## Search found 98 matches

Sun Feb 23, 2020 10:05 pm
Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
Topic: Test 2
Replies: 10
Views: 20

### Re: Test 2

The end of thermodynamics (like more in-depth on Gibbs Free Energy) and electrochemistry.
Sun Feb 23, 2020 10:04 pm
Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
Topic: n
Replies: 9
Views: 31

### Re: n

You're likely referring to R. In that case, you would use the constant that cancels out your units.
Tue Feb 18, 2020 7:45 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: reaction at equilibrium
Replies: 6
Views: 13

### Re: reaction at equilibrium

We calculate delta G by doing G of products - G of reactants. If at equilibrium, the G between products and reactants doesn't change. Therefore, delta G = 0
Tue Feb 18, 2020 7:44 pm
Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
Topic: Standard Gibbs Free Energy Conditions
Replies: 4
Views: 9

### Re: Standard Gibbs Free Energy Conditions

Room temperature - 298 K
Tue Feb 18, 2020 6:34 pm
Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
Topic: Answer is different for 5G.15
Replies: 5
Views: 21

### Answer is different for 5G.15

I keep getting -2.7 kJ/mol as my answer. However, the book says -27 kJ/mol. Is anyone else getting the same answer as me or did I just calculate something wrong.

Thanks
Wed Feb 12, 2020 12:11 pm
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: different equation in video?
Replies: 1
Views: 13

### Re: different equation in video?

I think you may be referring to the physics version of the equation. It's technically the same equation, but depends on the perspective of the system for work. I don't think you should worry about that; just focus on the one we have which is delta U = q+w !

Hope this helped
Wed Feb 12, 2020 12:00 pm
Forum: Thermodynamic Systems (Open, Closed, Isolated)
Topic: Temperature Changes Along Irreversible Pathway
Replies: 3
Views: 22

### Re: Temperature Changes Along Irreversible Pathway

Makes sense! Thank you!
Tue Feb 11, 2020 4:17 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: Why are exothermic reactions generally spontaneous?
Replies: 16
Views: 84

### Why are exothermic reactions generally spontaneous?

I get that exothermic means a -delta H but idk how to interpret the delta S part.

Thanks
Mon Feb 10, 2020 2:39 am
Forum: Thermodynamic Systems (Open, Closed, Isolated)
Topic: Temperature Changes Along Irreversible Pathway
Replies: 3
Views: 22

### Temperature Changes Along Irreversible Pathway

Why does temperature change along an irreversible pathway? Why does it decrease then increase?

Thanks
Mon Feb 10, 2020 2:30 am
Forum: Calculating Standard Reaction Entropies (e.g. , Using Standard Molar Entropies)
Topic: Why is delta U = 0 for isothermal reactions?
Replies: 10
Views: 48

### Why is delta U = 0 for isothermal reactions?

In my notes, it says that it's because delta U = 3/2(nR*delta T) and if delta T = 0, then delta U will be 0. I can understand that logic but where did that delta U = 3/2(nR*delta T) equation come from? And why is it 0?

Thanks
Mon Feb 10, 2020 12:41 am
Forum: Phase Changes & Related Calculations
Topic: equation for phase changes
Replies: 3
Views: 14

### Re: equation for phase changes

The mass should typically be in moles too but just double check it. For example, the enthalpy of fusion for water is known as 6.01 kJ/mol (I believe) so you would need to multiply it by moles.
Mon Feb 10, 2020 12:39 am
Forum: Calculating Work of Expansion
Topic: Derivation of Formula
Replies: 3
Views: 20

### Re: Derivation of Formula

I don't think we'll be expected to know how to derive it.
Mon Feb 10, 2020 12:38 am
Forum: Entropy Changes Due to Changes in Volume and Temperature
Topic: Cv
Replies: 3
Views: 15

### Re: Cv

Constant pressure may also be called isobaric and constant volume may be called isochoric.
Sat Feb 08, 2020 5:56 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Calculating Average Kinetic Energy
Replies: 1
Views: 20

### Calculating Average Kinetic Energy

For 4.19, we're supposed to use average kinetic energy = 3/2*RT. I did 3/2(8.314 J/mol.K)(328.85K) and got 4101.09 J/moles. However, the answer key says 4103.2 J/mol. I'm off by a pretty significant amount and I'm not sure what I'm doing wrong since it seems to be a pretty straightforward calculatio...
Sat Feb 08, 2020 4:51 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Help on 4.15
Replies: 1
Views: 30

### Help on 4.15

Can someone help explain how to do 4.15 to me? I don't understand why we have to find the limiting reagent and the tabulated enthalpies of formation.

