Search found 55 matches

by Jasmine Wu 1L
Sat Mar 17, 2018 1:28 pm
Forum: Reaction Mechanisms, Reaction Profiles
Topic: Steady State Approximation Vs Pre Equilibrium
Replies: 2
Views: 302

Re: Steady State Approximation Vs Pre Equilibrium

Technically, you can use both to get the same answer. Dr. Lavelle taught us the pre-equilibrium approach, which the the "preferred" method for less complex mechanisms. Pre-equilibrium is less flexible than steady-state and more difficult to extend to more complex mechanisms (i.e. with lots...
by Jasmine Wu 1L
Wed Mar 14, 2018 4:47 pm
Forum: Administrative Questions and Class Announcements
Topic: Practice Final?
Replies: 1
Views: 226

Re: Practice Final?

UA Lyndon has a practice final up on Chemistry Community already.

viewtopic.php?f=160&t=29688&p=92277&hilit=red+panda&sid=8519397833e3adfee6753eddb79ace3b#p92277

Good luck studying!
by Jasmine Wu 1L
Tue Mar 13, 2018 11:20 pm
Forum: *Enzyme Kinetics
Topic: Frequency factor A
Replies: 1
Views: 181

Re: Frequency factor A

A is the pre-exponential factor and it represents the frequency of collisions between the molecules in correct orientation. It is the constant obtained from the y-intercept in an Arrhenius plot. The Arrhenius plot is a graph of ln k against 1/T.
by Jasmine Wu 1L
Sun Mar 11, 2018 10:24 pm
Forum: *Enzyme Kinetics
Topic: Kinetics and Enzymes
Replies: 7
Views: 544

Re: Kinetics and Enzymes

Enzymes are "living" catalysts, and catalysts can increase the rate of a reaction.
by Jasmine Wu 1L
Sun Mar 11, 2018 10:16 pm
Forum: Arrhenius Equation, Activation Energies, Catalysts
Topic: What is A?
Replies: 4
Views: 162

Re: What is A?

A represents the frequency of collisions between the molecules in correct orientation and is the y-intercept in an Arrhenius plot. The Arrhenius plot is a graph of ln k against 1/T.
by Jasmine Wu 1L
Tue Mar 06, 2018 10:13 pm
Forum: Kinetics vs. Thermodynamics Controlling a Reaction
Topic: Increasing Concentration of Reactants
Replies: 5
Views: 305

Re: Increasing Concentration of Reactants

Yes, it does. For reactions to occur, the particles must collide and also have sufficient energy to cause that reaction. By increasing the concentration, you are also increasing the chances and frequency of collision between those particles.
by Jasmine Wu 1L
Sat Mar 03, 2018 4:39 pm
Forum: Kinetics vs. Thermodynamics Controlling a Reaction
Topic: Kinetics Test/Final
Replies: 2
Views: 118

Re: Kinetics Test/Final

On the kinetics lecture outline on Dr. Lavelle's website, it says that you should "know how to derive the differential and integrated rate laws for zero, 1st and 2nd order reactions and know how to derive their respective half-life equations". The constants and equations give the integrate...
by Jasmine Wu 1L
Thu Mar 01, 2018 6:26 pm
Forum: General Rate Laws
Topic: Rate Law dependent on Reactants [ENDORSED]
Replies: 4
Views: 229

Re: Rate Law dependent on Reactants [ENDORSED]

For a chemical reaction a A + b B \rightarrow c C + d D the formula for rate is k [A] a [B] b , where k is the rate constant, [A] is the concentration of reactant A, and [B] is the concentration of reactant B. Each reaction has its own unique rate law and rate constant, so Table 15.1 is just general...
by Jasmine Wu 1L
Thu Mar 01, 2018 6:18 pm
Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
Topic: Finding the value of n
Replies: 1
Views: 134

Re: Finding the value of n

"n" is the amount of electrons (in moles) of electrons transferred in the reaction. You'd find it by first writing out the balanced half-reactions for the redox reaction given. Then, from the balanced redox reaction, find the number of electron needed to balance the charges. For this probl...
by Jasmine Wu 1L
Wed Feb 28, 2018 10:06 am
Forum: Administrative Questions and Class Announcements
Topic: Kinetics Test Week 9
Replies: 2
Views: 155

