Search found 149 matches

by jisulee1C
Sat Mar 14, 2020 5:18 pm
Forum: Administrative Questions and Class Announcements
Topic: Final Submission
Replies: 8
Views: 64

Re: Final Submission

lavelle said the final will be on CCLE so we would submit the final online on CCLE
by jisulee1C
Sat Mar 14, 2020 5:11 pm
Forum: Arrhenius Equation, Activation Energies, Catalysts
Topic: Catalyst's effect on overall reaction
Replies: 7
Views: 31

Re: Catalyst's effect on overall reaction

Usually it is written if it is a slow step but if not assuming it's this problem we are looking at the activation energies. The step that takes the most activation energy will be the slowest step because it requires a lot of energy to overcome the barrier.
by jisulee1C
Sat Mar 14, 2020 5:10 pm
Forum: Administrative Questions and Class Announcements
Topic: Where to find the final exam
Replies: 5
Views: 30

Re: Where to find the final exam

There was an email sent out the final will be on CCLE and is 3 hours and 30 minutes (starts Sunday 11:15am and ends 2:45pm, extra 30 minutes for logging on). I'm pretty sure it's just filling out and answering online on CCLE so we won't have to print it out.
by jisulee1C
Sat Mar 14, 2020 8:11 am
Forum: Arrhenius Equation, Activation Energies, Catalysts
Topic: Catalyst's effect on overall reaction
Replies: 7
Views: 31

Re: Catalyst's effect on overall reaction

since the slow step is the rate determining step, changing the activation energy of an already fast step will not change the rate because it is not changing the rate of the slow step
by jisulee1C
Sat Mar 14, 2020 8:10 am
Forum: *Enzyme Kinetics
Topic: Heterogeneous catalyst
Replies: 3
Views: 11

Re: Heterogeneous catalyst

adsorption refers to the physical contact of reactants with the surface of a catalyst in a different state and it is when reactants sit on the surface of a catalyst versus absorption which is when the reactant breaches the surface of the catalyst therefore I would interpret it as being a liquid on t...
by jisulee1C
Sat Mar 14, 2020 8:07 am
Forum: Reaction Mechanisms, Reaction Profiles
Topic: How to determine the number of intermediates?
Replies: 1
Views: 14

Re: How to determine the number of intermediates?

since there are three peaks there are three overall steps in the reaction
for there to be intermediates they have to form in one reaction and be used up in another
therefore there are two intermediates involved in the three step reaction
by jisulee1C
Sat Mar 14, 2020 8:06 am
Forum: Arrhenius Equation, Activation Energies, Catalysts
Topic: Catalysts
Replies: 8
Views: 26

Re: Catalysts

a homogenous catalyst is in the same phase or state as the reactants and if it were a homogenous catalyst would absorb being in the same state of matter therefore we wouldn't consider adsorption since there is no contact between substances of different physical states while a heterogeneous catalyst ...
by jisulee1C
Sat Mar 14, 2020 8:01 am
Forum: Balancing Redox Reactions
Topic: QD3 Midterm
Replies: 5
Views: 35

Re: QD3 Midterm

At the pH of 6 you are assuming that the acetic acid dissolves into a higher concentration of it's conjugate base CHCH3COO- because the pKa (of acetic acid) =4.75 and the conjugate acid has a change of -1.
by jisulee1C
Sat Mar 14, 2020 7:56 am
Forum: *Enzyme Kinetics
Topic: 7.17
Replies: 3
Views: 16

Re: 7.17

An intermediate and catalyst are not the same thing as in an intermediate is produced and used up during the reaction while a catalyst is not used up in the reaction. You can tell if a catalyst is used if the activation energy is lower than before, you are assuming the intermediate steps involve cat...
by jisulee1C
Sat Mar 14, 2020 7:49 am
Forum: Reaction Mechanisms, Reaction Profiles
Topic: Slow step
Replies: 3
Views: 17

Re: Slow step

It should be given. If not given you can substitute values in to this step's rate law. When the rate law, which now includes these substituted values, matches with the overall rate law, then the rate-determining step has been found. This is assuming that every step is the slow one and finding the ac...
by jisulee1C
Fri Mar 13, 2020 6:18 pm
Forum: Reaction Mechanisms, Reaction Profiles
Topic: Slow Step Mechanism
Replies: 7
Views: 27

Re: Slow Step Mechanism

It is written in the problem whether or not the step is slow or not. If a step is slow you can assume there is a high activation energy, or the forward reaction is not spontaneous and therefore the reverse reaction does not occur for a slow step.
by jisulee1C
Fri Mar 13, 2020 6:17 pm
Forum: Reaction Mechanisms, Reaction Profiles
Topic: Identifying First and Second Order
Replies: 3
Views: 19

