Search found 58 matches
- Wed Mar 11, 2020 10:45 pm
- Forum: Non-Equilibrium Conditions & The Reaction Quotient
- Topic: Strong/weak acids & bases
- Replies: 14
- Views: 893
Re: Strong/weak acids & bases
yea memorize them
- Wed Mar 11, 2020 10:42 pm
- Forum: Administrative Questions and Class Announcements
- Topic: Format?
- Replies: 11
- Views: 798
Re: Format?
probably similar to the midterm
- Wed Mar 11, 2020 10:41 pm
- Forum: Concepts & Calculations Using First Law of Thermodynamics
- Topic: Meaning of q=-w
- Replies: 14
- Views: 2248
Re: Meaning of q=-w
isothermal reversible expansion
- Wed Mar 11, 2020 10:41 pm
- Forum: General Science Questions
- Topic: Test 2 Grades [ENDORSED]
- Replies: 23
- Views: 1552
Re: Test 2 Grades [ENDORSED]
mine is available on myucla gradebook right now
- Wed Mar 11, 2020 10:40 pm
- Forum: Concepts & Calculations Using Second Law of Thermodynamics
- Topic: spontaneity
- Replies: 39
- Views: 1822
Re: spontaneity
gibbs free energy!!!!
- Wed Mar 11, 2020 10:39 pm
- Forum: Arrhenius Equation, Activation Energies, Catalysts
- Topic: Microscopic Reversibility
- Replies: 3
- Views: 222
Re: Microscopic Reversibility
the same pathway both ways
- Wed Mar 11, 2020 10:37 pm
- Forum: Kinetics vs. Thermodynamics Controlling a Reaction
- Topic: Kinetics v Therodynamics
- Replies: 8
- Views: 538
Re: Kinetics v Therodynamics
i think one is more related to spontaneity and the other is more related to rate
- Wed Mar 11, 2020 10:36 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: Relationship Between Ecell and K
- Replies: 9
- Views: 3153
Re: Relationship Between Ecell and K
I remember my TA writing Ecell>0 than K>0 and vice versa, and you can prove this from the equations
- Wed Mar 11, 2020 10:35 pm
- Forum: Arrhenius Equation, Activation Energies, Catalysts
- Topic: K vs k1/k'1
- Replies: 6
- Views: 1457
Re: K vs k1/k'1
both should work
- Wed Mar 11, 2020 10:34 pm
- Forum: Second Order Reactions
- Topic: Finding out order
- Replies: 22
- Views: 951
Re: Finding out order
yes, if you look at the rate constant and its units
- Wed Mar 11, 2020 10:33 pm
- Forum: Reaction Mechanisms, Reaction Profiles
- Topic: Mechanisms
- Replies: 7
- Views: 632
Re: Mechanisms
According to Khan Academy, "The reaction mechanism describes the sequence of elementary reactions that must occur to go from reactants to products."
- Wed Mar 11, 2020 10:32 pm
- Forum: Reaction Mechanisms, Reaction Profiles
- Topic: Fast Step/Slow Step
- Replies: 7
- Views: 448
Re: Fast Step/Slow Step
^ no matter how "fast" the fast one is the slowest one is always the determinant because each other reaction depends on it to also occur
- Wed Mar 11, 2020 10:30 pm
- Forum: Administrative Questions and Class Announcements
- Topic: "Open Book" Final?
- Replies: 30
- Views: 1946
Re: "Open Book" Final?
im assuming open book means like textbook notes lecture notes etc
- Wed Mar 11, 2020 10:28 pm
- Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
- Topic: HCl and NaOH producing dT
- Replies: 4
- Views: 437
Re: HCl and NaOH producing dT
since mols are the same for each, I looked at volume of soln. where the delta temp change is greatest in the smallest volume. I thought of the soln volume like an absorbant, so the more water there is, the less a rxn will be able to shift its temp as compared to a little volume of water
- Wed Mar 11, 2020 10:27 pm
- Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
- Topic: endo/exo and temp
- Replies: 12
- Views: 1080
Re: endo/exo and temp
in these problems i tend to think of heat as a reactant (endothermic) or product (exothermic). Then depending on an increase or decrease in temp, I use le chatelier's principle treating heat as a R or P
- Wed Mar 11, 2020 10:25 pm
- Forum: Thermodynamic Systems (Open, Closed, Isolated)
- Topic: Kelvin or Celsius?
