CHEMISTRY COMMUNITY

Maya Pakulski 1D

Hoe do you know when to use the linear first order integrated rate law (ln[A]=-kt+ln[A initial]) versus the nonlinear form ([A]=[A initial]e^-kt)?

Maya Pakulski 1D

How would we determine what the intermediate reaction is if we are not given it?

Maya Pakulski 1D

PranaviKolla2B wrote:Just to confirm, the slowest step is the rate-determining step?

Yes, the slowest step is the rate determining step.

Maya Pakulski 1D

Yes these equations will be given but you will have to know which ones go with which order reactions. The equation sheet will be the same one on the class website and the one we got for the midterm.

Maya Pakulski 1D

How do you know when to use each equation? For example how would you know to use the integrated rate law versus the differential rate law?

Maya Pakulski 1D

What is each one used for?

Maya Pakulski 1D

k' signifies the reverse reaction rate specifically.

Maya Pakulski 1D

The units of k specifically in different order reactions are
zero-order M/s
first-order 1/s
second-order 1/M*s

Maya Pakulski 1D

Will we ever use [P]? If so when?

Maya Pakulski 1D

What is meant by the order of a reaction?

Maya Pakulski 1D

What are some applications of rate laws?

Maya Pakulski 1D

Test two will cover the last page of thermodynamics and all of electrochem.

Maya Pakulski 1D

When finding cell potential from Appendix B why are all the half reactions written with the electrons on the left regardless of how they are written in the half reaction?

Maya Pakulski 1D

What is this equation used for? When would we know to use it or to derive it?

Maya Pakulski 1D

805097738 wrote:
kristi le 2F wrote:The vant hoff equation can be used to calculate K at different temperatures if stand enthalpy of real lion is known.

what is real lion

probably "real ion" if I had to guess

Maya Pakulski 1D

When finding K or Q like in the 6N problems, how do we know what the products and reactants are? Do we look at the final combined equation after finding the half reactions?

Maya Pakulski 1D

On this question why do we have to switch to log instead of using ln and where does the 2.303 come from? Is there a reason you couldn't use ln and just take the e of both sides to cancel out the ln?

Maya Pakulski 1D

How do you find oxidation numbers?

Maya Pakulski 1D

On question 6L.5 part B, Write the half reactions, the balanced equation for the cell reaction, and the cell diagram for each of the following skeletal equations: B. Ce4+ +I- = I2 + Ce3+, how do we know to add Pt to the skeletal equation?

Maya Pakulski 1D

What are oxidation numbers used for?

Maya Pakulski 1D

There are two types of salt bridges, a glass tube bridge and a filter paper bridge. The glass tube bridge is filled with an electrolyte such as sodium chloride, potassium chloride or potassium nitrate. The second kind is either made of filter paper or a porous material soaked in an electrolyte.

Maya Pakulski 1D

Splitting the overall reaction into half reactions is also helpful when balancing redox reactions. This makes it easier to balance the H and the O atoms separately using H20 and H+ ions. It also helps to determine the total electrons needed to balance charges in the reaction. Is balancing the react...

Maya Pakulski 1D

Which equation to use is dependent on which information you were given in the problem or which information could be solved for and then plugged into another equation. You really have to combine equations and move things around to fit what info you were given.

Maya Pakulski 1D

You also can google examples of these problems are there are probably tons that will come up from other teachers or classes.

Maya Pakulski 1D

705087773 wrote:using 3/2R is for if there is constant volume in the process

5/2R is for constant pressure, correct?

Maya Pakulski 1D

Make sure also when looking at the values for delta H and delta S you take into account that one is given in J and the other in KJ so you will have to convert one or the other.

Maya Pakulski 1D

You look at the value for deltaG. If deltaG is negative it is spontaneous and if it is positive it is not spontaneous. Similarly there was a question about whether a compound would be stable or unstable based on its deltaG value and if the value is negative the compound is stable, is the value is po...

Maya Pakulski 1D

On a test question would it always specify that the reaction is happening irreversibly or reversibly?