Re: Identifying First and Second Order

you can look at the graphs, look at the units for the rate constant, and also determine using a table of concentrations
by jisulee1C
Fri Mar 13, 2020 6:16 pm
Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
Topic: electromotive force
Replies: 2
Views: 10

Re: electromotive force

electromotive force (emf) is mentioned as the same as the cell potential of a cell (voltage).
by jisulee1C
Fri Mar 13, 2020 6:14 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Reduction Potential
Replies: 4
Views: 12

Re: Reduction Potential

even if both are negative the more negative would still be the anode
if the total Ecell is negative then you can assume that it is not spontaneous in the forward reaction and however may proceed spontaneously in the opposite direction
by jisulee1C
Fri Mar 13, 2020 6:11 pm
Forum: Second Order Reactions
Topic: Termolecular
Replies: 15
Views: 273

Re: Termolecular

termolecular reactions are rare because all three molecules must collide simultaneously for it to occur. the more molecules needed, the lower the probability of the reaction occurring because they would all need to collide with a certain energy, speed, and in a certain direction to cause the reaction.
by jisulee1C
Fri Mar 13, 2020 6:09 pm
Forum: Thermodynamic Definitions (isochoric/isometric, isothermal, isobaric)
Topic: Isochoric/isometric
Replies: 4
Views: 26

Re: Isochoric/isometric

Isochoric process = constant volume and isometric means the same thing as isochoric.
by jisulee1C
Fri Mar 13, 2020 6:04 pm
Forum: Concepts & Calculations Using Second Law of Thermodynamics
Topic: Irreversible System
Replies: 2
Views: 15

Re: Irreversible System

Isothermal means a constant temperature, so we can use the formula ΔS = nR ln(V2/V1).Since entropy is a state function, only the initial and final states matter, not the pathway taken to get there. In this case for irreversible free expansion, the expansion is very fast therefore the surroundings do...
by jisulee1C
Fri Mar 13, 2020 5:57 pm
Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
Topic: Manipulating Cathode or Anode Concentration
Replies: 1
Views: 17

Re: Manipulating Cathode or Anode Concentration

In the nernst equation: E = Eo -(RT/nF)ln Q since the anode foes on top and cathode foes on the bottom for Q, as the reaction progresses, the concentration of the left (oxidation) anode as the solid electrode dissolves while the concentration in the right (reduction) cathode decreases as the electro...
by jisulee1C
Fri Mar 13, 2020 5:51 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: Midterm 3B
Replies: 2
Views: 29

Re: Midterm 3B

Because the two solutions HCl (a strong acid) and NaOH (a strong base) are reacting, the most enthalpy is produced because the answer choice B has both in their highest concentrations (both at 2M). Both strong will create the largest delta T in their strongest concentration because a neutralisation ...
by jisulee1C
Fri Mar 13, 2020 5:38 pm
Forum: Second Order Reactions
Topic: Second Order Rxn
Replies: 2
Views: 16

Re: Second Order Rxn

Once you plot the second order graph using 1/concentration versus time you can find slope which = k.
by jisulee1C
Fri Mar 13, 2020 5:28 pm
Forum: Entropy Changes Due to Changes in Volume and Temperature
Topic: relationship between entropy and enthalpy
Replies: 2
Views: 18

Re: relationship between entropy and enthalpy

at constant temperature and pressure, the two are related through this equation: ∆S=∆H/T (from ∆G = ∆H - T∆S, when ∆G = 0)
by jisulee1C
Thu Mar 12, 2020 10:38 pm
Forum: Reaction Mechanisms, Reaction Profiles
Topic: Methods
Replies: 3
Views: 18

Re: Methods

He said for the class pre-equilibrium would be used.
by jisulee1C
Thu Mar 12, 2020 10:33 pm
Forum: Method of Initial Rates (To Determine n and k)
Topic: K
Replies: 3
Views: 19

Re: K

k (the rate constant) units depend on the order of a reaction (which can be found online). For a first order reaction the units are 1/s, for a second order reaction the units are 1/ms. as for the K (equilibrium constant) there are no units.
by jisulee1C
Thu Mar 12, 2020 10:29 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Week 10 Review Problems
Replies: 4
Views: 31

Re: Week 10 Review Problems

Yes, you need to have a conducting solid metal for both the anode and cathode.
by jisulee1C
Thu Mar 12, 2020 11:13 am
Forum: Kinetics vs. Thermodynamics Controlling a Reaction
Topic: Textbook question 7.23
Replies: 2
Views: 14

