CHEMISTRY COMMUNITY

JadeSebti1L

You can derive the integrated rate law from -d[A]/dt= k bc and see that the rate is independent of concentration.

JadeSebti1L

You include whatever compounds are in your overall balanced cell rxn in your cell diagram.

JadeSebti1L

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.

JadeSebti1L

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?

JadeSebti1L

Can someone explain what exactly is meant by the term "reaction mechanism"?

JadeSebti1L

If water is liquid, you don't include it in the cell diagram if you have another aqueous solution.

JadeSebti1L

A zero order rxn usually occurs when a catalyst or enzyme is saturated by the reactants (substrate).

JadeSebti1L

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.

JadeSebti1L

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...

JadeSebti1L

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.

JadeSebti1L

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...

JadeSebti1L

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...

JadeSebti1L

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...

JadeSebti1L

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,...

JadeSebti1L

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.

JadeSebti1L

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.

JadeSebti1L

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.

JadeSebti1L

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.

JadeSebti1L

I am not sure there exists such a thing as a negative temperature system because basically all movement stops at 0 K.

JadeSebti1L

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...

JadeSebti1L

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)?

JadeSebti1L

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...

JadeSebti1L

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.

JadeSebti1L

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.

JadeSebti1L

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.

JadeSebti1L

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...

JadeSebti1L

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.

JadeSebti1L

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?

JadeSebti1L

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.

JadeSebti1L

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,...

JadeSebti1L

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.

JadeSebti1L

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...

JadeSebti1L

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.

JadeSebti1L

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.

JadeSebti1L

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.

CHEMISTRY COMMUNITY

Search found 35 matches

Re: Zero order reaction

Re: OH-(aq) in cell diagram

Re: Inert Electrodes

14.97

Reaction Mechanism

Re: Water in a cell diagram

Re: Enzymatic Reactions

Re: How to do 15.11 6th edition?

Re: Difference between instantaneous and unique rate

Re: Example of a zero order rxn

Re: Purpose of Kinetics

Re: Exponential Curve

Re: Initial reactions rates

Re: System vs Surroundings

Re: Microstates

Re: Microstates

Re: Negative Delta G

Re: Reversible vs. Irreversible

Re: Negative Temperature

Re: Work Equations

Re: when to use each equation

Re: Temperature in Work Equations

Re: Heat Capactiy

Re: Isolated Systems

Re: Finding Heat

Re: Analogy of Boulder

Re: Phase changes and enthaplies

6th Ed. 11.57

Re: Kw

Re: ICE table

Re: When is X negligible.

Re: Definition of Ideal Gases?

Re: Units

Re: Kp vs Kc

Re: Effects on Equilibrium