CHEMISTRY COMMUNITY

Claire Lo 3C

Conjugate acids and bases are bronsted acids and bases. They always appear in the same chemical reaction.

Claire Lo 3C

Oxidation number is also useful when looking at redox reactions.

Claire Lo 3C

By putting the 4 oxygens around the sulfur, you immediately have an octet. If it comes without a charge, then don't add a charge.

Claire Lo 3C

If the electron is taken from n=2, then it's represented as 2sp^3, etc. If it's taken from n=3, then 3sp^3, etc.
In general, you can just represent it with sp^3.

Claire Lo 3C

The bond angle would be less than the bond angles in a octahedral. The long pairs do affect the bond angle since they cause repulsion.

Claire Lo 3C

Polydentate is a ligand that binds at more than 1 site since it donates more than 1 e- pair.

You can draw out the lewis structure to figure out which atom has lone pairs.

a. 3, on the nitrogen atoms
b. 1 or 2 on oxygen atoms
c. not a polydentate
d. 2 on oxygen atoms

Claire Lo 3C

(a) Hexacyanoferrate (II) +2
(b) Hexaaminecobalt (III) +3
(c) Aquapentacyanocobalte (III) +3
(d) Pentaaminesulfatocobalt (III) +3

Claire Lo 3C

Since there is a space between potassium and hexacyanidochromate (III), it indicates that potassium is out of the bracket.

K3 [Cr(CN)6]

Claire Lo 3C

linear, square planar, tetrahedral, octahedral

Claire Lo 3C

1. Put the ligand name in alphabetical order then put the transition metal cation name. 2. Use prefix to indicate the number of ligands: mono, di, tri, tetra, penta, hexa 3. Add O to the end of anion name: for example Cyanide -> Cyano 4. If ligand has name with di, tri, tetra, or polydentate, then u...

Claire Lo 3C

The total charge is given so that you can calculate the charge of the Fe ion. In this case, since the total charge of 4-, and CN has a charge of -1, the charge of the Fe ion is +2

Claire Lo 3C

What exactly is a polydentate?

Claire Lo 3C

Bronsted acids are always lewis acids, but not all lewis acids are bronsted acids.

Claire Lo 3C

Also, although all bronsted acids are lewis acids, not all lewis acids are bronsted acids.

Claire Lo 3C

It dissociates partially to release hydrogen ions

Claire Lo 3C

You determine the VSEPR structure of the molecule first. Then you can use lines to represent atoms on the same plane with the paper, solid triangles as atoms coming towards you, and dashed lines as atoms going away from you.

Claire Lo 3C

Essentially yes. The number of bonded electron pairs represents X, and the number of lone pairs represets E.

Notice that a single bond, double bond, and triple bond all count towards a single X.

Claire Lo 3C

Also the bond angle is different. Trigonal planar has bond angles of 120 while trigonal pyramidal has bond angles of around 107, so these two are absolutely different.

Claire Lo 3C

Drawing lewis structures help you determine whether there are lone pairs or not, which influences the VSEPR structure. Thus to be safe, always draw out the VSEPR first.

Claire Lo 3C

Nope, because VSEPR relies on the lowest energy Lewis structure.

Claire Lo 3C

I know that to emit an electron, the photon has to reach a specific frequency. Is it true that the frequency of the photon has to double in order to emit the second electron?

Claire Lo 3C

Why are there 2 hydrogen bonds between A and T base pairs?

Claire Lo 3C

Does the H of H2O and O of CO form a hydrogen bond?

Claire Lo 3C

Remember that the key is to find the molar ratio of the elements. You find the number of moles of CO2, for example, through dividing the given grams by molar mass. This number of moles of CO2 is also the number of moles of C, since there is only 1 C atom in one CO2 molecule. For H2O, you need to tim...

Claire Lo 3C

Another way to think about it is that work function is the threshold energy need to emit one single electron from the metal. Thus the single photon needs to possess an adequate amount of energy, or at least the threshold energy.

Claire Lo 3C

If a hydrogen atom goes from n=3 to n=1, why is the change in energy negative and why is the energy of the photon emitted positive?

Claire Lo 3C

1keV = 1000 eV
1 eV = 1.60e-19 J

so 1keV = 1000 x 1.60e-19 J

Claire Lo 3C

Where does the 4 pi come from in the equation?

