CHEMISTRY COMMUNITY

AChoudhry_1L

Which of the following ligands can be polydentate? If the ligand can be polydentate, give the maximum number of places on the ligand that can bind simultaneously to a single metal center: (a) HN(CH2CH2NH2)2; (b) (CO3)2-; (c) H2O; (d) oxalate

Can someone explain the process of doing this problem?

AChoudhry_1L

With the help of Table 9C.1, determine the coordination number of the metal ion in each of the following complexes: (a) [NiCl4]2–; (b) [Ag(NH3)2]+; (c) [PtCl2(en)2]2+; (d) [Cr(edta)]-

How would we determine the coordination numbers for c and d?

AChoudhry_1L

If you have a molecule such as C2H2, there would be a triple bond between the carbons. How do you write out the hybridization with the triple bond?

AChoudhry_1L

Bond strength relates to how easy it is to pull electrons away from an atom. In regards to acids, strong acids are when bonds are further apart, making it easier for the electrons to be donated.

AChoudhry_1L

The two strands of the nucleic acid DNA are held together by hydrogen bonding between four organic bases. The structure of one of these bases, thymine, is shown below. (a) How many pro- tons can this base accept? (b) Draw the structure of each conjugate acid that can be formed. (c) Mark with an aste...

AChoudhry_1L

Decide whether an aqueous solution of each of the following salts has a pH equal to, greater than, or less than 7. If pH>7 or pH< 7, write a chemical equation to justify your answer. (a) NH4Br; (b) Na2CO3; (c) KF; (d) KBr; (e) AlCl3; (f) Cu(NO3)2 How would you determine the charge on the reactants i...

AChoudhry_1L

Hydrogen peroxide, H2O2, reacts with sulfur trioxide to form peroxomonosulfuric acid, H2SO5, in a Lewis acid–base reaction. (a) Write the chemical equation for the reaction. (b) Draw the Lewis structures of the reactants and product (in the product, one OOH group in sulfuric acid is replaced by an O...

AChoudhry_1L

Draw the Lewis structure of boric acid, B(OH)3. (a) Is resonance important for its description? (b) The proton transfer equilibrium for boric acid is given in a footnote to Table 6C.1. In that reaction does boric acid act as a Lewis acid, a Lewis base, or neither? Justify your answer by using Lewis ...

AChoudhry_1L

It is useful to know the common ones. However, in lecture Dr. Lavelle mentioned that if a problem provides you with an equilibrium constant, it is likely to be a weak acid/base. This may be helpful in making that distinction.

AChoudhry_1L

There are many distinctions between acids and bases. Some important ones to keep in mind are that acids generally have a pH lower than 7 and bases generally have a pH higher than 7. Acids are usually proton donors and bases are usually proton acceptors.

AChoudhry_1L

Identify the salt that is produced from the acid–base neutral- ization reaction between (a) potassium hydroxide and acetic acid, CH3COOH; (b) ammonia and phosphoric acid; (c) calcium hydroxide and bromous acid; (d) sodium hydroxide and hydrosul- furic acid, H2S (both H atoms react). Write the comple...

AChoudhry_1L

When writing out chemical equations with acids and bases, how do you know what pairs with what?

AChoudhry_1L

In each of the following salts, either the cation or the anion is a weak acid or a weak base in water. Write the chemical equation for the proton transfer reaction of this cation or anion with water: (a) NaC6H5O (b) KClO (c) C5H5NHCl (d) NH4Br What are the general guidelines for solving this problem...

AChoudhry_1L

Why is it that AsF3 has a higher boiling point than AsF5, despite AsF5 being a bigger molecule? I understand that AsF3 is polar and has dipole-dipole IMF, but do we ignore the molecular weight comparison?

AChoudhry_1L

Which would have a higher boiling point between C2H5OC2H5 (diethyl ether) and C4H9OH (butanol) and why is this? This is from homework problem 3F 5.

AChoudhry_1L

If there are 2 lone pairs, then it would be less than 109.5 degrees. If there is 1 lone pair, then it would be less than 120 degrees. Both are bent shape, but the bond angles differ depending on the amount of lone pairs.

AChoudhry_1L

Could someone describe the shape and bond angles of N2H4?

AChoudhry_1L

For 2F 11A, the molecule we are given is SCl4. This is both trigonal bipyramidal and described as seesaw. Which should we be memorizing? Which one will we be asked for on the test?

AChoudhry_1L

ALegala_3I wrote:London Dispersion forces act on all molecules and atoms. This includes nonpolar molecules, monoatomic gases, and in molecules that also exhibit dipole-dipole interactions.

Is it true then that London Forces also act on polar molecules as well?

AChoudhry_1L

How do you determine if a molecule is polar? I know that you would look at the electronegativity, but is there a cut off between what counts as being electronegative enough to be considered polar?

AChoudhry_1L

Is it true that bigger molecules have higher melting points? Is this the thought process behind figuring out which would have a higher melting point between CHI3 and CHF3?

AChoudhry_1L

Looking at the lewis structures may help, and examining the general types of the compound might further clarify which substance has a higher melting point. For example, in (a), between HCl and NaCl, NaCl will have a higher melting point because it's an ionic compound. In (b), Butanol is stronger be...

AChoudhry_1L

Why is it that London forces always occur when there are dipole-dipole interactions? Will London forces ALWAYS occur when they are dipole-dipole interactions?

AChoudhry_1L

What does charge have to do with polarizing power/how polarizable an atom is?

AChoudhry_1L

What does the unit MHz mean and how do we convert this to HZ?

AChoudhry_1L

How does intensity play a role in the photoelectric effect?

AChoudhry_1L

If we are given values for n, l, and ml, is it true that only one orbital can have these specific quantum numbers?

