CHEMISTRY COMMUNITY

A Raab 1K

Exactly! There isn't any resonance for this structure, so resonance is not important for its description.

A Raab 1K

Is Mg+2 bigger or smaller than Na+?
Is O-2 bigger or smaller than N-3?
Arrange the anions Cl- , Br- , N-3, and O-2 in order of increasing polarizability and give reasons for your decisions.
Thanks!

A Raab 1K

NH4I is a salt, so there isn't a conjugate acid or base. You can find which acids or bases it is derived from though, which is NH4+ and I -

A Raab 1K

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. (e) AlCl3; (f) Cu(NO3)2 For e and f, how do you get the equations that are given in the answer key? e. Al(H2O)6 +3...

A Raab 1K

The oxides of nonmetallic elements are called acidic oxides because they form acidic solutions in water. Write the balanced chemical equations for the reaction of 1 mol of formula units of each acidic oxide with 1 mol of water molecules to form an oxoacid and name the acid formed: (a) CO2 b) SO3 How...

A Raab 1K

6D.11 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 For part d, why is KBr neutral? Can't you wr...

A Raab 1K

How do you know when to write an equation with the arrow pointing one way versus the set of arrows pointing both ways?

A Raab 1K

How do you know the Cl goes with O instead of with K? (part b)

A Raab 1K

How do you tell the difference between a Bronsted acid and base? For example, in J1, it asks you to identify (a) NH 3 ; (b) HBr; (c) KOH; (d) H 2 SO 3 ; (e) Ca(OH) 2 I understand that for c and e, there's an OH in the compound which leads one to believe it's a base. Is this line of thinking correct?...

A Raab 1K

So because NH₃ and H₂O both have no charge, the charge of Fe has to be +3 in order for the charge of the whole molecule to also be +3. You find the charge of the metal that fits with the overall charge of the molecule.

A Raab 1K

Write: sodium bisoxalato(diaqua)ferrate(III)
Does it make a difference whether I write (OH₂) versus just (H₂O)?
For example, why is it Na[Fe(OH₂)₂(C₂O₄)₂], and not Na[Fe(H₂O)₂(C₂O₄)₂] or Na[Fe(C₂O₄)₂(H₂O)₂]?

A Raab 1K

If the complex is negatively charged, then you add -ate to the end of the metal name.

A Raab 1K

Radicals have an uneven number of electrons.
Do you mean the single electron instead of unpaired electron for the second question?

A Raab 1K

For each one, you would draw the Lewis structure and see the regions of electron density on each central atom. Then, in accordance with how many regions there are, you can assign the hybridization. For example, BeCl2 has 2 bonds from Be to Cl, so the hybridization would be sp.

A Raab 1K

AsF3 would not have any double bonds. Instead, there should be a single bond from As to F, with each F having three lone pairs and As having one lone pair. This adds up to 26 electrons and they all have a formal charge of 0, as As has 5 valence electrons, which the 3 bonds and 2 lone electrons satis...

A Raab 1K

2.63 Estimate the bond angles marked with arcs and lowercase letters in peroxyacetylnitrate, an eye irritant in smog. Sorry I'm not sure how to put an image in here from the problem in the textbook but there are 3 angles we have to estimate. I understand a and c, but for part b, why is the bond angl...

A Raab 1K

Noting that the bond angle of an sp 3 hybridized atom is 109.5 and that of an sp 2 hybridized atom is 120, do you expect the bond angle between two hybrid orbitals to increase or decrease as the s-character of the hybrids is increased?
Can anyone explain why the bond angle increases?

A Raab 1K

I'm still not quite sure how vapor pressure relates to the different intermolecular forces there are.

A Raab 1K

Bond lengths are the length of the bond between two atoms. Bond length has to do with a number of factors, one of them being the size of the atom. An example was given in class of the bond lengths between HF, HCl, HBr, and HI. The bond lengths between those molecules get progressively longer as the ...

