CHEMISTRY COMMUNITY

Maya Johnson 2a

They both end up with the same answer. A helpful tip is that it should end up with Ecell being positive.

Maya Johnson 2a

The Collision theory is basically that particles need to collide with sufficient energy and orientation for a reaction to occur.

Maya Johnson 2a

Yes, a vapor and a gas are the same for our class.

Maya Johnson 2a

Catalysts will not be in the reactants or products of the overall reaction.

Maya Johnson 2a

Yes, you should use platinum (Pt(s)) as your electrode when neither of the two half reactions have a metal in them to act as a conductor.

Maya Johnson 2a

The purpose of a salt bridge is to prevent charge build-up and keeps the solution neutral. It allows for a flow of e- without changing the cell reaction.

Maya Johnson 2a

Yes, states of matter are necessary for those sapling problems!

Maya Johnson 2a

n= moles of electrons, so when given a chemical equation you need to find the two half reactions from a balanced redox reaction. Then you can find how many electrons are needed for the balanced equation and that is your n value.

Maya Johnson 2a

Rate constants can change with changing temperature or the addition of a catalyst.

Maya Johnson 2a

Second order reactions are exponentially increasing/decreasing, which is why is depends on initial conc.

Maya Johnson 2a

Yes, n=1 for first order, and 0 and 2 for zero and second order.

Maya Johnson 2a

How can I determine if ΔG∘ will be positive or negative given K?

Maya Johnson 2a

It is helpful to balance the equations first, then add the amount of electrons needed to balance the charges. Also it is helpful to note that for the half reactions, one should have electrons added on the right, and the other reaction should have electrons on the left side.

Maya Johnson 2a

E cell naught is at standard conditions (25 degrees C, 1M, 1 atm).

Maya Johnson 2a

How can I determine the order of the best oxidizing agents?

Maya Johnson 2a

How can I figure out which reagents would oxidize Zn to Zn2+ , but not Sn to Sn2+?

Maya Johnson 2a

Hi, can someone explain textbook problem 4J.13 please?

Maya Johnson 2a

Hi, can someone explain Kekule structures please?

Maya Johnson 2a

Yes, because both are state functions, so addition works.

Maya Johnson 2a

How does the reaction being reversible or irreversible change the total entropy of a system? I know that for reversible the total entropy is equal to zero, but I do not understand why.

Maya Johnson 2a

How do I find the change in entropy given the initial and final pressures?

Maya Johnson 2a

ΔG° is Gibbs free energy under standard conditions, while ΔG is not under standard conditions.

Maya Johnson 2a

q=mcAT is for when you are given the mass.
q=ncAT is for when you are given the number of moles.
You can determine which to use whether you are given specific heat capacity of molar heat capacity.

Maya Johnson 2a

How can I tell the difference between reversible and irreversible in questions we are given?

Maya Johnson 2a

How do you find heat of vaporization given change in mass?

Maya Johnson 2a

Hi, can someone please explain the different variations of the entropy equations?

Maya Johnson 2a

Bond enthalpies are averages, which is why they are least accurate.

Maya Johnson 2a

Yes, this is true because when work (energy) is positive, it enters the system, and when the system performs work, it loses energy (negative).

Maya Johnson 2a

When work is done to the system, the value is positive. When a system does work, the value is negative.

Maya Johnson 2a

I believe it is just because week 5 has not been posted yet.

Maya Johnson 2a

I would use J/gºC.

Maya Johnson 2a

Hi!
Can someone explain residual entropy?

Maya Johnson 2a

If you are given the pH, you can solve for H+. Then use the H+ value in the Ka equilibrium equation to solve Ka.

Maya Johnson 2a

When K is large, there is a larger amount of products and therefore the products are more stable. On the other hand, when K is small, there is a greater amount of reactants.

Maya Johnson 2a

I believe the textbook gives us a table for Bond enthalpies, and for our midterm they would be provided for us.

Maya Johnson 2a

Yes, the ICE box can solve for partial pressures.

Maya Johnson 2a

Hi! Can someone help me with this textbook problem please:
Calculate the reaction Gibbs free energy of I2(g) →2 I(g) at 1200. K (K = 6.8) when the partial pressures of I2 and I are 0.13 bar and 0.98 bar, respectively.

