CHEMISTRY COMMUNITY

Kayla Ziebell 1H

Likhitha Yettela 1F wrote:I am still a little confused as to why we don't try and get rid of the OH- the way we did the HClO because both are intermediates?

I was wondering this same question. I see we substitute HClO because it is an intermediate but why do we not do it with OH-?

Kayla Ziebell 1H

Free expansion is when something can expand without an external force applied to it and it having to do any work. There is no work being done because it has no external force to combat in order to expand.

Kayla Ziebell 1H

the answer does come out to be negative but when referring to the rate of a reaction, we take the absolute value of it so that it is always positive.

Kayla Ziebell 1H

A catalysts speeds up the reaction rate in both the forward and reverse reactions. A catalysts decreases the activation energy of the reaction which allows the reaction to require less energy to happen, therefore it happens faster.

Kayla Ziebell 1H

Yes one big thing we learned about are catalysts. Catalysts speed up a reaction by decreasing the activation energy. The activation energy must be reached for the reaction to successfully happen, thus when a catalysts decreases this, the reaction needs less energy for it to happen, and therefore it ...

Kayla Ziebell 1H

Capital K is the equilibrium constant used in thermodynamics, whereas lowercase k is the rate constant.

Kayla Ziebell 1H

If you happen to freeze up during the test and feel like your mind has blanked, I would suggest to take a minute away and take deep breaths and move onto a different question. I would come back to the question with fresh eyes after taking deep breaths.

Kayla Ziebell 1H

Thank you so much!

Kayla Ziebell 1H

To add to what people are saying above, a catalyst is needed to start the reaction. This molecule is used but becomes regenerated which can go on to catalyze other reactions. On the other hand, intermediates are added and completely used up in the reaction.

Kayla Ziebell 1H

The F stands for faradays constant. this does not have to be memorized as it is on the equation sheet.

Kayla Ziebell 1H

n stands for the number of moles!

Kayla Ziebell 1H

After solving, I also got -0.00325 however when we look at the overall rate, we refer to it as a positive value.

Kayla Ziebell 1H

I believe it is just referring to how many molecules there are colliding in the reactants. So bimolecular is with 2 molecules and unimolecular is with one molecule.

Kayla Ziebell 1H

It is faradays constant which is just given on the equation sheet. There is nothing to solve for it and no need to remember it exactly.

Kayla Ziebell 1H

Not all of the answer choices will be used so everything is right besides the M^2/s in the first box.

Kayla Ziebell 1H

For a zero order equation, the half-life equation is
t=[A]o/(2k)
where [A]o is the initial concentration in the reaction
k is the rate constant

Kayla Ziebell 1H

When I solved this problem, I used the equation: lnk = -Ea/RT + lnA
Then plugging in the numbers for k, which is the rate constant, R which is 8.314, temperature which is added to 273 to be in Kelvin, and A, which is the frequency factor. Plugging in these numbers will get you the value of Ea.

Kayla Ziebell 1H

I think the main difference is that a catalyst is not used up and an intermediate is used up. You won't see an intermediate in the final reaction and product because it is completely used up, however you will see the catalyst.

Kayla Ziebell 1H

You have to look at the rate law to determine the order of each reactant. Therefore, A is first order so it is just 1/2 and B is second order so you are going to square the factor, 3^2. Therefore you multiply the constant by (1/2) and 9 to get the answer.

Kayla Ziebell 1H

It all depends on the units! You want certain units to be able to cancel out with the other factors in the equation, so you chose the R value that does that.

Kayla Ziebell 1H

A straight line plot of ln[reactant] vs time means the reaction is 1st order. This is useful because it tests if the reaction is 1st order and if it is then the slope is -k.

Kayla Ziebell 1H

Yes, the final is cumulative and on his website he includes a document with information for the final. there is information on how much of the exam covers each topic.

Kayla Ziebell 1H

k is the rate constant of the reaction and k' stands for the pseudo rate constant and can be used as the reverse reaction rate for a reaction.

Kayla Ziebell 1H

If the system is doing work then the value of w is negative. This gives us U=q-w. On the other hand, if the system is getting work done on it then you would use the equation U=q+w, where w is positive.