A Raab 1K

Formal charge = V - (L - S/2)
V is valence electrons of the element
L is lone pairs the atom has
S is shared/bonding electrons
You want a formal charge of 0 on an atom as that is the most stable.

A Raab 1K

Account for the following observations in terms of the type and strength of intermolecular forces. (b) The vapor pressure of diethyl ether (C2H5OC2H5) is greater than that of water. (c) The boiling point of pentane, CH3(CH2)3CH3, is 36.1 C, whereas that of 2,2-dimethylpropane (also known as neopenta...

A Raab 1K

I looked at the fact that b, c, and d were all uneven whereas a and e were even. This unevenness is due to the differing number of electrons on the hydrogen versus the chlorine.

A Raab 1K

Why does (part d) SO₂ have a dipole-dipole interaction?

A Raab 1K

It doesn't matter! It's probably better to convert to SI units so that when you plug numbers into equations, the equations work correctly, but for the final answer it doesn't matter if it's in (for example) km or m.

A Raab 1K

For a, draw the Lewis structure of (a) chlorine monoxide, ClO I drew the molecule as .. .. O=Cl . .. .. Why isn't this correct? The correct answer according to the answer key is .. .. :O - Cl . .. .. but I don't understand how this is correct, because the formal charges are not 0 for this answer, bu...

A Raab 1K

That wasn't a question that ever appeared on the homework so I don't think you have to worry about it!

A Raab 1K

You would usually use 6.022 * 10^23 to figure out the number of formula units. For example, the number of formula units in 1 mole of some atom is 6.022 * 10^23. It's pretty universal and can be used to find, for example, the number of molecules in 1 mole as well.

A Raab 1K

Do we have lecture on Wednesday? I heard some people say we didn't but Lavelle didn't say anything in class about it. I'm in the 10:00 lecture by the way.

A Raab 1K

The electron configuration for Sb is [Kr] 4D10 5S2 5P3. If you count the electrons in the highest level (5) then you can see that there's 5 valence electrons.

A Raab 1K

I think it just describes the wave function or a path that a given system will take. It has to do with potential energy and kinetic energy to find the total energy, and using it to find the behavior of an electron bound to a nucleus.

A Raab 1K

Give the ground-state electron configuration expected for each of the following ions: (a) Cu +1; (b) Bi +3 ; (c) Ga +3 ; (d) Tl +3 . For a, why is the answer [Ar] 3d10, instead of [Ar] 3d8 4s2? I understand for Cu normally the notation would be 3d10, but that's when the d orbital is at 9, not at 8, ...

A Raab 1K

They are the same thing. Resonance structures show how the same molecule can be drawn different ways depending on what orientation you draw the different bonds, whereas resonance hybrids is just another term to emphasis the actual structure of molecules, which is that the bonds all have the same len...

A Raab 1K

Let me know if the question is confusing, and I can try to rephrase!

A Raab 1K

2B9. Draw the complete Lewis structure for each of the following compounds: (a) ammonium chloride; (b) potassium phosphide; (c) sodium hypochlorite How come for these structures you draw the elements separately? For example in part b, the answer key shows K+ around a P -3 instead of lines connecting...

A Raab 1K

To add on the information already provided, the order goes s, p, d, f. For s, there's a maximum of 2 electrons; for p there's 6; for d there's 10 and for f there's 14. Hope that helps when you write it out.

A Raab 1K

Yes exactly! 64 J is the energy expended over 2 seconds (2 * 32)

A Raab 1K

The 4s orbital has more energy than the 3d orbital. However, for elements like potassium and calcium, the 3d orbitals have a higher energy than the 4s, as the 4s levels fill before than the 3d. But for the next 10 elements of the transition series, the 3d orbitals gradually fill with electrons, and ...

A Raab 1K

I'm not sure, but the midterm is 2 hours long, so however many questions can be done in that time. You can try asking your TA!