Re: Kinetics Test Week 9

According to the announcements on Dr. Lavelle's website, Sections 15.1 to the end of 15.6 of the textbook will be covered on Test 3 (Kinetics).
by Jasmine Wu 1L
Thu Feb 22, 2018 3:23 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: When writing cell diagrams, how do you know when to include an additional element at the electrode?
Replies: 5
Views: 197

Re: When writing cell diagrams, how do you know when to include an additional element at the electrode?

Xihui Yin 1I wrote:
Adrian Lim 1G wrote:Isn't I2 a solid though?

You need a conducting solid.


And how do you tell if something is or can act as a "conducting solid"?
by Jasmine Wu 1L
Tue Feb 20, 2018 6:14 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Cell Diagrams
Replies: 1
Views: 102

Re: Cell Diagrams

In the cell diagrams, the convention is: anodes on the left, and cathodes on the right.
by Jasmine Wu 1L
Tue Feb 20, 2018 6:04 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: IUPAC Notation
Replies: 1
Views: 95

Re: IUPAC Notation

The double-line ( || )part represents the salt bridge. To the left of the || is the anode, where oxidation half-reaction is taking place. To the right of the || is the cathode, where the reduction half-reaction happens. Platinum basically functions as an inert electrode that do not participate in th...
by Jasmine Wu 1L
Fri Feb 16, 2018 9:39 am
Forum: Concepts & Calculations Using Second Law of Thermodynamics
Topic: Gibbs free
Replies: 5
Views: 217

Re: Gibbs free

Veritas Kim 2L wrote:What is the difference between Gibbs free energy of reaction and Standard Gibbs free energy of reaction?


Standard Gibbs free energy of reaction is the Gibbs free energy collected under standard state conditions.
by Jasmine Wu 1L
Fri Feb 16, 2018 9:30 am
Forum: Balancing Redox Reactions
Topic: Oxidized vs oxidizing agent
Replies: 5
Views: 188

Re: Oxidized vs oxidizing agent

An oxidizing agent removes electrons from something that's being oxidized and is thus reducing itself, while a reducing agent gives electrons to the thing being reduced and oxidizes itself. The book gives examples for the oxidizing agent (O 2 , O 3 , MnO 4 - , and Fe 3+ ) and the reducing agent (H 2...
by Jasmine Wu 1L
Fri Feb 16, 2018 9:19 am
Forum: Thermodynamic Definitions (isochoric/isometric, isothermal, isobaric)
Topic: Is Enthalpy a State Function?
Replies: 2
Views: 211

Re: Is Enthalpy a State Function?

Yes, enthalpy is a state function. The formula for enthalpy (H=U+PV) consists of terms also defined as state functions. Enthalpy change relies solely on the initial and final states of the system and it does not matter how you get from the initial and final state, which is essentially the definition...
by Jasmine Wu 1L
Sat Feb 10, 2018 9:27 pm
Forum: Concepts & Calculations Using Second Law of Thermodynamics
Topic: Gibbs free
Replies: 5
Views: 217

Re: Gibbs free

Gibbs free energy is the system's energy that is available or free to do work at constant pressure and temperature. Formula: G=H-TS

Enthalpy(H) change (H) is the heat absorbed or released at a constant pressure, given by the equations: H=U+PV and H=q
by Jasmine Wu 1L
Sat Feb 10, 2018 4:15 pm
Forum: Biological Examples (*DNA Structural Transitions, etc.)
Topic: STP [ENDORSED]
Replies: 2
Views: 485

Re: STP [ENDORSED]

The standard temperature is 0*C (273K) and pressure is 1 bar, for STP.

However, STP is rare in lab settings, so SATP (Standard Ambient Temperature and Pressure) is used. In SATP, the temperature is 25*C and pressure is 1 bar.