Maya Pakulski 1D

Here's a website that has some rules on how to tell which molecule will have the higher molar entropy! https://opentextbc.ca/introductorychemi ... changes-2/

Maya Pakulski 1D

This is so helpful thank you!

Maya Pakulski 1D

I had this same question because when I first tried to solve it I calculated each volume using PV=nRT and then substituted them into the nRln(V2/V1) equation, however I got the wrong answer because I didn't realize we can just plug the inverse of the pressures right into the equation instead of usin...

Maya Pakulski 1D

When calculating for the micro states what number do we raise to the n?

Maya Pakulski 1D

Yes, the temperature stays constant while the energy continues to increase.

Maya Pakulski 1D

This is because by definition delta H only equals q at constant pressure.

Maya Pakulski 1D

Yes, every week you just pick 5 that go with whichever outline we are on in class. You could do all 5 problems from 4A if you wanted or do some from A, some from C and some from D.

Maya Pakulski 1D

It depends on what the problem gives you. Just make sure for any given problem that you use the units that match the constant you're given.

Maya Pakulski 1D

Unless specified by the problem would it matter on a test whether our answers are in J or KJ?

Maya Pakulski 1D

Emily Lo 1J wrote:It is the transfer of a proton between the same type of molecule. An example of it would be 2H2O $\rightleftharpoons$ H3O $^{+}$ + OH $^{-}$

What are some other common examples of autoprotolysis besides water?

Maya Pakulski 1D

MariahClark 2F wrote:I don't know about your reasoning, but heat capacity is extensive. It changes when it becomes specific heat capacity, as that is intensive instead.

What is the difference between intensive and extensive in general?

Maya Pakulski 1D

What are others examples of things that could be state properties?

Maya Pakulski 1D

Do problems from chapter 4 as that is the chapter we are starting. If we start a new topic halfway through the week it normally doesn't matter which section you do problems from as long as they were covered recently.

Maya Pakulski 1D

The internal energy change is the value of the potential energy plus the kinetic energy. We use this to tell whether energy is coming into or out of the system in the form of heat or work. The equation is deltaU=q+w where w is work and q is heat.

Maya Pakulski 1D

If the questions asks for just K, and not Kc or Kp, then you need to look at the equation. If the reactants and products are gases then you should use Kp, because it is implied. If the reactants and products of the equation are aqueous then you should use Kc because it is implied. However if it ask...

Maya Pakulski 1D

Neither would be favored because you have the same number of moles on either side.

Maya Pakulski 1D

Why can you never trust atoms?

Because they make everything up.

Maya Pakulski 1D

Kallista McCarty 1C wrote:
Kristina Rizo 2K wrote:I thought Kp was used for gas only? Can someone clarify this please.

Kp is used for gases to determine partial pressures! Kc is used for concentrations and Ka and Kb are for acids and bases.

This might be a dumb question but you calculate all of these the same way right, with products/reactants?

Maya Pakulski 1D

Liquids and pure solids are never included in equilibrium calculations.

Maya Pakulski 1D

Some of the UA's also give out review sheets during their Peer Learning sessions.

Maya Pakulski 1D

You will never include the concentrations of solids and liquids because, for example, when a solid is dissolved in water the concentration changes such a small amount that it is almost insignificant unlike with a gas where the concentration does change.

Maya Pakulski 1D

Yes, you would still omit solids and pure liquids. You also emit these when making an ICE table.

Maya Pakulski 1D

If you add something to either the products or reactant side the reaction will shift to the opposite side and if you take a product or reactant away the reaction shifts to the side you took it from. In this case it would shift to the right, as you took away a reactant, and the amount of H2 would inc...

Maya Pakulski 1D

Kp can only be used for gases because only gases can exert pressure on a container. Therefore, if you only have aqueous solutions in your chemical equation, then you know you must calculate for Kc since there are no gases. If you have only gases in your chemical equation, you can solve for either K...

Maya Pakulski 1D

I need this as well. I keep getting a different answer too.

Maya Pakulski 1D

ShastaB4C wrote:Does anyone know approximately how many questions the final exam will be?

On the page about final locations and review sessions it says there will be 8 questions on the final.

