## Search found 23 matches

Sat Jul 29, 2017 7:31 pm
Forum: Calculating pH or pOH for Strong & Weak Acids & Bases
Topic: Approximation in Calculations
Replies: 5
Views: 466

### Re: Approximation in Calculations

no, you only need to solve the quadratic equation if the approximation doesn't meet the 5% rule! :) If it does meet the rule then it means that x is small enough that the approximation gives an answer that's essentially the same as if you had done the quadratic equation
Sat Jul 29, 2017 5:34 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: calculating K
Replies: 2
Views: 256

### Re: calculating K

I know that the conversion is really close. I found online that 1 bar= 0.986923 atm. I think we're supposed to have it in atm units, but I think bar might be close enough that you don't have to actually do the conversion? I found this in a problem too though and was wondering the same thing.
Sat Jul 29, 2017 4:24 pm
Forum: Calculating pH or pOH for Strong & Weak Acids & Bases
Topic: Approximation in Calculations
Replies: 5
Views: 466

### Re: Approximation in Calculations

I believe that to start you can always assume that x is small enough to approximate, but at the end, once you have X you have to go back and make sure that it's less than 5% of the initial molarity. (You do this by doing X/Initial) If it is, then the approximation is okay. If it isn't then the appro...
Thu Jul 27, 2017 8:03 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: The whole range of pH value
Replies: 1
Views: 296

### Re: The whole range of pH value

The pH scale does change if the temperature changes. If it were to happen in any of our problems I believe they would give you the Kw value so you could do the problem following the same steps as ones with a temp of 25 ℃. You'd get the pKw value from the given Kw (pKw=-log(Kw)) and then solve the pr...
Sun Jul 23, 2017 7:18 pm
Forum: Lewis Structures
Topic: ClO2 ... ?
Replies: 1
Views: 343

### Re: ClO2 ... ?

So, I think you're actually correct! I was wondering what source you were looking at that said it was the "O-Cl-O" (with 3 electrons around Cl) option and not the double bonded one you suggested? I've looked at a couple sources and they all say it's the double bonded option, and that's wha...
Sun Jul 23, 2017 7:03 pm
Forum: Ionic & Covalent Bonds
Topic: covalent bond
Replies: 7
Views: 696

### Re: covalent bond

Yes, that's correct!
Sun Jul 23, 2017 6:57 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: Exothermic vs. Endothermic?!
Replies: 5
Views: 2298

### Re: Exothermic vs. Endothermic?!

Endothermic means that the reaction requires heat, and exothermic means it expels heat during the reaction. To help remember, you can think of, for ex othermic, the heat is ex iting the system. I'm not exactly sure what you mean about the chemical equilibrium calculations part, but another helpful t...
Sun Jul 23, 2017 6:45 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Covalent and Ionic Bonds
Replies: 1
Views: 233

### Re: Covalent and Ionic Bonds

In Ionic bonds, there is a transfer of electrons and ions are formed. In covalent bonds there is a sharing of electrons between the two atoms. Covalent bonds are formed by nonmetallic elements. Ionic bonds are formed when the lowest energy can be achieved by ion formation, whereas when the lowest en...
Sun Jul 16, 2017 6:40 pm
Forum: Lewis Structures
Topic: Formal Charge
Replies: 2
Views: 437

### Re: Formal Charge

Yes it is. You want the formal charges to be zero or if you're picking between varying lewis structures, you want the structure where the formal charges are lowest, if not zero. But the sum of the formal charges must add up to the overall charge of the compound, so in some cases you wouldn't have al...
Sun Jul 16, 2017 6:32 pm
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: Unpaired electrons
Replies: 4
Views: 520

### Re: Unpaired electrons

Hi, I was wondering if you could clarify what you mean by 2n^2+.
Do you mean like if an element is ^2+?
Sun Jul 16, 2017 6:14 pm
Forum: Lewis Structures
Topic: P, S, Cl can have more than 8 electrons?
Replies: 2
Views: 514

### Re: P, S, Cl can have more than 8 electrons?

The s2p6 octet is usually what gets filled with electrons. But once you pass the second period on the periodic table and reach n=3 there is the d sublevel, in addition to the s and p orbitals, which can accommodate more electrons.
Sun Jul 16, 2017 5:47 pm
Forum: Ionic & Covalent Bonds
Topic: Homework problem chapter 3
Replies: 3
Views: 508

