## Search found 62 matches

Mon Mar 11, 2019 1:08 am
Forum: Second Order Reactions
Topic: 2nd order
Replies: 4
Views: 175

### Re: 2nd order

The second order graph has nothing to do with the concentration, but rather the second derivative.
Mon Mar 11, 2019 1:07 am
Forum: General Rate Laws
Topic: Solving for the rxn order
Replies: 3
Views: 148

### Re: Solving for the rxn order

That probably means that one of the reactants is zero order (meaning that the rate is independent of its concentration).
Mon Mar 11, 2019 1:05 am
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Final Exam
Replies: 23
Views: 591

### Re: Final Exam

The final exam will usually have a question on each topic covered, and chemical equilibrium is one of those topics. There will probably be acid-base equilibrium on the final as well.
Sat Mar 09, 2019 5:47 pm
Forum: Van't Hoff Equation
Topic: pH and van’t hoff
Replies: 6
Views: 577

### Re: pH and van’t hoff

The neutral pH can change with temperature, because pH is not constant with temperature.
Sat Mar 09, 2019 5:46 pm
Forum: General Science Questions
Topic: 14BL [ENDORSED]
Replies: 3
Views: 745

### Re: 14BL[ENDORSED]

I'm in 14BL right now too, and I'm taking it with 14B. I would say that everything you learned in 14A and 14B is covered. However, even if you don't remember everything fully, Professor Casey does a good job of explaining old and new concepts.
Sat Mar 09, 2019 5:45 pm
Forum: Second Order Reactions
Topic: Final
Replies: 30
Views: 809

### Re: Final

I think that there might be some electrochemistry questions too!
Mon Feb 25, 2019 11:00 pm
Forum: Balancing Redox Reactions
Replies: 5
Views: 260

Oxidation has its name because in the early days of chemistry, the loss of electrons was associated with the gain of oxygen atoms. (It is a little confusing, though)
Mon Feb 25, 2019 10:56 pm
Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
Topic: Redox Reaction Oxidizing Agent
Replies: 1
Views: 97

### Re: Redox Reaction Oxidizing Agent

Yes, the oxidizing agent has the higher cell potential and the reducing agent has the lower cell potential.
Mon Feb 25, 2019 10:54 pm
Forum: Balancing Redox Reactions
Topic: balancing redox reaction
Replies: 2
Views: 147

### Re: balancing redox reaction

Use the half-reaction method and add H2O and either H+/OH- to balance the reaction!
Wed Feb 20, 2019 7:17 pm
Forum: Balancing Redox Reactions
Topic: H+ vs H3O+
Replies: 10
Views: 330

### Re: H+ vs H3O+

I think you should use H+.
Wed Feb 20, 2019 7:16 pm
Forum: Ideal Gases
Topic: units
Replies: 15
Views: 572

### Re: units

K is a ratio, so it has no units.
Wed Feb 20, 2019 7:16 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: Free energy of reaction
Replies: 1
Views: 79

### Re: Free energy of reaction

The free energy equation is deltaG = deltaG(standard) + RTlnK.
K is the equilibrium constant, so the free energy depends on the equilibrium constant. Sometimes, when given partial pressures, they are used to calculate the equilibrium constant.
Tue Feb 12, 2019 12:44 am
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: Question 8.19 (Sixth Edition)
Replies: 3
Views: 191

### Re: Question 8.19 (Sixth Edition)

0.38 J/g C is the specific heat capacity of copper.
Tue Feb 12, 2019 12:43 am
Forum: Thermodynamic Systems (Open, Closed, Isolated)
Topic: Extensive vs Intensive
Replies: 7
Views: 419

### Re: Extensive vs Intensive

Heat capacity is extensive because it is the amount of heat required to raise a substance by one degree Celsius/Kelvin. It depends on mass because if a substance is more massive, then it is capable of maintaining more heat. Specific heat capacity and molar heat capacity are per unit of mass, so they...
Tue Feb 12, 2019 12:40 am
Forum: Third Law of Thermodynamics (For a Unique Ground State (W=1): S -> 0 as T -> 0) and Calculations Using Boltzmann Equation for Entropy
Topic: Explaining Boltzmann's Equation
Replies: 6
Views: 682

### Re: Explaining Boltzmann's Equation

Boltzmann's equation calculates positional/residual entropy using statistics.