Re: Textbook question 7.23

Increasing the pH would mean that the solution is becoming more basic with more OH- ions. And because the OH- ions are products of the first step of the mechanism (the fast equilibrium step), increasing the pH, increases OH-, which increases the amount of products favoring the reverse reaction there...
by jisulee1C
Thu Mar 12, 2020 11:09 am
Forum: Kinetics vs. Thermodynamics Controlling a Reaction
Topic: Textbook question 7.17
Replies: 4
Views: 22

Re: Textbook question 7.17

The third step when looking at the illustration is doesn't take a lot of potential energy and therefore is one of the fast steps. However, since the overall reaction rate depends on the slow step as the rate-determining step, since adding a catalyst to accelerate third step doesn't accelerate the sl...
by jisulee1C
Wed Mar 11, 2020 9:07 pm
Forum: Zero Order Reactions
Topic: Orders
Replies: 8
Views: 37

Re: Orders

the order can also be determined by the given rate constant and the units or from a table with given concentrations and rates
by jisulee1C
Wed Mar 11, 2020 9:05 pm
Forum: General Science Questions
Topic: Chemistry Final
Replies: 16
Views: 151

Re: Chemistry Final

I don't think there will be the same three hour time limit as was scheduled before because he wrote "The three-hour closed-book exam that was scheduled for Sunday is also cancelled."
by jisulee1C
Wed Mar 11, 2020 9:04 pm
Forum: Administrative Questions and Class Announcements
Topic: final
Replies: 14
Views: 132

Re: final

In its place will be a short, straightforward, open-book, take-home final posted on my class website. Again, I will email you the link when the take home final is posted on my class website along with instructions. He sent ^^ this in the most recent email so for now it's going to be a take home fina...
by jisulee1C
Wed Mar 11, 2020 5:55 pm
Forum: Arrhenius Equation, Activation Energies, Catalysts
Topic: Catalysis
Replies: 11
Views: 32

Re: Catalysis

Catalysis is the process of increasing the rate of a chemical reaction by adding a substance known as a catalyst and are purely mechanisms that lower activation energy and are not included in the equation, therefore, they will not be in the rate law
by jisulee1C
Wed Mar 11, 2020 5:54 pm
Forum: General Rate Laws
Topic: Fast and Slow Step Reactions
Replies: 5
Views: 23

Re: Fast and Slow Step Reactions

The slow step is the rate determining step and therefore we use the slow step when determining the rate of the reaction mechanism.
by jisulee1C
Wed Mar 11, 2020 5:53 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: concentration cells
Replies: 3
Views: 17

Re: concentration cells

Changing the mass of the cathode doesn't change the concentration of the cathode solution therefore changing the mass of the electrode would have no change / affect on the cell potential.
by jisulee1C
Wed Mar 11, 2020 5:38 pm
Forum: Reaction Mechanisms, Reaction Profiles
Topic: Fast Step/Slow Step
Replies: 7
Views: 28

Re: Fast Step/Slow Step

Usually for the reaction mechanism it states whether or not the reaction is fast or slow. If the reaction step is slow than that is the rate determining step for the reaction. In addition you would know that the reverse reaction for the slow step is almost nonexistent while for the fast reaction the...
by jisulee1C
Wed Mar 11, 2020 5:21 pm
Forum: Administrative Questions and Class Announcements
Topic: Test 2
Replies: 3
Views: 33

Re: Test 2

I am pretty sure your TA will send an email about picking up test 2.
by jisulee1C
Wed Mar 11, 2020 5:21 pm
Forum: Arrhenius Equation, Activation Energies, Catalysts
Topic: Catalysts
Replies: 2
Views: 10

Re: Catalysts

Catalysts provide an alternative pathway with a lower activation energy therefore affecting the kinetics of the reaction by speeding up the rate of both the forward and reverse reactions.
by jisulee1C
Wed Mar 11, 2020 3:10 pm
Forum: Balancing Redox Reactions
Topic: Ecell values
Replies: 12
Views: 47

Re: Ecell values

Since most tables give the reduction potential for the half reaction, the higher (more positive) reduction potential determines the cathode which is the species that will undergo reduction.
by jisulee1C
Wed Mar 11, 2020 3:08 pm
Forum: General Rate Laws
Topic: Rate limiting step
Replies: 13
Views: 40

Re: Rate limiting step

the rate limiting step is the slowest step
by jisulee1C
Wed Mar 11, 2020 3:05 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: text problem 4A.9
Replies: 2
Views: 16