Maya Johnson 2a

Use Kelvin.

Maya Johnson 2a

Ka is the equilibrium constant for acids, and Kb is the equilibrium constant for bases. Ka*Kb=Kw=1*10^-14

Maya Johnson 2a

A larger Ka is a stronger acid.

Maya Johnson 2a

What K value do I use for solving pH of diprotic acids, K1 or K2?

Maya Johnson 2a

Hi!
Can someone explain the idea that temperature does not change when heat is added during boiling?
Thank you

Maya Johnson 2a

Equilibrium constants are only a set value for a certain temperature, and Kw is the equilibrium constant for water at 25 degrees celsius, which is why it always equals 10^-14.

Maya Johnson 2a

If you know whether the reaction is endothermic or exothermic, you can determine which would be favored. In an exothermic reaction, if temperature is increased, the reaction shifts left, as heat can be seen as a product of the reaction. In an endothermic reaction, if temperature is increased, the re...

Maya Johnson 2a

We typically use 25 degrees Celsius as our standard temperature.
Le Chatelier's principle says that in an endothermic reaction, Ka increases and therefore pKa decreases.
As far as acids and bases, it does not change their 100% ionization though, if that is what you're asking.

Maya Johnson 2a

The statements are the same!

Maya Johnson 2a

If you are given pKa, use -log(Ka) to solve, and Ka= [H+][A-]/[HA]. I believe that the whether or not you are given pKa just depends on the question.

Maya Johnson 2a

K decreases with an increase in temperature (exothermic!) and K increases when temperature decreases (endothermic!).

Maya Johnson 2a

How do I convert Kc to Kp?

Maya Johnson 2a

Hi!
Can someone explain how to find Kc when given a reaction and its eq. constant K?

Maya Johnson 2a

It becomes the inverse reaction, or 1/K

Maya Johnson 2a

When we are using ICE for to find equilibrium values, do we always use molarity?

Maya Johnson 2a

Are there other amphoteric compounds outside of the metalloids?

Maya Johnson 2a

For the general rule that metal oxides react with water to form strong bases, and nonmetal oxides react with water to form acids, are there any exceptions to this rule?

Maya Johnson 2a

What type of products form in proton transfer equilibria?

Maya Johnson 2a

Do strong vs weak conjugate bases play a role in determining the pH of a salt solution?

Maya Johnson 2a

On the test, if we are asked to give the shape of a molecule, do we give the electron-group shape name, or the molecular shape?

Maya Johnson 2a

Bonds that are longer are more easily broken, making them present in strong acids because they dissociate well.

Maya Johnson 2a

We don't need to distinguish between the two, just know that the coordination number is 4!

Maya Johnson 2a

I agree, I don't think that formula order matters, only when writing out the name.

Maya Johnson 2a

Hi! Can someone explain what denticity is?

Maya Johnson 2a

What is an example of a bidentate ligand?

Maya Johnson 2a

When naming coordinate compounds, does it matter if it is one long name or if we separate each part of the name with spaces in between?

Maya Johnson 2a

When naming ligands, why is ammonia changed to ammine? Or what is the rule for naming?

Maya Johnson 2a

How do we know where to put lone pairs, such as in the axial or equatorial position?

Maya Johnson 2a

I believe s and p orbitals will only be tested on.

Maya Johnson 2a

What is the difference between a pi bond and a delocalized pi bond?

Maya Johnson 2a

Ionization energy and electronegativity both follow the same trend- they increase across a period and decrease down a group.

Maya Johnson 2a

Yes, every area with a lone pair or bond is an area of e- density.

Maya Johnson 2a

I believe we just have to know that it would be less than a certain value, and not a specific value.

Maya Johnson 2a

Hi,
I usually look for lone pairs or symmetry when looking to see if a molecule is polar or not. Also, I look to see if the central atom has all the same types of atoms surrounding it, as sometimes if one is more electronegative than the other it cause cause a slight pull of e-.

