CHEMISTRY COMMUNITY

alexfwang3g

Could somebody explain the difference between pi bonds and sigma bonds in addition to how unhybridized orbitals allow pi bonds to form?

alexfwang3g

pH, pKa, pKb are all calculated through -log[] or hydrogen ions, hydronium ions, and hydroxide ions respectively.

alexfwang3g

Draw the ligand and find out which atoms have lone pairs and then the denticity should be able to be found.

alexfwang3g

Each lone pair on an oxygen, nitrogen, or fluorine is a potential hydrogen bonding site. Also, a hydrogen that is attached to an oxygen, nitrogen, or fluorine is also a potential hydrogen bonding site.

alexfwang3g

As long as you have the concentration, just plug it into the formula. It's pretty rudimentary for 14A.

alexfwang3g

Anywhere where F, O, or N can bond with one another through a Hydrogen atom.

alexfwang3g

Strong bases contain group 1/2 elements. Strong acids should just be memorized. There's only 6 - HCl, H2SO4, HI, HNO3, HBr, HClO4.

alexfwang3g

They're the same thing - it's just a difference in whether you view them in terms of electrons or protons (h+).

alexfwang3g

Strong acids fully dissociate in solution, same with strong acids. As for specific acids, they're usually HCl, H2SO4, HI, HNO3, HBr, HClO4. Strong bases are usually hydroxide paired with cations from the first two groups.

alexfwang3g

HBr is a proton giver and a lone pair/electron acceptor.

alexfwang3g

No hybridization is on the test.

alexfwang3g

Depends on the number of lone pairs. If it's two, then <109.5 and if it's one <120.

alexfwang3g

No, just IMF's and shapes and sigma/pi bonds.

alexfwang3g

Fluorine, Oxygen, or Nitrogen with Hydrogen in between two of any of the three elements.

alexfwang3g

Draw it out and identify dipole or lack of dipole. Consider if there is F, O, or N for hydrogen bonding. Every molecule has LDF.

alexfwang3g

Question stated above.

alexfwang3g

A synopsis of the question above in addition to an explanation of why they have to be F, O, or N.

alexfwang3g

Between an ion and a neutral atoms with a dipole.

alexfwang3g

Question stated above. Also, is there a mathematical way of determining which imf's are stronger?

alexfwang3g

The respective sizes of the molecules usually determines the molecule's polarizability - its ability to be polarized. Larger elements such as I usually are easily polarized instead of smaller elements like F. Polarizability doesn't necessarily determine the state of the molecule, but instead it is t...

alexfwang3g

Do we have to know how to do things with the wave function calculations or do we just have to know of them?

alexfwang3g

I know that double bonds are shorter than single bonds. But in a resonance structure, they're the same length. Why?

alexfwang3g

On the periodic table, 4s comes before 3d so shouldn't it be put before 3d in the electron config?

alexfwang3g

Put the least electronegative element in the middle and the remaining elements around it. Then, count the total valence electrons and proceed accordingly.

alexfwang3g

Midterm covers up to chemical bonds.

alexfwang3g

Just do quantum questions since the syllabus says to do recently covered material.

alexfwang3g

l values can exceed 3 when the atom is excited.

alexfwang3g

The l value is the subshell. The ml value gives the orbitals.

alexfwang3g

Make sure to include the +1/2 and -1/2 for electric spin. Therefore, multiple the answer you would originally get by 2.

alexfwang3g

3d comes before 4s due to its lower energy state.

alexfwang3g

Use Heisenberg's indeterminacy equation. Uncertainty of position * Uncertainty of momentum must be greater than Planck's constant divided by 4pi. The closer it is to the constant of h/4pi, the less uncertain it is. However, there is always uncertainty in these equations due to light's momentum.

alexfwang3g

We say light has no mass, therefore it moves at the speed of light. However, it is able to affect small particles such as electrons and can affect them due to its momentum. Since momentum is calculated by m*v, it is naturally contradictory. Can someone explain??

alexfwang3g

Calculatively, momentum is calculated as mass * velocity. It is very different than velocity in terms of units and in terms of concept.

alexfwang3g

Cycles per second. Think of it as things done or cycles completed per second. Therefore, finding the inverse of frequency would give you how many cycles or things were done.

alexfwang3g

All EMR moves at the speed of light. Since the calculations utilized is regarding to a type of light, then naturally we should use 3x10^-8 m/s as well.

alexfwang3g

No, one photon only interacts with one electron. Any excess energy is transformed into kinetic energy for the ejected electron.

alexfwang3g

Atoms cannot be lost or created in the grand scheme of things due to the law of conservation of mass. However, they can be transformed but ultimately, there are the same number of total atoms left in the universe.

alexfwang3g

You can use this equation to find the variables for everything but light as light's photons do not have a measurable mass.

alexfwang3g

Frequency is the cycles per second whereas intensity is number of photons. Increasing the intensity in the photon model does not assist with freeing bound electrons because no matter how many electrons you fire at the metal, if the strength or frequency is not high enough, no electrons will be eject...

alexfwang3g

They're constant at around 9.11 x 10^-31 kg.

alexfwang3g

If the total molar mass of the molecular formula coincides with the empirical formula, then the empirical formula is the molecular formula. Otherwise, the empirical formula is just a ratio in the form of the lowest possible whole numbers of a molecule. The molecular formula is the actual molecule an...

alexfwang3g

Should be specified in the question.

alexfwang3g

Five questions in total, pick and choose among the assigned ones. Due in lecture tomorrow.

alexfwang3g

For multiplication/division, the result should have the same number of sig figs as the value that has the least number of sig figs which is being multiplied/divided. For example, if you are multiplying a value with two sig figs and a value with three sig figs, then the result should have two sig fig...

alexfwang3g

The speed of light is always constant.

alexfwang3g

Yes, visualize the atoms as next to each other so the diameter would be 288 pm which would be the value you'd use in the dimensional analysis to multiply the number of atoms to find the total distance.

alexfwang3g

Yes, it is common practice to only apply the sig figs rules for the final answer.

alexfwang3g

It was determined off of Avagadro's number and the number of atoms in 12 grams of carbon-12.

alexfwang3g

For multiplication, the final product should have the same number of sig figs as the value that is being multiplied with the least number of significant figures. In this case, since 7.1 is the least precise value being multiplied with 2 sig figs, the resulting answer would have 2 sigfigs.

alexfwang3g

I know that in everyday language, these two terms can be interchangeable. What is the primary difference between the two terms in chemistry.

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