Re: text problem 4A.9

You are assuming for this problem that the heat (q) lost by the water is equivalent to the heat (q) gained by the calorimeter (in this case the copper pot?) therefore you can use mc(delta)T=mc(delta)T to calculate the heat lost by the water and find the final temperature of the water.
by jisulee1C
Wed Mar 11, 2020 12:11 pm
Forum: Arrhenius Equation, Activation Energies, Catalysts
Topic: Catalysts vs. Intermediates
Replies: 8
Views: 25

Re: Catalysts vs. Intermediates

A catalyst cannot be an intermediate because intermediates are produced by the reaction and used up in another following step of the reaction mechanism while a catalyst is not used up during the reaction. Because a catalyst is not used up, a small amount can be used to speed up the reaction and cont...
by jisulee1C
Wed Mar 11, 2020 12:09 pm
Forum: Administrative Questions and Class Announcements
Topic: Review Packet
Replies: 5
Views: 84

Re: Review Packet

Lavelle just sent out an email with a link to his week 10 review powerpoint slides.
by jisulee1C
Wed Mar 11, 2020 12:17 am
Forum: Equilibrium Constants & Calculating Concentrations
Topic: memorizing acids?
Replies: 4
Views: 30

Re: memorizing acids?

I would memorize the strong acids. There are 7 strong acids: chloric acid, hydrobromic acid, hydrochloric acid, hydroiodic acid, nitric acid, perchloric acid, and sulfuric acid. Knowing which acids are strong are important to solve problems for dissociation, Ka, and pH of the solution.
by jisulee1C
Wed Mar 11, 2020 12:09 am
Forum: Arrhenius Equation, Activation Energies, Catalysts
Topic: Derivation of Arrhenius Equation
Replies: 6
Views: 28

Re: Derivation of Arrhenius Equation

I think this equation is derived using the Arrhenius equation for two different temperatures but it is not on the objectives sheet as something we need to do. Instead, I would memorize the equation because it is useful and not on the equations sheet.
by jisulee1C
Wed Mar 11, 2020 12:06 am
Forum: Arrhenius Equation, Activation Energies, Catalysts
Topic: 7E.1
Replies: 3
Views: 21

Re: 7E.1

Because a catalyst only affects the reaction rate because it provides a separate pathway with a lower activation energy the reaction rates will increase (be faster) while changing the rates (due to kinetics) has no effect on thermodynamics and therefore there is no change for delta H of the reaction.
by jisulee1C
Wed Mar 11, 2020 12:04 am
Forum: Student Social/Study Group
Topic: Lyndon Review
Replies: 6
Views: 114

Re: Lyndon Review

I believe all review sessions will be canceled.
by jisulee1C
Tue Mar 10, 2020 8:55 pm
Forum: Method of Initial Rates (To Determine n and k)
Topic: Memorization?
Replies: 4
Views: 44

Re: Memorization?

The integrated rate laws are on the constants and equations sheet but you have to know which rate law corresponds to which order reaction. In addition, it also has the half life equations. I think for outline 6 it states that one of the objectives is to ... Know how to derive the differential and in...
by jisulee1C
Tue Mar 10, 2020 8:52 pm
Forum: Administrative Questions and Class Announcements
Topic: Chemistry 14B Final
Replies: 9
Views: 126

Re: Chemistry 14B Final

I think Lavelle finished his course outline and the topics so if anything maybe practice problems and explanations will be posted online or on Bruincast. If posted on Bruincast you can usually access the media files through UCLA CCLE.
by jisulee1C
Tue Mar 10, 2020 8:48 pm
Forum: Student Social/Study Group
Topic: Curve?
Replies: 31
Views: 825

Re: Curve?

The curve utilizes the total number of points that you can earn and factors in the highest student's score but I think it varies each quarter depending on the student's scores on tests, the final, and midterm.
by jisulee1C
Tue Mar 10, 2020 8:44 pm
Forum: Phase Changes & Related Calculations
Topic: Phase changes
Replies: 8
Views: 56

Re: Phase changes

What calculation do we also have to incorporate when going from a gas to a liquid or vice versa? When calculating q for the reaction you can use the phase change graph and calculate the different q for both the heating and the phase change to calculate the q for the phase change from liquid to gas ...
by jisulee1C
Tue Mar 10, 2020 2:19 am
Forum: General Rate Laws
Topic: 7A.15
Replies: 6
Views: 31