Its form is S=kBlnW.

W is equal to the number of microstates (how many positions an element can be in in a molecule) raised to the power of the number of molecules in the system.

kB is a constnant.
Wed Feb 06, 2019 5:39 pm
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: Unit for Heat Capacity
Replies: 2
Views: 129

### Re: Unit for Heat Capacity

That's a fair point. However, the question simply asks for you to identify the optimal heating curve based on the heat capacities given (just say that it defines how much the substance can contain before moving on to the next phase).
Wed Feb 06, 2019 5:36 pm
Forum: Third Law of Thermodynamics (For a Unique Ground State (W=1): S -> 0 as T -> 0) and Calculations Using Boltzmann Equation for Entropy
Topic: Isothermal reaction
Replies: 3
Views: 257

### Re: Isothermal reaction

Another thing to note is that isothermal reactions mean that the temperature is not changing/constant. This means that delta U (change in internal energy) is zero because internal energy depends on the temperature.
Wed Feb 06, 2019 5:34 pm
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: Q. 8.27
Replies: 1
Views: 126

### Re: Q. 8.27

The internal pressure does not matter because the only pressure that is inputted into the equation is the pressure that contributes to the work to the system - i.e. the external pressure. The initial volume was used to find the moles of gas because it is the initial state that can be accurately plug...
Tue Jan 29, 2019 11:52 pm
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: Lecture
Replies: 5
Views: 199

### Re: Lecture

Ultimately, the heating curve for water shows how the phases (solid, liquid, gas) of water change over time as the water is consistently heated. It also relates with the enthalpy of fusion and the enthalpy of vaporization because the heat accumulates, resulting in these phase changes.
Tue Jan 29, 2019 11:49 pm
Forum: Calculating Work of Expansion
Topic: Work
Replies: 2
Views: 120

### Re: Work

You have to consider whether the path is reversible and isothermal or whether it is irreversible.
Tue Jan 29, 2019 11:48 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: pH of AlCl3
Replies: 1
Views: 127

### Re: pH of AlCl3

Use this reaction to calculate the pH!
AlCl3 + 3H2O <=> Al(OH)3 + 3HCl
Sat Jan 26, 2019 9:38 am
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Stable carbon
Replies: 3
Views: 129

### Re: Stable carbon

As far as I know, it depends on crystalline structure. Dr. Lavelle mentioned in class that graphite is sp2 hybridized, while diamond (which forms when graphite is subject to high pressure) is sp3 hybridized.
Sat Jan 26, 2019 9:36 am
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: methods
Replies: 2
Views: 93

### Re: methods

You will need to calculate the enthalpy of the reaction based on the information given to you by the question! e.g. if they give you bond enthalpies, you would need to draw the Lewis structures (or deconstruct/reconstruct all the bonds) to figure out the change in enthalpy.
Sat Jan 26, 2019 9:34 am
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: Increase in Volume Effect on Equilibrium
Replies: 6
Views: 293

### Re: Increase in Volume Effect on Equilibrium

This is for moles of gas only!
Tue Jan 15, 2019 12:27 am
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Activity
Replies: 2
Views: 99

### Re: Activity

Activity is a measure of the effective concentration of a species under non-ideal (e.g., concentrated) conditions.
Tue Jan 15, 2019 12:26 am
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Acids and Bases
Replies: 7
Views: 264

### Re: Acids and Bases

You can also tell from the pKa of the reaction. The smaller the pKa value, the stronger the acid.
Tue Jan 15, 2019 12:24 am
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Change in temperature and K
Replies: 2
Views: 117

### Re: Change in temperature and K

If you increase the temperature of a reaction, you drive the equilibrium backwards (in the endothermic direction), and therefore increase the concentration of reactants and decrease the concentration of products. The two are inherently connected! This does not apply to either pressure or concentrati...
Tue Jan 15, 2019 12:23 am
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: Change in K
Replies: 2
Views: 124

