Search found 61 matches

by Annalyn Diaz 1J
Fri Mar 15, 2019 11:29 am
Forum: Biological Examples
Topic: biological examples for final
Replies: 5
Views: 167

Re: biological examples for final

I would probably also know any industrial and and environmental examples that Dr. Lavelle has gone over in class just in case. I think it's safe to assume there might be a small question on them.
by Annalyn Diaz 1J
Fri Mar 15, 2019 11:19 am
Forum: Arrhenius Equation, Activation Energies, Catalysts
Topic: Catalysts
Replies: 3
Views: 56

Re: Catalysts

Additionally, catalysts speed up the rate of reaction by lowering the activation energy, which changes the reaction mechanism. Although this occurs, adding a catalyst doesn't affect reaction enthalpy or the equilibrium position and neither does it alter reaction yields at equilibrium.
by Annalyn Diaz 1J
Fri Mar 15, 2019 9:02 am
Forum: Environment, Ozone, CFCs
Topic: Homogeneous Catalysts and Ozone
Replies: 2
Views: 230

Homogeneous Catalysts and Ozone

How do homogeneous catalysts play a role in the formation of ozone in the lower atmosphere?
by Annalyn Diaz 1J
Sat Mar 09, 2019 3:06 pm
Forum: Second Order Reactions
Topic: Straight-Line Plot for Second-Order Reactions
Replies: 1
Views: 37

Straight-Line Plot for Second-Order Reactions

Why is the straight-line plot for second-order reactions have a positive slope rather than a negative one like zero-order and first-order reactions?
by Annalyn Diaz 1J
Sat Mar 09, 2019 2:50 pm
Forum: First Order Reactions
Topic: Half-Life 1st Order Reaction
Replies: 6
Views: 85

Re: Half-Life 1st Order Reaction

Why is it that the half-life of a first order reaction doesn't depend on initial concentration?
by Annalyn Diaz 1J
Sat Mar 09, 2019 2:41 pm
Forum: Reaction Mechanisms, Reaction Profiles
Topic: integrated rate law
Replies: 2
Views: 38

Re: integrated rate law

To add on, we only consider reactants with the integrated rate law because if we consider products, we also have to keep into account the reverse reaction, which complicates the math. We only consider reactants to "keep the math simple".
by Annalyn Diaz 1J
Sat Mar 02, 2019 1:07 pm
Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
Topic: Nernst
Replies: 4
Views: 66

Re: Nernst

The 0.0592 comes from changing the natural log in the original equation ( E=E(standard)-(RT/nF)lnQ ) to log base 10, which yields E=E(standard)-(2.303RT/nF)logQ. At standard temperature (298K), 2.303RT/F = 0.0592, which gives you the representation of the Nernst equation that first mentioned, E = E ...
by Annalyn Diaz 1J
Sat Mar 02, 2019 1:01 pm
Forum: Method of Initial Rates (To Determine n and k)
Topic: Order of a Reaction
Replies: 2
Views: 47

Order of a Reaction

Why is determining the order of a reaction important?
by Annalyn Diaz 1J
Sat Mar 02, 2019 1:00 pm
Forum: Method of Initial Rates (To Determine n and k)
Topic: Finding n
Replies: 4
Views: 251

Re: Finding n

Michelle Lee 2E wrote:What if the n value we calculate using the method of initial rates was not a whole number but some weird decimal?


Dr. Lavelle also said in lecture that he wouldn't give us any fractional orders or anything that you couldn't round to a whole number.
by Annalyn Diaz 1J
Fri Feb 22, 2019 10:25 am
Forum: Van't Hoff Equation
Topic: Overview
Replies: 8
Views: 209

Re: Overview

Basically the Van’t Hoff equation is used to calculate the equilibrium constant when the temperature is different as long as you know dH. It shows the temperature dependence of K, the equilibrium constant.
by Annalyn Diaz 1J
Fri Feb 22, 2019 10:22 am
Forum: Gibbs Free Energy Concepts and Calculations
Topic: Gibbs free energy at phase changes
Replies: 2
Views: 60

Re: Gibbs free energy at phase changes

I believe that Gibbs free energy is 0 at phase changes because there’s an equilibrium that exists during that phase change and dG =0 at equilibrium.
by Annalyn Diaz 1J
Fri Feb 15, 2019 11:50 am
Forum: Gibbs Free Energy Concepts and Calculations
Topic: Gibbs Free Energy and Equilibrium
Replies: 5
Views: 82