Re: 7b.15

it depends on whether the reaction is the elementary rate law. If the reaction is the elementary reaction one can assume that the exponent is the order in relation to the reactant. Therefore if b is squared the it is in second order while if a is to the power of 1 it is in first order. If you cannot...
by jisulee1C
Tue Mar 10, 2020 2:14 am
Forum: Reaction Mechanisms, Reaction Profiles
Topic: Determining reaction rate for overall reaction
Replies: 3
Views: 19

Re: Determining reaction rate for overall reaction

Usually the proposed reaction mechanism has steps that are labeled with either slow or fast which can be used to determine which step is the rate determining step and therefore calculate the rate of the reaction.
by jisulee1C
Tue Mar 10, 2020 1:47 am
Forum: First Order Reactions
Topic: Determining Order
Replies: 7
Views: 31

Re: Determining Order

It depends on how the problem is given to you. If there is the chart, with different concentrations and rates you can determine the order with respect to a reactant. Or if the rate constant is given in units you can determine the overall reaction order.
by jisulee1C
Tue Mar 10, 2020 1:46 am
Forum: Reaction Mechanisms, Reaction Profiles
Topic: 7D.2 collision theory equation?
Replies: 1
Views: 33

Re: 7D.2 collision theory equation?

None of the homework questions in this section required you to use the collision frequency equation so I am assuming that being familiar with the concepts is more important.
by jisulee1C
Tue Mar 10, 2020 1:43 am
Forum: Arrhenius Equation, Activation Energies, Catalysts
Topic: 7D.7
Replies: 1
Views: 13

Re: 7D.7

After finding the equilibrium constant for the reaction which can be calculated by dividing the forward reaction constant by the reverse rate constant = 0.676. Because the equilibrium constant is less than 1, reactants (the reverse reaction) is favored there this is an endothermic reaction because i...
by jisulee1C
Sun Mar 01, 2020 9:46 pm
Forum: Balancing Redox Reactions
Topic: anode/cathod reversible
Replies: 4
Views: 35

Re: anode/cathod reversible

To determine which half reaction is the cathode and anode you have to look at the standard reduction potential. For Co2+ reaction the standard reduction potential is -0.28V and for the Ce4+ reaction the standard reduction potential is +1.61V. Since Ce4+ reaction has a more positive higher voltage it...
by jisulee1C
Sun Mar 01, 2020 9:34 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: 5G. 13
Replies: 2
Views: 40

Re: 5G. 13

Since the problem is asking to calculate the reaction Gibbs Free energy at 1200K and standard conditions are at 298K the given K is at standard condition. Since the reaction is not at standard condition to calculate the total Gibbs Free energy of the reaction you have to calculate both the standard ...
by jisulee1C
Wed Feb 12, 2020 4:11 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Multistep reactions
Replies: 6
Views: 64

Re: Multistep reactions

Yep. The K would be 1/41 because that's the inverse.
by jisulee1C
Wed Feb 12, 2020 4:10 pm
Forum: Thermodynamic Definitions (isochoric/isometric, isothermal, isobaric)
Topic: Adiabatic process
Replies: 3
Views: 38

Re: Adiabatic process

Since an adiabatic process has no transfer of heat q = 0 therefore the only energy would be as work. For a reversible expansion the temperature stays constant so I think the temperature would be greater for an irreversible expansion compared to a reversible expansion.
by jisulee1C
Wed Feb 12, 2020 3:19 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: Pizza Rolls 5H
Replies: 1
Views: 25

Re: Pizza Rolls 5H

Pb lead which has 82 electrons has a higher molar entropy than C carbon which has 6 electrons because overall lead has more particles (82 protons / 82 electrons and some number of neutrons) than carbon which has only 6 protons / 6 electrons and some lower number of neutrons. Because lead has more pa...
by jisulee1C
Wed Feb 12, 2020 3:14 pm
Forum: Concepts & Calculations Using Second Law of Thermodynamics
Topic: spontaneity
Replies: 34
Views: 224

Re: spontaneity

Gibbs Free Energy. If delta G is negative you know that the forward reaction is spontaneous.
by jisulee1C
Wed Feb 12, 2020 3:09 pm
Forum: Entropy Changes Due to Changes in Volume and Temperature
Topic: Pizza Rolls #5
Replies: 5
Views: 78

Re: Pizza Rolls #5

Use the Cv of the ideal gas for both because they are ideal gases. Ideal gas, Cv = (3/2) R. and plug into the equation to calculate the change of entropy of change of volume.
by jisulee1C
Wed Feb 12, 2020 8:31 am
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Multistep reactions
Replies: 6
Views: 64

