Search found 65 matches

by Casandra
Sun Mar 17, 2019 11:14 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: Le Chatlier Principle
Replies: 7
Views: 736

Re: Le Chatlier Principle

adding a catalyst has no effect on the equilibrium, it just speeds up reaction.
by Casandra
Sat Mar 16, 2019 1:45 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: applying Le Chatelier's Principle
Replies: 4
Views: 231

Re: applying Le Chatelier's Principle

You determine the reaction is not at equilibrium and that Q<K, therefore there is too much reactant, meaning to reach equilibrium the reaction will need to produce more product, thus going in the forward reaction.
by Casandra
Sat Mar 16, 2019 1:40 pm
Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
Topic: Final [ENDORSED]
Replies: 9
Views: 171

Re: Final [ENDORSED]

They should give us the Ecell values needed like in test 2.
by Casandra
Sat Mar 16, 2019 1:37 pm
Forum: Balancing Redox Reactions
Topic: How to tell if its in acidic or basic
Replies: 6
Views: 99

Re: How to tell if its in acidic or basic

They should tell you if it's acidic or basic.
by Casandra
Sat Mar 16, 2019 1:23 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: Standard Conditions
Replies: 2
Views: 205

Re: Standard Conditions

n is the moles of electrons, and to find n you should do the half reactions and determine how many electrons were exchanged in the half reactions.
by Casandra
Thu Mar 07, 2019 12:19 am
Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
Topic: E cell
Replies: 5
Views: 98

Re: E cell

E^o is the standard reduction potential, which means under standard conditions: 1atm, 1M, and at 25 degrees Celsius
E is the cell potential, which changes.
by Casandra
Thu Mar 07, 2019 12:15 am
Forum: General Rate Laws
Topic: Reaction Order
Replies: 4
Views: 76

Re: Reaction Order

For a zero order rate the units are mol/L*s
For a 1st order rate the units are 1/s
For a 2nd order rate the units are L/mol*s
by Casandra
Thu Mar 07, 2019 12:05 am
Forum: Second Order Reactions
Topic: graph for second order
Replies: 7
Views: 126

Re: graph for second order

The graph for a 2nd order reaction is a linear graph with a positive slope.
by Casandra
Thu Mar 07, 2019 12:04 am
Forum: Van't Hoff Equation
Topic: Temp Units
Replies: 11
Views: 316

Re: Temp Units

For the Van Hoff equation you use units of K for temp, and if given in C, convert by adding 273.
by Casandra
Thu Mar 07, 2019 12:02 am
Forum: First Order Reactions
Topic: 1/2 life
Replies: 7
Views: 150

Re: 1/2 life

The 1/2 life for a first order does not depend on the initial concentration.
by Casandra
Wed Mar 06, 2019 11:58 pm
Forum: General Rate Laws
Topic: Which law?
Replies: 2
Views: 60

Re: Which law?

Sometimes the question tells you which order it is, and from there you can determine the rate. Otherwise, there should be sufficient data given to dtermine which rate to use.
by Casandra
Wed Feb 20, 2019 10:51 pm
Forum: Ideal Gases
Topic: units
Replies: 15
Views: 357

Re: units

K doesn't have any units, due to it being a ratio (in which the units cancel)
by Casandra
Wed Feb 20, 2019 10:44 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: When does delta U equal zero?
Replies: 17
Views: 341

Re: When does delta U equal zero?

delta U is equal to zero when the reaction is isothermal, meaning temperature is constant.
by Casandra
Wed Feb 20, 2019 10:42 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: Delta G a state function?
Replies: 23
Views: 324

Re: Delta G a state function?

