so the grading for each problem is uniform.

anjali41

For part 2, I believe you can set the delta G equal to 0. Then solve the equation 0 = delta H - (delta S x T). By solving for T, you find the temperature for which the reaction becomes spontaneous.

anjali41

Another way to think about it is in terms of exothermic and endothermic reactions. If the reaction is exothermic and is releasing heat, then the q will be negative. If the reaction is endothermic and absorbing energy, the q will be positive.

anjali41

For the change in volume, the equation would be delta S = n x R x ln(V2/V1). From the formula sheet, it seems that the equation to calculate the positional/residual entropy is delta S = KB x ln (W).

anjali41

The only difference between the two is that specific heat capacity is per gram of the substance. On the other hand, molar heat capacity is simply measured per mole of the substance. Besides the difference in units, they measure the same thing.

anjali41

A state property is not dependent on path taken to obtain that state. Additionally, state properties can be added and subtracted. This is all true for delta U.

anjali41

At least for last quarter, he posted the midterm review on Chemistry Community a couple days before the midterm review session. As of now, I don't think it is up yet.

anjali41

The midterm takes place in the middle of Week 6. However, the review sessions for the midterm started today and extend up until the midterm.

anjali41

I think that I would err on the side of caution and be mindful of sig figs. Additionally, my TA mentioned that using the correct units was something they focus on as well.

anjali41

A state function is a property of a substance that is independent of how the sample was prepared. According to the textbook definition, it seems that enthalpy is listed as a state function.

anjali41

Test #1 may come back this week or next week most likely, depending on when the TAs grade them. In 14A, they usually were returned outside of lecture or during the discussion section.

anjali41

There was no extra credit opportunities in 14A, so I assume there would be no extra credit opportunities in 14B as the grading and assignments seem to be the same format.

anjali41

Usually the outlines are listed in the order we complete them on the website. So, I think doing anything from outline three, Thermochemistry, would be acceptable.

anjali41

According to the textbook, enthalpy is a state property; a change in enthalpy is equal to the heat transferred at constant pressure. Heat on the other hand is the energy that is transferred as the result of a temperature difference between a system and its surroundings.

anjali41

The answer would be no change. This is due to the fact that there are an equal number of moles of gas on both sides of the reaction equation. Thus, an increase in pressure will not affect the equilibrium.

anjali41

Approximation is okay when the K value is less than 10^-3. To check if your approximation was appropriate at the end of the problem, you can calculate the percent ionization. If this percent is less than 5%, approximation was acceptable.

anjali41

Since this calculator is non-programmable, I think it would be acceptable for all the exams.

anjali41

Typically in the textbook problems, water is seen in liquid form. Since liquid and solids are not included in ice tables, do not include water. However if water was in gas form and depending on the problem, I think you might have to include it.

anjali41

Discussions are not graded on attendance, as the TAs do not take roll. However, handing in homework can be thought of as a participation/attendance grade that we do turn in during discussion.

anjali41

You would use this equation to convert between partial pressure and concentration. If you were asked specifically for Kp or Kc and given the opposite units, you would use this equation.

anjali41

The equilibrium composition is referring to the concentration of each product and reactant provided in the chemical equation. An ICE table could be helpful in this kind of question.

anjali41

When NO is removed, the product of the forward reaction is being decreased. In order to reach equilibrium again, the forward reaction will proceed and use the reactants to make more product. So, the reactants, including NH3, decrease as a result.

anjali41

In an email Dr. Lavelle sent out last quarter, it said that finals exams would be available during the 3rd week of Winter quarter at 3034 Young Hall.

anjali41

In equilibrium, the rate of reaction for the products and reactants are the same. When increasing one of the reactants, more products must be formed to balance out the increase in reactants, which will preserve the equilibrium. So, the H2 concentration will increase.

anjali41

I think a large K is considered to be greater than 10^3 and a small K is considered to be less than 10^-3

anjali41

Since both parts a and b consist of only molecules in the gas phase, partial pressures are used throughout instead of concentrations. So, when solving for the K value, you would be solving for the Kp value more specifically.

anjali41

I think they should be included, as they are not a solid, liquid, or solvent.

anjali41

Both are found using the same equation, but they differ because the reaction quotient is not specifically limited to equilibrium.

