CHEMISTRY COMMUNITY

Jessica Katzman 4F

If delta G (the measure of Gibb's free energy) is positive, the reaction is not spontaneous. If it is negative, the reaction is spontaneous and therefore favorable.

Jessica Katzman 4F

The standard enthalpy of formation for elements in their standard, most stable state is zero.

Jessica Katzman 4F

When your system is isothermal and your reaction is reversible, s = 0 because the reaction is considered at equilibrium throughout.

Jessica Katzman 4F

Because delta S is measures the change in disorder, a delta S value less than zero signifies a decrease in entropy for the whole system.

Jessica Katzman 4F

The temperature is constant for reversible reactions

Jessica Katzman 4F

Gas has a higher entropy than liquid because the molecules can move more freely and therefore occupy many more states.

Jessica Katzman 4F

if work is done on the system, w is positive because the system is gaining heat. If work is done by the system, w is negative because it is giving heat.

Jessica Katzman 4F

Entropy is an extensive property, meaning its value changes with the amount of the substance. An intensive property does not depend on the amount.

Jessica Katzman 4F

Hi Nick! It's all about truly understanding the material and simplifying what can be some tricky concepts and equations. Good luck on the midterm:)

Jessica Katzman 4F

A sudden expansion occurs all at once, such as with the piston example. This represents an irreversible reaction. A gradual expansion occurs in infinitesimal increments and represents a reversible reaction.

Jessica Katzman 4F

If work is done BY the system, w is negative. If work is done on the system, w is positive.

Jessica Katzman 4F

The -deltaS implies a non spontaneous reaction.

Jessica Katzman 4F

Isothermal refers to the constant temperature of a system. No heat is added or lost to the environment.

Jessica Katzman 4F

Since it is isothermal and reversible, the temperature of the system remains constant. Therefore, deltaU=0, so 0 = q+w, and q = -w.

Jessica Katzman 4F

The substance can change phases at a constant temperature. This is why ice can melt into water at room temperature, and if you check on the ice at different times you will see the ratio of ice to water change.

Jessica Katzman 4F

The temperature does not change during a phase change- for example, you can have both ice and water at the same temperature.

Jessica Katzman 4F

You use the integral when P is not constant, and when it is, you can move it to the outside of the integral.

Jessica Katzman 4F

The dog bones were all of the possible states that two atoms could be in and represented the degeneracy of the two atoms.

Jessica Katzman 4F

A closed system is sealed, but can still interact with the outside environment. An isolated system is sealed and insulated and cannot interact with the environment.

Jessica Katzman 4F

Adding or removing substance in a system changes the energy of an open system, changing the temperature of a closed system will change its energy, and doing work on the system/letting the system do work on the environment changes the energy of a closed system

Jessica Katzman 4F

Yes, H2O gas is included in K expressions.

Jessica Katzman 4F

I think it can also be equal to 10^-3

Jessica Katzman 4F

The homework problems, learning outcomes, and step-up sessions are really helpful for me!

Jessica Katzman 4F

The "C" is determined by the number of moles of products and reactants created or decreased. The "C" column is filled with +x or -x multiplied by the stoichiometric coefficient of the product or reactant.

Jessica Katzman 4F

The pH scale is from 0-14. A solution is considered acidic if it has a pH below 7, and basic if above 7.

Jessica Katzman 4F

An exothermic reaction creates heat- therefore if heat is considered a "reactant," the reaction will lean to the product side as it can produce more products with the increase in heat.

Jessica Katzman 4F

X is such a small value that it is not drastically affected by coefficients, so you can use an approximation.

Jessica Katzman 4F

Usually the problem should give you some initial or equilibrium condition either in mol or bar- if given moles or mol/L you use Kc, if given bar you use Kp

Jessica Katzman 4F

Because K is a constant, the only factor that can change it is temperature, as certain reactions will go further toward completion when heat is added and vice versa.

Jessica Katzman 4F

When you expand the volume, you are decreasing the pressure, so the reaction shifts toward the side with more moles to minimize the impact of the decrease in pressure of the reaction.

Jessica Katzman 4F

Kc denotes the equilibrium constant in terms of molar concentrations. Aqueous solutions have concentrations so they are included in the expression, but solids do not so they do not factor into the Kc expression.

Jessica Katzman 4F

Le Chatelier's principle states that a system in equilibrium will shift in response to a change in pressure, temp, concentrations etc. in order to minimize its effects on the reaction.

Jessica Katzman 4F

Brackets are used to denote molar concentrations, and parenthesis are used to denote partial pressure.

Jessica Katzman 4F

ICE boxes are used to calculate K given a set of initial conditions and their change, but not the equilibrium conditions. When you know the conditions at equilibrium, you can solve for K without ICE.

Jessica Katzman 4F

K is the general notation for the equilibrium constant. Kc is used when we are specifically defining the ratio of the molar concentrations of products and reactants.

CHEMISTRY COMMUNITY

Search found 35 matches

Re: Spontaneous

Re: Standard Enthalpies of Formation

Re: S = 0

Re: change in entropy

Re: How to interpret reversible/irreversible graphs

Re: Gas v Liquids

Re: work on the system or by the system

Re: Intensive

Re: MIdterm

Re: Sudden vs. Gradual

Re: Work done on or by the system

Re: calculating entropy

Re: Isothermal

Re: Question from Wednesday Lecture

Re: Heating Curve Phase Changes

Re: Phase Changes

Re: When to Use the Integral

Re: Degeneracy

Re: Isolated vs Closed [ENDORSED]

Re: Energy of Systems

Re: H2O in K Expressions

Re: Approximation

Re: Prepping for Test

Re: ICE table

Re: Acid and Bases

Re: exothermic reactions

Re: Checking the approximation of "x"

Re: partial pressure vs concentrations

Re: Changing K

Re: expanding the volume

Re: Kc

Re: What is this?

Re: Units for Kc and Kp

Re: ICE vs Normal Concentrations

Re: Different types of K