### Re: Change in K

If you increase the temperature of a reaction, you drive the equilibrium backwards (in the endothermic direction), and therefore increase the concentration of reactants and decrease the concentration of products. The two are inherently connected! This does not apply to either pressure or concentrati...
Wed Jan 09, 2019 10:17 am
Forum: Ideal Gases
Topic: Ideal vs Real Gas
Replies: 6
Views: 229

### Re: Ideal vs Real Gas

Ideal gases and real gases have no physical/chemical differences! Rather, ideal gases are theoretical (meaning they do NOT exist). They fit perfectly into the equation PV=nRT, meaning that their particles obtain a negligible volume and have no attractive forces. However, this is not true for real ga...
Wed Jan 09, 2019 10:14 am
Forum: Non-Equilibrium Conditions & The Reaction Quotient
Topic: p. 435 Gibbs Free Energy Curve
Replies: 1
Views: 83

### p. 435 Gibbs Free Energy Curve

Hello,
Would someone explain the two graphs of the Gibbs Free Energy curve at the bottom of page 435?

Sincerely,
Ashley Kim
Wed Jan 09, 2019 10:13 am
Forum: Ideal Gases
Topic: p. 170 Effusion Equations
Replies: 2
Views: 182

### p. 170 Effusion Equations

Hello,
I was reading Chapter 5 and I was unsure of how Graham's Law of Effusion eventually was derived into an expression involving temperature. The equations are on page 170. Could someone explain the derivation/process to me?

Thank you!
Ashley Kim
Sat Dec 01, 2018 10:48 pm
Forum: Naming
Topic: Oxidation State
Replies: 4
Views: 150

### Re: Oxidation State

Some of these oxidation states are simply the charge of the molecule, e.g. O2- will have an oxidation state of -2. An easier way to think about oxidation states is that they are if covalent bonds were split like ionic bonds - merely an intellectual model to determine which atoms are more charged tha...
Sat Dec 01, 2018 10:45 pm
Forum: Lewis Acids & Bases
Topic: Strength of Acids
Replies: 3
Views: 151

### Re: Strength of Acids

You can tell by finding the hydrogen that will be donated to form a hydronium ion, and then determining which bond between that hydrogen and the rest of the molecule is stronger.
Mon Nov 26, 2018 1:44 pm
Forum: Biological Examples
Topic: Cisplatin Articles [ENDORSED]
Replies: 1
Views: 179

### Cisplatin Articles[ENDORSED]

If anyone is interested, here are a couple of fairly recent abstracts on cisplatin (the chemical we talked about in lecture today). One of these is about general cisplatin chemotherapy and the second is about targeted chemotherapy, which avoids healthy cells. Both are fascinating! Hope you enjoy! ht...
Mon Nov 26, 2018 9:47 am
Forum: Hybridization
Topic: Hybridization with Lone Pairs
Replies: 4
Views: 171

### Re: Hybridization with Lone Pairs

Yes, the hybridization is still sp3 and the regional geometry is tetrahedral. However, the molecular shape is only based on the existence of atoms and not lone pairs.
Mon Nov 26, 2018 9:46 am
Forum: Determining Molecular Shape (VSEPR)
Topic: VSEPR
Replies: 9
Views: 317

### Re: VSEPR

Tetrahedral has the VSEPR formula AX4 (no lone pairs, four bonds).
Square planar has the VSEPR formula AX4E2 (two lone pairs, four bonds).
Mon Nov 26, 2018 9:44 am
Forum: Hybridization
Topic: Sigma and pi bond
Replies: 2
Views: 142

### Re: Sigma and pi bond

You would do separate sigma and pi bond descriptions for each resonance structure. Since they are two different structures, you would not count them together.
Mon Nov 26, 2018 9:43 am
Forum: Hybridization
Topic: Bonds
Replies: 5
Views: 175

### Re: Bonds

Sigma bonds are larger and stronger covalent bonds formed by the direct overlap of atomic orbitals.