Thanks!
Sun Feb 02, 2020 5:26 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: Calculating q
Replies: 5
Views: 30

### Calculating q

I'm doing some heat problems from 4A. I've noticed that to calculate q, sometimes you do q = mass x specific heat capacity x delta T. Other times, it's just q = specific heat capacity x delta T. When do you know to multiply mass or not?

Thanks
Sun Feb 02, 2020 4:28 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: w = -P*delta V
Replies: 4
Views: 14

### w = -P*delta V

This might be a dumb question, but is a negative sign in front of the P*delta V always there? And then if the volume is decreasing (so -deltaV), then work is positive?

Thanks
Sun Feb 02, 2020 4:26 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: Positive or negative work?
Replies: 8
Views: 29

### Positive or negative work?

How do I know when to put a negative or positive sign when calculating work on a system? For example, pushing a piston into a system?
Sun Feb 02, 2020 3:38 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: delta U = delta H - P delta V
Replies: 3
Views: 17

### delta U = delta H - P delta V

Am I supposed to use this equation to find internal energy of a system that's at constant pressure?

Thanks
Sun Feb 02, 2020 3:34 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Difference between delta H and q
Replies: 2
Views: 16

### Difference between delta H and q

If delta H = qp under constant pressure, what's the difference between them? Like when should I use delta H and qp if the system is under constant pressure or does it not matter?

Thanks
Sat Feb 01, 2020 6:29 pm
Forum: Thermodynamic Systems (Open, Closed, Isolated)
Topic: Pressure in an open beaker
Replies: 12
Views: 42

### Re: Pressure in an open beaker

Pressure should be the pressure of the atmosphere
Tue Jan 21, 2020 11:24 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Conjugate seesaw
Replies: 3
Views: 31

### Re: Conjugate seesaw

Yes. Strong base = weak conj. acid. Weak base = strong conj. acid. And the same for strong/weak acids.
Tue Jan 21, 2020 11:23 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: 6D13 part d
Replies: 2
Views: 22

### Re: 6D13 part d

The reaction is a base + water. Therefore, it's important that you use Kb to figure out this question. From then, you can find pOH and then pH.

Hope this helped!
Tue Jan 21, 2020 11:21 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: Prep for Test 1
Replies: 16
Views: 103

### Re: Prep for Test 1

Nope just be careful that you use Ka for acids and Kb for bases.
Tue Jan 21, 2020 11:21 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: If [H3O+] < 10^-7
Replies: 2
Views: 26

### If [H3O+] < 10^-7

In our notes it says if [H3O+] < 10^-7, then the solution is considered neutral. But if it's less than 10^-7, wouldn't it be considered basic? I don't understand what Dr. Lavelle meant by "neutral".

Thanks
Tue Jan 21, 2020 11:17 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Where is the Practice WS?
Replies: 3
Views: 51

### Re: Where is the Practice WS?

Tue Jan 21, 2020 11:16 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Why does changing the stoichiometric coefficients by a factor also change the value of K?
Replies: 3
Views: 40

### Why does changing the stoichiometric coefficients by a factor also change the value of K?

Doesn't change in concentration not affect K as long as temperature is constant? And if every concentration in the reaction is changed by the same amount, it shouldn't make a difference? I understand it from a mathematical perspective but I don't understand it conceptually.

Thanks
Sat Jan 18, 2020 3:45 pm
Forum: Administrative Questions and Class Announcements
Topic: Getting Back 14A Final Exam
Replies: 3
Views: 25

### Re: Getting Back 14A Final Exam

I heard it'll be available during Week 3 as well!
Thu Jan 16, 2020 4:51 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Help on 5.35
Replies: 5
Views: 27

### Re: Help on 5.35

Rohit Ghosh 4F wrote:You can then use the partial pressures given by the graph along with the reaction A (g) --> B (g) + C (g) to calculate the equilibrium constant.

