Search found 31 matches
- Sun Mar 17, 2019 7:13 am
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Approximations
- Replies: 1
- Views: 451
Approximations
Will we be told to make/ not make approximations? Or will we have to decide on our own?
- Sat Mar 16, 2019 8:54 pm
- Forum: *Enzyme Kinetics
- Topic: Collision theory
- Replies: 3
- Views: 756
Collision theory
How can you tell if a reaction would be least likely to occur?
- Sat Mar 16, 2019 12:58 pm
- Forum: Arrhenius Equation, Activation Energies, Catalysts
- Topic: 15.85 6th Edition
- Replies: 1
- Views: 254
Re: 15.85 6th Edition
This was posted earlier this week: "An activated complex is the the structure that occurs when the molecule is at the highest energy along the reaction path (ie the transition state at the top of that curve at Ea). You will not be asked to draw the structure on the exam."
- Sat Mar 16, 2019 12:04 pm
- Forum: Arrhenius Equation, Activation Energies, Catalysts
- Topic: HW problem 15.73
- Replies: 1
- Views: 163
HW problem 15.73
Part b) a catalyst is not consumed in the course of a reaction
True of False
The answer is True
I don't understand why the answer is true because when we are looking for a catalyst in a reaction mechanism aren't we supposed to look for a catalyst that is being consumed and then formed?
True of False
The answer is True
I don't understand why the answer is true because when we are looking for a catalyst in a reaction mechanism aren't we supposed to look for a catalyst that is being consumed and then formed?
- Sat Mar 16, 2019 11:24 am
- Forum: Arrhenius Equation, Activation Energies, Catalysts
- Topic: HW problem 15.67
- Replies: 1
- Views: 226
HW problem 15.67
The presence of a catalyst provides a reaction pathway in which the activation energy of a certain reaction is reduced from 125 kJ/mol to 75 kJ/mol. (a) By what factor does the rate of the reaction increase at 298 K, all other factors being equal? (b) By what factor would the rate change if the reac...
- Fri Mar 15, 2019 11:58 pm
- Forum: Arrhenius Equation, Activation Energies, Catalysts
- Topic: Exothermic vs Endothermic
- Replies: 6
- Views: 653
Re: Exothermic vs Endothermic
I love chemistry community because everyone replies so fast!
- Fri Mar 15, 2019 11:51 pm
- Forum: Arrhenius Equation, Activation Energies, Catalysts
- Topic: Exothermic vs Endothermic
- Replies: 6
- Views: 653
Exothermic vs Endothermic
How can you tell if a reaction is endothermic or exothermic based off Arrhenius equation, or given Ea and k?
- Fri Mar 15, 2019 10:33 am
- Forum: General Rate Laws
- Topic: Overall Rate Law
- Replies: 1
- Views: 216
Overall Rate Law
If I'm given a reaction mechanism with 2 steps I can just combine products on one side and reactants on the other side and cancel out like terms to get the overall reaction? And for a reaction mechanism with 3 or more steps, I have to use the pre-equilibrium approach? Or, how do I know when to use t...
- Thu Mar 14, 2019 12:16 pm
- Forum: Second Order Reactions
- Topic: solving for time elapsed
- Replies: 1
- Views: 223
solving for time elapsed
15.35 The half-life for the second-order reaction of a substance A is 50.5 s when [A]0 0.84 molL. Calculate the time needed for the concentration of A to decrease to (a) one-sixteenth; (b) one-fourth; (c) one-fifth of its original value. Can someone please explain how to solve part (a)? I'm pretty s...
- Tue Mar 12, 2019 6:39 pm
- Forum: First Order Reactions
- Topic: 15.23 c) Determining rate constant
- Replies: 2
- Views: 339
Re: 15.23 A) Determining rate constant
Determine the rate constant for each of the following first-order reactions, in each case expressed for the rate of loss of A: (a) A --->B, given that the concentration of A decreases to one-half its initial value in 1000. s
How do you solve part a) for this question?
How do you solve part a) for this question?
- Tue Mar 12, 2019 3:20 pm
- Forum: Zero Order Reactions
- Topic: Reaction Rate
- Replies: 10
- Views: 1241
Reaction Rate
Given a table of rates and concentrations, when you find the rate constant k, is it the same k for all of the other concentrations?
- Tue Mar 12, 2019 2:07 pm
- Forum: First Order Reactions
- Topic: Rate law with 2 reactants
- Replies: 3
- Views: 378
Rate law with 2 reactants
What is the rate law if the reaction is in 1st order, but there are 2 reactants?
- Sun Feb 24, 2019 11:53 am
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: Spontaneous cell reaction
- Replies: 2
- Views: 368
Spontaneous cell reaction
After writing the corresponding cell reaction using the cell diagram how can you tell if the cell reaction is spontaneous as written?
(If the problem only tells you that the cell potential is positive)
(If the problem only tells you that the cell potential is positive)
- Sat Feb 23, 2019 9:17 pm
- Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
- Topic: Finding n in Delta G = -nFE
- Replies: 3
- Views: 630
Finding n in Delta G = -nFE
Can someone explain how to find n in Delta G = -nFE ?
- Fri Feb 22, 2019 7:46 pm
- Forum: Balancing Redox Reactions
- Topic: Acidic Vs. Basic Redox Rxn
- Replies: 3
- Views: 465
Acidic Vs. Basic Redox Rxn
How will I know if I am balancing an acidic or basic redox reaction? Or will the problem specify which one it is?