Gibbs Free Energy and Equilibrium

Why is Gibbs free energy 0 at equilibrium?
by Annalyn Diaz 1J
Fri Feb 15, 2019 11:37 am
Forum: Thermodynamic Definitions (isochoric/isometric, isothermal, isobaric)
Topic: Isobaric
Replies: 11
Views: 302

Re: Isobaric

Also in relation to the change in internal energy, heat under constant pressure is dH, which could help with the manipulation of dU=q+w.
by Annalyn Diaz 1J
Fri Feb 15, 2019 11:30 am
Forum: Gibbs Free Energy Concepts and Calculations
Topic: Gibbs free energy
Replies: 5
Views: 89

Re: Gibbs free energy

It also tells us the free energy of a system at any point in time. The fact that it a state function makes it easier to calculate as you would with dH° and dS°.
by Annalyn Diaz 1J
Fri Feb 08, 2019 1:03 am
Forum: Calculating Work of Expansion
Topic: 4F.1 7th Edition
Replies: 4
Views: 65

Re: 4F.1 7th Edition

I'm not entirely sure, but it may be negative because the question is asking how body heat affects the entropy in your surroundings?
by Annalyn Diaz 1J
Fri Feb 08, 2019 12:58 am
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: Closed Systems and q
Replies: 1
Views: 35

Closed Systems and q

I understand that in a closed system, energy can be exchanged with its surroundings but matter cannot. If this is the case, why is it that in a closed system, q=0 is always true? Isn't heat a form of energy? Just some clarification for question 4B.9 in the 7th edition of the textbook.
by Annalyn Diaz 1J
Fri Feb 08, 2019 12:55 am
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: Spontaneity
Replies: 2
Views: 51

Re: Spontaneity

To address the spontaneity, think of the example he mentioned about the boulder on the mountain; it will roll down the side by itself (spontaneously), but it won't roll up the mountain itself. Energy through the form of work is needed to push that boulder up the mountain. If something can occur by i...
by Annalyn Diaz 1J
Mon Feb 04, 2019 11:44 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: W=2^NA
Replies: 3
Views: 75

W=2^NA

I understand Avogadro’s number can be used when calculating degeneracy, but I’m confused as to when we would use it. Can someone clarify that please?
by Annalyn Diaz 1J
Fri Feb 01, 2019 11:42 am
Forum: Thermodynamic Systems (Open, Closed, Isolated)
Topic: Universe as a Thermodynamic System
Replies: 2
Views: 44

Universe as a Thermodynamic System

Why is the universe considered an isolated system?
by Annalyn Diaz 1J
Fri Feb 01, 2019 11:34 am
Forum: Calculating Work of Expansion
Topic: Equations for w
Replies: 5
Views: 88

Re: Equations for w

The integral equation is used when calculating reversible expansion done by a gas, since in this case it is set up so that the change in pressure occurs in small increments till it reaches the volume it should be at in equilibrium. In reversible expansion, the external and internal pressures are ne...
by Annalyn Diaz 1J
Fri Feb 01, 2019 11:21 am
Forum: Phase Changes & Related Calculations
Topic: U and its relations to work
Replies: 8
Views: 127

Re: U and its relations to work

Additionally in a closed system, internal energy relates to work in this equation:

delta U = q + w
by Annalyn Diaz 1J
Fri Jan 25, 2019 11:44 am
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Standard States
Replies: 1
Views: 44

Standard States

I know that the standard state for a gas is 1atm. How do you determine standard states of something other than a gas, such as a liquid or solid, or an element?
by Annalyn Diaz 1J
Fri Jan 25, 2019 11:36 am
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: 3 Methods
Replies: 3
Views: 62

3 Methods

In lecture, Dr. Lavelle mentioned that using bind enthalpies is the least accurate method. Why is that so?
by Annalyn Diaz 1J
Thu Jan 24, 2019 9:52 pm
Forum: Phase Changes & Related Calculations
Topic: Thermochemistry Video Modules
Replies: 1
Views: 38

Re: Thermochemistry Video Modules

I don't think there will be any video modules on thermochemistry. I believe that the video modules stop after chemical equilibrium.
by Annalyn Diaz 1J
Fri Jan 18, 2019 10:16 am
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: Le Chatelier's Principle
Replies: 3
Views: 38

Re: Le Chatelier's Principle

Le Chatelier’s Principle is applied to equilibrium reactions in trying to determine the direction in which a reaction will go when changes are introduced to the system.
by Annalyn Diaz 1J
Fri Jan 18, 2019 10:06 am
Forum: Non-Equilibrium Conditions & The Reaction Quotient
Topic: bases and acids
Replies: 2
Views: 83