- Replies: 86
- Views: 5164
Re: Kelvin or Celsius?
it depends on the unit of the gas constant. if its .08206 Latm/Kmol then use Kelvin, but another gas constant COULD have its units in celcius for whatever reason and then you should use celcius (but it probably will never ever come up in real life or a problem)
- Wed Mar 11, 2020 10:24 pm
- Forum: General Rate Laws
- Topic: intermediates
- Replies: 12
- Views: 692
Re: intermediates
yes, since they are made in one step and used up in the next they are not included in the overall final one
- Thu Feb 27, 2020 11:11 pm
- Forum: Balancing Redox Reactions
- Topic: Direction of Reaction
- Replies: 3
- Views: 234
Re: Direction of Reaction
positive E naught is equal to negative delta G meaning spontaneous
- Thu Feb 27, 2020 11:07 pm
- Forum: Gibbs Free Energy Concepts and Calculations
- Topic: 5G.13
- Replies: 8
- Views: 1603
Re: 5G.13
you should use delta G = -RTlnK + RTlnQ.
- Thu Feb 27, 2020 11:01 pm
- Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
- Topic: When to apply Pt into cell diagrams
- Replies: 9
- Views: 499
Re: When to apply Pt into cell diagrams
my TA during discussion says it's always safe to put Pt(s) as the electrode when there is no other metal to act as it
- Thu Feb 27, 2020 10:59 pm
- Forum: Administrative Questions and Class Announcements
- Topic: Test 2 Topics
- Replies: 5
- Views: 838
Re: Test 2 Topics
i think all of electrochem and 2nd page thermodynamics so if its on the electrochem learning outcomes then yes
- Thu Feb 27, 2020 3:29 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: Drawing Cell Diagram
- Replies: 7
- Views: 479
- Wed Feb 19, 2020 11:06 pm
- Forum: Entropy Changes Due to Changes in Volume and Temperature
- Topic: converting T to kelvin
- Replies: 46
- Views: 3278
Re: converting T to kelvin
i would always use the equation sheet and look at the units, especially for constants. for example, .08206 = R, R has units in L, atm, K, and mol. So, on a test you should make sure when plugging into PV=nRT, for example, to match up those units to the R constant.
- Wed Feb 19, 2020 11:04 pm
- Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
- Topic: Adding Inert Gas
- Replies: 20
- Views: 1036
Re: Adding Inert Gas
It increases pressure, but it has no effect on the reaction because volume stays the same and therefore the concentrations of species also do
- Wed Feb 19, 2020 11:00 pm
- Forum: Balancing Redox Reactions
- Topic: Reduction vs. oxidation
- Replies: 29
- Views: 1111
Re: Reduction vs. oxidation
oil rig
oxidation is loss
reduction is gain
oxidation is loss
reduction is gain
- Wed Feb 19, 2020 10:58 pm
- Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
- Topic: Midterm Q6B
- Replies: 5
- Views: 489
Re: Midterm Q6B
From the equation ∆G= ∆H-T∆S. ∆G= ∆H when the second term is close to 0. Therefore, you should find an equation with very little entropy change, which is often when the reactants and products are in the same state with the same amount of moles (best when all solid).
- Wed Feb 19, 2020 10:57 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: midterm Q4
- Replies: 4
- Views: 624
Re: midterm Q4
i think because the pH of the stomach is so acidic and there are already so many H+ floating around that the high pKa of the compound (and the natural dissociation of it) is too weak to "compete" with the already established acidity
- Wed Feb 12, 2020 5:04 pm
- Forum: Ideal Gases
- Topic: STP
- Replies: 12
- Views: 1474
Re: STP
i think 298 is 25+273 and 25 is considered "room temperature" not "standard"
- Wed Feb 12, 2020 5:03 pm
- Forum: Concepts & Calculations Using Second Law of Thermodynamics
- Topic: Entropy of the System for irreversible expansions
- Replies: 8
- Views: 523
Re: Entropy of the System for irreversible expansions
i believe they are the same, or at least you assume its always reversible
- Wed Feb 12, 2020 5:01 pm
- Forum: Non-Equilibrium Conditions & The Reaction Quotient
- Topic: pizza rolls question 2D
- Replies: 2
- Views: 328
Re: pizza rolls question 2D
ignore the solid since it is not apart of the K expression, and multiply the other two together to find Q.