Gibbs Free Energy is a state function, all the properties of the equation deltaG = deltaH - T(deltaS) are also state functions.
by Casandra
Wed Feb 20, 2019 10:38 pm
Forum: General Science Questions
Topic: Midterm
Replies: 5
Views: 284

Re: Midterm

Ka2 is the second deprotonation of phosphoric acid
by Casandra
Mon Feb 11, 2019 2:12 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Conversions
Replies: 4
Views: 102

Re: Conversions

Most, if not all the equations and conversions we will need are on the constants and formulas page. Of course we do need to know how to rearrange the equations for certain problems.
https://lavelle.chem.ucla.edu/wp-conten ... ations.pdf
by Casandra
Mon Feb 11, 2019 2:06 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Bond enthalpies
Replies: 10
Views: 161

Re: Bond enthalpies

knowing the Lewis structure is helpful but the bond dissociation energies will be given which will also help you figure out how the bonds are formed or broken.
by Casandra
Mon Feb 11, 2019 2:01 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Hess's Law
Replies: 5
Views: 110

Re: Hess's Law

The test should provide the chemical equations, but knowing the format of a combustion and how acids go from HA--> A- + H+
by Casandra
Mon Feb 04, 2019 1:38 pm
Forum: Phase Changes & Related Calculations
Topic: Heat and Condensation
Replies: 9
Views: 133

Re: Heat and Condensation

Condensation releases energy.
by Casandra
Mon Feb 04, 2019 1:34 pm
Forum: Thermodynamic Systems (Open, Closed, Isolated)
Topic: Closed and Isolated
Replies: 10
Views: 143

Re: Closed and Isolated

In a closed system matter can't exchange with the surroundings but energy can in forms of heat or work, a closed system can also have a fixed volume.
In an isolated system nothing exchanges with the surroundings .
by Casandra
Mon Feb 04, 2019 1:32 pm
Forum: Thermodynamic Systems (Open, Closed, Isolated)
Topic: Examples of Open Closed Isolated
Replies: 5
Views: 93

Re: Examples of Open Closed Isolated

In an open system matter and energy can exchange with the surroundings, an example is a beaker of water. In a closed system energy can exchange with the system, an example is a sealed beaker of water. In a isolated system nothing exchanges with the surroundings, an example is a combustion of glucose...
by Casandra
Mon Jan 28, 2019 1:04 am
Forum: Ideal Gases
Topic: pH and pOH
Replies: 18
Views: 503

Re: pH and pOH

The question will ask you to solve for pH or pOH, and the problem will also give you sufficient information to be able to solve for this.
by Casandra
Thu Jan 24, 2019 4:21 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Tricks for identifying Strong/Weak Acids & Bases
Replies: 5
Views: 117

Re: Tricks for identifying Strong/Weak Acids & Bases

Does anyone know of any tips or tricks that will allow you immediately to identify an acid or base as weak or strong? For strong bases and strong acids, it would help to memorize the list of strong acids and bases, because then you know anything that is not a strong base or acid, has to be weak. Al...
by Casandra
Wed Jan 23, 2019 9:39 pm
Forum: Phase Changes & Related Calculations
Topic: ∆Hsub=∆Hfus+∆Hvap
Replies: 3
Views: 61

Re: ∆Hsub=∆Hfus+∆Hvap

How does ∆Hsub=∆Hfus+∆Hvap work? Thanks! Because Enthalpy is a state function, its properties can be added or subtracted. We know that ∆Hvap= Hvapor-Hliguid and that ∆Hfus=Hliquid-Hsolid. For sublimation we are going from a solid to a liquid and a liquid to a vapor, which is two steps, therefore we...
by Casandra
Fri Jan 18, 2019 7:22 pm
Forum: Non-Equilibrium Conditions & The Reaction Quotient
Topic: Pressure
Replies: 3
Views: 85

Pressure

How does a change in pressure affect the equilibrium in a reaction?
by Casandra
Fri Jan 18, 2019 7:18 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Buffers - weak acid
Replies: 4
Views: 88

Re: Buffers - weak acid

Buffers can consist of a weak acid and its conjugate base, as well as the salt. Or vice-versa, a weak base and its conjugate base with the salt.
by Casandra
Fri Jan 18, 2019 7:16 pm
Forum: Non-Equilibrium Conditions & The Reaction Quotient
Topic: Understanding Q
Replies: 9
Views: 132