Hope this helped you!
by Jasmine Wu 1L
Sat Feb 10, 2018 11:36 am
Forum: Gibbs Free Energy Concepts and Calculations
Topic: Units Confusion [ENDORSED]
Replies: 3
Views: 156

Units Confusion [ENDORSED]

Hello! Hopefully I'm not alone with this, but I feel that there are so many equations in Chapter 8, 9, and 11! A lot of them look quite similar, too. How would you know when to use what the book describes as "molar" convention (i.e. which formula to use). Sometimes I see that the units of ...
by Jasmine Wu 1L
Tue Feb 06, 2018 8:32 pm
Forum: Balancing Redox Reactions
Topic: oxidation
Replies: 4
Views: 175

Re: oxidation

Toolbox K.1 does a good job explaining how to assign oxidation numbers. Use it as a reference to help you! In summary, the oxidation number for groups 1 and 2 is equal to their group number. The halogens have an oxidation number of -1. For oxygen it is -2. Hydrogen combined with nonmetals is +1, whi...
by Jasmine Wu 1L
Tue Feb 06, 2018 8:24 pm
Forum: Balancing Redox Reactions
Topic: Transition Metals
Replies: 4
Views: 145

Re: Transition Metals

For transition metals: uncombined elements have an oxidation state of zero. The oxidation state for ions equals the charge of the ion, and for neutral compounds it equals zero.
by Jasmine Wu 1L
Tue Feb 06, 2018 8:10 pm
Forum: Concepts & Calculations Using Second Law of Thermodynamics
Topic: formula
Replies: 3
Views: 142

Re: formula

You can use this to calculate the change in the entropy of a system, provided that the temperature is constant. The "rev" subscript of q signifies that the energy must have been transferred reversibly. Recall that, for a reversible energy transfer, the surrounding's and the system's temper...
by Jasmine Wu 1L
Mon Feb 05, 2018 10:09 am
Forum: Gibbs Free Energy Concepts and Calculations
Topic: Homework 9.69
Replies: 1
Views: 77

Re: Homework 9.69

For 9.69: yes, I believe that you would use Hess's Law approach. The chemical equation for the oxidation of 1 mole NADH can be obtained by adding equations (2) and (3) given. Then just multiply what you got after you added by 3 (because you want to find for delta G for 3 moles NADH). Remember to add...
by Jasmine Wu 1L
Mon Feb 05, 2018 10:02 am
Forum: Concepts & Calculations Using Second Law of Thermodynamics
Topic: Types of Disorders [ENDORSED]
Replies: 5
Views: 211

Re: Types of Disorders [ENDORSED]

For question 9.85 part c, the entropy change in the system is due to change in positional disorder, because it is doing from a solid to aqueous state. In the aqueous state, molecules/ions can move more freely as opposed to when they are rigidly packed together in a solid. Thus, entropy is higher in ...
by Jasmine Wu 1L
Thu Feb 01, 2018 9:48 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: 8.85
Replies: 3
Views: 198

Re: 8.85

To answer this question: a) Find the correlation between the enthalpy change and the number of moles of NO from thermochemical equation. The heat absorbed to form 2 mol NO is the given 180.6 kJ. Then, just multiply the 1.55 mol NO by the ratio described above: (180.6kJ / 2 mol). b) Use the ideal gas...
by Jasmine Wu 1L
Wed Jan 24, 2018 6:19 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: 8.73
Replies: 1
Views: 93

Re: 8.73

I find that, when doing bond enthalpy problems, it really helps to draw the Lewis structures because they really help you "visualize" what bonds are there and what is to be broken and formed. Once you have determined what bonds there are to be broken/formed, then using Table 8.6 or 8.7 wou...
by Jasmine Wu 1L
Wed Jan 24, 2018 6:10 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Combustion
Replies: 3
Views: 187

Re: Combustion

Combustion of a hydrocarbon produces carbon dioxide in the gaseous phase, water in the liquid phase, and heat.
by Jasmine Wu 1L
Wed Jan 24, 2018 6:02 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Question 8.59 [ENDORSED]
Replies: 1
Views: 86

Question 8.59 [ENDORSED]

