CHEMISTRY COMMUNITY

Haley Chun 4H

Geometry would be the parent shapes: linear, trig planar, tetrahedral, trigonal pyramidal, octahedral. The shape would be like bent, see-saw, etc.

Haley Chun 4H

I believe you would use 'ammine' when referring to a ligand and 'amine' when referring to a functional group.

Haley Chun 4H

I read online that bases like amines do not produce water when reacted with acid, but bases like hydroxides, oxides, and carbonates do (this would explain why ammonia and phosphoric acid would produce only a salt).

Haley Chun 4H

Are we expected to know the chemical formulas of acids from their names. ex) phosphoric acid is H3PO4

Haley Chun 4H

I think so. It is on the ligand worksheet Lavelle emailed to the class.

Haley Chun 4H

I think you have to know the strength first and from there you can determine whether the compound is 100% ionized (strong) or not 100% ionized (weak). But you wouldn't be able to go the other way around unless say you were given the chemical equation.

Haley Chun 4H

I found the step-up sessions extremely helpful. The UA's go through worksheets that they have adapted specifically from Lavelle's old midterms/finals, so they better prepare you for his tests.

Haley Chun 4H

I don't believe we have to differentiate between the two, so either answer would be correct.

Haley Chun 4H

Yes, for hybridization you just need to draw the lewis structure and count the bonds/lone pairs.

Haley Chun 4H

I think you just have to memorize the names. There is a list on page 723/724 in the textbook.

Haley Chun 4H

1 (AX2E) or 2 (AX2E2)

Haley Chun 4H

I would draw the lewis structure to determine the shape of the molecule and identify as symmetrical or non symmetrical. With symmetrical shapes, the dipoles can each other out cancel out (tetrahedral is a special case where all four attached atoms must be the same in order to be able to cancel).

Haley Chun 4H

I plan to go through all of the problems I was confused on or did wrong on the homework, midterm, and tests.

Haley Chun 4H

The Covel workshops really help since the UA's go over the material from the lecture and answer questions. Some post their worksheets on chem community so you practice the past material too.

Haley Chun 4H

Doesn't O2 have a bond angle of 180?

Haley Chun 4H

With a tetrahedral shape, the molecule cannot be nonpolar unless all four attached atoms are the same (CH4). Thus, it will be polar.

Haley Chun 4H

Why is CH2CL2 polar when the shape is symmetrical and there are two dipoles pointing towards Cl. Shouldn't they cancel?

Haley Chun 4H

Content that wasn't on the midterm to Monday's lecture (11/18). I think material such as chemical bonds/forces, VSEPR (shapes, angles) and some sigma/pi bond stuff.

Haley Chun 4H

Polarizability is a measure of how easily an atom's electron cloud can be distorted (so larger atoms will have higher polarizability). Electronegativity refers to the atom's ability to attract electrons (top right of the periodic table has the highest electronegativities). Thus, I don't think that t...

Haley Chun 4H

in IF4, the central atom only has 4 bonding regions (square planar). With an octahedral, the central atom has 6 bonding regions.

Haley Chun 4H

You have to consider shape and the dipole moments. For example, if a molecule had two polar bonds both pointing towards the central atom and the shape was linear, the dipole moments would cancel (vectors) and the molecule would be non-polar. However, if you had water (where the shape is a tetrahedra...

Haley Chun 4H

^ Lavelle said that we would just have to write the shape and possibly describe it, but we would never have to draw wedges/dashes.

Haley Chun 4H

yes, a larger difference in electronegativity would indicate more ionic character, while a smaller difference indicates more covalent character.

Haley Chun 4H

Yes, the smaller the atomic radius, the more polarizing power the atom has. The larger the atomic radius, the more polarizable the atom is because it is more easily distorted.

Haley Chun 4H

Oxygen also has 4 electrons in the 2p orbital, yet it would rather have a half-full shell. Thus, it would be easier to remove the 4th electron.

Haley Chun 4H

C and Br both have electronegativities on the lower side, while F has the highest electronegativity in the periodic table.
C(low) - Br (low) < C (low) - F (high)

Haley Chun 4H

I think the dots should be paired since they represent electrons (which must also be paired).

Haley Chun 4H

Which of the following ranks the following bonds from most polar to least polar? a) Mg-O > Cl-O > C-O > O-O b) Cl-O > Mg-O > C-O > O-O c) Cl-O > O-O > Mg-O > C-O d) Mg-O > C-O > B-O > O-O The correct answer was d, but don't Boron and oxygen have a greater electronegativity difference than C-O, makin...

