CHEMISTRY COMMUNITY

juliasloan_4g

no the only way to find the rate law is with experimental data, not the equation on its own

juliasloan_4g

You can only find orders based on experimental data so this depends on the reaction. If you double the concentration and nothing happens to the rate, this is a zero order reaction. If you double the concentration and the rate also doubles, this is a first order reaction. If you double the concentrat...

juliasloan_4g

I believe you include H+ and OH- but exclude H2O

juliasloan_4g

In cell diagrams it is standard to leave out water but put H+

juliasloan_4g

I am confused in part c of this problem. When I solved for k i used the values from the first row of the table and got 2.85 however the answer is 2.85x10^12. I don't understand the solution for this and why everything is multiplied by .457 when that is nowhere in the problem. Is this because of units?

juliasloan_4g

we should probably be familiar with it but it would be very unlikely for him to ask you to do it

juliasloan_4g

it may be easier to understand where the units come from by solving for it rather than memorizing them

juliasloan_4g

all graphs are linear but the slopes and axis vary

juliasloan_4g

One Ta said that we should be familiar with the derivation but it would be very unlikely for it to be asked on the exam

juliasloan_4g

Reduction means gaining an electron

juliasloan_4g

juliasloan_4g

One of the questions asks you to comment on the relative stability of reactants and products. How were you suppose to go about solving this problem?

juliasloan_4g

isothermal reversible reactions

juliasloan_4g

yes it is a state function, and can be added like enthalpy and calculated in very similar ways

juliasloan_4g

Ka2 is the second deprotonation, when an acid is polyprotic and can give away multiple hydrogens

juliasloan_4g

I believe that the porous disk serves the same function as the salt bridge

juliasloan_4g

yes on his website under midterm information

juliasloan_4g

Also generally when you use the boltzmann equation it will ask you for either residual or positional entropy rather than just entropy.

juliasloan_4g

You can answer this question by looking at the equation delta s = q/T. If the temperature is higher than the delta s will go down, and vise versa

juliasloan_4g

You should use the equation that has the n in it. The other one is assuming that if you have an amount other than 1 mole you will account for this and multiply by that as well

juliasloan_4g

I believe no work and 0 work are interchangeable

juliasloan_4g

I also like to redo the tests we have done before the midterm to test myself again and make sure I've learned from my mistakes

juliasloan_4g

you can both change the matter within it (the tea) and transfer energy by holding it and making it warmer or cooler

juliasloan_4g

I think those are the only units for Joules that you should know about

juliasloan_4g

you need to use the quadratic equation when you can not estimate the x in the denominator and must solve it fully by hand

juliasloan_4g

I dont think it matters in terms of units, however it could matter in relativity to other transitions

juliasloan_4g

work is the process of achieving motion against an opposing force

juliasloan_4g

This is the same idea as adding a drop of water into the ocean. A drop of water compared to the volume of the ocean is so small that it will not affect it just like how the whole universe is tiny compared to the beaker

juliasloan_4g

the 5 percent rule can be used in any calculation of K

juliasloan_4g

In the homework problems they sometimes do not put the Ka value in the question but they instead expect you to refer to a chart in the reading that lists many of the Ka values.

juliasloan_4g

yes, ice boxes work with pressures, molarity, and moles

juliasloan_4g

you can always do homework from any relevant section, or whichever section you think will help you the most to practice at the level you are at

juliasloan_4g

Whenever you are dealing with equilibrium and have unknown values, setting up an ice table can be helpful in order to know which parts you are missing as well as how to solve for them

juliasloan_4g

Yes you should be given delta h in order to determine whether the action is endo( taking in heat) or exo(giving off heat)thermic

juliasloan_4g

I understand that solids and liquids should not be included in the calculation of K values, but could someone explain why this is? Why are they insignificant?

juliasloan_4g

Could someone please explain why Kp changes when temperature is changed but not when the pressure is changed. Thanks

juliasloan_4g

both of them always work, you just have to see which information you are given to work with. If you are given moles and liters molarity can be found so Kc can be used but if pressures are given use Kp. Kp is also most commonly with gases

juliasloan_4g

#6B3 in the textbook edition seven asks about calculating the difference between 200 ml of 0.025M HCL solution and accidentally using a 250 ml flask to make this solution. I know that HCl completely dissociates so calculations with ph can be calculated with the 0.025M. However, i dont understand the...

juliasloan_4g

It was mentioned in the lectures briefly and it is also in the assigned reading so I think it would be best to know how to calculate it and what it represents, however in one of the review sessions a TA said he didn't think we would be tested on that so im not sure.

juliasloan_4g

HF is weaker than HI because Iodine is a larger atom and thus it is going to have a weaker bond with hydrogen. Because of this it can give away the hydrogen very easily making it a stronger acid.

juliasloan_4g

I'm having a hard time knowing where to put each element with more complicated Lewis structures. For example, in question 2E19. in the seventh edition it asks for the shape and bond angles of (CH3)2Be. I drew the Lewis structure and it seemed correct. I drew it as H-C-C-Be with two more hydrogens on...