8.59 asks us to use Appendix 2A calculate the standard reaction enthalpy for the reaction of pure nitric acid with hydrazine, which is: 4HNO 3 (l) + 5N 2 H 4 (l) \rightarrow 7N 2 (g) + 12H 2 O(l) According to Appendix 2A: \Delta H f for HNO 3 (l) is -174.10 kJ/mol \Delta H f for N 2 H 4 (l) is +50.6...
by Jasmine Wu 1L
Thu Jan 18, 2018 4:21 pm
Forum: Thermodynamic Systems (Open, Closed, Isolated)
Topic: Adiabatic [ENDORSED]
Replies: 8
Views: 368

Re: Adiabatic [ENDORSED]

An adiabatic process is a process in which energy is transferred by just work, not heat. Think of it as something that is thermally insulating.
by Jasmine Wu 1L
Thu Jan 18, 2018 4:10 pm
Forum: Thermodynamic Systems (Open, Closed, Isolated)
Topic: Reversible, Irreversible
Replies: 4
Views: 212

Re: Reversible, Irreversible

In a reversible process, the system and surroundings can be "reversed" to its initial state by an infinitely small change, thus not changing the thermodynamic properties of the universe. In an irreversible process, which is most natural, the infinitely small change does not reverse to the ...
by Jasmine Wu 1L
Thu Jan 18, 2018 4:00 pm
Forum: Phase Changes & Related Calculations
Topic: Heat Capacity
Replies: 6
Views: 273

Re: Heat Capacity

The units for heat capacity/specific heat capacity are in Joules. For example, the specific heat capacity for water is 4.18 J.K -1 .g -1 I guess it would be fine to use kJ or J, as long as you do your conversions in the end to match the units for heat capacity/specific heat capacity. Remember: (1 kJ...
by Jasmine Wu 1L
Thu Jan 11, 2018 1:16 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: Relating energy and heat [ENDORSED]
Replies: 2
Views: 136

Re: Relating energy and heat [ENDORSED]

The term "energy" is the ability and capacity to transfer heat or do work. But, "heat" is the flow of energy transferred because of a temperature difference .
by Jasmine Wu 1L
Wed Jan 10, 2018 9:09 pm
Forum: Calculating Work of Expansion
Topic: Example 8.2: Calculating the work in isothermal expansion
Replies: 1
Views: 121

Example 8.2: Calculating the work in isothermal expansion

Given in this example: A piston confines 0.100 mol Ar(g) in 1.00L at 25 degrees Celsius. a) The gas is allowed to expand through an additional 1.00L against a constant pressure of 1.00 atm. The book says to use Equation 3 (w= -P ex \Delta V ) to part a because it is an "irreversible path"....
by Jasmine Wu 1L
Wed Jan 10, 2018 1:26 pm
Forum: Calculating Work of Expansion
Topic: Work vs. Work Function
Replies: 2
Views: 170

Work vs. Work Function

Just out of curiosity, does work (as defined in Chapter 8.2 in the book) have anything to do with the work function we learned about in CHEM 14A?
by Jasmine Wu 1L
Wed Dec 06, 2017 8:16 am
Forum: Calculating pH or pOH for Strong & Weak Acids & Bases
Topic: ICE Chart [ENDORSED]
Replies: 9
Views: 394

Re: ICE Chart [ENDORSED]

Strong acids/bases are completely ionized in solution, but weak acids/bases are not. So you would need to calculate the concentrations, which is what the ICE box is for.
by Jasmine Wu 1L
Tue Dec 05, 2017 9:22 pm
Forum: Lewis Acids & Bases
Topic: 12.29
Replies: 2
Views: 160

Re: 12.29

I think you would multiply by 2 because, in the formula Ba(OH)2, there are 2 moles of OH- (look at the subscript) for 1 mole of Ba(OH)2. So, there's a 2:1 ratio.
by Jasmine Wu 1L
Tue Dec 05, 2017 9:00 pm
Forum: Calculating pH or pOH for Strong & Weak Acids & Bases
Topic: 12.53 (B)
Replies: 1
Views: 154

Re: 12.53 (B)

According to the Solutions Manual, Formic Acid, HCOOH, withdraws more electrons than Acetic Acid, CH3COOH, does because of the H attached to the carboxyl group. The CH3 in Acetic Acid has "electron-donating properties".