The answer key says the chemical equation is 2A (g) --> B (g) + 2C (g)
Thu Jan 16, 2020 4:50 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Help on 5.35
Replies: 5
Views: 27

### Re: Help on 5.35

Selena Yu 1H wrote:It says in the problem that compound A decomposes into compounds B and C. So the chemical equation would be A (g) --> B (g) + C (g)

The answer key says the chemical equation is 2A (g) --> B (g) + 2C (g)
Thu Jan 16, 2020 4:49 pm
Forum: Calculating pH or pOH for Strong & Weak Acids & Bases
Topic: 6B.9
Replies: 3
Views: 29

### 6B.9

For 6B.9 i and ii, I keep getting different answers from the answer key. For i), I do the negative log of 1.50 and get the pH to be -0.176, [OH-] to be 6.67x10^-15, and pOH to be 14.17. This doesn't match the textbook that says pH = 0.176, [OH-] = 1.50x10^-14, and pOH = 13.824. I just don't know wha...
Wed Jan 15, 2020 11:32 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Help on 5.35
Replies: 5
Views: 27

### Help on 5.35

I'm not understanding how to find the chemical equation on 5.35. Can someone help me explain?

Thanks
Wed Jan 15, 2020 9:31 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Help on 5I.17
Replies: 1
Views: 13

### Help on 5I.17

After I do the ICE table and try to calculate the equilibrium constant, I'm having trouble. For Kc, I have written Kc = (2x)^2/(0.114-x)^2 = 1.00 x 10^-5. I originally did this by multiplying it out and then doing quadratic equation. I got an answer, x = 7.52 x 10^-4 but the answer key did a differe...
Wed Jan 15, 2020 9:25 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: When to use Kc or Kp
Replies: 2
Views: 8

### Re: When to use Kc or Kp

Kc can also be used for gas problems. It just depends on the units the equilibrium concentrations are in. If its in atm or bars, you would use Kp because it's based on partial pressure. But sometimes gas concentrations can be in molarity too, which would be given in mol/L where you can use Kc to cal...
Sun Jan 12, 2020 5:40 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Units for K
Replies: 21
Views: 57

### Re: Units for K

No because K is a constant. We use brackets around equilibrium concentration. The brackets indicate molar concentration so we omit actual units.
Sun Jan 12, 2020 5:39 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Difference between Kc/Kp and Q
Replies: 2
Views: 17

### Re: Difference between Kc/Kp and Q

Kc is typically used for molar concentrations for aqueous and gasses. Kp is used for gas equilibrium when we use partial pressure (which will typically be indicated by equilibrium concentration in bars or atm). Q stands for the reaction quotient. On its own, it doesn't mean much. To use it, we compa...
Sun Jan 12, 2020 4:29 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Help on 5H.3
Replies: 1
Views: 8

### Help on 5H.3

Can someone help me explain how 5H.3 works?

Thanks
Sun Jan 12, 2020 4:28 pm
Forum: Administrative Questions and Class Announcements
Topic: Test 1 date
Replies: 4
Views: 20

### Re: Test 1 date

Starts on Tuesday, 1/21, and will be in your discussion.
Sun Jan 12, 2020 3:55 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Units for Kc and Kp
Replies: 3
Views: 15

### Units for Kc and Kp

I understand that when we calculate Kc, we omit the units and put brackets instead to indicate molar concentration. However, is it the same rule for when we calculate Kp? Do parentheses indicate gas concentration so therefore we don't need to put units like bars or atms?

Thanks
Sat Dec 07, 2019 11:45 pm
Forum: Calculating pH or pOH for Strong & Weak Acids & Bases
Topic: Explanation on a Part of the Notes
Replies: 2
Views: 42

### Explanation on a Part of the Notes

Can someone explain to me a section of the notes? It was when he asked "Q2: A biological acid, HA, has pKa = 4.22. What's the Ka value of the acid?" I don't understand the part after that says "Is the acid neutral or negatively charged at pH 6?" and the little section under it. T...
Sat Dec 07, 2019 10:59 pm
Forum: Bronsted Acids & Bases
Topic: List of Strong/Weak Acids/Bases
Replies: 2
Views: 32

### List of Strong/Weak Acids/Bases

I tried looking for a list on Dr. Lavelle's website but I can't find it. Can someone tell me what are the strong and weak acids and bases that we need to know for the class. Thanks!
Sat Dec 07, 2019 6:35 pm
Forum: Shape, Structure, Coordination Number, Ligands
Topic: EDTA 6 Bonding Sites
Replies: 1
Views: 19