Re: Multistep reactions

For the problem given it's not a multistep reaction. In fact, you are asked to manipulate the K of the given chemical reaction to find the other K values. For example A since the reaction is reversed you would find the inverse of the given K to find the new K value for the new reaction.
by jisulee1C
Wed Feb 12, 2020 8:28 am
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Hess' Law with formulas of combustion and formation
Replies: 1
Views: 19

Re: Hess' Law with formulas of combustion and formation

This would depend on the problem. But for the given enthalpies such as the enthalpy of formation they usually give it in KJ or J/ mol and you can manipulate that value depending on how much reactant they give. If no values are given, 1 mol can be used.
by jisulee1C
Wed Feb 12, 2020 8:25 am
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Strong Acids
Replies: 2
Views: 23

Re: Strong Acids

There are common strong acids and bases. For acids there is HClO4 , HCl, HBr, HI, HNO3, and H2SO4 although there is the pattern of halogens forming strong acid because they easily dissociate it's better to memorize the more common strong acids and bases.
by jisulee1C
Tue Feb 11, 2020 6:03 pm
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: Enthalpy
Replies: 12
Views: 77

Re: Enthalpy

A state function means that only the initial state and final state are needed to determine the value. I think Lavelle's example of how only the initial and final destinations matter when you hike a mountain and how the pathway you took is irrelevant explains conceptually what a state function is.
by jisulee1C
Tue Feb 11, 2020 6:01 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: When is q equal to dH
Replies: 1
Views: 17

Re: When is q equal to dH

q is equal to delta H if there is constant pressure
by jisulee1C
Tue Feb 11, 2020 6:00 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: 5 Percent Rule
Replies: 1
Views: 19

Re: 5 Percent Rule

Yes, you use the five percent rule to check if the product concentration formed is less than five percent of the initial concentration which allows you to use the approximation. Use the reactant with the smallest concentration given. If it passes the five percent rule for the smaller concentration t...
by jisulee1C
Tue Feb 11, 2020 5:58 pm
Forum: Entropy Changes Due to Changes in Volume and Temperature
Topic: Entropy of Surroundings vs Entropy of Systems
Replies: 1
Views: 15

Re: Entropy of Surroundings vs Entropy of Systems

In a reversible reaction there is a change of entropy and because it is isothermal delta U will be zero. However, in an irreversible reaction there is no work done because only free expansion occurs. Therefore since w = 0 and delta U = 0 the q = 0 so the q of surroundings =0 and delta S of the surro...
by jisulee1C
Tue Feb 11, 2020 5:50 pm
Forum: Calculating Standard Reaction Entropies (e.g. , Using Standard Molar Entropies)
Topic: Standard Molar Entropies
Replies: 1
Views: 19

Re: Standard Molar Entropies

According to the second law of thermodynamics the entropy of a system will increase over time because the universe is always tending toward disorder. Thus standard molar entropies are positive.
by jisulee1C
Tue Feb 11, 2020 5:47 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: pKa and pKb
Replies: 4
Views: 27

Re: pKa and pKb

A greater pKa results in a smaller Ka because pKa = -log Ka. If you plug in values you can see that a stronger acid will have a larger Ka and thus a smaller pKa.
by jisulee1C
Tue Feb 11, 2020 5:46 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Bond Enthalpies
Replies: 1
Views: 23

Re: Bond Enthalpies

I am assuming that since the problem in the review session included the structure of glucose, you won't need to remember the structure and instead will be tested on whether or not you understand the concept of calculating delta H of the reaction using bond enthalpies.
by jisulee1C
Tue Feb 11, 2020 5:39 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Acid base titrations
Replies: 2
Views: 32

Re: Acid base titrations

In an acid base titration the acid is reacting with the base to form water H2O. Therefore when writing out chemical reactions, the acid and base can react to form water. Depending on whether the acid or base is strong or weak will influence the reaction however in the example HBr + KOH = H2O + KBr f...
by jisulee1C
Tue Feb 11, 2020 5:37 pm
Forum: Calculating Work of Expansion
Topic: Constant pressure in a calorimeter
Replies: 3
Views: 37

Re: Constant pressure in a calorimeter

In a reaction there are variables that change. If the pressure is constant, the temperature or volume or number of moles or other things could be changing. In fact if the pressure is constant it would be an isobaric process where heat could be used to both do work and change the internal energy of t...
by jisulee1C
Tue Feb 11, 2020 5:34 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: Delta H and Delta U
Replies: 2
Views: 18

Re: Delta H and Delta U

Delta H would be zero if the total heat energy of the reaction is zero but remember that only in constant pressure is delta equivalent to q. Delta U is always zero in an isothermal process because the internal energy is proportional to temperature and since the temperature remains constant the chang...
by jisulee1C
Sun Jan 26, 2020 9:16 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Standard Reaction Enthalpy
Replies: 3
Views: 29