Re: Understanding Q

Q alone tells you nothing, but once compared to K, it tells you where the reaction is in terms of reaching the equilibrium concentration.
by Casandra
Tue Jan 15, 2019 9:26 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Hydrofluoric Acid
Replies: 3
Views: 70

Re: Hydrofluoric Acid

HF, hydrofluoric acid is a weak acid.
by Casandra
Tue Jan 15, 2019 8:59 pm
Forum: Non-Equilibrium Conditions & The Reaction Quotient
Topic: Equilibrium in relation to K and Q
Replies: 5
Views: 81

Re: Equilibrium in relation to K and Q

Calculating the values of K and Q requires the same process of solving. The only difference is that K tells you the equilibrium of the reaction, whereas Q tells you where you are on the path to equilibrium. This is why Q is useful when comparing it to K.
by Casandra
Tue Jan 15, 2019 8:54 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Aqueous solution
Replies: 2
Views: 53

Aqueous solution

I know solids and liquids aren't included when calculating the equilibrium constant. Are aqueous solution included when calculating the equilibrium constant?
by Casandra
Sat Dec 08, 2018 5:44 pm
Forum: *Making Buffers & Calculating Buffer pH (Henderson-Hasselbalch Equation)
Topic: Final Exam
Replies: 8
Views: 867

Re: Final Exam

Just to be clear we only need to conceptually understand Ka and Kp values and equilibrium constants but we do not actually have to solve for this or use these factors for anything except determining which acid or base is stronger? Yes that's right, we only need to conceptually understand Ka and Kp....
by Casandra
Sat Dec 08, 2018 5:43 pm
Forum: Shape, Structure, Coordination Number, Ligands
Topic: Determining the Coordination number
Replies: 3
Views: 46

Re: Determining the Coordination number

Anna O 1A wrote:Is the coordination number determined by the number of atoms attached to a central atom, the number of bonds (including double and triple) or the number of regions of electron density?

The coordination number is determined by the number of bonds.
by Casandra
Sat Dec 08, 2018 5:41 pm
Forum: Properties & Structures of Inorganic & Organic Acids
Topic: Acid Strength
Replies: 2
Views: 233

Re: Acid Strength

Isabel Nakoud 4D wrote:Why is Structure 2 a stronger acid than Structure 4?

Because the electron withdrawing ability of H is greater than CH3 and as there is more electron withdrawing ability, the acidity increases.
by Casandra
Sat Dec 08, 2018 5:35 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: VSEPR
Replies: 4
Views: 134

Re: VSEPR

jane_ni_3b wrote:For something with the formula AXE3, would the bond angles be 180 because the molecular shape is linear?

Yes the bond angles would be 180 because its shape is linear.
by Casandra
Sat Dec 08, 2018 5:33 pm
Forum: Bronsted Acids & Bases
Topic: How to tell the difference between Lewis + Bronsted
Replies: 1
Views: 90

Re: How to tell the difference between Lewis + Bronsted

I understand the electron/proton acceptor/donor concept, but how can you tell if a molecule is a Lewis acid/base or Bronsted acid/base? Examples would be much appreciated A molecule can be more than one type of acid or base, it just depends on which definition you apply. For most of the problems we...
by Casandra
Sat Dec 08, 2018 5:26 pm
Forum: Coordinate Covalent Bonds
Topic: polydentates
Replies: 5
Views: 267

Re: polydentates

There's no easy way to know whether a coordination compound is polydentate, for this it is helpful to draw the lewis structure. But it is also good to know that bidentate ligands are ethylenediamine (en), and the oxalate ion (ox). Ethylenediaminetetraaceticacid acid (EDTA) is a hexadentate ligand an...
by Casandra
Sat Dec 08, 2018 5:21 pm
Forum: Bronsted Acids & Bases
Topic: Oxoacids
Replies: 1
Views: 82