### EDTA 6 Bonding Sites

I don't completely understand why EDTA 4- has 6 bonding sites. I understand that there is 2 from the 2 nitrogen atoms which each has a lone pair. However, there are 4 double bonded oxygen atoms with 2 lone pairs each and 2 single bonded oxygens with 3 lone pairs each. Why is it that the single bonde...
Thu Dec 05, 2019 12:34 am
Forum: Biological Examples
Topic: Biological Significance
Replies: 2
Views: 50

### Re: Biological Significance

Our notes mention cisplantin for chemotherapy, myoglobin/hemoglobin for oxygen transportion in blood cells, chromium to assist insulin, iron for myoglobin/hemoglobin, cobalt for vitamin B12, and Mn, Ni, Cu, Zn for enzyme function.
Thu Dec 05, 2019 12:29 am
Forum: Bronsted Acids & Bases
Topic: Strong Bases
Replies: 3
Views: 25

### Re: Strong Bases

Oxides and hydroxides with group 1 and 2 elements. Also, metal oxides react with water to form strong bases.
Thu Dec 05, 2019 12:28 am
Forum: Properties & Structures of Inorganic & Organic Acids
Topic: Equilibrium sign?
Replies: 1
Views: 19

### Re: Equilibrium sign?

You would typically use it for weak acids and bases because the ions wouldn't completely dissociate and thus, an equilibrium is formed. A strong acid or base in water would completely dissociate, which is when you would use an arrow.
Thu Dec 05, 2019 12:26 am
Forum: Acidity & Basicity Constants and The Conjugate Seesaw
Topic: Ice tables
Replies: 3
Views: 25

### Re: Ice tables

No. That will be 14B.
Thu Dec 05, 2019 12:24 am
Forum: DeBroglie Equation
Topic: Quantum Help
Replies: 4
Views: 50

### Re: Quantum Help

I typically start off by writing all of the variables the problem gives me. For example, if it gives me wavelength = 900 nm. Then, I write the variable the problem is asking for, so like energy = ? for example. Lastly, I write out all the equations that contains the variables (like wavelength and en...
Sun Dec 01, 2019 8:33 pm
Forum: Bronsted Acids & Bases
Topic: For J. 9., when do we separate H+ from the acid?
Replies: 2
Views: 41

### For J. 9., when do we separate H+ from the acid?

J. 9. says: Identify the salt that is produced from the acid–base neutralization reaction between (a) potassium hydroxide and acetic acid, CH 3 COOH; (b) ammonia and phosphoric acid; (c) calcium hydroxide and bromous acid; (d) sodium hydroxide and hydrosulfuric acid, H2S (both H atoms react). Write ...
Sun Dec 01, 2019 8:31 pm
Forum: Bronsted Acids & Bases
Topic: Explanation for J. 17.
Replies: 1
Views: 25

### Explanation for J. 17.

Can someone help me explain how to do J.17.:
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.

Thanks!
Fri Nov 29, 2019 5:06 pm
Forum: Naming
Topic: New Naming Rules or Old Ones?
Replies: 1
Views: 20

### New Naming Rules or Old Ones?

Did Dr. Lavelle ask us to use the new naming rules or it doesn't matter? For example, cyano (old) vs cyanido (new). Thanks
Fri Nov 29, 2019 3:48 pm
Forum: Interionic and Intermolecular Forces (Ion-Ion, Ion-Dipole, Dipole-Dipole, Dipole-Induced Dipole, Dispersion/Induced Dipole-Induced Dipole/London Forces, Hydrogen Bonding)
Topic: Test 2: Number of Hydrogen Bonding Sites Question
Replies: 3
Views: 52

### Test 2: Number of Hydrogen Bonding Sites Question

I've been hearing mixed answers. What's the correct number of H-bonding sites and what's the explanation? Thanks
Fri Nov 29, 2019 3:45 pm
Forum: Bronsted Acids & Bases
Topic: Difference between Bronsted and Lewis
Replies: 2
Views: 18

### Difference between Bronsted and Lewis

What's the difference between a Bronsted acid/base and a Lewis acid/base? It seems that they're opposite of each other but that's making me confused. Thanks
Fri Nov 29, 2019 3:40 pm
Forum: Calculating the pH of Salt Solutions
Topic: pH vs. pOH
Replies: 17
Views: 127

### Re: pH vs. pOH

To add onto Mingdah, pH and pOH have an inverse relationship.
Fri Nov 29, 2019 3:39 pm
Forum: Calculating pH or pOH for Strong & Weak Acids & Bases
Topic: pH scale
Replies: 4
Views: 25

### Re: pH scale

It could but I think all that we should know will stay in between 1 and 14.
Tue Nov 26, 2019 7:21 pm
Forum: Shape, Structure, Coordination Number, Ligands
Topic: Summary for Naming Coordination Compounds
Replies: 3
Views: 30

### Summary for Naming Coordination Compounds

I am extremely confused while reading the notes for naming coordination compounds. Is anyone able to give me a brief summary to help me better understand the rules?