juliasloan_4g

This question also states that the bond angle for sp3 is 109.5 and bond angle for sp2 is 120. You can think of it as sp3 being 25 percent s characteristics and 75 percent p characteristics (1:3 ratio), and for sp2 this would be 33.3 percent s characteristic and 66.6 percent p characteristic (1:2 rat...

juliasloan_4g

London dispersion forces are present between all molecules, including polar molecules

juliasloan_4g

I believe the arrow should point towards the more electronegative element or you can write the greek letter (not sure what its called) with the positive and negative signifying that it is partially negative or partially positive on each element in the molecule

juliasloan_4g

Someone asked this question in my lecture, and Dr. Lavelle showed that because octahedral is completely symmetrical no matter where you put a lone pair is is exactly the same. There is no "top" or "bottom." It was easier to visualize when he showed us with his 3D props, but octah...

juliasloan_4g

Do the regions of electron density surrounding the atom always match up with the hybridization state? So far I have been doing this and it has been working ex: if there are two regions of electron density it is sp hybridization,3 is sp2 and so on. However in the solution manual for 2F13. (seventh ed...

juliasloan_4g

the dash shows that the atom is farther away from you and the wedge shows that the atom is coming towards you. We do not need to draw the Lewis structures this way it is just helpful to visualize the 3d nature of molecules on a 2d surface. However, if you were to draw them this way, where the dashes...

juliasloan_4g

I believe the reason you would have received half credit for this answer is because it asked for the full electron configuration. You gave the short hand noble gas version. Your configuration was correct it just should have started at 1s2 etc.

juliasloan_4g

yes, in this question you were suppose to take the average of the bond lengths. This is because of resonance and how electrons are delocalized and double and single bonds are just used as visual representations for Lewis structures.

juliasloan_4g

ionization energy and electronegativity do follow the same trends so technically you could use either. Using electronegativity makes more sense to me because if something was extremely electronegative it is not likely to want to share a lot of electrons therefore will not be in the middle

juliasloan_4g

How do you count valence electrons when an element is in the d block? Do you only count the s block or the d block as well up until that element? If you don't include the d block why is this?

juliasloan_4g

you will not need to calculate bond lengths. Professor Lavelle just included this in order to show that Lewis structures have a limitation, and this is why we need to show resonance

juliasloan_4g

to find the number of valence electrons you count across the period the s and p elements including the element you are looking at. You cant only look at the column numbers because for example carbon is in the 14th column but only has 4 valence electrons

juliasloan_4g

What do roman numerals next to an elements name mean? Ex: in 2A.23 indium(III) sulfide

juliasloan_4g

Could someone please explain what the difference is between electronegativity and electron affinity. In lecture they seemed like the same thing and they seem to have the same trends on the periodic table. Can these terms be used interchangeably?

juliasloan_4g

Whatever is given in the prompt is what should be used because it is about uncertainty, not the same exact measurement each time. It will depend on the situation

juliasloan_4g

Just make sure each side has one before pairing them. This applies to hund's rule from quantum mechanics. Same spin electrons should be put in different orbitals before pairing them.

juliasloan_4g

I think this is individual to the person. As long as you do 7 problems you should get full credit, however it may be more helpful to work on the sections you need the most help with

juliasloan_4g

I think having an understanding of the equation and what it is used for will be helpful on the test, rather than knowing how to actually compute it

juliasloan_4g

The energy is released as positive electromagnetic radiation (photons)

juliasloan_4g

Personally I just have the very common units memorized such as kilo and milli. You generally memorize these just through using them so much. I would just memorize the units as they come up in the different topics of chem, because there are likely some that won't come up. However if you are intent on...

juliasloan_4g

Using the fraction is a good idea, or just keeping as many decimals as possible until the end result when you can round to the proper number of sig figs. As long as you keep a reasonable amount of decimal places, the end result shouldn't change

juliasloan_4g

Professor Lavelle said a black body is a hypothetical material that can absorb all frequencies of light (it's not real).

juliasloan_4g

I've always found that the easiest way to find the LR(but maybe not the fastest) is converting both reactants into one product. You do this by taking the mass given to you of both products and using molar mass and molar ratios to convert into product. You can convert to either moles of grams, both w...

juliasloan_4g

The actual yield is the amount that is produced within a lab setting. The theoretical yield is the amount produced assuming there are no errors, outside reactions etc. The actual yield will typically be given to you in a problem where you must find the percent yield. Here you would divide the actual...

juliasloan_4g

In lecture, Dr. Lavelle said that reactant is used in the hypothetical sense when doing calculations but reagent is when you are referring to a lab setting and actually doing the experiment. For the purposes of the class, because there is no lab component they can be interpreted as the same thing.

juliasloan_4g

Both molar masses would be adequate and likely get you the same result because the difference is so small. In general the more accurate one would be preferable. You should keep as many sig figs as possible until the very end of the calculation when you have your answer

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