CHEMISTRY COMMUNITY

AveryAgosto

You should use Kelvin because R uses Kelvin.

AveryAgosto

k has no units because it is a ratio

AveryAgosto

when energy is released, that energy can be used to do work. So if the reaction has a -delta G you know that energy is being released.

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n is the moles being transferred.

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Dr. Lavelle sent an updated link for the solution manual errors. I would check that out to see if that's one of them

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Thermochemistry is a branch of thermodynamics.

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When delta H is negative, the rxn is exothermic and releases heat. When delta H is positive the rxn is endothermic and absorbs heat.

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We talked about it in discussion and it just means that it is scaled the same. If you were to add one degree to each that wouldn't change the ratio.

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Closed can not interact with the environment at all. Isolated can interact slightly.

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A lot of equations are derived from one central equation and that is typically shown on the equation sheet. As long as you are able to derive the specific equations to set it equal to the variable you are looking for than you should be fine.

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Everything in outlines 1-4 are covered.

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Internal energy is found using the delta U equation which will contain q.

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We aren't required to have previous knowledge of calculus so I don't think it will be on the exam.

AveryAgosto

I think that has to do with the derivation of other equations and its more conceptual. I don't think it will be used to solve problems.

AveryAgosto

The reaction between the two chemicals in the glow stick tube is catalyzed by a base, usually sodium salicylate. The sticks consist of a tiny inner container that can be easily broken and that sits within a flexible outer container. Each container holds a different solution and when the glow stick i...

AveryAgosto

There was a list of acids and bases that Lavelle made for 14A that were the ones he suggested memorizing but I can't seem to find the list.

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Longer bond length means that it is a weaker bond which results in it being a stronger acid.

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You are given credit for all posts at the end of the quarter.

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Every reaction is either exothermic or endothermic. You are correct about the relationship to delta H

AveryAgosto

He said that it won't be required to draw them but it is a helpful way to visualize the reaction.

AveryAgosto

You can determine the units by what will cancel out and if not than it can be unitless.

AveryAgosto

Boyle's Law states that pressure and volume have an inverse relationship when temperature is help constant. That is why double the original pressure would result in half of the original volume.

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It is also called "The Equilibrium Law" because it states that when any system is at equilibrium for a long period of time it is subjected to change in concentration, temperature, volume, or pressure. The system changes to a new equilibrium and this change partly counteracts the applied ch...

AveryAgosto

n/V is how concentration is calculated and the derived equation includes concentration. I believe it is written that way to show that it means concentration.

AveryAgosto

You are usually told which variable you are looking for but I believe Q is found when the reaction is not at equilibrium and K is found when the reaction is at equilibrium.

AveryAgosto

Ka refers to the pH formula and Kb refers to the pOH formula. Kw is a constant.

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Water can act as either an acid or a base

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As long as an acid and base react to form salt and water it is considered neutralization

AveryAgosto

Yes. A lone pair is a region of electron density along with a bond

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-log[H+] and I think we just need to know that pH+pOH= 14

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Dr. Lavelle posted a chart to help but I don’t think we need to know how to name them

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convert the g/mol mass to moles and multiply that by the molar ratio and then multiply by the g/mol mass of Si to get grams of Si

AveryAgosto

yes. Water can act as an acid or a base

AveryAgosto

on page F75 in the textbook there is a little chart that gives you the common strong acids and bases that are the ones we should memorize.

AveryAgosto

Yes. F, O, and N are the only ones that hydrogen bond.

AveryAgosto

the longer and weaker a bond is, the more likely it is to be soluble in water and dissociate. it is the opposite for short and strong bonds

AveryAgosto

My TA showed us in a table like this:

Acid Base

Bronsted : proton donor proton acceptor

Lewis : electron acceptor electron donor

AveryAgosto

Bronsted Acid = proton donor
Bronsted Base = proton acceptor

AveryAgosto

I think Lavelle emailed us a chart that is supposed to help.

AveryAgosto

I felt the same as you did. I did all the homework problems and still felt unprepared for the midterm. I think going to TA and peer learning workshops where extra problems are provided is another good way. Review sessions and khan academy videos can be helpful too.