Thanks
Fri Nov 22, 2019 1:54 am
Forum: Determining Molecular Shape (VSEPR)
Topic: Molecular Shape and Polarity
Replies: 5
Views: 41

### Re: Molecular Shape and Polarity

If you're talking about a molecule like CHCl3, it's polar. However, the polarity of it doesn't affect the fact that its tetrahedral and all bond angles are 109.5 degrees. The only time bond angles/shape is affected would be due to lone pairs.
Fri Nov 22, 2019 1:53 am
Forum: Interionic and Intermolecular Forces (Ion-Ion, Ion-Dipole, Dipole-Dipole, Dipole-Induced Dipole, Dispersion/Induced Dipole-Induced Dipole/London Forces, Hydrogen Bonding)
Topic: QUiz 2
Replies: 2
Views: 44

### Re: QUiz 2

I think the most significant thing we need to know about ion-ion forces is that its the strongest IMF. But I believe the test will mainly focus around dipole-dipole, LDF, and H-bonds.
Fri Nov 22, 2019 1:51 am
Forum: Interionic and Intermolecular Forces (Ion-Ion, Ion-Dipole, Dipole-Dipole, Dipole-Induced Dipole, Dispersion/Induced Dipole-Induced Dipole/London Forces, Hydrogen Bonding)
Topic: Hydrogen Bonding Atoms
Replies: 6
Views: 34

### Re: Hydrogen Bonding Atoms

I believe hydrogen can form H-bonds with any N, O, F that have lone pairs regardless of whether it's already attached to a hydrogen or not.
Fri Nov 22, 2019 1:49 am
Forum: Interionic and Intermolecular Forces (Ion-Ion, Ion-Dipole, Dipole-Dipole, Dipole-Induced Dipole, Dispersion/Induced Dipole-Induced Dipole/London Forces, Hydrogen Bonding)
Topic: london forces
Replies: 9
Views: 43

### Re: london forces

The one with the bigger molar mass (and more electrons). It allows for more interactions which increases the London Dispersion Force.
Fri Nov 22, 2019 1:47 am
Forum: Sigma & Pi Bonds
Topic: significance
Replies: 2
Views: 23

### Re: significance

Sigma bonds allow for the molecule to rotate while pi bonds don't allow it to rotate because they are side by side. Like Lavelle showed in class, if you put 3 EXPO markers in between your two pointer fingers and twist, two markers would fall (pi) while one marker remains in place (sigma).
Sat Nov 16, 2019 6:20 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Long pairs
Replies: 3
Views: 25

### Re: Long pairs

Lone pairs create a strong electron-electron repulsion which pushes all other atoms closer to together. For example, if you had a trigonal pyramidal with a lone pair at the top, it would push the atoms that are part of the structure closer together, creating a smaller bond angle between the atoms.
Sat Nov 16, 2019 6:17 pm
Forum: Bond Lengths & Energies
Topic: Quiz for Next week dashes/wedges
Replies: 11
Views: 89

### Re: Quiz for Next week dashes/wedges

Even if there is, it's easy to remember that wedges mean the bond is towards you and dashes are pointing away from you.
Sat Nov 16, 2019 6:15 pm
Forum: Formal Charge and Oxidation Numbers
Topic: Formal Charge vs Octet Rule
Replies: 5
Views: 51

### Re: Formal Charge vs Octet Rule

Just treat drawing Lewis structures for molecules as drawing a normal Lewis structure. Afterwards, go onto VSEPR.
Sat Nov 16, 2019 6:13 pm
Forum: Interionic and Intermolecular Forces (Ion-Ion, Ion-Dipole, Dipole-Dipole, Dipole-Induced Dipole, Dispersion/Induced Dipole-Induced Dipole/London Forces, Hydrogen Bonding)
Topic: 3F.5 c)
Replies: 3
Views: 24

