Search found 35 matches
- Sun Mar 17, 2019 11:00 am
- Forum: Zero Order Reactions
- Topic: Zero order reaction
- Replies: 8
- Views: 982
Re: Zero order reaction
You can derive the integrated rate law from -d[A]/dt= k bc and see that the rate is independent of concentration.
- Sun Mar 17, 2019 10:58 am
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: OH-(aq) in cell diagram
- Replies: 3
- Views: 652
Re: OH-(aq) in cell diagram
You include whatever compounds are in your overall balanced cell rxn in your cell diagram.
- Sun Mar 17, 2019 10:57 am
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: Inert Electrodes
- Replies: 3
- Views: 568
Re: Inert Electrodes
Use Platinum as an inert conductor even if an electrolyte is solid because you have to make sure it's a metal because metals are good conductors.
- Sat Mar 09, 2019 3:02 pm
- Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
- Topic: 14.97
- Replies: 2
- Views: 298
14.97
The two standard potentials are +2.87V and +3.03V so wouldn't the latter be the cathode, making the total cell potential positive?
The solutions manual makes +2.87V potential the cathode potential.
Also, why do you get Ka when you take the square root of K?
The solutions manual makes +2.87V potential the cathode potential.
Also, why do you get Ka when you take the square root of K?
- Fri Mar 08, 2019 3:15 pm
- Forum: Reaction Mechanisms, Reaction Profiles
- Topic: Reaction Mechanism
- Replies: 2
- Views: 375
Reaction Mechanism
Can someone explain what exactly is meant by the term "reaction mechanism"?
- Fri Mar 08, 2019 2:58 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: Water in a cell diagram
- Replies: 5
- Views: 577
Re: Water in a cell diagram
If water is liquid, you don't include it in the cell diagram if you have another aqueous solution.
- Fri Mar 08, 2019 2:52 pm
- Forum: Zero Order Reactions
- Topic: Enzymatic Reactions
- Replies: 2
- Views: 312
Re: Enzymatic Reactions
A zero order rxn usually occurs when a catalyst or enzyme is saturated by the reactants (substrate).
- Wed Mar 06, 2019 4:50 pm
- Forum: First Order Reactions
- Topic: How to do 15.11 6th edition?
- Replies: 4
- Views: 516
Re: How to do 15.11 6th edition?
I assume that because you're only looking for the initial rate of decomposition, the problem doesn't consider "being heated to 65*C" as factoring into the rate because it happens after the N2O5 is added.
- Wed Mar 06, 2019 4:45 pm
- Forum: General Rate Laws
- Topic: Difference between instantaneous and unique rate
- Replies: 3
- Views: 456
Re: Difference between instantaneous and unique rate
As everyone said, the instantaneous rate refers to the rate of change in the concentration of reactants and products at ONE moment, given by -d(R)/dt. The unique rate of the reaction is the one average rate of the reaction taking into consideration that the reactant/product concentrations are all ch...
- Wed Mar 06, 2019 4:33 pm
- Forum: Zero Order Reactions
- Topic: Example of a zero order rxn
- Replies: 4
- Views: 549
Re: Example of a zero order rxn
The reverse Haber process, 2NH3(g) -> N2 (g) + 3H2 (g), is an example of a zero order reaction because the rxn's rate is completely independent on the concentration of ammonia.
- Tue Mar 05, 2019 6:25 pm
- Forum: Kinetics vs. Thermodynamics Controlling a Reaction
- Topic: Purpose of Kinetics
- Replies: 6
- Views: 1667
Re: Purpose of Kinetics
Kinetics is the study of the rate of reactions which can be useful in studying enzymes, drugs, and so many other types of chemical reactions. Kinetics are especially applicable to biology because the infinite number of chemical reactions that happen in biological systems are all in an effort to main...
- Tue Mar 05, 2019 5:47 pm
- Forum: First Order Reactions
- Topic: Exponential Curve
- Replies: 6
- Views: 637
Re: Exponential Curve
The integrated rate law can be expressed in exponential form as [A]=[A].e−kt First order reactions show an exponential decay of reactants as a function of time. Because natural log (ln) was introduced into the integration, we had to use "e" to make calculations easier. In doing that, the r...
- Tue Mar 05, 2019 5:32 pm
- Forum: Zero Order Reactions
- Topic: Initial reactions rates
- Replies: 3
- Views: 443
Re: Initial reactions rates
By focusing on only reactants, you are also somewhat tracking the rate of product formation because molecules in your solution are either reactants or products, nothing else. The rate of the reaction is also defined by the rate at which reactants form products, so looking at the concentration of rea...
