CHEMISTRY COMMUNITY

David Zhang 1B

Why doesn't the Cl- react with water in a reaction involving FeCl3 and water?

David Zhang 1B

How can we tell which part of an acid/base molecule is a spectator ion and doesn't react?

David Zhang 1B

I think the shape of the molecule also plays a role since the way the electron pairs are positioned doesn’t really allow it to form 2 bonds.

David Zhang 1B

For the homework solution for Fundamentals J.9 (b), the equation written for the neutralization of ammonia and phosphoric acid doesn't include water. Do some neutralization reactions not produce water?

David Zhang 1B

I think that's just the names that are used for naming these compounds. Cyano and cyanido are the same compound but cyano is just the older term. For iron, the Fe in the periodic table stands for ferrum, the Latin word for iron.

David Zhang 1B

It can bond with a metal at 6 different sites, creating the ring structure around the atom known as a chelate.

David Zhang 1B

We will probably have to memorize them for the final. I think we only get the constants/equation sheet and the periodic table for all tests.

David Zhang 1B

I think it's because the large radius of the atom negates part of the hold that the nucleus has on the valence electrons. When combined with a very electronegative atom, it can form bonds.

David Zhang 1B

Yes, we will most likely be tested on that during the final. It's also a part of the homework questions so it would be good to know how to do it.

David Zhang 1B

AX3E2 is more a T-shaped molecule with the bound atoms in a side-ways T-shape. Imagine the trigonal bipyramidal structure of AX5 but remove two of the bound atoms of the trigonal part of the molecule.

David Zhang 1B

Lewis acids are the molecule that has the ability to accept an entire electron pair rather than sharing the electrons. The Lewis base is the donor of the electrons.

David Zhang 1B

I don't think it really matters since the molecule will still be the same with the same bonds.

David Zhang 1B

Would we have to know how to predict bond angles based on the shape of a molecule on a test?

David Zhang 1B

A bond that is polar has atoms with a difference in electronegativity, where one atom is slightly more positive and the other is slightly more negative. This causes an unequal distribution of e- as the more electronegative atom has a greater pull on the electrons.

David Zhang 1B

The numerals indicate the charge of the atom in the molecule since transition metals can often have several ionic forms. For indium, the 3 indicates In 3+.

David Zhang 1B

Intermolecular forces are forces that are responsible for interactions between different individual molecules. Intramolecular forces are the forces that act within a molecule, binding together the atoms that make up a molecule.

David Zhang 1B

Will we always be given the molecular formula on tests? In the homework, we're sometimes given only the names of the molecule such as periodate ion (2C.3).

David Zhang 1B

Formal charge depends on the bonds and lone pairs assigned to each atom in a structure. It compares the charge in the atom, calculated by the number of bonds divided by 2 and the number of electrons in the lone pairs, to the normal number of valence electrons.

David Zhang 1B

Will we have to have questions on test 2 as complicated as 2B.13 where we have to draw out all the resonance structures for molecules like C14H10?

David Zhang 1B

Why does increasing the size or molar mass result in stronger attractive interactions?

David Zhang 1B

The polarizing power of a cation allows it to distort the electron field of the cation since the negative charge of the electrons is attracted to the positive charge on the cation.

David Zhang 1B

Those atoms have a d-orbital that can be filled after the s and p orbitals have been filled, allowing them to break the octet rule.

David Zhang 1B

It's the charge on each individual atom that can be calculated after drawing a Lewis structure. Each variation of the Lewis structure has different formal charges and the structure with the most neutral charge is often the best structure.

David Zhang 1B

The [Xe] fills in the 5s part. Xe's electron configuration is 1s2 2s2 2p6 3s2 3p6 3d10 4s2 4p6 4d10 5s2 5p6. The 4f14 5d10 6s2 come after the 5p6 to create the full electron configuration.

David Zhang 1B

There are tables that list out the electronegativity values that you can use to compare to determine the difference in electronegativity. However, we won't get to use one on a test so it's mostly about understanding electronegativity trends in the periodic table. Electronegativity generally increase...