Kayla Ziebell 1H

yes you do not have to convert between moles and grams. the variable n has units of moles and the variable m is used for the mass in grams.

Kayla Ziebell 1H

The difference between them is that one is for reactions that are reversible and one for reactions that are irreversible. You use w=p*deltaV for reactions that are irreversible. Furthermore, you use w=-nRT*ln(V2/V1) for reactions that are reversible.

Kayla Ziebell 1H

In order to do this we just multiple Cv,m by moles. In the term Cv,m it is the specific heat capacity per mole, where moles are in the denominator of the units, therefore in order to get rid of moles, we multiple the term by the moles.

Kayla Ziebell 1H

Happy (late) valentines day!!

Kayla Ziebell 1H

Yes, delta G is positive when a reaction is not spontaneous.

Kayla Ziebell 1H

I love the song "space song" by beach house when I study

Kayla Ziebell 1H

I believe just having delta G as negative will make the reaction spontaneous.

Kayla Ziebell 1H

ln has log base e, therefore the inverse of it is e to the exponent x. However just log has a base of 10, where the inverse is 10 to the exponent of x.

Kayla Ziebell 1H

Midterm 2 is going to be online and proctored.

Kayla Ziebell 1H

You want to double check your conversion to Kelvin. You have to subtract it from 273 instead.

Kayla Ziebell 1H

It is just the ratio of the products being multiplied together over the reactants being multiplied together.

Kayla Ziebell 1H

I heard that Oxygen and Magnesium were going out and I was like OMg.

Kayla Ziebell 1H

I believe that pOH is usually associated with using or solving for Kb and pH is used with Ka, but other than that I believe they are just used to calculate one another.

Kayla Ziebell 1H

It basically says that because enthalpy is a state property, enthalpies can be added to find a total value for enthalpy. By manipulating different reaction equations, one can find the total enthalpy of a reaction through addition using Hess' law.

Kayla Ziebell 1H

Using the quadratic equation is always more accurate. By simplifying the math and assuming x is very small and disregarding it, we are only getting an approximation.

Kayla Ziebell 1H

If x is less than 5% ionization, then when calculating using ICE, you can simplify the math and make an approximation by taking out the "-x" in the equilibrium term. However, if it is more than 5%, then you have to solve using the quadratic equation.

Kayla Ziebell 1H

K is the equilibrium constant. Q can be calculated whenever and K is used sort of as a basis for comparison to see how the reaction has changed when comparing Q to K.

Kayla Ziebell 1H

If something is being used up in the reaction, it is being subtracted out as -x, and if something is being produced in the reaction, it is being added in as +x.

Kayla Ziebell 1H

Kw is the equilibrium constant of water. It is found in this equation: Ka x Kb = Kw, where Kw equals 10^-14, therefore Ka x Kb = Kw = 10^-14.

Kayla Ziebell 1H

Yes if you have K, and solve the ratio of products over reactants and find that Q is equal to K, then you can assume that the reaction is at equilibrium.

Kayla Ziebell 1H

In ICE tables, you only include gases and aqueous solutions!

Kayla Ziebell 1H

In lecture, Dr. Lavelle stated that a good buffer has an equal of amount of acid and its conjugate base or an equal amount of base and its conjugate acid.

Kayla Ziebell 1H

I think pH is more commonly used and talked about because it deals with protons and keeps everyone on the same page, but pOH is still very easy to solve for once having the pH so it is easy to move between them.

Kayla Ziebell 1H

I think it is because if you decrease the amount of product, in order to bring it back to equilibrium, more product will have to be formed.

Kayla Ziebell 1H

I also read that a 50% in this class is a C- ! HAPPY WINTER BREAK

Kayla Ziebell 1H

Anyone know any jokes about salt? Na.

Kayla Ziebell 1H

What do you say when you run out of chemistry jokes . . .
I should zinc of a new one.

Kayla Ziebell 1H

Anyone heard any good jokes about sodium . . .
Na

Kayla Ziebell 1H

Charge is determined by whether or not the atom posses more or less electrons in the lewis structure bonding than what its supposed to have in its valence shell according to the periodic table. If it has extra electrons, it will take on a negative charge, and fewer electrons will result in a positiv...