Claire Lo 3C

What exactly is the definition of work function? If it's the energy needed to remove a single electron from solid metal, why is the unit sometimes J per mole?

Claire Lo 3C

As long as it's greater than 10^-15 m, then it's considered to have measurable wavelike properties.

Claire Lo 3C

Hydrogen in some cases has lower ionization energy than other atoms. But it's almost never used as the central atom, except if the molecule is H2.

Claire Lo 3C

First of all, BrF3 has a total of 28 valence electrons, instead of 24. Br has a lower ionization energy than F, so Br is the central atom. Each F-Br bond constitutes to 2 electrons, so that's a total of 6, and you still need to assign the rest of the 22 valence electrons. Put 4 electrons on Br so th...

Claire Lo 3C

And by charge, he meant the calculated formal charge.

Claire Lo 3C

also P, S, Cl may exceed the octet rule

Claire Lo 3C

Basically put the negative charge on the atom with the highest electron affinity

Claire Lo 3C

c = wavelength x frequency c= speed of light wavelength = 1850 nm (be sure to convert it to meters) You will get frequency. Plug the frequency value into E=hv, where h is planck's constant. You will get the energy of a single photon. Then use the total number of Energy, which is 11J, divide it by th...

Claire Lo 3C

E = hv

So after u calculate v from c=wavelength x frequency, u plug it into E=hv with h as Planck's constant

Claire Lo 3C

How many nodal planes do f orbitals have?

Claire Lo 3C

I know that psi represents the height of a wave at position x,y, z. But I don't understand why psi^2 represents the probability of finding an e-.

Claire Lo 3C

If Schrodinger wave equation with 3 quantum numbers can only be used to solve for 1 e- atoms, then can you use 4 quantum numbers to solve for more electrons since the fourth number indicates the spin state?

Claire Lo 3C

If we're asked to calculate the %mass composition of a compound, how many sig figs should we keep?

Claire Lo 3C

Yea, as long as they are spectra of the same atom.

Claire Lo 3C

Also this equation only applies to the H-atom

Claire Lo 3C

It is grouped by the type of electromagnetic radiation or wavelength/frequency that is shone on the material. Thus it is grouped as UV, infrared, and visible and since they have different energies, the electrons will return to different shells.

Claire Lo 3C

If the question asks that a certain amount of energy is needed to remove 1 mole of electrons, you first divide the energy by Avogadro's number before proceeding to the rest of the calculation right?

Claire Lo 3C

The first volume given usually allows you to calculate the molarity. Typically we use the second volume in the calculation.

Claire Lo 3C

I would write down my calculation first: 0.3moles / 2 = 0.15moles of B 0.2 moles /1 = 0.2 moles of A. Since 0.15 moles of B is less than 0.2 moles of A, B is the limiting reactant. I think your explanation is also acceptable, as long as you explain that since we only have .3 moles of B right now and...

Claire Lo 3C

A combustion analysis allows you to deduce the formula of an organic compound, which is usually CxHy or CxHyOz. It can also be used to determine the percentage purity by mass of a given compound.

Claire Lo 3C

You can convert it to a fraction first (using your calculator) then just multiply by the denominator.

Claire Lo 3C

Hey guys Im confused about M.26. It states that a combustion analysis of the compound C14H20O2N gave the following data: 68.50%C, 8.18%H by mass. Because the data were considerably different from that expected for pure C14H20O2N, the sample was examined and found to contain a significant amount of C...

Claire Lo 3C

So I was doing E5 on the textbook and it asks how many moles of people inhabit Earth if the estimated population is 7.0 billion people. This made me question the definition of 1 mole and Avogadro's number.

Claire Lo 3C

Does anyone know the difference between molarity and molality?

Claire Lo 3C

Becuz ur asked to prepare a solution. When copper (ii) sulfate pentahydrate is dissolved in water, the attached H2O joins with the surrounding water. Since copper (ii) sulfate pentahydrate contains 1 mole of CuSO4, the amount of copper (ii) sulfate pentahydrate you need is the same as the amount of ...

Claire Lo 3C

Could someone please explain the difference between a formula unit and a molecule? Thanks.

Claire Lo 3C

In inter-problem calculations, how many sig figs do u keep? Same as the question or one more?

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