Re: Oxoacids

For oxoacids, the more electronegative the central atom, the more acidic the molecule will become. For a binary acid, strong acids like HCl are always strong, but the weaker the bond between the nonmetallic and hydrogen bond, the esier it is for H2O to remove the H+
by Casandra
Sat Dec 08, 2018 5:14 pm
Forum: Lewis Structures
Topic: Lewis Acids & Bases
Replies: 3
Views: 237

Re: Lewis Acids & Bases

To tell if an element is a lewis acid or base just remember that a lewis acid is a species that accepts an electron pair like BF3 and a lewis base is a species that donates an electron pair like NH3.
by Casandra
Sat Dec 08, 2018 5:10 pm
Forum: SI Units, Unit Conversions
Topic: Final Time
Replies: 1
Views: 218

Re: Final Time

The time given to us is 3 hours, and its just up to one to distribute the time between each question evenly or however one would like.
by Casandra
Sat Dec 08, 2018 4:55 pm
Forum: Lewis Acids & Bases
Topic: salts in acids and bases
Replies: 2
Views: 37

Re: salts in acids and bases

905085650 wrote:Can someone explain to me the effect that salts have on acids and bases respectively?

Thank you!!

A salt containing an acid will lower the solutions pH whereas a salt containing a base will raise the solutions pH.
by Casandra
Sat Dec 08, 2018 4:41 pm
Forum: Shape, Structure, Coordination Number, Ligands
Topic: Concept of Chelation
Replies: 3
Views: 68

Re: Concept of Chelation

A chelate is a coordination compound containing a ligand bonded to a central at two or more points, usucally froming a ring. so if a coordination compound contains at least one non-monodentate ligand it's considered a chelate. An exapmle is ironn in hemoglobin.
by Casandra
Sat Dec 08, 2018 4:35 pm
Forum: Amphoteric Compounds
Topic: Amphoteric vs. Amphiprotic
Replies: 1
Views: 183

Re: Amphoteric vs. Amphiprotic

905085650 wrote:Can someone explain the difference between amphoteric and amphiprotic and give me an example of each?

Thank you!!

Amphoteric is a compound that can act as a base and an acid, like H2O
Amphiprotic is a substance that can donate and accept protons or H+, like amino acids
by Casandra
Sat Dec 08, 2018 4:12 pm
Forum: Properties & Structures of Inorganic & Organic Acids
Topic: Acids and Bases
Replies: 5
Views: 283

Re: Acids and Bases

404905747 wrote:Is there any easy way to identify a strong acid or strong base besides just memorizing them?

No, just memorize them, and if you have memorized them, then anything that is not a strong acid, is a weak acid.
by Casandra
Sat Dec 08, 2018 4:11 pm
Forum: Properties & Structures of Inorganic & Organic Acids
Topic: Acids and Bases
Replies: 5
Views: 283

Re: Acids and Bases

Some basics are that there is a Lewis and a Bronsted definition to acids and bases. A lewis acid a species that accepts an electron pair(ex. BF3) and a lewis base is a species that donates and electron pair (ex. NH3). Whereas, a bronsted acid is a proton donor and donates a hydrogen ion (ex. HCl) an...
by Casandra
Sat Dec 08, 2018 3:56 pm
Forum: Amphoteric Compounds
Topic: polydentate
Replies: 4
Views: 237

Re: polydentate

What are polydentates and monodentates? Is there a certain list we should memorize? monodentate is a ligand that binds at 1 site and a polydentate is when a ligand binds to more than 1 site. I don't know of there is a list to memorize, but it would be helpful to know that some bidentate ligands are...
by Casandra
Sat Dec 08, 2018 3:49 pm
Forum: Conjugate Acids & Bases
Topic: Strong acids and bases to memorize
Replies: 9
Views: 421

Re: Strong acids and bases to memorize

Why would strong acids be conjugates of weak bases and vis versa? This concept escapes me. A conjugate base is the molecule that is formed after an acid loses a proton. An acid or base and its conjugate are inversely proportional in terms of strength. Therefore the stronger the acid the weaker its ...
by Casandra
Sat Dec 08, 2018 3:37 pm
Forum: Conjugate Acids & Bases
Topic: Strong acids and bases to memorize
Replies: 9
Views: 421