Maya Johnson 2a

H2O has a bent structure because it has two lone pairs on the oxygen atom. This causes repulsion of the two hydrogen atoms and pushes them downwards, causing a bent structure.

Maya Johnson 2a

What are the bond angles in a seesaw shape?

Maya Johnson 2a

Hi!
Can someone explain why the lone pair in the seesaw shape is found on the equatorial plane and not the axial plane?

Maya Johnson 2a

In square planar, the four atoms are all in the same plane and make up the four corners of it. While in tetrahedral, they are not all in the same plane.

Maya Johnson 2a

Between two anions in the same row, would an anion with a -2 charge be more or less polarizable than an anion with a -1 charge? I think it is just by anion size. So whichever one is larger will be more polarizable even if the charge is a smaller magnitude. Someone, please correct me if I am wrong! ...

Maya Johnson 2a

What is the multiplicity of a covalent bond?

Maya Johnson 2a

Yes, use the octet rule to draw your lewis diagrams, then assign formal charges to the atoms.

Maya Johnson 2a

Radicals are any molecules that have an unpaired electron, and they form when atoms or molecules gain or lose electrons.

Maya Johnson 2a

Are the dipole-dipole the same as polar covalent bonds?

Maya Johnson 2a

Hi, I know that the polarizability is how easily the electrons are distorted, but can someone explain what the Polarizability of Anions, The Polarizing Power of Cations is specifically pertaining to?

Maya Johnson 2a

Does electronegativity affect bond length?

Maya Johnson 2a

When you move across the periodic table, the atomic radius gets smaller because with more protons, there is a greater pull on the electrons. Ultimately, this results in a smaller atomic radius.

Maya Johnson 2a

What are some examples of when we ingest radicals?

Maya Johnson 2a

I know that it is better to have negative charges on the most electronegative elements, but for a structure that has an overall charge of -1, would it be better to have a +1 on N and two -1 oxygen charges, or just one -1 charge on a single O atom?

Maya Johnson 2a

For ions that all have the same electron configuration, so the same number of elements, but are different elements, such as Na+ and F-, how do you determine which has the smaller radius?

Maya Johnson 2a

Hi, I am having difficulties with Sapling Problem 24. I am not sure how to determine whether or not a wavelength is compatible or not?

Maya Johnson 2a

Hi!
I think that Dr. Lavelle said we would not need to memorize polyatomic ions, and that they would be given to us if we had to write out chemical equations.

Maya Johnson 2a

Hi!
The 3d state has less energy than the 4s energy state, which is why it is written first when writing out electron configurations.

Maya Johnson 2a

What is the significance of the negative sign in Bohr's equation?

Maya Johnson 2a

Would 4s^2 3d^1 be wrong instead of 3d^1 4s^2 on tests?

Maya Johnson 2a

Hi, I am a little bit confused as to when I should be using Schrodinger's equation, or what the overall purpose of it is for?

Maya Johnson 2a

Will we be tested on the particle in a box on the midterm?

Maya Johnson 2a

Hi!
Can someone elaborate on what H is in the Schrodinger equation?
Thank you

Maya Johnson 2a

I know that if you calculate a velocity greater than the speed of light, then it is physically impossible and an incorrect model, but can the velocity be equal to the speed of light?

Maya Johnson 2a

Hi, I have having issues with problem 1B.20 from the book:
What is the wavelength of an electron when the distance it travels in 1 s is equal to its wavelength?
and was wondering how I should set up this problem?

Maya Johnson 2a

When I use the DeBroglie equation, should the units for mass be in g or kg?

Maya Johnson 2a

Hi!
I was doing problem 1.A.9 in the textbook, and was given the frequency= 300 MHz and was told to find the wavelength. Each time I solve it I keep getting 0.1 m, while the answer is 1 nm.
If anyone could help I would appreciate it!

Maya Johnson 2a

In the lecture, Dr. Lavelle mentioned that the energy of the photon is energy/electron, while the work function is in energy/mol, and that we would need to use Avogadro's number to convert the energy of the work function to energy/atom. What would a question look like where we would need to convert ...

Maya Johnson 2a

Yes, the work function, or threshold energy, is the amount of energy required to eject an electron from the surface!

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