Kayla Ziebell 1H

we use the VSEPR model. A tetrahedral has four regions of electron density and when drawing the lewis structure, the regions of density should all be as far away from each other as possible. This is due to its repulsion tendencies.

Kayla Ziebell 1H

I really don't think they have to be very different. Just by simply switching a double and single bond between two of the same atoms would do it. I remember him giving an example in class where there were 6 of the same atoms bonded to the central atom, and he simply put the double and single bonds i...

Kayla Ziebell 1H

Yes they will always be neutral and have no net charge

Kayla Ziebell 1H

Hi, yes lone pairs do not play a role in determining sigma and pi bonds. Sigma and pi bonds are based on the bonds and whether or not they are single, double, triple, etc.

Kayla Ziebell 1H

You can use the lewis structure to determine shape. The shape is determined by the regions of electron density, both including the number of atoms attached to the central atom and the number of lone pairs on the central atom.

Kayla Ziebell 1H

Is it possible to have fractions as coefficients when balancing chemical reactions? I came across a problem where I had 2/3 as a coefficient, and I wasn't sure as to whether that's acceptable or not? Thank you! Hi! I would multiple the whole reaction by the denominator, in this case, 3. It would ma...

Kayla Ziebell 1H

I would probably go through the textbook and textbook problems for the topics we covered at the beginning of school because those are least fresh in our minds!

Kayla Ziebell 1H

I am not sure but I am not thinking they are having any, as I would assume they would've emailed us if they were.

Kayla Ziebell 1H

Electronegativity increases as it moves right because the electrons are getting closer to 8 valence shell electrons and want to complete their shell by getting more electrons. The electronegativity decreases down the table because as you move down, the element gets another shell added, and thus the ...

Kayla Ziebell 1H

Typically you write it in increasing energy levels. So you would write the s level before the p level. Also, typically you would want to write it in increasing shell level. For example: [Ar] 3d10, 4s2, 4p3

Kayla Ziebell 1H

I have been feeling really stressed these past few days, but just a little bit ago I started feeling a lot better and more confident for finals!

Kayla Ziebell 1H

The structure is bent because of the lone pairs. When there are lone pairs, the affect the geometry of atoms attached to the central atom. For example, if there is a lone pair on the central atom with two atoms bonded to it, the shape will be bent because the electrons on the lone pair have repulsion.

Kayla Ziebell 1H

The coordination number is just the number of atoms that is bonded to the central atom. This includes all types of bonds; single, double, etc.

Kayla Ziebell 1H

They have longer, weaker bonds and thus that makes a strong acid because they are stretched out and are able to release H+ ions and dissociate easier.

Kayla Ziebell 1H

The Home Alone series have my favorite comfort movies.

Kayla Ziebell 1H

I think doing the suggested book problems will be a good study tool for the final.

Kayla Ziebell 1H

Keep your ion the prize!

Kayla Ziebell 1H

Lose an electron?
Gotta keep an ion it hahahah

Kayla Ziebell 1H

I think for the final we will have the same tools - just a periodic table and equation sheet so I don't think we will get the coordination compound sheet.

Kayla Ziebell 1H

How I go about finding the oxidation number of a metal ion is by first finding the formal charges of all the ligands in the compound both inside and outside the bracket. If the compound has a neutral charge, then the metal ion takes on the formal charge with an opposite sign as the total in order to...

Kayla Ziebell 1H

We add -o to the end of an anion when naming, and I believe you take out the -ide completely, so chloride would become chloro. I also have in my notes that cyanide would become cyano.

Kayla Ziebell 1H

Im pretty sure it gets factored in as the other ones do. In our notes, I have down that the oxidation state for Cobalt in [Co(NH3)5Cl]Cl.2H20 is 2 (Cobalt(II)). When looking at the formula, both he Cl atoms have a charge of -1, therefore the compound has a total charge of -2, and to make it neutral,...

Kayla Ziebell 1H

It is basically how many ligands are on the central atom - so basically just count the atoms. There are 3 NH3 and 3 F atoms, therefore there is a total of 6 that the central atom is going to bind to.

Kayla Ziebell 1H

craving some sushi always !!

Kayla Ziebell 1H

Tocaya is a must its so good!