Re: Strong acids and bases to memorize

Strong Acids: HCl, HBr, HI, HNO3, HClO3, HClO4, and H2SO4
Stong Bses: LiOh, NaOH, KOH, RbOH, CsOH, Ca(OH)2, Ba(OH02, and Sr(OH)2
by Casandra
Sat Dec 08, 2018 3:32 pm
Forum: Naming
Topic: en and edta
Replies: 3
Views: 73

Re: en and edta

Bijan Mehdizadeh 1E wrote:Could someone please explain to me what en and edta are?

en and edta are ligands.
en is a neutral ligand named ethylenediamine
edta is an anionic ligand named ethylenediaminetetraacetato
by Casandra
Sat Dec 08, 2018 3:12 pm
Forum: Naming
Topic: Do we have to memorize some of the ligand names?
Replies: 3
Views: 93

Re: Do we have to memorize some of the ligand names?

Will we be asked to name a compound in final? If so, do we have to memorize some of the ligand names? Yes you do have to memorize the ligand names. Lavelle has a link that leads to the name of the ligands on the class website. https://lavelle.chem.ucla.edu/wp-content/supporting-files/Chem14A/Naming...
by Casandra
Sat Dec 08, 2018 3:10 pm
Forum: Lewis Acids & Bases
Topic: H vs H30+
Replies: 2
Views: 72

Re: H vs H30+

Soyoung Park 1H wrote:How are hydrogen atoms and hydronium ions the same?

H+ and H3O+ are the same in that the hydronium ion is just the H+ attached to a water molecule.
by Casandra
Sat Nov 10, 2018 6:07 pm
Forum: Resonance Structures
Topic: Bond Lengths
Replies: 6
Views: 401

Re: Bond Lengths

[quote="Daniela Alvarado 3B"]Does the bond length change depending on where the double bond is in the resonance structures?[/quot The bond lengths are the average all the bonds in the resonance structures , so where the double bond is in the resonance structure is already taken into consid...
by Casandra
Sat Nov 10, 2018 5:44 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Shapes
Replies: 5
Views: 113

Re: Shapes

Are all molecules with four bonding pairs tetrahedral? What makes the difference if they are not? All molecules with four bonding pairs and no lone pairs are tetrahedral. But if there was a lone pair, then it would be a trigonal pyramid, and so on. If a molecule has more or less than four bonding p...
by Casandra
Sat Nov 10, 2018 5:37 pm
Forum: Ionic & Covalent Bonds
Topic: Dissociation Energy
Replies: 3
Views: 107

Re: Dissociation Energy

Why is the dissociation energy of a covalent bond, like N2, 932 kJ/mol and an ionic bond's, like NaCl, is -250 kJ/mol? (I wrote these down on my notes from the lecture). Since ionic bonds are stronger, wouldn't it have a much higher dissociation energy than N2? Why is it's dissociation energy negat...
by Casandra
Sun Nov 04, 2018 3:47 pm
Forum: Octet Exceptions
Topic: Lewis acids and bases
Replies: 3
Views: 103

Re: Lewis acids and bases

What are some other examples of Lewis acids and bases other than the examples from lecture? A lewis base is a molecule that will donate a pair of electrons to another atom. Some examples are NH3 and F-. A lewis acid is a molecule that will accept a pair of electrons. Some examples are AlCl3 and BH3.
by Casandra
Sun Nov 04, 2018 3:41 pm
Forum: Lewis Structures
Topic: Exceptions to the Octet Rule
Replies: 4
Views: 62

Re: Exceptions to the Octet Rule

claireg wrote:What are some examples of elements in compounds that exemplify exceptions to the octet rule and the reasons behind them?