Pi bonds are due to less overlap and are generally weaker. They consist of double and triple bonds.
Mon Nov 26, 2018 9:42 am
Forum: Hybridization
Topic: Hybridization
Replies: 2
Views: 93

### Re: Hybridization

As far as I know, hybridization can go into orbitals like the f and g ones. It's basically how all atoms, especially ones in the later periods, bond. However, the scope of CHEM 14A only covers up to the d orbitals.
Mon Nov 26, 2018 9:40 am
Forum: Hybridization
Topic: Just Kind of Confused
Replies: 13
Views: 381

### Re: Just Kind of Confused

The order doesn't matter as long as you know that the hybridized orbitals combine to make bonding occur.
Fri Nov 16, 2018 10:01 am
Forum: Determining Molecular Shape (VSEPR)
Topic: CH 4- 4.1 HW Prob.
Replies: 2
Views: 57

### Re: CH 4- 4.1 HW Prob.

Some shapes must have lone pairs because the angle is determined by the lone pair and bonding pair repulsion. Others, like the linear shape, may or may not have lone pairs depending on the structure.
Fri Nov 16, 2018 9:58 am
Forum: Determining Molecular Shape (VSEPR)
Topic: Linear Shape of O2
Replies: 4
Views: 168

### Re: Linear Shape of O2

O2 is not an exception, necessarily. All diatomic molecules are nonpolar.
Sun Nov 04, 2018 3:45 pm
Forum: Quantum Numbers and The H-Atom
Topic: degeneracy in quantum numbers
Replies: 3
Views: 142

### Re: degeneracy in quantum numbers

Degeneracy means that the first two quantum numbers are the same and that the orbitals are equivalent.

e.g. 2px, 2py, 2pz
Sun Nov 04, 2018 3:43 pm
Forum: Lewis Structures
Topic: Exceptions to the Octet Rule
Replies: 4
Views: 91

### Re: Exceptions to the Octet Rule

Looking at it through the hybridization lens, any atom past the 2p orbital can be an exception to the octet rule because the orbitals become degenerate.
Sun Nov 04, 2018 3:41 pm
Forum: Ionic & Covalent Bonds
Topic: Midterm questions
Replies: 5
Views: 176

### Re: Midterm questions

The textbook readings are up to 3.11!
Mon Oct 29, 2018 12:04 am
Forum: Ionic & Covalent Bonds
Topic: Covalent Bonds
Replies: 16
Views: 606

### Re: Covalent Bonds

Nonmetals also tend to gain electrons more frequently due to their high electronegativity.
Mon Oct 29, 2018 12:02 am
Forum: Lewis Structures
Topic: Lines that Represent Bonds
Replies: 7
Views: 256

### Re: Lines that Represent Bonds

I honestly prefer the one where you use the lines to represent the bonds. In a Lewis structure, it's important to distinguish between the bonded electrons and the lone pairs. However, it's more difficult to do so if you represent the bonds with dots instead of lines.
Sun Oct 28, 2018 11:58 pm
Forum: Ionic & Covalent Bonds
Topic: Roman numerals next to element
Replies: 8
Views: 2036

### Re: Roman numerals next to element

It's important to note that some transition metals are capable of having multiple charges, hence the need for the Roman numerals in the first place. Transition metal ions involve a rearrangement of both the d and s orbitals. This is because according to the Aufbau principle, the electrons fill the 4...
Sun Oct 28, 2018 5:18 pm
Forum: Quantum Numbers and The H-Atom
Topic: Degeneracy
Replies: 5
Views: 247

### Re: Degeneracy

This is because the p orbital has three degenerate orbitals: px, py, and pz. There are 3 orbitals (electron probability clouds) that have the same energy. The electrons in these clouds have the chance of moving in different places with the SAME energy.
Sun Oct 28, 2018 5:16 pm
Forum: Ionic & Covalent Bonds
Topic: Ionic Bonds vs Covalent Bonds
Replies: 7
Views: 316

### Re: Ionic Bonds vs Covalent Bonds

It depends on both the type of ionic or covalent bonds. It's also important to remember that no bonds are truly ionic or covalent. All charges are shared to a degree. In ionic bonds, the charges are more unequally distributed than those on covalent bonds.
Sun Oct 28, 2018 5:05 pm
Forum: Ionic & Covalent Bonds
Topic: Covalent Bonds
Replies: 7
Views: 336