Re: bases and acids

As mentioned above, you would be able to calculate Q in the same manner in which K is calculated. The only difference in its application is that Q represents any point in the reaction that is not at equilibrium.
by Annalyn Diaz 1J
Fri Jan 18, 2019 10:04 am
Forum: Equilibrium Constants & Calculating Concentrations
Topic: The Quadratic Equation
Replies: 3
Views: 52

The Quadratic Equation

Is there a reason why we can “bypass” the quadratic equation when calculating for x with weak acids?
by Annalyn Diaz 1J
Fri Jan 11, 2019 11:07 am
Forum: Ideal Gases
Topic: Use of the Ideal Gas law vs Combined Gas Law
Replies: 2
Views: 59

Re: Use of the Ideal Gas law vs Combined Gas Law

I know that the combined gas law has more restrictions than the ideal gas law, such as the fact that moles (n) has to stay constant. In this sense, this is why the ideal gas law is used more often in regards to equilibrium.
by Annalyn Diaz 1J
Fri Jan 11, 2019 11:01 am
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Kp
Replies: 9
Views: 131

Kp

I understand that K is often used to represent either Kc or Kp and that they are found in the same manner. Why do we use Kp for gases when we could also use Kc? Is one more preferred than the other?
by Annalyn Diaz 1J
Fri Jan 11, 2019 10:57 am
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Liquids in Chemical Equilibrium
Replies: 1
Views: 33

Re: Liquids in Chemical Equilibrium

It’s to my belief that any liquid or solid in its pure form is negligible in calculating the equilibrium constant because their change in concentration during the equilibrium reaction is so small that it’s not counted.
by Annalyn Diaz 1J
Thu Dec 06, 2018 10:01 pm
Forum: Naming
Topic: Final Exam
Replies: 9
Views: 171

Re: Final Exam

For Gail's review session she recommended that we do know both just in case.

The chemical formula of EN is C2H8N2.
The chemical formula of EDTA is C10H16N2O8.
by Annalyn Diaz 1J
Wed Dec 05, 2018 10:50 am
Forum: Calculating pH or pOH for Strong & Weak Acids & Bases
Topic: Kw
Replies: 3
Views: 89

Kw

I’ve seen that Kw=Ka*Kb, but I’ve also seen Kw=10^-14. Can someone clarify that concept for me? Thanks.
by Annalyn Diaz 1J
Wed Dec 05, 2018 10:43 am
Forum: Polyprotic Acids & Bases
Topic: Significance of Polyprotic Acids & Bases
Replies: 6
Views: 193

Significance of Polyprotic Acids & Bases

What is the importance/function of polyprotic acids and bases?
by Annalyn Diaz 1J
Fri Nov 30, 2018 10:37 am
Forum: Properties & Structures of Inorganic & Organic Bases
Topic: Weak Bases with Nitrogen
Replies: 4
Views: 179

Weak Bases with Nitrogen

Dr. Lavelle said something about nitrogen in the compound needing a lone pair or else it can’t act as a base. Can someone remind me why that lone pair is necessary?
by Annalyn Diaz 1J
Fri Nov 30, 2018 10:26 am
Forum: Biological Examples
Topic: Myoglobin vs Hemoglobin
Replies: 2
Views: 48

Re: Myoglobin vs Hemoglobin

To add on, because hemoglobin has 4 myoglobin-like molecules, it therefore has four times the carrying capacity of myoglobin, which is very important for the transport of oxygen in blood.
by Annalyn Diaz 1J
Fri Nov 30, 2018 10:19 am
Forum: Naming
Topic: Transition metal oxidation states
Replies: 3
Views: 52

Re: Transition metal oxidation states

I believe that transition metals can have multiple oxidation states because of their electrons in the 3d orbitals.
by Annalyn Diaz 1J
Sun Nov 25, 2018 5:18 pm
Forum: Octet Exceptions
Topic: Radicals
Replies: 16
Views: 423

Re: Radicals

Quick question, are we going to have to know in-depth about radicals or just know a basic application of it for the final?
by Annalyn Diaz 1J
Sun Nov 25, 2018 5:16 pm
Forum: Formal Charge and Oxidation Numbers
Topic: Formal charge vs octet rule
Replies: 4
Views: 187

Re: Formal charge vs octet rule

I would have to agree, having the most stable molecule possible would be the priority over the octet rule (especially since the octet rule becomes violated in and after period3 due to expanded octets) although for the most part having the octet for elements before period 3 does contribute to the ove...
by Annalyn Diaz 1J
Sun Nov 25, 2018 5:13 pm
Forum: Ionic & Covalent Bonds
Topic: Ionic & covalent character
Replies: 6
Views: 176