### Re: Homework problem chapter 3

Hi!
Was there a specific one you were stuck on, like a,b,c,d or e? Or are you just asking about drawing them in general?
Sun Jul 09, 2017 10:32 pm
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: Quantum numbers are atomic orbitals
Replies: 1
Views: 262

### Re: Quantum numbers are atomic orbitals

ml labels different orbitals (for example as, px, py, pz) Though note that for this class, Professor Lavelle said that we wouldn't have to worry about which number corresponds to which orbital (for example for n=2, l=1, and ml=-1,0 or +1, you wouldn't need to know which of -1,0,1 corresponds to px,p...
Sun Jul 09, 2017 9:10 pm
Forum: Student Social/Study Group
Topic: Thoughts after Test 1?
Replies: 13
Views: 1295

### Re: Thoughts after Test 1?

Amy, to answer your question about how precise you need to be, I would suggest that you use all the numbers written out on the formula sheet. To save some time, you don't have to write out all the numbers when showing your work, you could probably even just write 'me', just as long as it's all in th...
Sun Jul 09, 2017 8:53 pm
Forum: Trends in The Periodic Table
Topic: Exercise 2.67
Replies: 4
Views: 462

### Re: Exercise 2.67

Electron affinity is less periodic, and therefore doesn't always follow a specific trend, but generally the elements in the top right, group 17, have a high affinity for electrons. In this case, I think that carbon has a higher e- affinity than nitrogen because carbon has a half-filled "p"...
Sun Jul 09, 2017 8:41 pm
Forum: Properties of Light
Topic: Quantum Spin Number
Replies: 1
Views: 231

### Re: Quantum Spin Number

I believe that the number 1/2 comes from some equation or calculations that we don't cover in this course. From what I've read, it's pretty complicated and I don't think it's important for us to know why, just to remember that it's +/- 1/2.
Sorry, that's not much help.
Sun Jul 02, 2017 7:10 pm
Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
Topic: Electron transition from principal quantum levels
Replies: 1
Views: 271

### Re: Electron transition from principal quantum levels

Yes, light is only emitted if it makes a transition down to a lower level, because it's releasing energy and emitting light. When you move up an energy level the energy is absorbed and no light would be emitted.
Sun Jul 02, 2017 7:05 pm
Forum: Photoelectric Effect
Topic: Photoelectric Effect
Replies: 1
Views: 302

### Re: Photoelectric Effect

For electrons to be ejected, you would have higher frequencies, but another important part is that each incoming photon must have enough energy to eject one electron because one photon interacts with one electron. This amount of energy that the photon needs is the threshold energy(or work function).
Sun Jul 02, 2017 6:56 pm
Forum: Photoelectric Effect
Topic: Question from the online post assessments
Replies: 4
Views: 483

### Re: Question from the online post assessments

The formula sheet gives the mass of an electron as 9.1095 x 10^-31 kg, so I think you would just use this.
Sun Jul 02, 2017 5:38 pm
Forum: Photoelectric Effect
Topic: Question from the online post assessments
Replies: 4
Views: 483

### Re: Question from the online post assessments

The answer is B. Threshold energy, because when the energy per photon is equal to the energy required to remove an electron, the energy is reaching the "threshold" amount of energy for an electron to be ejected.
Sun Jul 02, 2017 1:19 pm
Forum: Photoelectric Effect
Topic: electrons "removed"/not attracted to nucleus anymore
Replies: 1
Views: 291

### electrons "removed"/not attracted to nucleus anymore

In lecture on Friday, we were talking about how as the electron moves up energy levels at some point it is not attracted to the nucleus or is considered "removed" and at this point the energy goes to zero. This concept confused me a bit and I was hoping someone could expand or explain the ...
Sun Jul 02, 2017 12:41 pm
Forum: Empirical & Molecular Formulas
Topic: Exercise F.23
Replies: 1
Views: 480

### Re: Exercise F.23

So for each element you calculate the molar mass and use it as the denominator. Then you would put the mass of carbon in that element in the numerator and multiply you're answer by 100 to get the percentage. Then you would just compare all you're answers to rank them. For example, for ethene (C2H4),...
Sun Jul 02, 2017 12:19 pm
Forum: SI Units, Unit Conversions
Topic: Dimensional Analysis/ Unit conversion [ENDORSED]
Replies: 5
Views: 771

### Re: Dimensional Analysis/ Unit conversion[ENDORSED]

I think it's fine to break up long dimensional analysis problems into parts, but it does take a little longer. I used to do it in parts but the more used to the problems you get, the easier it is to write it out all together. When writing out the problem just think how many steps you need for get to...