- Wed Feb 12, 2020 5:00 pm
- Forum: Thermodynamic Definitions (isochoric/isometric, isothermal, isobaric)
- Topic: Isothermal Reversible
- Replies: 6
- Views: 355
Re: Isothermal Reversible
maybe there are exceptions but i think for this class and the midterms isothermal is always reversible
- Wed Feb 12, 2020 3:09 am
- Forum: Concepts & Calculations Using Second Law of Thermodynamics
- Topic: Irreversible Expansion
- Replies: 7
- Views: 423
Re: Irreversible Expansion
irreversible expansion refers to a gas expanding against a constant external pressure. use the equation w= -Pex(deltaV)
- Tue Feb 11, 2020 7:07 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: pKa and pKb
- Replies: 4
- Views: 184
Re: pKa and pKb
it just happens to be this way because of the math. its similar to how a higher pH is less H+ concentration, just like how higher pKa is weaker acid
- Tue Feb 11, 2020 7:03 pm
- Forum: Gibbs Free Energy Concepts and Calculations
- Topic: ∆G, ∆H, ∆S
- Replies: 6
- Views: 508
Re: ∆G, ∆H, ∆S
basically, deltaG depends on deltaH and deltaS to be a spontaneous(-) or nonspontaneous(+) rxn. Since it is a new topic i dont think we need to know much more than that
- Tue Feb 11, 2020 7:01 pm
- Forum: Calculating Standard Reaction Entropies (e.g. , Using Standard Molar Entropies)
- Topic: State of matter affect entropy
- Replies: 3
- Views: 252
Re: State of matter affect entropy
typically, liquids occupy more space or are more disorderly than solids, and same for gas and liquids
- Tue Feb 11, 2020 7:00 pm
- Forum: Gibbs Free Energy Concepts and Calculations
- Topic: Midterm Material
- Replies: 10
- Views: 490
Re: Midterm Material
probably only the first page of outline 4
- Tue Feb 11, 2020 6:57 pm
- Forum: Calculating Work of Expansion
- Topic: Midterm equation sheet
- Replies: 16
- Views: 680
Re: Midterm equation sheet
yes im pretty sure
- Sun Feb 02, 2020 10:23 pm
- Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
- Topic: q vs H
- Replies: 9
- Views: 455
Re: q vs H
i think q
- Sun Feb 02, 2020 10:23 pm
- Forum: Phase Changes & Related Calculations
- Topic: Pressure in an Open Beaker
- Replies: 10
- Views: 546
Re: Pressure in an Open Beaker
if u imagine an open beaker, the constant pressure will be the force of air pressure acting down on it from the environment
- Sun Feb 02, 2020 10:22 pm
- Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
- Topic: Enthalpy of Rxn
- Replies: 9
- Views: 390
Re: Enthalpy of Rxn
i personally dont think about multiplying or dividing, i look at the units of each (kJ, and kJ/mole), and i try to format it so the units cancel. i think its called dimensional analysis or something
- Sun Feb 02, 2020 10:21 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Test 1
- Replies: 3
- Views: 205
Re: Test 1
i got mine back in discussion!