### Re: 3F.5 c)

You are correct in that they both have London forces. However, CHI3 has stronger London forces because it has more electrons than CHF3, therefore stronger London forces.
Sat Nov 16, 2019 6:11 pm
Forum: Octet Exceptions
Topic: Octet expansion
Replies: 6
Views: 55

### Re: Octet expansion

I think the most important thing we need to know is that the atoms C, N, O, F must fulfill the octet rule. Any other atoms can either have an expanded octet (or don't fulfill the octet rule at all).
Mon Nov 04, 2019 11:17 pm
Forum: Bond Lengths & Energies
Topic: Midterm
Replies: 8
Views: 81

### Re: Midterm

8 but it's likely that there'll be different parts to each questions such as a. b. c. etc.
Mon Nov 04, 2019 11:12 pm
Forum: Photoelectric Effect
Topic: Details about the photoelectric experiment
Replies: 3
Views: 61

### Re: Details about the photoelectric experiment

I highly doubt it. Just know about the concepts that came to light (haha) about the photoelectric experiment (ex. particle-like properties.)
Mon Nov 04, 2019 11:10 pm
Forum: SI Units, Unit Conversions
Topic: Unit Conversion
Replies: 2
Views: 51

### Re: Unit Conversion

You can put it in any unit you want unless the question specifies what unit it wants your answer to be in.
Mon Nov 04, 2019 11:09 pm
Forum: Polarisability of Anions, The Polarizing Power of Cations
Topic: Polarizability Periodic Trend
Replies: 5
Views: 46

### Re: Polarizability Periodic Trend

The smaller radius and highly charged cations have the strongest polarizability.
For anions, larger atomic radius and less electronegativity are more highly polarizable.
Mon Nov 04, 2019 11:06 pm
Forum: Administrative Questions and Class Announcements
Topic: Class Wed 11/6
Replies: 3
Views: 33

### Re: Class Wed 11/6

I'm in the 12:00 pm lecture. Dr. Lavelle said that we won't be having any class this Wednesday. He just forgot to tell the other lectures.
Sat Nov 02, 2019 5:27 pm
Forum: Polarisability of Anions, The Polarizing Power of Cations
Topic: Ionic Character in Covalent Molecules and Vice-Versa
Replies: 2
Views: 22

### Ionic Character in Covalent Molecules and Vice-Versa

Hi, I'm getting confused on the difference between ionic character in covalent molecules and covalent character in ionic molecules. Based on my notes, it seems like for both types of molecules, the ionic/covalent character is that electrons are unevenly distributed. For example of ionic character in...
Thu Oct 31, 2019 4:17 pm
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: Which orbital would contain the highest ionization energy?
Replies: 3
Views: 21

### Re: Which orbital would contain the highest ionization energy?

Orbitals don't necessarily have to do with the ionization energy levels. Just know the periodic table trend for ionization energy: The further right you go in a row, the higher the ionization energy is. The further down you go in a column, the lower the ionization energy.
Thu Oct 31, 2019 4:09 pm
Forum: Student Social/Study Group
Topic: Video Module For New Material
Replies: 4
Views: 82

### Re: Video Module For New Material

He told me that there are no more video modules for the topics after Heisenberg. He said the best way to get something similar to the video modules was to use Sapling Learning.
Thu Oct 31, 2019 4:07 pm
Forum: Lewis Structures
Topic: Question 2A9
Replies: 4
Views: 39

### Re: Question 2A9

The 2+ charge means that 2 electrons are removed. The outermost/highest energy electrons are usually the first to go, thus the removal of the 2 4s electrons.
Thu Oct 31, 2019 4:06 pm
Forum: Ionic & Covalent Bonds
Topic: Lewis structure
Replies: 3
Views: 31

### Re: Lewis structure

The atom that goes in the middle is the one with the lowest ionization energy. You can figure that out using the periodic table trends for ionization energy. The further right you go in a row, the higher the ionization energy is. The further down you go in a column, the lower the ionization energy. ...
Thu Oct 31, 2019 4:02 pm
Forum: Formal Charge and Oxidation Numbers
Topic: Formal Charge equation
Replies: 9
Views: 45