David Zhang 1B

Resonance is referring to the different ways that you could write out a Lewis structure since there are usually multiple valid ways you write one with differing types of bonds or lone pairs. While all the ways are valid, there are usually some structures that seem more stable.

David Zhang 1B

The 4+ means that 4 electrons have been removed. A natural Sn atom would have [Kr]4d^10 5s^2 5p^2. Taking away 4 electrons from the valence would make it [Kr] 4d^10.

David Zhang 1B

Orbital number is determined by the equation n^2. With n=2, you have both l=0 (s subshell) and l=1 (p subshell). For l=0, the s subshell only has 1 orbital (0). For l=1, the p subshell has 3 orbitals (+1,0,-1). Combined, there are 4 orbitals total.

David Zhang 1B

For the periodic table that we use during tests, do we have to know the abbreviations for all the elements or will the names be written out for us?

David Zhang 1B

What are the exceptions for chromium and copper that we need to know?

David Zhang 1B

What does it mean for an electron to penetrate the nucleus? In 1E.5 (b), it says that an electron in an s-orbital can penetrate the nucleus of an atom.

David Zhang 1B

I think it's easier to focus on one element at a time, usually starting with the element that only appears once on both sides. You equalize the amount on both sides with coefficients and then you see how that coefficient affects the other element amounts. Once you've figured that out, you just simpl...

David Zhang 1B

I would appreciate a picture of today's notes as well. A picture of Wednesday's notes would be an extra bonus. My email is davidzhang211@yahoo.com. Thanks in advance!

David Zhang 1B

It's a unit of energy. In Joules, it's about 1.602x10^-19 J.

David Zhang 1B

You would use the equation: total energy of photon= threshold energy + kinetic energy. You would need to find/be given the energy of the photon and the kinetic energy in order to determine the threshold energy.

David Zhang 1B

I don't think there would be any change in the structural properties of the metal with a change in the electrical charge.

David Zhang 1B

There is only a certain amount of energy in a photon. If there is more energy than is needed to release the electron, then the extra energy is kinetic. If the energy to release the electron is the exact same as the photon, then there is 0 kinetic energy.

David Zhang 1B

I missed the lecture for today (Wednesday). Could somebody give me a basic summary of what topics the professor went over?

David Zhang 1B

How was Test 1 for you all? I wasn't able to make it that day to take the test. What was the average difficulty of the problems? Were they multiple choice, short answer, or both?

David Zhang 1B

It's just a standard for the experiment environment since some reactions may change under certain pressures and temperatures.

David Zhang 1B

The professor only mentioned metals when talking about the photoelectric effect. Can it happen to other materials as well?

David Zhang 1B

The equation should be balanced so that there are the same elements on both side of the equation. If there is nitrogen present in the fuel, it would also be present in one of the products of the combustion equation.

David Zhang 1B

0 degrees Kelvin is the lowest theoretical possible temperature.

David Zhang 1B

You first have to find the concentration of the diluted solution. You can find the moles of the initial solution since they give you the molarity of the solution and an initial volume of 1 Liter. Since molarity is moles per volume, the initial solution has 0.20 moles.When the florist adds water, the...

David Zhang 1B

If you're looking at the solution manual for that problem, they use Liters as the unit of measurement. 250 mL is .250 Liters.

David Zhang 1B

I would keep everything at whole numbers just to be safe. I haven't seen any chemical equations that have decimals or fractions as the stoichiometric coefficient.

David Zhang 1B

What does a dot in a chemical formula mean such as in problem E.23 when it asks about Na2CO3 (dot) 10H2O?

David Zhang 1B

You first have to convert the 2.111g of the solid sodium carbonate into mmol of Na+. I used dimensional analysis to do the conversion. Then you can take that answer to set up a proportion since you know that n/v = n/v. You know the values of mmol and volume for the initial solution and the mmol for ...

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