- Tue Feb 19, 2019 11:39 am
- Forum: Thermodynamic Systems (Open, Closed, Isolated)
- Topic: System vs Surroundings
- Replies: 14
- Views: 2067
Re: System vs Surroundings
System vs. surrounding should be evident depending on the question that is given. It usually just determines whether a certain value is positive or negative in relation to the system at hand. For example, if the question states the surroundings gained x amount of energy, then energy left the system,...
- Tue Feb 19, 2019 10:34 am
- Forum: Thermodynamic Definitions (isochoric/isometric, isothermal, isobaric)
- Topic: Microstates
- Replies: 7
- Views: 1032
Re: Microstates
Microstates are the possible number of same energy configurations of a set of molecules. Because it is a statistical calculation of entropy, you put it to the power of the number of molecules you are handling in a certain problem.
- Tue Feb 19, 2019 10:33 am
- Forum: Thermodynamic Definitions (isochoric/isometric, isothermal, isobaric)
- Topic: Microstates
- Replies: 7
- Views: 1032
Re: Microstates
Microstates are the possible number of same energy configurations of a set of molecules. Because it is a statistical calculation of entropy, you put it to the power of the number of molecules you are handling in a certain problem.
- Tue Feb 19, 2019 10:21 am
- Forum: Gibbs Free Energy Concepts and Calculations
- Topic: Negative Delta G
- Replies: 7
- Views: 3975
Re: Negative Delta G
Reactions with a negative delta G are very spontaneous, and therefore highly favorable! The more favorable a reaction is, the more it will proceed towards the products. That means that K is rather large at equilibrium because the ratio of products is high compared to reactants.
- Mon Feb 18, 2019 8:42 am
- Forum: Thermodynamic Definitions (isochoric/isometric, isothermal, isobaric)
- Topic: Reversible vs. Irreversible
- Replies: 5
- Views: 1023
Re: Reversible vs. Irreversible
Just remember that more work is done in an isothermal reversible system than an irreversible system. Think of the work as the integral of the graphs we were shown in class when the irreversible system is basically held at constant P.
- Mon Feb 18, 2019 8:36 am
- Forum: Entropy Changes Due to Changes in Volume and Temperature
- Topic: Negative Temperature
- Replies: 5
- Views: 498
Re: Negative Temperature
I am not sure there exists such a thing as a negative temperature system because basically all movement stops at 0 K.
- Sat Feb 09, 2019 10:41 am
- Forum: Thermodynamic Definitions (isochoric/isometric, isothermal, isobaric)
- Topic: Work Equations
- Replies: 2
- Views: 332
Re: Work Equations
As Alexa said, the first is for the irreversible reaction (the graph shown in class with the box-shaped integral). The second and third are under reversible conditions and are ultimately integrals of V and P in respect to one another (think about the area under the curve shaped graph that Lavelle sh...
- Sat Feb 09, 2019 10:35 am
- Forum: Calculating Work of Expansion
- Topic: when to use each equation
- Replies: 2
- Views: 381
Re: when to use each equation
An easy way to remember it is that whatever variable is constant is included in the equation.
CONSTANT P: w = -Pex(deltaV)
CONSTANT T: w = -nRTln(V2/V1)?
CONSTANT P: w = -Pex(deltaV)
CONSTANT T: w = -nRTln(V2/V1)?
- Sat Feb 09, 2019 10:32 am
- Forum: Calculating Work of Expansion
- Topic: Temperature in Work Equations
- Replies: 3
- Views: 454
Re: Temperature in Work Equations
I think you have to include T in the first equation because when you derive it you have to use the integral of P in respect to volume, but you ultimately replace P with the other side of the ideal gas equation (nRT/V). When you take the integral, you can pull out the "-nRT" because it's te...
- Fri Feb 01, 2019 3:09 pm
- Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
- Topic: Heat Capactiy
- Replies: 5
- Views: 469
Re: Heat Capactiy
Heat capacity refers to raising the "temperature of a body" by one degree whereas specific heat capacity is more SPECIFIC and refers to how much energy you have to put in to raise a single gram of said "substance/body" by one degree.
- Fri Feb 01, 2019 2:58 pm
- Forum: Thermodynamic Systems (Open, Closed, Isolated)
- Topic: Isolated Systems
- Replies: 6
- Views: 745
Re: Isolated Systems
There are no actually isolated systems other than the universe, but I think for the sake of this class we just assume an isolated system is merely one that does not exchange energy or matter with its surroundings. ex: soup in a closed thermos, bomb calorimeter, etc.