AChoudhry_1L

If n=2, how many possible orbitals are there?

AChoudhry_1L

Because the p subshell has 3 different orbitals, the x, y, and z help differentiate between those three.

AChoudhry_1L

The way that I would approach this problem is by first writing out the ground state electron configurations. The electron would be removed from the last orbital and this is easier to see when you have the configuration written out.

AChoudhry_1L

How do we convert keV to joules? This was needed for homework problem 5 from section 1B.

AChoudhry_1L

In homework problem 15 from section 1B, part d asks what what kind of electromagnetic radiation was used from a wavelength of 8.8 nm. The answer was x-ray/gamma rays, however, is this something we will have to know for exams?

AChoudhry_1L

In homework problem 9 from section 1B, we are given 2 seconds which eventually needs to be converted to joules. The solution manual says that 2 seconds is equal to 64 J. How do we convert seconds to joules?

AChoudhry_1L

In this case, you would fill the d subshell. You should try to completely fill or half fill the d subshell because doing this allows the atom to be as stable as possible. Because of this, 4d105s1 would be the correct electron configuration.

AChoudhry_1L

For the ml values, you have to account for the negatives as well. For n=3, the ml values would be -2,-1,0,1,2.

AChoudhry_1L

He did this in order to demonstrate Hund's Rule, that electrons fill each orbital before they are paired in one orbital. He was representing each electron in its own orbital instead of just giving the total number of electrons in the subshell. He said that it's BETTER and more specific to do it in ...

AChoudhry_1L

In lecture, we went over the trends shown in the periodic table, however, Dr. Lavelle mentioned that there were a few exceptions to these trends. Which ones do we have to know and why do they not follow the trends?

AChoudhry_1L

Being familiar with the f- orbitals can be helpful in having a more holistic understanding of electron configurations and orbitals, but Dr. Lavelle mentioned that we do not have to worry about them for exams. Just be familiar with the s, p, and d blocks.

AChoudhry_1L

An orbital must have 3 quantum numbers, and no two orbitals can have the same quantum numbers. Knowing this, b and d both indicate only 1 orbital because they list 3 quantum numbers. For a and c, since all 3 quantum numbers are not given we must list the other possible numbers to find the number of...

AChoudhry_1L

RichBollini3C wrote:Does anyone know what section problems we should be turning in for homework #4? Is it still quantum?

Yes, homework #4 can be on quantum since we were still doing the quantum unit this week.

AChoudhry_1L

Molarity refers to the concentration of a solution. The formula for finding molarity is M=n/V. This means that to find molarity, you divide the moles of solute by the volume of solution. The units for molarity are mol/L so make sure you watch your units.

AChoudhry_1L

At the end if today's lecture, Dr. Lavelle described the electron as being in the 2px state. What does he mean by this?

AChoudhry_1L

You would only be able to do this if the problem provides the molar mass of the molecular formula. This mass is usually provided in problems if they want you to find the molecular formula. You would then divide the given molar mass by the mass of the empirical formula mass. The answer you get is wha...

AChoudhry_1L

Can someone explain how to find the answer to this problem?

1B.25) What is the minimum uncertainty in the speed of an electron confined within a lead atom of diameter 350. pm? Model the atom as a one-dimensional box with a length equal to the diameter of the actual atom.

AChoudhry_1L

Could someone explain this problem me?

1D23) How many orbitals can have the following quantum numbers in an a tom:(a)n=2, l=1;(b)n=4, l=2, ml=-2; (c)n=2;(d)n=3, l=2, ml=+1?

AChoudhry_1L

I would also use the M1*V1=M2*V2 formula in this situation. Plug in the known values and solve for the unknown. The only thing I would say is to be careful of units. Sometimes the units provided and the units asked for are different and you must convert them.

AChoudhry_1L

In terms of percentage calculations, I would leave 4 sig figs such as 56.41%, however in answers with decimals I would leave at least have three digits after the decimal, such as 0.379 or 15.255. Remember to keep as many digits as possible when calculating and only round when you get your final answ...

AChoudhry_1L

When finding the ratio, divide the total molar mass by the empirical mass. Sometimes, this will give you 1 and that means that the molar mass is the same as the empirical mass and therefore, the formulas are the same as well.

AChoudhry_1L

The amount of energy levels depends on what element we are talking about. Each element's atoms have different amounts of energy levels. For example, Hydrogen has electrons in the first energy level and Oxygen has electrons in the second energy level.

AChoudhry_1L

When approaching quantum problems, what is your method to determine which equation we should be using?

AChoudhry_1L

One thing that helps me to write down the formulas from the word is to analyze the prefixes of the words. For example, dioxide means 2 atoms of oxygen because di means 2 and hexafluoride has 6 atoms of fluorine because the prefix hexa means 6. This helps with figuring out what subscript each element...

AChoudhry_1L

An easy way for me to determine what number to multiple a decimal by to get a whole number is to divide 1 by the decimal. For example: If there are 2.5 mols of C, do 1/0.5 = 2. You should multiply the 2.5 mols by 2 to get a whole number (5). If it's a more difficult value, maybe like 2.125 mols of ...

AChoudhry_1L

I was wondering the same thing, but as I was doing practice problems I noticed that you need to use Avogadro's number when you want your answer to be in atoms. This is useful when your units are moles, but you want it to be a certain amount of atoms or molecules.

AChoudhry_1L

If a question asks how much of something you will need, should your answer be in grams or moles?

AChoudhry_1L

The rules for multiplication/division and addition/subtraction are similar. For addition/subtraction, the number of decimal places in your answer must be the same as the smallest number of decimal places in your equation. For example, 0.032 + 0.40 = 0.43. For multiplication/division, your answer sho...

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