Re: Ionic & covalent character

when (if) this happens how can we differentiate between the two characters? I think Dr. Lavelle mentioned a rough guideline based on the difference in electronegativity: if difference is >2, ionic character if difference is <1.5,covalent character It's tougher to determine the character if the elec...
by Annalyn Diaz 1J
Fri Nov 16, 2018 12:53 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Lone Pairs in Molecular Shape
Replies: 4
Views: 79

Re: Lone Pairs in Molecular Shape

I believe that for the most part what you are saying is correct but I’ll clarify just in case. Lone pair electrons do repel the other electrons on the substituent atoms, which cause the bond angle to be slightly greater than what’s normally expected; in the same case, as a result, the bond angle bet...
by Annalyn Diaz 1J
Fri Nov 16, 2018 10:38 am
Forum: Determining Molecular Shape (VSEPR)
Topic: VSEPR Models with 5 bonding regions
Replies: 3
Views: 57

VSEPR Models with 5 bonding regions

It’s pretty easy to see the trends when it comes to VSEPR models with three or even four bonding regions (lone pairs included) but why does having five bonding regions make these trends harder to see? Or rather, why does having 5 domains somehow break the trend?
by Annalyn Diaz 1J
Fri Nov 16, 2018 10:29 am
Forum: Determining Molecular Shape (VSEPR)
Topic: Distance from Central Atom
Replies: 8
Views: 94

Distance from Central Atom

So I understand that in drawing VSEPR diagrams (or even just a 2D representation with Lewis structures) we use the wedges to represent distance from the central atom. For my question, I was confused on which type of wedge indicated a further distance: the completely shaded or the hatched wedges?
by Annalyn Diaz 1J
Fri Nov 09, 2018 10:52 am
Forum: Determining Molecular Shape (VSEPR)
Topic: Tetrahedral molecules
Replies: 4
Views: 74

Re: Tetrahedral molecules

Don’t quote me on this, but I believe that if the shape is tetrahedral, the bond angle should be 109.5° for the most part.
by Annalyn Diaz 1J
Wed Nov 07, 2018 7:03 pm
Forum: Bond Lengths & Energies
Topic: MIDTERM Bond Length Question
Replies: 15
Views: 278

MIDTERM Bond Length Question

There was a question on the midterm about determining the bond length for N-O in NO2, given that the a single bond is 140Å(?) and a double bond is 120Å(?) (I don’t quite remember the units). Any clue on how to determine that?
by Annalyn Diaz 1J
Wed Nov 07, 2018 6:57 pm
Forum: Polarisability of Anions, The Polarizing Power of Cations
Topic: Polarizability
Replies: 2
Views: 85

Re: Polarizability

I believe that having a higher polarity increases the chances of the distortion of electrons because the electrons from one atom are being pulled/attracted more strongly by another atom. In a sense, I think having a larger atomic radius would also increase the chances of electron distortion.
by Annalyn Diaz 1J
Thu Nov 01, 2018 9:37 pm
Forum: Formal Charge and Oxidation Numbers
Topic: Formal Charge of Ions
Replies: 9
Views: 194

Re: Formal Charge of Ions

I think the central charge only contributes to the overall net charge of the atom, so as long as the charge of the central atom in addition to the other atoms equal the overall charge, it'll be fine because that's what you're looking for.
by Annalyn Diaz 1J
Thu Nov 01, 2018 9:31 pm
Forum: Resonance Structures
Topic: Double Bonds and Single Bonds in Resonance Structures
Replies: 3
Views: 83

Double Bonds and Single Bonds in Resonance Structures

I remember from high school chemistry that double bonds are shorter than single bonds. If that's the case, could someone explain why the bond lengths in resonance structures are experimentally the same bond length? I didn't quite get that.
by Annalyn Diaz 1J
Thu Nov 01, 2018 9:23 pm
Forum: Octet Exceptions
Topic: H, He, Li, Be Rule
Replies: 3
Views: 88

Re: H, He, Li, Be Rule

I would think that the first four elements on the periodic table don't need an octet because they would rather lose electrons than gain them. It would be very difficult and unstable if they were to somehow try to get an octet.
by Annalyn Diaz 1J
Wed Oct 24, 2018 10:49 pm
Forum: Electron Configurations for Multi-Electron Atoms
Topic: Electron configurations
Replies: 2
Views: 68