Kayla Ziebell 1H

I am so nervous for this final. Something I find really helpful when im nervous is taking a walk outside or just getting fresh air outside in general.

Kayla Ziebell 1H

I am confused on the last question on #5. How do we go about determining the coordination number for Cd(en)Br2? What is the (en)? Would it be 3?

Kayla Ziebell 1H

I start by looking in the brackets and basically seeing how many ligands are bonded around the central atom!

Kayla Ziebell 1H

Sometimes I also get intimidated reading the textbook. I recommend searching on YouTube 'The Organic Chemistry Tutor.' I have found his videos really helpful and he's had videos on every topic I've had trouble on. I have found that he breaks it down and goes over the content very slowly. Sometimes w...

Kayla Ziebell 1H

In order to determine the shape, you count how many regions of electron density that atom has, including both lone pairs and bonded pairs. Lone pairs and bonded pairs play different roles so never skip of a set of lone pairs. Lone pairs is what makes a tetrahedral different from a square planar even...

Kayla Ziebell 1H

When hybridization occurs, the atom becomes more stable! The goal is to always become more stable

Kayla Ziebell 1H

You have a -1 formal charge when one of the atoms in the lewis structure has an extra electron. Electrons take on a negative charge, therefore if an atom has an extra electron than what its supposed to have based on its valence electron number, it will take on a -1 formal charge. For example, in OH-...

Kayla Ziebell 1H

In a bond, each atom is putting one electron in, therefore a bond essentially makes up two electrons. Therefore, when trying to find the number of electrons of an atom to find the formal charge, we associate one electron from each bond to that atom being bonded. So if there is a double bond, that at...

Kayla Ziebell 1H

If there are only single bonds, then there will not be any pi bonds. In order to have a pi bond, there must be a double or triple bond. In this case, the first bond would be a sigma bond and the second bond would be a pi bond. When there are only single bonds, there are just sigma bonds.

Kayla Ziebell 1H

We thank you so much for your teaching and bright and welcoming personality! We love you!

Kayla Ziebell 1H

I am definitely very stressed right now for finals and these upcoming weeks, but I am staying positive and will be excited when its all over. Thanksgiving break has been nice to relax and see family so that has been good

Kayla Ziebell 1H

Im out of chemistry jokes, I should zinc of a new one

Kayla Ziebell 1H

Carbon and Hydrogen went on a date the other day... I heard they really BONDED :)

Kayla Ziebell 1H

What was avogadros favorite number?
Golf! He always got a mole-in-one!

Kayla Ziebell 1H

Some elements take on an expanded octet in order to get an octet for other elements. I am pretty sure that elements such as Nitrogen, Oxygen, and others in that row are unable to take on octets, however elements elsewhere such as phosphorus can take on an expanded octet.

Kayla Ziebell 1H

I get super nervous before my tests and sometimes what I do is take a little break and get my heart rate up by doing some jumping jacks or something where im moving my body. I find this helps reset me and takes away some anxiety.

Kayla Ziebell 1H

A helpful tip I caught on to was when we say the hybridization is sp, the s always has a subscript of 1. Therefore if the atom has 3 regions of electron density, the hybridization I think would be sp^2, where there is 1 s and 2 p in order to have a total of 3.

Kayla Ziebell 1H

Why is the atomic radius trend in the periodic table that atomic radius decreases across a period and increases down a group? Could someone explain why exactly that is in relation to the periodic table? I think explaining the reasoning to the trend might help me understand it instead of memorizing ...

Kayla Ziebell 1H

Yesterday, I brought a bag of sliced apples for lunch with me but by the time I got to eat it, it was already browning. Then I remembered how my mom used to cover apples with lemon juice to keep them fresh all day long! The acidity of the lemon slows down the browning because ascorbic acid reacts w...

Kayla Ziebell 1H

How I always think of it is the third quantum number, ml, is based on the second quantum number, l, therefore if l is 3, then ml could be -3, -2, -1, 0, 1, 2, 3.

Kayla Ziebell 1H

I remember learning that wavelength and frequency are inversely proportional, meaning that as one increases, the other decreases. Frequency and wavelength of the wave get multiplied together to get the speed of light, which always equals 3x10^8 m/s. Therefore, as one increases, the other must decrea...

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