Maya Pakulski 1D

When looking at pH and pOH there are different significant figure rules, here's a website that explains what they are. http://abacus.bates.edu/acad/depts/biobook/How-SigF.pdf

Maya Pakulski 1D

The chemical equations that produce acid rain are done in a few parts. In regards to nitric acid the first equation that takes place is N2 +O2 =2NO, then the second equation is 2NO + O2 = 2NO2. The last equation that happens is 3NO2 + 3H2O = (2H3O+) + (2NO3-) + NO. Sulfuric acid is formed in three d...

Maya Pakulski 1D

Here's a good video that goes through types of hybridization with lots of examples!
https://www.youtube.com/watch?v=otYj92d7rB0

Maya Pakulski 1D

My TA said the same thing which is they will most likely give us the obvious ones that follow the pattern of the diagonal band, which you can find charts of online, instead of the ones on the edge that aren't as obvious.

Maya Pakulski 1D

How do you convert between [H3O+] and [OH-] such as in problem 6B.9?

Maya Pakulski 1D

Mt TA told us some tips which are that inorganic acids are typically strong acids and organic acids are typically weak. To tell the inorganic from the organic, the inorganic normally have the H at the front ( ex. HCl, H2SO4, HClO3) while the organic have the H at the end (ex. CH3COOH, CH3CH(OH)).

Maya Pakulski 1D

Midori Hupfeld 3D wrote:Do acids always have a hydrogen ion in them?

Yes, acids always have hydrogen as acids form hydrogen when they disassociate in water.

Maya Pakulski 1D

How would you determine which compound is an acid and a base in the equation on question 6A.5?

Maya Pakulski 1D

Here's a website that explains all the shapes based on the coordination number and tells a little about each. https://chem.libretexts.org/Bookshelves/Inorganic_Chemistry/Supplemental_Modules_(Inorganic_Chemistry)/Coordination_Chemistry/Structure_and_Nomenclature_of_Coordination_Compounds/Coordinatio...

Maya Pakulski 1D

Is there a way to tell if something is amphiprotic?

Maya Pakulski 1D

Why are there there two definitions for acids and bases? Why not just one?

Maya Pakulski 1D

In 9C there is mention of them and there is a table with all the common ligands, the chapter isn't specifically about ligands however.

Maya Pakulski 1D

If it is positively charged do we add anything to the end like we do when its negative?

Maya Pakulski 1D

How many of the common ligands do we need to know? Just the ones on the chart on page 724 of the textbook or are there more we need to know as well?

Maya Pakulski 1D

In 9C.7 the question asks "Which of the following isomers of diaminobenzene can form chelating complexes" and then gives three example. How would you go about answering this question?

Maya Pakulski 1D

So we basically just have to memorize which bond angles go with which shapes?

Maya Pakulski 1D

Pi bonds are also more commonly found in double and triple bonds, while they are not included in single bonds. Pi bonds add bond strength to the bonds - hence why double and triple bonds are stronger than single bonds. All types of bonds have sigma bonds. So basically most first bonds are sigma bon...

Maya Pakulski 1D

The order of inter molecular forces from strongest to weakest are ion-ion, ion-dipole, hydrogen bonds, dipole-dipole, and dipole induced- dipole.

Maya Pakulski 1D

The stronger the intermolecular forces the higher the boiling point/melting point will be. Generally, polar molecules have dipole-dipole forces, making them have stronger intermolecular forces than nonpolar molecules, thus, they will boil/melt at a higher temperature. How do we find these intermole...

Maya Pakulski 1D

Are N, O and F the only atoms that will be involved with hydrogen bonds. Say you had a molecule without one of these could it form a hydrogen bond?

Maya Pakulski 1D

Everything from after the midterm up until the test.

Maya Pakulski 1D

Dr. Lavelle said we will get them back on Wednesday during lecture.

Maya Pakulski 1D

Is there a trend on the periodic table that tells polarisability and polarizing power or we just have to know based on the size of the cation?

Maya Pakulski 1D

Most of the conversions will be given but some of them you might have to memorize. A sample sheet of the constants, equations, and conversions we are given for tests is on Dr. Lavelle's website.