### Re: Formal Charge equation

I think you should just stick with the one Dr. Lavelle gave us. The problem probably wouldn't give you bond length in the first place so you couldn't figure out the formal charge with the equation your TA gave you.
Tue Oct 22, 2019 9:06 pm
Forum: General Science Questions
Topic: Units
Replies: 4
Views: 41

### Re: Units

velocity: m/s
threshold energy: J or kg. m^2. s^-2
Planck's constant: 6.626 x 10^-34 Js or kg.m^2. s^-1
frequency: Hz or s^-1
Tue Oct 22, 2019 8:58 pm
Forum: Administrative Questions and Class Announcements
Topic: Homewrok
Replies: 2
Views: 22

### Re: Homewrok

One question.
Tue Oct 22, 2019 8:57 pm
Forum: Properties of Electrons
Topic: Electron with wavelike/particle like properties?
Replies: 1
Views: 30

### Re: Electron with wavelike/particle like properties?

Depending on the different experiments that have been done, we can determine whether an light acts like a particle or wave depending on the situation. Particle-like property: This can refer to the Photoelectric experiment. So basically, if we shoot light at a piece of metal, it has to surpass the th...
Tue Oct 22, 2019 8:47 pm
Forum: Photoelectric Effect
Topic: Work Function?
Replies: 7
Views: 58

### Re: Work Function?

Work function is the threshold energy. It basically means that its the minimum energy needed from the light source to shoot off an electron.
Tue Oct 22, 2019 8:46 pm
Forum: Trends in The Periodic Table
Topic: 1F. 21
Replies: 2
Views: 26

### 1F. 21

Hi,

F. 21.: 1F.21 Identify the following elements as metals, nonmetals, or
metalloids: (a) lead; (b) sulfur; (c) zinc; (d) silicon; (e) antimony;

Will we have to know the answer for elements like antimony or cadmium?

Thanks
Tue Oct 15, 2019 3:42 pm
Forum: DeBroglie Equation
Topic: 1B.5
Replies: 3
Views: 44

### Re: 1B.5

The equation sheet should provide the conversion from keV to J is 1 keV = 1.6022 x 10^-16 J.
Tue Oct 15, 2019 3:41 pm
Forum: Properties of Light
Topic: 1A.3
Replies: 1
Views: 37

### Re: 1A.3

C is correct because the electrical field corresponds to the amplitude of the wave. And as the frequency goes down, the waves broaden causing the slope of the waves to decrease. This will mean that the change in the electrical field will decrease. This is all according to the solutions manual. Hope ...
Tue Oct 15, 2019 3:38 pm
Forum: Einstein Equation
Topic: Meaning of h [ENDORSED]
Replies: 5
Views: 59

### Re: Meaning of h[ENDORSED]

H stands for the constant of proportionality of energy and frequency. If we were to graph energy (y-axis) and frequency (x-axis) we would have a constant, positive slope. We can use y = mx to model this line meaning y = energy and x = frequency. So it's currently energy = m(frequency). The slope (m)...
Tue Oct 15, 2019 3:34 pm
Forum: Properties of Light
Topic: 1A. 15 HW Problem
Replies: 2
Views: 32

### Re: 1A. 15 HW Problem

You will need to find the frequency of 102.6 nm which will be 2.924 x 10^15 Hz. Afterwards, plug the frequency into E = hv to find the energy emitted from the frequency which will be 1.94 x 10^-18 J. Based on the wavelength the problem gives us (102.6 nm), we know that this is in the UV region which...
Tue Oct 15, 2019 3:27 pm
Forum: Properties of Light
Topic: Electromagnetic Spectrum
Replies: 1
Views: 16

### Electromagnetic Spectrum

Will we have to memorize the electromagnetic spectrum? Or will it be given to us on the test?
For example, knowing that 8.8 nm is in the x-ray/gamma region.
Thu Oct 10, 2019 7:30 pm
Forum: Limiting Reactant Calculations
Topic: Test 1 Calculator
Replies: 6
Views: 114

### Re: Test 1 Calculator

It's possible for people to program cheats and other unfair advantages into a graphing calculator. A non-graphing, scientific calculator helps prevent that because it's not as advanced as a graphing calculator.
Thu Oct 10, 2019 7:28 pm
Forum: Student Social/Study Group
Topic: Pen or Pencil for Homework Problems?
Replies: 8
Views: 72