- Fri Feb 01, 2019 2:55 pm
- Forum: Concepts & Calculations Using First Law of Thermodynamics
- Topic: Finding Heat
- Replies: 4
- Views: 398
Re: Finding Heat
You can use either because you can convert between Celsius and Kelvin like this: Kelvin = Celsius + 273.15.
The conversion only adds, so the differences temperature (whether K or C) are the same values.
The conversion only adds, so the differences temperature (whether K or C) are the same values.
- Fri Feb 01, 2019 2:49 pm
- Forum: Thermodynamic Systems (Open, Closed, Isolated)
- Topic: Analogy of Boulder
- Replies: 5
- Views: 1004
Re: Analogy of Boulder
I think Lavelle was also referring to the idea of doing work on surroundings vs. on a system. If the boulder rolls down the hill, it does work on the surroundings because it releases energy (work is positive- exergonic). When the boulder is pushed up the hill, it's an endergonic process because work...
- Fri Feb 01, 2019 2:44 pm
- Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
- Topic: Phase changes and enthaplies
- Replies: 3
- Views: 359
Re: Phase changes and enthaplies
Remember that Lavelle said that enthalpy is a state function, meaning its value depends on the phase of the substance which you are referring to. However, enthalpy change is a two-state function so wouldn't even be considered a state function.
- Wed Jan 23, 2019 5:47 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: 6th Ed. 11.57
- Replies: 1
- Views: 189
6th Ed. 11.57
In 11.57, the solution manual includes the conc. of water in the ICE table. I thought we didn't include the concentrations of water in ICE tables and especially when calculating Kc. Can someone please clarify?
- Fri Jan 18, 2019 5:59 pm
- Forum: Non-Equilibrium Conditions & The Reaction Quotient
- Topic: Kw
- Replies: 6
- Views: 555
Re: Kw
Kw=[H3O+][OH-]
Kw= constant 1.0x10^-14
In neutral water with pH=7, the H3O+ and OH- concentrations are equal so
1.0x10^-14=[H3O+][OH-] with both of them being 1.0 x 10^-7.
Kw= constant 1.0x10^-14
In neutral water with pH=7, the H3O+ and OH- concentrations are equal so
1.0x10^-14=[H3O+][OH-] with both of them being 1.0 x 10^-7.
- Fri Jan 18, 2019 4:43 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: ICE table
- Replies: 2
- Views: 261
Re: ICE table
You have to keep in mind molar ratio when doing your ice tables. If the product of a reaction was "3HCl" you would subtract "3x" from the initial concentration. Then it just carries over to your quadratic as a coefficient and when everything is foiled out, you will end up with a,...
- Fri Jan 18, 2019 4:33 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: When is X negligible.
- Replies: 6
- Views: 532
Re: When is X negligible.
My TA also said today it is not mandatory to do the shortcut and that the quadratic works fine. But, if you have to do the shortcut because of time constraints you have to check that x is less than 5% of the initial concentration to get credit for that step.
- Fri Jan 11, 2019 6:28 pm
- Forum: Ideal Gases
- Topic: Definition of Ideal Gases?
- Replies: 3
- Views: 336
Re: Definition of Ideal Gases?
Ideal gases are all theoretical. They are made up of point-sized randomly moving particles whose interactions are perfectly elastic collisions, meaning no energy loss or gain occurs when the particles hit each other. Ideal gases also don't take into account intramolecular forces and volume created b...
- Fri Jan 11, 2019 6:16 pm
- Forum: Ideal Gases
- Topic: Units
- Replies: 19
- Views: 1106
Re: Units
Yes, as people said before you should always use Kelvin. It is also important to note that you must match pressure units for whatever R constant you are using or else your answer will be incorrect. You can also convert to whatever units the question asks before plugging in your values to PV=nRT.
- Fri Jan 11, 2019 6:12 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Kp vs Kc
- Replies: 6
- Views: 579
Re: Kp vs Kc
Yes, Kc or Kp totally depends on the question you're asked. If the formula uses gases, use Kp for partial pressure instead of concentration. If you want to find Kc after, you have to a derivation of Kc in terms of Kp using PV=nRT.
- Thu Jan 10, 2019 10:19 am
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Effects on Equilibrium
- Replies: 2
- Views: 218
Re: Effects on Equilibrium
I believe that a temperature change can have the greatest effect on K. Also, the concentration of reactants and products and the pressure of the system can also affect K.