Maya Pakulski 1D

Most likely we will just need to know that electronegativity increases up a a group and to the right across a period.

Maya Pakulski 1D

On the topic of the midterm, will we need to know content up to Mondays lecture or last Fridays lecture?

Maya Pakulski 1D

Can someone explain how to find the lone pair electrons when trying to find the formal charge? When finding lone pair electrons you just count the pairs of electrons that are not bonded to another element. For example in the Lewis structure for water, the O has two bonds and two lone pairs because ...

Maya Pakulski 1D

Are bond lengths different for each molecule or are they always the same length?

Maya Pakulski 1D

Here's a really good website that explains it! Basically you just divide the number of bonds by the number of bond groups within a certain compound. https://chem.libretexts.org/Bookshelves/Physical_and_Theoretical_Chemistry_Textbook_Maps/Supplemental_Modules_(Physical_and_Theoretical_Chemistry)/Chem...

Maya Pakulski 1D

you could think about it as f-d-s-p i guess. for ex, if you wanted the electron configuration for gold (Au), you would write it as [Xe]4f^14 5d^10 6s^1. you would do the same thing for 5f too On the exceptions like Cr and Cu where we take an electron away from the s orbital and put it in the d orbi...

Maya Pakulski 1D

As on last night you should have posted 20 times I think because we just finished week 4.

Maya Pakulski 1D

zoedfinch1K wrote:In addition to Brianna Becerra 1F, you would typically use this equation when being asked for the minimum uncertainty in speed/velocity when given the physical constraints or vice versa.

Is minimum uncertainty something different or when we solve this equation we get minimum uncertainty?

Maya Pakulski 1D

If you go to one of the peer learning sessions and ask they will go over it and do practice problems.

Maya Pakulski 1D

In a cases like this we write the d block before the s block right? I've seen example where the electron configurations are written either way so I wasn't sure if we are supposed to do it a certain way.

Maya Pakulski 1D

For question 1F.6, we're asked to find the element in a given pair that has the smaller second ionization energy, how do you find the second ionization energy?

Maya Pakulski 1D

Besides chromium and copper are there any other ones we should know?

Maya Pakulski 1D

We know that the ultraviolet region of hydrogen has an energy level of n=1. With 102.6 nm we can find the frequency using v=speed of light/wavelength 2.998*10^8 m.s^-1 / (102.6*10^-9 m) = 2.922*10^15 s^-1 We then use the Rydberg formula, so v=R((1/n1 ^2) - (1/n2 ^2)) 1/n2 ^2 = 1- ((2.922*10^15 s^-1...

Maya Pakulski 1D

How would I start to answer this question? For each orbital listed in exercise 1D.15, give possible values of the magnetic quantum number.

Maya Pakulski 1D

Depending on what values you are given you also can rearrange each equation and combine them to find unknown variables. For instance if you were asked to solve for energy and you were only given wavelength not frequency, you can solve the equation lambda*v=c for v so that you can then plug your new ...

Maya Pakulski 1D

Threshold energy is the energy needed to make effective collisions while activation energy is the energy needed to make these collisions even occur. A molecule normally doesn't have enough threshold energy to make this occur so it needs activation energy to start these collisions.

Maya Pakulski 1D

Yes, even if the photon has some energy, but not enough to get the electron the the next energy level, then the electron will not be ejected as it cannot go halfway between energy levels.

Maya Pakulski 1D

Can somebody explain to me why it isn't B?

Maya Pakulski 1D

If we hadn't been given the molar mass of the compound would there have been anyway to tell what the molecular formula was?

Maya Pakulski 1D

My TA said we should write them, but I also heard from a UA that we probably won't need to, so maybe write them if you know them just to be safe.

Maya Pakulski 1D

Jaklin Astvatsatryan 3G wrote:
Lauren Sanchez 3D wrote:Just to make sure, the homework problems are now due during our actual discussions right?

Yes. Our TA's will be collecting them the day of your discussion.

Our answers on chemistry community will always be due Sunday night though right?

Maya Pakulski 1D

For the question 1A.9, how would you find the the wavelength and frequency that go along with the second line that says 3.3X10^-19J?

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