Re: Standard Reaction Enthalpy

If the bond enthalpies are not available you can calculate the standard reaction enthalpy using the standard enthalpy of formation of all products and subtracting that from the standard enthalpy of formation of all reactants.
by jisulee1C
Sun Jan 26, 2020 9:13 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Meaning of State Function
Replies: 8
Views: 33

Re: Meaning of State Function

In lecture, Lavelle highlighted that a state property (such as enthalpy) is not dependent on the path taken to obtain that state. Some state property examples include E, P, V, T, density, and heat capacity. On the other hand some that are not state peroperties include work (w) and heat (q).
by jisulee1C
Sun Jan 26, 2020 9:11 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: Negative Square Root solving an ICE box
Replies: 13
Views: 47

Re: Negative Square Root solving an ICE box

When solving the quadratic formula, two answers are usually calculated. You should use the positive x value calculated for concentration because concentration itself cannot be a negative value.
by jisulee1C
Sun Jan 26, 2020 9:09 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Bond Enthalpies
Replies: 2
Views: 14

Re: Bond Enthalpies

Bond enthalpy are given to us in the problems however most of the time the bond enthalpy given is the breaking of bonds in gases. Therefore usually an enthalpy for phase change must be added for liquids and solids.
by jisulee1C
Sun Jan 26, 2020 9:06 pm
Forum: Phase Changes & Related Calculations
Topic: Enthalpy Calculations
Replies: 5
Views: 19

Re: Enthalpy Calculations

I am assuming that if we were asked to calculate enthalpy of a reaction, either the enthalpy of formation or bond enthalpies would be given to us in the problem.
by jisulee1C
Tue Jan 21, 2020 9:19 am
Forum: Equilibrium Constants & Calculating Concentrations
Topic: K vs Kc
Replies: 1
Views: 11

Re: K vs Kc

Kc means that concentrations were used for the values when finding the equilibrium constant. K would vary depending on what form of values were used, for example Kp for partial pressures and Kc for concentrations.
by jisulee1C
Tue Jan 21, 2020 9:15 am
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Expansion within an equation
Replies: 1
Views: 12

Re: Expansion within an equation

Expansion of volume would be the opposite of decreasing volume therefore you would be decreasing the pressure which would shift the reaction to favor the side with more moles of gas because the reaction will shift to minimize the effect of the stress.
by jisulee1C
Tue Jan 21, 2020 2:57 am
Forum: Lewis Acids & Bases
Topic: acids
Replies: 2
Views: 40

Re: acids

Strong acids are protonated fully and dissociate fully into hydronium ions while weak acids are not fully deprotonated therefore do not fully dissociate and in equilibrium there are leftover acid molecules that show the acid is too weak to fully dissociate.
by jisulee1C
Tue Jan 21, 2020 12:31 am
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: Le Chatelier's Principle
Replies: 19
Views: 100

Re: Le Chatelier's Principle

For example if product is added the reaction will shift to reactants to undo the stress and vice versa. In addition, lowering or raising the temperature would depend on the reaction and whether it is endothermic or exothermic. For an exothermic reaction raising temperature would shift the reaction t...
by jisulee1C
Tue Jan 21, 2020 12:24 am
Forum: Equilibrium Constants & Calculating Concentrations
Topic: determining which way the reaction is going
Replies: 5
Views: 23

Re: determining which way the reaction is going

For gases, the same rule applies except that you would be using partial pressures and the Kp instead of concentrations and Kc when comparing to Q.
by jisulee1C
Sun Jan 12, 2020 11:47 am
Forum: Non-Equilibrium Conditions & The Reaction Quotient
Topic: ICE
Replies: 5
Views: 52

Re: ICE

ICE charts can be used to find equilibrium molar concentration using molar ratios and the change in molar concentration if the initial molar concentration for either reactants or products are given and the equilibrium constant is also given.
by jisulee1C
Sun Jan 12, 2020 11:44 am
Forum: Equilibrium Constants & Calculating Concentrations
Topic: solids and liquids
Replies: 3
Views: 16

Re: solids and liquids

Solids and liquids (pure substances) are not included in the K expression because the molar concentration does not change in a reaction.
by jisulee1C
Sun Jan 12, 2020 11:42 am
Forum: Non-Equilibrium Conditions & The Reaction Quotient
Topic: Q
Replies: 6
Views: 36

Re: Q

If Q is less than K at some point during the reaction, then the forward reaction is favored while if Q is greater than K at some point during the reaction, the reverse reaction is favored.
by jisulee1C
Sun Jan 12, 2020 11:41 am
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: pressure change
Replies: 4
Views: 18