anjali41

Dr. Lavelle hasn't mentioned anything yet about using the ionic equations, so I think it might be a strategy specific to this problem/problems like it.

anjali41

I was confused in lecture today when learning that CH2FCOOH was a stronger acid than CH2ClCOOH because F is more electronegative than Cl. However, we also learned that HF was a weaker acid than HCl because it is lower on the periodic table and has a longer bond I think. These trends seem to contradi...

anjali41

I would say that hypobromite is the stronger base. The justification might be due to electronegativity of the elements making up the molecule. In general, Br and O seem to be more electronegative than C H N and O.

anjali41

I agree that the most important part to memorize is probably that the visible light spectrum ranges from 400 nm (violet)-700 nm (red).

anjali41

I think we are supposed to write them as 3D, 4S because it is then easier to see where the electron is being removed from in ions.

anjali41

All ligands are Lewis bases and the central atom would be the Lewis acid.

anjali41

Getting in the right mindset to take finals can be tough. I think not cramming right before the test is important and instead just relaxing could be helpful. Maybe set-up practice exams for yourself where you have the same materials/time you do for the final. I hope you find what works well for you :)

anjali41

According to the textbook, resonance is a blending of Lewis structures into a single composite, hybrid structure. Additionally, a resonance hybrid is the composite structure that results from resonance.

anjali41

I think the best way to review would to do a mix of everything suggested. I think going to review sessions, study groups, youtube videos, and a lot of practice problems are all great review for the final. I think the more comfortable you are with the concept, the better off you will be for the final.

anjali41

HCl is a stronger acid because it is lower on the periodic table, indicating that it is less electronegative and larger. This makes it easier to dissociate, making it a stronger acid. HF for this reason is often not considered a strong acid.

anjali41

The ones that donate protons are acids. The ones that accept these protons are bases.

anjali41

A polydentate ligand is simply a ligand that can attach at several binding sites

anjali41

As the textbook mentions all of these as strong acids, I would try to remember that they are all strong acids. Additionally, I think it is important to know not only that they are all strong acids, but also what makes them all strong acids.

anjali41

You would use the suffix ate if the complex has an overall negative charge. The suffix is added to the end of the metal.

anjali41

The prefixes bis-, tris-, and tetrakis- are used when a ligand already has a Greek prefix or the ligand is polydentate.

anjali41

According to the textbook, an oxidation number is "the effective charge on an atom in a compound, calculated according to a set of rules (see Toolbox K.1). An increase in oxidation number corresponds to oxidation; a decrease corresponds to reduction."

anjali41

Finding the electorn configuration refers to the distribution of electrons into different energy levels (such as 1s2 2s2 2p4). The VSEPR model is about finding the geometry of molecules based on the interactions of the electrons (arrangement of electron density). The shapes of tetrahedral and trigon...

anjali41

SiF4 would have a higher boiling point than SIH4 even though their Lewis structures look similar. This is due to the fact that Fluorine has a larger mass, which indicates more electrons than Hydrogen. Thus, it is more polarizable and has stronger intermolecular forces.

anjali41

Yes, option 1 has the largest dipole moment because the two dipoles are closer together and are separated by a smaller angle. An easy way to think about this is to think to imagine that if the dipoles were on opposite sides, they would be more likely to cancel out and would not be as strong of a dip...

anjali41

First you should look at the periodic table and determine how many valence electrons that the element should have. Next, count the total electrons present in the form of both lone pairs and bonds. Then compare this to the ideal number of valence electrons that the element should have. If there are m...

anjali41

In the case of CO2 for example, the dipoles created by the Carbon and Oxygen are both pointing towards the central Carbon, they would cancel each other out and there would be no dipole moment. CO2 is nonpolar in this example.

anjali41

There are 3. A coordinate covalent bond according to the textbook is a bond formed between a Lewis base and a Lewis acid by sharing an electron pair originally belonging to the Lewis base. A polar covalent bond is a covalent bond between atoms that have partial electric charges. A nonpolar covalent ...

anjali41

A good example to think of is a water molecule. There is a great difference in electronegativity between the Oxygen and Hydrogen, so the molecule is not balanced in a way. So you know the water molecule is a dipole.

anjali41

Yes, London forces act on all molecules. It does not matter if they are polar or nonpolar, or ionic or covalent.