- Thu Feb 21, 2019 5:11 pm
- Forum: Gibbs Free Energy Concepts and Calculations
- Topic: Gibbs Free Energy Meaning
- Replies: 6
- Views: 758
Re: Gibbs Free Energy Meaning
Can someone explain this from the learning outcomes: Understand why reaction free energy depends on pressure and the equilibrium constant
- Tue Feb 19, 2019 3:19 pm
- Forum: Calculating Standard Reaction Entropies (e.g. , Using Standard Molar Entropies)
- Topic: irreversible v reversible
- Replies: 4
- Views: 667
Re: irreversible v reversible
yes, I think S tot for a reversible process is = to 0
- Sun Feb 17, 2019 8:02 pm
- Forum: Gibbs Free Energy Concepts and Calculations
- Topic: Non-spontaneous and spontaneous processes
- Replies: 2
- Views: 333
Non-spontaneous and spontaneous processes
What does a non-spontaneous process need to become spontaneous?
- Sun Feb 17, 2019 7:45 pm
- Forum: Gibbs Free Energy Concepts and Calculations
- Topic: Spontaneity
- Replies: 4
- Views: 538
Re: Spontaneity
Can someone explain this from the textbook? "At constant temperature and pressure, the direction of spontaneous change is the direction of decreasing Gibbs free energy."
- Tue Feb 12, 2019 10:44 am
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Solids and Liquids in K expression
- Replies: 2
- Views: 395
Solids and Liquids in K expression
When writing the K expression and there's a solid or liquid in the reaction, should I balance the whole equation first and then not include the solid or liquid in my K expression? Or ignore the solid or liquid from the beginning and balance my the equation without them?
- Wed Feb 06, 2019 5:19 pm
- Forum: Administrative Questions and Class Announcements
- Topic: Dr. Lavelle's In-class Review Sessions
- Replies: 2
- Views: 297
Dr. Lavelle's In-class Review Sessions
Since Professor has review sessions during his lectures next week, will he be presenting the same past exam questions in each lecture, or different ones?
- Tue Feb 05, 2019 7:03 pm
- Forum: Concepts & Calculations Using First Law of Thermodynamics
- Topic: Delta H and q
- Replies: 3
- Views: 524
Delta H and q
Can someone please explain the concept behind why Delta H is equal to q at constant pressure?
- Sun Jan 27, 2019 1:49 pm
- Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
- Topic: Hess' Law Confirmation
- Replies: 3
- Views: 358
Re: Hess' Law Confirmation
Can someone explain how I know which equation to start with for Hess' Law?
- Sun Jan 27, 2019 1:47 pm
- Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
- Topic: Biological Example
- Replies: 1
- Views: 159
Biological Example
Can anyone explain and apply the concept of reaction enthalpies to a biological or organic example? I'm not really sure what the outline means by being able to do that.
- Sun Jan 27, 2019 1:42 pm
- Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
- Topic: heat capacity
- Replies: 7
- Views: 803
Re: heat capacity
Heat Capacity is measurement of heat absorbed or released. Since temperature change is directly proportional to the heat added, with the heat capacity as the proportionality constant, we can use the heat capacity to convert the temperature change into energy.
- Sun Jan 27, 2019 1:38 pm
- Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
- Topic: q(cal)= -q
- Replies: 2
- Views: 754
Re: q(cal)= -q
I'm not exactly sure how it was derived but I know that it means the Heat lost in a reaction is gained by the calorimeter -q= qcal (- heat required is = + calorimeter constant) I think it applies to when you are Calibrating the calorimeter: the heat capacity is measured by supplying a quantity of he...
- Sun Jan 27, 2019 1:18 pm
- Forum: Phase Changes & Related Calculations
- Topic: closed vs isolated system
- Replies: 3
- Views: 804
Re: closed vs isolated system
Open system: Opened to both heat and matter (Ex. a test tube with liquid inside without a lid) Closed system: Closed to matter, but open to heat (Ex. a test tube with a closed lid, sitting in hot water; the liquid inside the test tube cannot escape but it can get warmer.) Isolated system: Closed to ...
- Sun Jan 27, 2019 1:12 pm
- Forum: Phase Changes & Related Calculations
- Topic: State Property
- Replies: 3
- Views: 359
Re: State Property
A State Property being independent of its path just means that how the system attained that state doesn't matter. For example how fast or slow the change happened doesn't matter, only its actual initial and final state matter. The value only depends on its current state not how it got there.
- Sun Jan 13, 2019 8:26 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Equilibrium constant
- Replies: 6
- Views: 555
Re: Equilibrium constant
Kc is just referring to calculating the eq of given concentrations and Kp refers to calculating the eq of given pressures.
- Sun Jan 13, 2019 5:42 pm
- Forum: Non-Equilibrium Conditions & The Reaction Quotient
- Topic: reaction quotient [ENDORSED]
- Replies: 4
- Views: 551
Re: reaction quotient [ENDORSED]
Is the reaction quotient unit-less as well?
- Fri Jan 11, 2019 11:41 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Calculating Kc
- Replies: 4
- Views: 481
Calculating Kc
Can someone please explain to me why it’s necessary to balance a reaction equation when calculating Kc? I don’t understand why it mattters if concentration changes dont affect Kc.