Re: Electron configurations

You can write the shorthand configuration of elements by going back to the nearest noble gas before it (in atomic number), then account for the electrons after that noble gas. Say, for example, you have Arsenic (As). The shorthand would be As: [Ar]4s^2 3d^10 4p^3.
by Annalyn Diaz 1J
Wed Oct 24, 2018 10:39 pm
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: Writing an Electron Configuration Format
Replies: 3
Views: 95

Re: Writing an Electron Configuration Format

Although both are correct, I believe that Dr. Lavelle prefers 1s^2 2s^2 2px^1 2py^1 over the 1s^2 2s^2 2p^2 because it gives better insight on whether or not the electrons are paired.
by Annalyn Diaz 1J
Wed Oct 24, 2018 10:35 pm
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: Subshells/Orbitals
Replies: 5
Views: 158

Re: Subshells/Orbitals

Although I'm not entirely sure which SPECIFIC orbitals the f subshell would have, I do know that it should have 7 orbitals.
(s=1 orbital, p=3 orbitals, d=5 orbitals, f=7 orbitals)
by Annalyn Diaz 1J
Tue Oct 16, 2018 9:46 pm
Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
Topic: Rydberg Equation
Replies: 4
Views: 81

Re: Rydberg Equation

This has become a string of questions for now, but to (hopefully) answer most of the questions, one of the UAs told me that Dr. Lavelle prefers that we use the En = -hR/n^2 equation over the other one because it makes more sense conceptually. In this manner, we won't learn the other version but I th...
by Annalyn Diaz 1J
Tue Oct 16, 2018 9:41 pm
Forum: Heisenberg Indeterminacy (Uncertainty) Equation
Topic: Indeterminacy vs. Uncertainty?
Replies: 4
Views: 116

Indeterminacy vs. Uncertainty?

I understand that the two are the same, but I don't quite remember why Dr. Lavelle prefers "indeterminacy" over "uncertainty"... Can someone clarify that really quick for me?
by Annalyn Diaz 1J
Mon Oct 15, 2018 10:24 am
Forum: DeBroglie Equation
Topic: Rest Mass?
Replies: 4
Views: 113

Rest Mass?

During lecture Dr. Lavelle said that the De Broglie equation only works if the particles have “rest mass”. Can someone clarify what that means?
by Annalyn Diaz 1J
Thu Oct 11, 2018 2:30 pm
Forum: Properties of Light
Topic: HW 1A.7
Replies: 2
Views: 59

Re: HW 1A.7

I believe the original problem (part (b)) asked for the final wavelength to be in picometers, which is 10^-12. Hope that clears it up!
by Annalyn Diaz 1J
Wed Oct 10, 2018 4:44 pm
Forum: Photoelectric Effect
Topic: work function
Replies: 4
Views: 116

Re: work function

The work function is also called the "threshold energy", so watch for that too! The way I remember how the threshold energy function is by relating it in my mind as something similar to "activation energy" because in both cases, if the minimum requirement is not met, then nothing...
by Annalyn Diaz 1J
Wed Oct 10, 2018 4:31 pm
Forum: Properties of Light
Topic: Balmer series vs Lyman series
Replies: 4
Views: 66

Re: Balmer series vs Lyman series

To add on, don't forget that the Balmer series represents the visible region and that the Lyman series represents the ultraviolet region!
by Annalyn Diaz 1J
Wed Oct 03, 2018 10:11 pm
Forum: SI Units, Unit Conversions
Topic: Naming Compounds
Replies: 9
Views: 229

Re: Naming Compounds

Per Dr. Lavelle, over time you'll pick up how to name compounds through working through more problems just like this. To add further elaborate on the post above: -ite : used when the same compound has lesser amount of oxygen (ex. phosphite, PO3) -ate: used when the same compound has the larger amoun...
by Annalyn Diaz 1J
Wed Oct 03, 2018 9:40 pm
Forum: Empirical & Molecular Formulas
Topic: Multiplying to get an integer in the empirical formula
Replies: 4
Views: 131

Re: Multiplying to get an integer in the empirical formula

For an empirical formula, the numbers must be whole numbers, not numbers like 1.33 or 2.5, etc. In such case that you don't get a whole number, you would multiply that by another number to make it whole. But to address your question regarding the threshold for rounding, I believe Dr. Lavelle mention...
by Annalyn Diaz 1J
Wed Oct 03, 2018 9:32 pm
Forum: SI Units, Unit Conversions
Topic: Formula Units??
Replies: 3
Views: 114

Re: Formula Units??

From my understanding, I think you are correct in regards to finding the formula units. I believe you would have to find the amount of moles first, then multiply by Avogadro's number.

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