anjali41

CHI3 has a higher boiling point because on the periodic table, Iodine is on a lower period than Fluorine. Following the periodic trends, this indicates that iodine has a larger size. With this larger size, Iodine can have stronger induced dipoles.

anjali41

According to the textbook, a London interaction is the interaction between instantaneous electric dipoles on neighboring molecules. Van der Waals interactions are Intermolecular interactions that depend on the inverse sixth power of the separation.

anjali41

An important step to remember is that combustion always involves Oxygen gas as a reactant, even though it is often not states in the problem. So always remember to add Oxygen gas to the chemical equation of a combustion reaction before balancing, and you should be good.

anjali41

Intramolecular forces refer to the forces that hold atoms within the molecule together. On the other hand, intermolecular forces are referring to the forces between different molecules.

anjali41

Elements in the 3p block actually can have a 3d orbital, but the orbital does not have to be completely filled in the case of some elements.

anjali41

According to the textbook, polarizing power is the ability of an ion to polarize a neighboring atom or ion. On the other hand, polarizability is a measure of the ease with which the electron cloud of a molecule can be distorted.

anjali41

According to the textbook, electron affinity is the energy released when an electron is added to a gas-phase atom or monatomic ion. Electronegativity is the ability of an atom to attract electrons to itself when it is part of a compound. I think just knowing the periodic trends should be a good start.

anjali41

The x, y, and z refer to different orbitals in the p subshell. The x, y, and z are just three variables used to represent the three different subshells.

anjali41

I don't think the formula charge equation will be provided on the front page of our test along with the equations and constants. I think it may be beneficial to memorize it either way.

anjali41

Electronegativity is the ability of an atom to attract electrons to itself when it is part of a compound. I think electronegativity decreases down a group and increases across a period.

anjali41

Ionization energy and electronegativity are related in the sense that they generally follow similar trends on the periodic table. Ionization energy and electronegativity both tend to be lower in the bottom left corner and higher in the top right corner.

anjali41

Yes, the s orbital will get filled first, then the d orbital, then the p orbital. It is important to note that the s orbital that gets filled first is one period higher than the d orbital (4s will get filled before 3d).

anjali41

I think it's better to err on the side of caution and say yes. Antimony is a metalloid and cadmium is a metal. This can be deduced from which block on the periodic table the element is in.

anjali41

Under what situations am I supposed to use the DeBroglie equation? When should I use this equation instead of other equations to find wavelength (like c= lambda x v)?

anjali41

Don't get hung up on the 6 for this question. Instead just focus on the d-orbital, which as you stated has 5 m values. The 6 just indicates how many other shells there are in addition.

anjali41

I was just wondering what the difference between an atomic radius and ionic radius is. Do they follow the same periodic table trends?

anjali41

An anion is a negatively charged ion. On the other hand, a cation is a positively charged ion. I think when you have a neutral atom and it either loses or gains an atom (which creates a cation or anion), the radius either decreases or increases respectively.

anjali41

The difference is in the energy level that he electron rests at. The Lyman series involves the ground state, which is when n=1. On the other hand, Balmer series corresponds to n=2.

anjali41

I think that the use of angstroms will just depend on the unit we are in. While it could come up in any question, it seems like angstroms won't occur as frequently in this Quantum unit as some other units, such as out chemical bonds unit. As long as you know how to convert with angstroms, you should...

anjali41

Just remember that the values of m and l are related. The values of m range from l, l-1, ..., -l. When asking about orbitals, you want to think about the m value. So if l =0, you can only have one orbital. If l=1, you can have 3 orbitals. When l=2, you can have 5 orbitals. When l=3, you can have 7 o...

anjali41

Today in lecture, it was mentioned that p,d, and f -orbitals all have nodal planes. Why do s-orbitals not have nodal planes?

anjali41

Molarity is simply just the concentration of solution that is expressed as the number of moles of solute/ the number of liters in the solution. Molarity is used frequently in the textbook during dilution problems and often uses the formula:
Molarity = mols of solute/Liters of solution.

anjali41

What I've noticed in the textbook problems is that they generally give you the state of matter, especially when the compound is not very common. Usually reading the context clues for the problem will hint at the state of matter as well.

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