Re: pressure change

Le Chatelier's principle states that the chemical reaction will adjust to minimize the effects of changes such as the change of reactant added, change of product added, or change of pressure. Specifically for pressure, if the pressure of the reaction increases or the volume decreases then the reacti...
by jisulee1C
Sun Jan 12, 2020 11:35 am
Forum: Equilibrium Constants & Calculating Concentrations
Topic: K vs Kc
Replies: 3
Views: 22

Re: K vs Kc

Kc stands for the equilibrium constant when using concentration values to calculate. Often K is used to represent either Kc or Kp.
by jisulee1C
Sun Dec 08, 2019 6:47 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: bond angles
Replies: 5
Views: 59

Re: bond angles

Bond angles will depend on electrons and the molecular shape. Lone pair electrons have greater repulsion than bonded electrons and will therefore create a smaller bond angle.
by jisulee1C
Sun Dec 08, 2019 6:46 pm
Forum: Calculating pH or pOH for Strong & Weak Acids & Bases
Topic: Equilibrium calculations
Replies: 6
Views: 57

Re: Equilibrium calculations

Equilibrium calculations are not on the final.
by jisulee1C
Sun Dec 08, 2019 6:44 pm
Forum: Octet Exceptions
Topic: Octet exception
Replies: 13
Views: 148

Re: Octet exception

Any element in the beyond 3s2 will be able to form more than four bonds and is therefore an exception because the d orbital begins in principle energy level 3 and is therefore able to accomodate more than the standard 8 electrons.
by jisulee1C
Sun Dec 08, 2019 6:43 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: vsepr formula
Replies: 7
Views: 81

Re: vsepr formula

The VSEPR formula depends on the valence electron bonding to the central atom. Therefore depending one whether it is lone pair electron or bonded electron pair it will change the molecular shape of the molecule.
by jisulee1C
Sun Dec 08, 2019 6:42 pm
Forum: Naming
Topic: Abbreviations
Replies: 6
Views: 73

Re: Abbreviations

Abbreviations are fine for the final, including ox.
by jisulee1C
Sun Dec 08, 2019 6:40 pm
Forum: Naming
Topic: -ate
Replies: 10
Views: 105

Re: -ate

Nope for a positive charge you don't need to add anything.
by jisulee1C
Sun Dec 08, 2019 6:39 pm
Forum: Hybridization
Topic: double and triple bonds
Replies: 6
Views: 78

Re: double and triple bonds

The hybridization depends on the number of electron density regions around the central atom so having a single versus double versus triple bond won't really affect the hybridization for the central atom.
by jisulee1C
Sun Dec 08, 2019 6:36 pm
Forum: Properties & Structures of Inorganic & Organic Acids
Topic: Oxoacid Strength
Replies: 6
Views: 95

Re: Oxoacid Strength

HOCl would act as the stronger acid.
by jisulee1C
Sun Dec 08, 2019 11:09 am
Forum: Polyprotic Acids & Bases
Topic: Polyproptic Acids/Bases
Replies: 4
Views: 49

Re: Polyproptic Acids/Bases

Polyprotic acids can donate more than one proton. Examples include H2CO3.
by jisulee1C
Wed Dec 04, 2019 10:41 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Molecular Shape vs. Molecular Geometry
Replies: 4
Views: 43

Re: Molecular Shape vs. Molecular Geometry

If there are no lone pairs then the molecular shape is the same as the molecular geometry. In the geometry the arrangement considers a bonded electron pair the same as a lone pair of electrons. The geometry will be either linear, trigonal planar, tetrahedral, trigonal bipyramidal, or octahedral.
by jisulee1C
Sat Nov 30, 2019 11:55 pm
Forum: Shape, Structure, Coordination Number, Ligands
Topic: Coordination Number
Replies: 1
Views: 30

Re: Coordination Number

Coordination number is the number of parts at which ligands are attached to the central metal atom. mono dentate has one binding site (an example would be chloride ions), bidentate has two donor atoms, and polydentate ranges in the bonding sites. For 9C part c en is bidentate therefore assume there ...
by jisulee1C
Sat Nov 30, 2019 11:45 pm
Forum: Naming
Topic: Naming
Replies: 4
Views: 35

Re: Naming

Because the coordinate complex has an overall negative charge it is an anion and therefore when naming the overall complex with negative charge -ate is added to the metal. If the symbol of the metal originates from the Latin name, the latin stem is used, therefore for iron Fe, the latin ferrum is us...

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