CHEMISTRY COMMUNITY

EmilyJoo_1G

You would need to add a subscript of 3 for the hydrogen because phosphate has a 3- charge.

EmilyJoo_1G

H-F is a very weak acid, which means its conjugate base is strong.

EmilyJoo_1G

Yes, because Bronsted bases are proton acceptors and HPO42- accepts a proton to become H2PO4-.

EmilyJoo_1G

Why do we use the prefix di- and tri- for some ligands and bis- and tris- for others?

EmilyJoo_1G

How do you use the 5% rule when doing ICE tables?

EmilyJoo_1G

You'll know it's a weak base if it has a low Kb value. A Kb value below 10^-3 will indicate a low level of dissociation.

EmilyJoo_1G

Arsenic trioxide is amphoteric because it can donate protons or accept protons in chemical reactions.

EmilyJoo_1G

If I recall correctly, Lavelle said we would need to be able to identify the amphoteric compounds he showed us in class

EmilyJoo_1G

What is the difference between amphoteric and amphiprotic substances?

EmilyJoo_1G

What is the difference between strong and weak acids that make strong acids more likely to completely dissociate?

EmilyJoo_1G

It's mentioned in the textbook in the VSEPR chapter, but I don't recall Lavelle ever going over that model in class.

EmilyJoo_1G

I believe test 2 will cover intermolecular forces and sigma and pi bonds, but not hybridization.

EmilyJoo_1G

The bond angles for the seesaw model are always less than 90 and less than 120 due to the presence of lone pairs.

EmilyJoo_1G

It's polar because Cl has a delta negative charge due to its negativity, which means it would cause a temporary polarization of electrons of atoms around it.

EmilyJoo_1G

The atoms of an AX2E3 molecule would be most stable and experience the least repulsion in a 180 degree linear model.

EmilyJoo_1G

Yes I believe he mentioned during lecture that we will need to know the bond angles of each model

EmilyJoo_1G

Will a central atom with four bonding pairs always be considered tetrahedral? Are there any exceptions?

EmilyJoo_1G

I believe Test 2 will cover all the topics that Lavelle has lectured on since the first lecture after our midterm.

EmilyJoo_1G

I was wondering the same thing. There are several other VSEPR shapes in the textbook he hasn't gone over, so he probably will in the next few lectures or so.

EmilyJoo_1G

Will we need to know pentagonal pyramidal, seesaw, square pyramidal, or t-shape? They're in the textbook but he didn't go over them in class.

EmilyJoo_1G

Yes. Small ions have high polarizing power because their nucleus is closer in distance to a neighboring ion's valence electrons, and therefore small ions far more able to distort the neighboring ion's electron cloud.

EmilyJoo_1G

Doesn't ionization energy increase as you move from left to right on the periodic table?

EmilyJoo_1G

You can also determine which molecule to put the extra electron on to by using the formal charge.

EmilyJoo_1G

The midterm will only cover up concepts up to 2D in the Chemical Bonds unit, so you don't need to worry about lattice energy

EmilyJoo_1G

Yes. They must follow the octet rule where as elements in energy level three and higher can hold more than eight electrons since they have an empty d-orbital.

EmilyJoo_1G

What's the difference between atomic radius and ionic radius?

EmilyJoo_1G

Does anyone know if the questions on the midterm will only have free-response questions like Test 1?

EmilyJoo_1G

A complete 3d10 subshell is lower in energy, which increases stability. It's preferable to complete the 3d subshell than leaving the 4s subshell with only one electron.

EmilyJoo_1G

It'll cover Fundamentals, Chemical Bonds, and the Quantum World.

EmilyJoo_1G

We're supposed to choose problems that are related to Lavelle's most recent lecture but I'm sure the TA wouldn't mind.

EmilyJoo_1G

We're on Chemical Bonds. Lavelle told us that weekly homework should consist of questions that are related to the topic he most recently taught.

EmilyJoo_1G

The electron affinity equation is as follows: electron affinity (E) = E(x)(g) - E(x-)(g). What does each component mean?

EmilyJoo_1G

Hydrogen, beryllium, and helium only have space for two electrons in their valence shell. Lithium only has space for three.

EmilyJoo_1G

Compounds with resonance have greater stability because they have delocalized electrons that occupy a greater volume.

EmilyJoo_1G

Prof mentioned the "valence of an atom" today during lecture and I was wondering if he's referring to valence electrons or something else.

EmilyJoo_1G

Today, Prof went over an example where an atom with the quantum numbers n=2, l=2, and ml= -1 would be in the 2px state. What does the "x" mean and how did he arrive at 2px using the quantum numbers?

EmilyJoo_1G

The 5 questions we pick from the list of assigned problems should be related to Lavelle's most recent lectures.

EmilyJoo_1G

The E=hv equation is used to find the energy of a photon. The variables in the C=(lambda)(v) equation are usually rearranged to find wavelength or frequency. The Rydberg formula is used to find the wavelength of the light emitted by electrons jumping between different energy levels.

EmilyJoo_1G

Use the Rydberg formula for atomic hydrogen to calculate the wavelength of radiation generated by the transition from n=2 to n=1. (c) Use Table 1A.1 to determine the region of the spectrum in which the transition takes place. I used the Rydberg formula and got 121.54 (nanometers?) for wavelength. I ...

EmilyJoo_1G

I have seen 3.29 x 10^15 Hz as well as 1.097 x 10^7 m^-1. Which one will we be using for homework and exams?

EmilyJoo_1G

I know that there are 3 significant figures in 7.00, but 7.00 x 10^2 is the same thing as 700. Trailing zeroes are only significant if the number contains a decimal, so wouldn't 7.00 x 10^2 have 1 significant figure since it basically is 700? Or does it still have 3?

EmilyJoo_1G

(a) That procedure is not allowed because adding an oxygen atom violates the law of conservation of mass. It's impossible for another oxygen atom to just show up at the end of a reaction if it wasn't present in the reactants to begin with.

(b) 2Cu + SO2 ~~> 2CuO + S

Hope that helps!

EmilyJoo_1G

You should be answering problems that are related to what we learned in the most recent lecture.

EmilyJoo_1G

Generally, if a question is asking for you to add or subtract, you round your answer based on the value in your working with the least number of decimal places. For example, 33.567+2.1 = 35.7. For multiplication and division questions, you round off your answer based on the value in your working wi...

EmilyJoo_1G

Or are we being tested only on the review of chemical principles?

EmilyJoo_1G

I was wondering the same thing. I just checked his syllabus and it says we only have to turn in 5 problems a week. So yes, 5 problems total from any of the assigned sections.

EmilyJoo_1G

There's a helpful document on Dr Lavelle's Chem 14A website on determining significant figures. The number in the problem with the least amount of sigfigs determines the number of sigfigs in your answer because the final value shouldn't be more precise/accurate than the least precise value.

EmilyJoo_1G

Will we be docked points on homework assignments and exams if our answers do not have the correct number of significant figures?

EmilyJoo_1G

Question E9 from Handout #1 asks the following:

Epsom salts consist of magnesium sulfate heptahydrate. Write its formula. (b) How many formula units of the compound are present in 5.15 grams?

Im unsure as to what exactly we are supposed to calculate for part b.

EmilyJoo_1G

HNO3 would be its chemical formula because the polyatomic ion Nitrate (NO3-) is attached to a hydrogen ion. Acids are proton donors when they dissociate hence the H+ in front of NO3-. That's the Bronstead Lowry definition of acids and bases.

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