### Re: Covalent Bonds

You can also figure out that nonmetals have higher electronegativity by considering the following: The electrons in the valence shell of a nonmetal have a higher attraction because they are closer to having a full valence shell. Therefore, it makes sense that nonmetals would have a higher electroneg...
Tue Oct 09, 2018 8:44 am
Forum: Properties of Light
Topic: Wavelength vs Frequency
Replies: 7
Views: 224

### Re: Wavelength vs Frequency

I thought this question was interesting, so I decided to search it up. It turns out that you cannot change the frequency of a specific sample of light (as far as I know, you would have to get a different sample), but you can change the wavelength by passing light through a filter. There is also a ph...
Tue Oct 09, 2018 8:40 am
Forum: Properties of Light
Topic: Exam
Replies: 7
Views: 265

### Re: Exam

Solving all the problems (both in the modules and in the textbook) is a good way to prepare for the test. Mark the ones you got wrong, and then resolve the wrong ones to understand the concepts.
Tue Oct 09, 2018 8:38 am
Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
Topic: Confused on Problem 1.57 (regarding the Balmer Series)
Replies: 9
Views: 2223

### Re: Confused on Problem 1.57 (regarding the Balmer Series)

Hello, I'm reviving an old post. However, I don't understand why you can figure out that n2=7 using the Balmer series. Can someone please explain?
Wed Oct 03, 2018 12:38 am
Forum: Molarity, Solutions, Dilutions
Topic: Module question
Replies: 4
Views: 256

### Re: Module question

This might be repetitive, but I used the M1V1=M2V2 equation. I converted the grams of KCl to moles and then found the molarity - then multiplied that value by the original volume (in liters). Then, I put in 0.125 L on the other side and solved for the second molarity. It's definitely quite repetitiv...
Wed Oct 03, 2018 12:35 am
Forum: Limiting Reactant Calculations
Topic: M.11
Replies: 8
Views: 900

### Re: M.11

I thought of a comprehensive solution! First, find the moles of P4O6 formed for each reactant. The substance that makes the lowest amount is the LM. With that value, you now know how many moles of P4O6 you have for the next reaction. You still need to figure out how much O2 is left for the next reac...
Wed Oct 03, 2018 12:30 am
Forum: Administrative Questions and Class Announcements
Topic: Advice from a Medical Student [ENDORSED]
Replies: 217
Views: 115286

### Re: Advice from a Medical Student[ENDORSED]

Hello Ashley!
Thank you so much for your tips to study chemistry. I will definitely take advantage of them as I go through college at UCLA!
Fri Sep 28, 2018 4:28 pm
Forum: Empirical & Molecular Formulas
Topic: Problem E5
Replies: 6
Views: 1669

### Re: Problem E5

Is it one pea per second per PERSON, or just one pea per second OVERALL?
Fri Sep 28, 2018 1:11 pm
Forum: Limiting Reactant Calculations
Topic: Is there a specific way to solve limiting reactant problems?
Replies: 4
Views: 255

### Re: Is there a specific way to solve limiting reactant problems?

Thank you! I appreciate it.
Fri Sep 28, 2018 1:06 pm
Forum: Balancing Chemical Reactions
Topic: Balancing Equation
Replies: 7
Views: 709

### Re: Balancing Equation

Other than beginning with the least abundant element and using inspection, you can also try the proportions method. This is similar to the matrix method, where you put variables to represent each coefficient in the equation. Then, you solve it like a mathematical equation with multiple variables. Ho...
Fri Sep 28, 2018 1:01 pm
Forum: Limiting Reactant Calculations
Topic: Is there a specific way to solve limiting reactant problems?
Replies: 4
Views: 255

### Is there a specific way to solve limiting reactant problems?

I found that there were two ways to solve stoichiometric calculations regarding limiting reactants. The first way is to find the number of moles of each reactant and calculate the mole ratio of the reactants. Personally, I don't use this one because I find it impossible to use with more than two rea...
Fri Sep 28, 2018 12:55 pm
Forum: Limiting Reactant Calculations
Topic: Two limiting reactants?
Replies: 10
Views: 1231

### Re: Two limiting reactants?

However, the case where there are two limiting reactants is pretty rare - most chemistry problems will result in only one limiting reactant. (It also doesn't happen often in real life, because experiments usually put one reactant in excess.)