### Re: Pen or Pencil for Homework Problems?

I don't think it matters whether you do the homework in pen or pencil. Just make sure to properly label what the title of the homework is, your name, UID, date, and discussion. In addition to that, clearly showing your work and final answer. TAs are looking for completion and accuracy of homework.
Thu Oct 10, 2019 7:27 pm
Forum: Empirical & Molecular Formulas
Topic: Mass Percent Calculations
Replies: 4
Views: 57

### Re: Mass Percent Calculations

You should first find the molar mass of C7H15NO3 which is 161.199 g/mol. After that, find the mass percentage of each element in the molecule. For carbon: (7 x 12.011 g/mol)/(161.199 g/mol) = 0.52157 x 100% = 52.157% For hydrogen (15 x 1.008 g/mol)/(161.199 g/mol) = 0.09380 x 100% = 9.380% Repeat th...
Thu Oct 10, 2019 7:21 pm
Forum: Significant Figures
Topic: Sig Figs on Tests
Replies: 24
Views: 284

### Re: Sig Figs on Tests

You should be basing the number of sig figs in your answer on what information the problem gives you. You should be using the least number of sig figs that are in the problem. For example, the question may say, "uses 650. mL for 30.00g of NaCl." You should use 650. (3 sig figs) as an indic...
Thu Oct 10, 2019 7:19 pm
Forum: Accuracy, Precision, Mole, Other Definitions
Topic: sig figs
Replies: 20
Views: 160

### Re: sig figs

When doing the actual work for the problem, don't round off and try to keep intermediate answers 3-4 decimal places. However, at the very end, you want to round off based on the lowest number of sig figs. If you don't know the rules for sig figs, I'd suggest you to look at Professor Lavelle's websit...
Thu Oct 10, 2019 7:14 pm
Forum: SI Units, Unit Conversions
Replies: 6
Views: 103

There isn't a course reader for Lavelle's Chem 14A class. Course readers are typically reserved for humanities and GE classes.
Sat Oct 05, 2019 6:25 pm
Forum: Empirical & Molecular Formulas
Topic: Naming P4O10
Replies: 1
Views: 25

### Naming P4O10

Hi, I'm currently doing G. 27 from the worksheet my TA gave me during discussion. ("Phosphorus and oxygen react to form two different phosphorus oxides. The mass percentage of phosphorous in one of these oxides in 43.64%; in the other, it is 56.34%. A. Write the empirical formula of each phosph...
Tue Oct 01, 2019 4:30 pm
Forum: Molarity, Solutions, Dilutions
Topic: Help on G. 21
Replies: 2
Views: 52

### Help on G. 21

Hi, G.21: In medicine, it is sometimes necessary to prepare solutions with a specific concentration of a given ion. A lab technician has made up 100.0 mL of a solution containing 0.50 g of NaCl and 0.30 g of KCl, as well as glucose and other sugars. What is the concentration of chloride ions in the ...
Tue Oct 01, 2019 4:19 pm
Forum: Balancing Chemical Reactions
Topic: Tips for Balancing Chemical Equations [ENDORSED]
Replies: 14
Views: 166

### Re: Tips for Balancing Chemical Reactions[ENDORSED]

I use a method that can be repetitive and take a little longer but it's easier for me to keep track of what I have and haven't balanced. I usually start with the reactant that appears the least then go from there. Afterward, I will write down the next element I balance as a new step and continue tha...
Tue Oct 01, 2019 4:16 pm
Forum: Empirical & Molecular Formulas
Topic: Module Empirical Question
Replies: 3
Views: 92

### Re: Module Empirical Question

There's always a possbility that the empircial formula IS the molecular formula. You can tell when you find the molar mass of the empircal formula. Then, divide the mass the problem gives you by the empirical mass. If the factor is 1, then molecular and empirical formula is the same. Say if it's 2 o...
Tue Oct 01, 2019 4:13 pm
Forum: SI Units, Unit Conversions
Topic: Textbook
Replies: 7
Views: 79

### Re: Textbook

You don't need the bring the textbook to lecture or discussion! However, it's nice to have a PDF version if you have a laptop or something so you can take a look at the problems or readings.
Tue Oct 01, 2019 4:12 pm
Forum: Empirical & Molecular Formulas
Topic: 5 Homework Problems Due
Replies: 21
Views: 221

### Re: 5 Homework Problems Due

We have 5 problems due this Friday at the lecture. However, it's best to do all the practice problems to help prepare you for the test.