AveryAgosto

Homework and chemistry community responses are worth 50 points each and each test is also worth 50 points each.

AveryAgosto

We didn't go over this scenario in lecture so I would assume it's not something we need to know for this week. However, you could determine that the bond angle would be 180 between the central atoms and the structure around each central atom would depend on the atoms around it.

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In regards to VSEPR I think that multiple bonds have higher electron density than a single bond, because the electrons take up more space.

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By drawing the most stable lewis structure, you will be able to determine the correct shape.

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The strength of the bonds determine the repulsion and the shape of the molecule. LP-LP has the strongest repulsion.

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I think all life science chemistry classes are curved so that the average is a B. So if the class average was a 70 than a 70 would become a B and everything else would shift as well.

AveryAgosto

Repulsion helps to determine shape and bond angle. The stronger bonds must be further apart.

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Talking to your TA or go to office hours

AveryAgosto

Yes it is a special kind of dipole dipole interaction

AveryAgosto

This isn't anything in the homework problems so I think its not necessary to know.

AveryAgosto

Anything covered before the midterm that we weren't tested on and anything covered up until Friday.

AveryAgosto

I think memorizing them would be a good idea but he didn't specifically say we needed to memorize it.

AveryAgosto

VSEPR stands for Valence shell electron pair repulsion but he said we didn't need to memorize it.

AveryAgosto

Any points not on the midterm from Chemical Bonds section and material covered last week.

AveryAgosto

Memorizing the specific melting points isn't necessary but you can assume the boiling point from the interaction.

AveryAgosto

A dipole-induced dipole attraction is a weak attraction that happens when a polar molecule induces a dipole in an atom or in a nonpolar molecule by disturbing the arrangement of electrons in the nonpolar species.

AveryAgosto

The work function is the required about of energy to remove an electron. It refers to the photoelectric effect.

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My TA didn't mention anything about it in section so I don’t think we would be tested over it unless he mentions it in class Monday before the midterm.

AveryAgosto

fundamentals, quantum, and chemical bonds up to 2D

AveryAgosto

You cant have negative energy of a photon so just because the energy change is negative it doesn't mean you have negative energy.

AveryAgosto

I think it is the amount of energy in each individual photon because of the wave model.

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Yes eventually we will need to be able to write a chemical equation from the name of the equation.

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Any problem referring to wavelength, velocity, and mass.

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De Broglie refers to wavelength, velocity and mass whereas Heisenberg refers to position and nuclear diameter.

AveryAgosto

Most exam questions will tell you specifically what units to convert your answer to.

AveryAgosto

I find that writing the amount of each reactant and each product helps me visualize what I need to add to make the equation balanced.

AveryAgosto

To determine mass percentage composition you find the molar mass of the compound then find the molar mass of each element in the compound and divide each elements mass by the total mass and multiply by 100 to find the percentage.

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You definitely receive credit for coming to the correct answer but in order to get the most partial credit possible you should write it out step by step.

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Anything smaller than 10^-15 is not detectable.

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I would recommend reading the textbook to facilitate what is taught in lecture. If you don't feel confident about a certain topic reading the chapter and reading along with the examples in the chapter is really helpful.

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It is a written exam so all questions will be answered in the test booklet you are provided in discussion.

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I would assume changing the fraction to an integer is the only way you would get full credit. The purpose of making a fraction is so that it's easy to convert all of the elements coefficients to whole numbers.

AveryAgosto

I think for the material we are learning in 14A, the order is not important. I think the ratio's are the important part.

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The law of conservation of mass states that mass cannot be created are destroyed and the reactants and products must have the same mass.

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The theoretical yield is the amount produced when a reaction is completed with 100% efficiency. The actual yield is the amount that is actually produced by the reaction.

AveryAgosto

I would recommend showing all of your work regardless of the method you use. For free response tests its always better to show more work for partial credit purposes. I feel like showing that you know the process will be more important and get you more credit than getting the answer correct.

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