Haley Chun 4H

I don't think it is necessary to show every step because most of the time it is just a matter of dividing/multiplying/adding variables (mental math).

Haley Chun 4H

In all of the problems I have seen, the electron configurations have been written in order of increasing energy ([Ar] 3d2 4s2]). I would just write it like that in case, but I don't think it's technically wrong.

Haley Chun 4H

My TA said that we will most likely be given all the formulas because we did not cover nomenclature in the course. However, for molecular compounds you generally put the name of the first element, then second with the correct prefix (depends on number). For example, carbon monoxide would be CO and s...

Haley Chun 4H

Yes I think that is the general guideline, but there are exceptions so you have to check the formal charges of your final structure.

Haley Chun 4H

I find it helpful to kind of know the reasoning behind the trends (more electron shells means larger radius as you go down a column, more protons means smaller radius as you go down a row, etc)

Haley Chun 4H

I think he meant that resonance structures do not exist in real life and they just predict that a compound is more stable than expected (if you were to go to a lab and actually test it). In real life where quantum mechanics is considered, the bond length is an average of the 2 lengths. Resonance is ...

Haley Chun 4H

I think you can always do the shortcut with the noble gases, as some of the full electron configurations can get pretty long. But if the element were Cl-, you couldn't just put [Ar] and would have to start with [Ne]....

Haley Chun 4H

When light acts as a particle (as in the photoelectric effect), increasing intensity means increasing the # of photons.

Haley Chun 4H

subshells are the l value and tell you the shape (spdf), while orbitals are the ml value and tell you the orientation (xyz)

Haley Chun 4H

I don't think the order of the sides necessarily matters but generally 1 electron should be put on each first, then the 2nd can be distributed.

Haley Chun 4H

Shells are the n value, subshells are the l value, and orbitals are the ml value (s,p,d)

Haley Chun 4H

the "extent of the change" means the slope of the wave. Then, as frequency decreases, amplitude decreases (the waves get farther apart) and the extent of the change decreases.

Haley Chun 4H

I agree with the person above. There are uncertainties in the momentum and velocity of a particle since it can take multiple paths (the actual one cannot be determined accurately).

Haley Chun 4H

The equation means that there is uncertainty in the momentum and position of a particle, so it basically measures this uncertainty. The questions will probably ask things like "What is the minimum uncertainty in its position?" or "What is the minimum uncertainty in the speed?"

Haley Chun 4H

Are we expected to memorize which frequencies/wavelength correspond to the type of radiation (microwaves, gamma, etc.)?

Haley Chun 4H

When light acts as a particle, higher intensity means higher number of photons. When light acts like a wave, higher intensity means higher kinetic energy.

Haley Chun 4H

You can convert to grams, but the solution manual kept the mg because they converted to mmol. As long as you keep the units consistent (gram to mole or mg to mmol) you should get the same answer.

Haley Chun 4H

the amount of energy required to remove an electron from the metal surface. ex) if the energy of the photon is less than the threshold energy, no electrons will be ejected

Haley Chun 4H

My TA suggested starting with the elements that occur the least and (if applicable) leaving elements that stand alone like oxygen for last.

Haley Chun 4H

My TA suggested starting with the elements that occur the least and (if applicable) leaving elements that stand alone like oxygen for last.

Haley Chun 4H

When you are given the grams of each element in the problem, I don't think it is necessary to find the %mass composition because you can just convert to moles right away and find the mole ratio (goal). I believe you only need to use the 100 gram sample when the problem gives the % composition only (...

Haley Chun 4H

I think you have to use molar ratios for this question because the number of atoms of H and O do not add up to the number of water molecules. There are 2 moles of Hydrogen and 1 mole of O for every 1 mole of H2O, so i think you do:
(3.14 mol H2O) x (2 mol H/1 mol H2O) x (6.022 x 10*23 atoms/1 mol H)

Haley Chun 4H

I think it should be the first (6.63 x 10*5) since the definition of scientific notation is a number between 1-10 (excluding 10) is multiplied by a power of 10.

Haley Chun 4H

I think it gives the chemical formula in the question (CH4N2O). so the reactants would be: C10H15N and oxygen gas and the products would be carbon dioxide, water, and CH4N2O

Haley Chun 4H

In this question, I think formula units basically means the number of molecules (which you can find by multiplying the number of moles of KNO3 given by Avogadro's number).

Haley Chun 4H

I don't think there is a faster way because you need the empirical formula to know the ratios of each element in the compound. The molecular formula is like a multiple of the empirical.

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