Exceptions to the octet rule are atoms like, phosphorus, Sulfur, and Chlorine, this is because these elements have the d-orbital.
by Casandra
Sun Nov 04, 2018 3:38 pm
Forum: Photoelectric Effect
Topic: intensity
Replies: 4
Views: 115

Re: intensity

how does increasing the intensity of the incoming photon affect the energy of the photon. Does it increase its energy, and if so, does that increase the number of electrons that will be emitted? Increasing the intensity increases the number of photons, because intensity and the number of photons ar...
by Casandra
Sun Oct 28, 2018 4:44 pm
Forum: Trends in The Periodic Table
Topic: Exceptions to electron configuration
Replies: 3
Views: 159

Re: Exceptions to electron configuration

How are the exceptions to electron configuration determined? It explains in the textbook why they set up the configuration in certain elements this way but what differentiates copper and another metal? The exceptions to electron configuration are the groups of 6( chromium) and 11(copper). These two...
by Casandra
Sun Oct 28, 2018 4:31 pm
Forum: Lewis Structures
Topic: octets
Replies: 13
Views: 265

Re: octets

How can you distinguish if an element has a full octet? Does each orbital have to have a full octet before moving to the next orbital? Only noble gasses in their natural state have an octet. However, there are two ways to figure out how many electrons an element needs to complete an octet. One, you...
by Casandra
Sun Oct 28, 2018 4:22 pm
Forum: Ionic & Covalent Bonds
Topic: Trend of Ionic Radii
Replies: 5
Views: 92

Re: Trend of Ionic Radii

The radius increases you go down a group(column) and the radius decreases as you go from left to right of a period.
by Casandra
Fri Oct 12, 2018 9:13 am
Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
Topic: Balmer and Lyman series
Replies: 4
Views: 86

Re: Balmer and Lyman series

Why are these important? What are they? The Balmer and Lyman series are important because they help determine the energy level of electrons, and this is important when using Rydberg's equation. The Balmer series is used when in the visible spectrum, with n1=2. The Lyman series is used in the UV spe...
by Casandra
Thu Oct 11, 2018 11:14 pm
Forum: *Black Body Radiation
Topic: The Importance of Black Body Radiation (?)
Replies: 5
Views: 349

Re: The Importance of Black Body Radiation (?)

In Monday's notes we wrote that the description if light as photons explains the intensity profile of black body radiation but have yet to talk about it again. Are we supposed to know the concept/definition of black body radiation? Is there any importance or significance to black body radiation? Gr...
by Casandra
Thu Oct 11, 2018 11:05 pm
Forum: Properties of Light
Topic: How light behaves
Replies: 8
Views: 204

Re: How light behaves

I cannot conceptualize light being both photon (PACKETS) of energy and wavelengths. I find it difficult to exercise this into equations when I do not understand how it can be both and have one number. Please explain and possibly use equations in your explanation if possible. If not that is okay, an...
by Casandra
Fri Oct 05, 2018 12:53 pm
Forum: Accuracy, Precision, Mole, Other Definitions
Topic: answer accuracy
Replies: 4
Views: 126

Re: answer accuracy

When I solve problems I don’t round until the very end and keep all my sigfigs but sometimes the answer I get is 0.01-0.02 digits different from the one in the solution manual. Will this be a big problem on the homework/test? I would ask your TA, because they will be grading our homework and test, ...
by Casandra
Fri Oct 05, 2018 12:34 pm
Forum: Properties of Light
Topic: Energy Function
Replies: 1
Views: 46

Re: Energy Function

In the equation E= -hR/n^2 h, represent Plank's constant which is 6.626x10^-34J/s R, is Rydberg's constant which is 3.29x10^15 Hz n, is the number of the energy level of an electron (this is the quantized value) Overall, this contributes to finding the amount of energy contained in one electron whil...
by Casandra
Fri Oct 05, 2018 12:17 pm
Forum: SI Units, Unit Conversions
Topic: SI Units on tests
Replies: 5
Views: 159

Re: SI Units on tests

I would expect that he would want us to write our final answers in SI units unless otherwise stated, like if the final answer is looking for an answer in g as opposed to kg. I do know that our TA's are grading our exams, therefore it might vary per TA too.

Go to advanced search