- Sun Feb 02, 2020 10:21 pm
- Forum: Thermodynamic Systems (Open, Closed, Isolated)
- Topic: Steam burns
- Replies: 8
- Views: 258
Re: Steam burns
steam has more energy than boiling water at the same temp
- Fri Jan 24, 2020 6:26 am
- Forum: Non-Equilibrium Conditions & The Reaction Quotient
- Topic: Ka and Kb
- Replies: 10
- Views: 480
Re: Ka and Kb
No, strong acids and bases also have Ka and Kb i think, it is just very large (and they also dissociate completely) so there's no real need to use it in problems
- Fri Jan 24, 2020 6:24 am
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Calculating Kp
- Replies: 6
- Views: 241
Re: Calculating Kp
I'm pretty sure you can use partial pressures as well as concentration because partial pressures is based on the similar idea as concentration
- Fri Jan 24, 2020 6:23 am
- Forum: Ideal Gases
- Topic: R Constant
- Replies: 26
- Views: 1100
Re: R Constant
on the equations sheet look at the units for R and make sure they match up with those given in the problem, or those that you may convert to/use
- Fri Jan 24, 2020 6:22 am
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Percent Ionization
- Replies: 11
- Views: 327
Re: Percent Ionization
Yea I always check to see if K is small but if its around like 10 to -3 or -4, you can do the approximation but make sure to check if x is less than 5% of the initial concentration
- Fri Jan 24, 2020 6:20 am
- Forum: Phase Changes & Related Calculations
- Topic: Steam vs. Boiling Water
- Replies: 10
- Views: 445
Re: Steam vs. Boiling Water
there requires a large heat of vaporization (delta H) change to convert water molecules from the liquid to gas phase, so steam has much more "energy" in it
- Fri Jan 24, 2020 6:18 am
- Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
- Topic: k<10^-3
- Replies: 9
- Views: 333
Re: k<10^-3
there's no set number that makes something definitely "weak" or "strong" i'd say but compared to strong acids like HCl, an acid that only dissociates 1 proton per 1000 other molecules is much weaker relatively speaking.
- Sat Jan 18, 2020 4:59 pm
- Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
- Topic: Effect of Temperature on Halogen Reaction (Homework 5J.11)
- Replies: 3
- Views: 166
Re: Effect of Temperature on Halogen Reaction (Homework 5J.11)
it is an endergonic reaction i think so base your answer off delta H
- Sat Jan 18, 2020 4:56 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Acids and Bases Ice Box
- Replies: 5
- Views: 132
Re: Acids and Bases Ice Box
i suggest writing out the chemical reaction taking place and looking at the reactants side. If its like a base dissociating, then use kb, for example.
- Sat Jan 18, 2020 4:54 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Exponents and the K constant
- Replies: 4
- Views: 170
Re: Exponents and the K constant
i dont think you need to know how its derived but prof. jukka keranen teaches you how K is derived in his ls30A lecture if youre interested.
- Sat Jan 18, 2020 4:39 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Percent Ionization
- Replies: 11
- Views: 327
Re: Percent Ionization
yea, and then afterwards do the x value over initial concentration just to double check it is under 5%
- Sat Jan 18, 2020 4:38 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Kc sig figs
- Replies: 4
- Views: 157
Re: Kc sig figs
i think it would be 2 unless otherwise specified but im not too sure
- Sun Jan 12, 2020 11:41 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Calculating K
- Replies: 9
- Views: 201
Re: Calculating K
water is a pure liquid and a solvent. while it "takes part" in the reaction, the change is so small its negligible
- Sun Jan 12, 2020 11:40 pm
- Forum: Ideal Gases
- Topic: Vapor Pressure
- Replies: 4
- Views: 157
Re: Vapor Pressure
the pressure the gas above a liquid exerts down on it
- Sun Jan 12, 2020 11:39 pm
- Forum: Ideal Gases
- Topic: Molar Concentration
- Replies: 4
- Views: 118
Re: Molar Concentration
Usually if there are no products yet and only reactants, the reactants will decrease and the products will increase by a multiple of X depending on the co-efficients.
- Sun Jan 12, 2020 11:36 pm
- Forum: Non-Equilibrium Conditions & The Reaction Quotient
- Topic: Q and K
- Replies: 6
- Views: 374
Re: Q and K
K = equilibrium constant, K is the same for a given reaction at a given temperature. Q = reaction quotient, it is the ratio of P/R at any given moment during a reaction.
- Sun Jan 12, 2020 11:33 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: K's
- Replies: 3
- Views: 125
Re: K's
Kc is when you use concentrations of reactants/products to calculate K and Kp is when you use the partial pressures of the gases