Formic Acid is the stronger acid in this case.
by Jasmine Wu 1L
Sun Dec 03, 2017 10:41 pm
Forum: Amphoteric Compounds
Topic: 12.17 Part c and Part d
Replies: 1
Views: 174

12.17 Part c and Part d

In the solutions manual, it says that the compound As2O3 (from part c) and that Bi2O3 are amphoteric. How do you tell that those compounds are amphoteric?

Thank you!
by Jasmine Wu 1L
Sun Dec 03, 2017 9:26 pm
Forum: Sigma & Pi Bonds
Topic: Delocalized Pi-Bonding
Replies: 5
Views: 420

Delocalized Pi-Bonding

What is a delocalized pi-bond, and how do you find them?

Thanks! :)
by Jasmine Wu 1L
Sat Nov 25, 2017 11:16 pm
Forum: Naming
Topic: Latin stem
Replies: 1
Views: 137

Re: Latin stem

Appendix 2D of the textbook has a whole list of the elements and their name origins. Some have Latin names. I really don't believe that you would have to know all of the Latin names, just some of the most common ones. Use the Latin stem is the symbol for the metal comes from the Latin name. Like, fo...
by Jasmine Wu 1L
Sat Nov 25, 2017 5:41 pm
Forum: Non-Equilibrium Conditions & The Reaction Quotient
Topic: Quadratic Equations from ICE Box [ENDORSED]
Replies: 2
Views: 273

Quadratic Equations from ICE Box [ENDORSED]

When you solve for x after completing the ICE box and setting up the quadratic equation, I noticed that sometimes you could get two positive answers. How would you choose which solution for x is relevant to the question and answer? I know for the solutions with one positive and one negative answer, ...
by Jasmine Wu 1L
Sat Nov 25, 2017 5:28 pm
Forum: Naming
Topic: Table 17.4 [ENDORSED]
Replies: 2
Views: 188

Re: Table 17.4 [ENDORSED]

Hi :) Both versions would be acceptable- my TA said so. Also, on Dr. Lavelle's class site, there's a file on there called "Naming Coordination Compounds" and it's got those anionic compounds you were talking about on there. On the top of the 2nd page of that document, it says that for the ...
by Jasmine Wu 1L
Sat Nov 25, 2017 5:20 pm
Forum: Naming
Topic: Cyano vs Cyanido
Replies: 3
Views: 195

Re: Cyano vs Cyanido

My TA said both versions would be acceptable for the class (like on Test 4)
by Jasmine Wu 1L
Sat Nov 25, 2017 5:17 pm
Forum: Naming
Topic: Roman Numerals
Replies: 1
Views: 108

Re: Roman Numerals

In Toolbox 17.1> B. Naming the complex> (1), it says that the Roman numerals represent the oxidation state of the central metal atom. So, in your example, the Roman numerals are describing iron. But, sorry, I am actually not sure of the rules about where to put the Roman numerals in parentheses. Tha...
by Jasmine Wu 1L
Sat Nov 25, 2017 5:07 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Experimentally Determined/Confirmed Bond Angles [ENDORSED]
Replies: 1
Views: 165

Experimentally Determined/Confirmed Bond Angles [ENDORSED]

It is my understanding that lone pairs repel other atoms and alter the shape of the VSEPR model. For example, we would have to predict that, for an AX3E species, the angle will be less than 109.5 degrees, but the actual angle can't be predicted. By experiment, we would find that the actual value wou...
by Jasmine Wu 1L
Sun Nov 05, 2017 10:57 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: VSEPR Formula?
Replies: 3
Views: 189

VSEPR Formula?

What does it mean when a question asks for a VSEPR formula and the hybridization of the central atom? Would it be the same thing as the VSEPR models Dr. Lavelle drew in class?