A Raab 1K

d. Z_effe for an electron in a p-orbital is lower than for an electron in an s - orbital in the same shell
What does Z_effe represent? And why is this true?

A Raab 1K

How do we know what wavelengths correspond to which types of electromagnetic radiation? Do we have to know them for the tests or will they be given to us?
For ex, when a question asks what electromagnetic radiation has a wavelength of 8.84 nm?

A Raab 1K

I just looked up what keV was, so hopefully we don't have to know that for tests (maybe it'll be provided?)
1 keV = 1.60217662e-16 joules

A Raab 1K

The way it was described in class was that the size of a baseball is much larger than the size of an electron, and therefore an electron can be affected by photons whereas a baseball is much too big to be noticeably affected. Light affects an electron because photons can hit the electrons passing th...

A Raab 1K

Momentum is the mass of an object times velocity, or p = m * v. So yes, we might have to solve for momentum for Heisenberg's equation.

A Raab 1K

1.A.15 In the ultraviolet spectrum of atomic hydrogen, a line is observed at 102.6 nm. Determine the values of n for the initial and final energy levels of the electron during the emission of energy that leads to this spectral line. I was trying to use the Rydberg formula for this problem, so I trie...

A Raab 1K

There isn't a course reader for Lavelle's class.

A Raab 1K

I don't think there's any readings that you are required to do. You can read the textbook that correspond to the lectures in class if you want to.

A Raab 1K

I'm pretty sure that you always go to the lowest number of sigfigs of a number that's present in a problem.

A Raab 1K

A formula unit can be an atom, compound, or molecule. For example, if a question asks how many formula units of H2O are in one mole of H2O, then you would just find the number of atoms in one mole of H2O.

A Raab 1K

Which of the following are conserved in a chemical reaction? Select all that apply.
a. mass
b. number of atoms
c. number of molecules
d. number of electrons
e. number of protons

I think a and b are conserved, but I'm not sure if d and e are also conserved. Can anyone confirm?

A Raab 1K

Which of the following happens when the frequency of electromagnetic radiation decreases? Explain your reasoning. (c) The extent of the change in the electrical field at a given point decreases I'm not sure what exactly "c" means by the change in the electrical field at a given point. Can ...

A Raab 1K

Along that same theme, how would I know what to do for metal solids such as magnesium or for a nitrogen atmosphere? Magnesium is just Mg, whereas the nitrogen atmosphere is N2.

A Raab 1K

H7a. Write a balanced chemical equation for each of the following reactions. (a) Calcium metal reacts with water to produce hydrogen gas and aqueous calcium hydroxide.
For calcium hydroxide, how would one know if the molecule is CaOH or Ca(OH)2? (and for other molecules that include hydroxide too)

A Raab 1K

G5. A student prepared a solution of sodium carbonate by adding 2.111 g of the solid to a 250.0-mL volumetric flask and adding water to the mark. Some of this solution was transferred to a buret. What volume of solution should the student transfer into a flask to obtain (a) 2.15 mmol Na1; (b) 4.98 m...

A Raab 1K

You're actually correct! Since the question gave you the same number of atoms, that means that the moles of atoms would also be the same.

A Raab 1K

For b: The molar mass of Ag2SO4 is 2(107.87) + 32.06 + 4(15.999) = 311.80 g/mol Then, multiply 311.80 g/mol * (2.39*10^23)/(6.022*10^23) = 123.75 mg which is about 124 mg For c: The molar mass of 22.99 + 1.008 + 12.011 + 2(15.999) = 68.007 g/mol Divide 3.429 g / 68.007g/mol = 0.05 mol Multiply 0.05 ...

A Raab 1K

I've heard that if you can imagine yourself being anything else besides a doctor, than the medical route may not be the right path for you. Do you think there's any truth to that statement; does medicine really need to be a calling in order to succeed? I'm on the fence about different career options...

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