Thanks :)
by Jasmine Wu 1L
Sun Oct 29, 2017 10:14 pm
Forum: Quantum Numbers and The H-Atom
Topic: Direction of the Spin Magnetic Quantum Number
Replies: 5
Views: 358

Re: Direction of the Spin Magnetic Quantum Number

What about the clockwise/counter-clockwise direction? Which direction do -1/2 and 1/2 belong to?
by Jasmine Wu 1L
Sun Oct 29, 2017 10:09 pm
Forum: Quantum Numbers and The H-Atom
Topic: Direction of the Spin Magnetic Quantum Number
Replies: 5
Views: 358

Direction of the Spin Magnetic Quantum Number

It is my understanding that the spin magnetic quantum number, m_s, has a value of either 1/2 or -1/2. Which way does the electron spin if it has a m_s value of 1/2 and if it has a m_s value of -1/2?

Thanks!
by Jasmine Wu 1L
Sun Oct 29, 2017 3:02 pm
Forum: Trends in The Periodic Table
Topic: Diagonal Relationships of the Periodic Table [ENDORSED]
Replies: 4
Views: 976

Diagonal Relationships of the Periodic Table [ENDORSED]

Section 2.13 of the textbook briefly explains the concept of diagonal relationships, but I don't quite understand it.

Do you know if we need to know this for Test 3, or if it would be a good idea to commit this concept to memory for future reference?

Thanks!
by Jasmine Wu 1L
Sun Oct 22, 2017 5:59 pm
Forum: Heisenberg Indeterminacy (Uncertainty) Equation
Topic: post-module question #22
Replies: 2
Views: 183

Re: post-module question #22

Hi! I had a similar question to this.

You would multiply the kinetic energy that you found by Avogadro's constant to get J/mol.
by Jasmine Wu 1L
Sun Oct 22, 2017 4:41 pm
Forum: Heisenberg Indeterminacy (Uncertainty) Equation
Topic: Post-Module Question #20 [ENDORSED]
Replies: 2
Views: 239

Post-Module Question #20 [ENDORSED]

Hello! I'm having some trouble doing #20 from the Heisenberg Indeterminacy Equation post-module. Use the above uncertainty in velocity (which I calculated to be delta v = 3.4*10^10 m/s) to calculate the electron's uncertainty in kinetic energy. Then calculate the uncertainty in kinetic energy per mo...
by Jasmine Wu 1L
Sun Oct 15, 2017 10:15 pm
Forum: Properties of Light
Topic: Electromagnetic Spectrum for Test
Replies: 2
Views: 140

Electromagnetic Spectrum for Test

Hello! Does anyone know whether or not we will be given an electromagnetic spectrum for the test? I've only memorized that the Balmer series is in the visible region and that the Lyman series is in the UV region, but it would be really helpful if we get the wavelengths that correspond to each region...
by Jasmine Wu 1L
Sun Oct 15, 2017 1:51 pm
Forum: Photoelectric Effect
Topic: Work Function vs. Threshold Energy [ENDORSED]
Replies: 5
Views: 379

Work Function vs. Threshold Energy [ENDORSED]

Hello!

What is the difference between the work function and the threshold energy?
by Jasmine Wu 1L
Wed Oct 04, 2017 6:31 pm
Forum: Molarity, Solutions, Dilutions
Topic: What is the little m?
Replies: 2
Views: 408

Re: What is the little m?

Hello!

The little capital m is the molarity.

So, for G.9, the molarity of AgNO3 is 0.179 mol/L

Hope that helps :)
by Jasmine Wu 1L
Wed Oct 04, 2017 6:21 pm
Forum: Empirical & Molecular Formulas
Topic: Fundamentals M.19
Replies: 2
Views: 514

Fundamentals M.19

Hello! I'm having some trouble with fundamentals M.19... The question is: A stimulant in coffee and tea is caffeine, a substance of molar mass 194 g/mol. When 0.376 g of caffeine was burned, 0.682 g of carbon dioxide, 0.174 g of water, and 0.110 g of nitrogen were formed. Determine the empirical and...

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