Chemistry - The Molecular Science, Chap. 14

Front 1

Chemical Equilibrium

Back 1

Finite concentrations of reactants and products, and their concentrations remain constant

Front 2

Product-favored reaction

Back 2

Products predominate over reactants

Front 3

Reactant-favored reaction

Back 3

Reactants predominate over Products

Front 4

If a catalyst is present, the ____ equilibrium state will be achieved, but more _____. A catalyst speeds up the ________ reaction, but it also speeds up the ________ reaction

Back 4

If a catalyst is present, the _same_ equilibrium state will be achieved, but more _quickly_. A catalyst speeds up the _forward_ reaction, but it also speeds up the _reverse_ reaction

Front 5

The ratio of _______ concentrations is equal to the ratio of _______ constants

Back 5

The ratio of _equilibrium_ concentrations is equal to the ratio of _rate_ constants

Front 6

Equilibrium constant

Back 6

A Quotient of equilibrium concentrations of product and reactant substances that has a constant value for a given reaction at a given temperature.

Front 7

Equilibrium constants can be used to answer three important questions about a reaction

Back 7

1. When equilibrium has been reached, do products dominate over reactants
2. Given initial concentrations of reactants and products, in which direction will the reaction fo to achieve equilibrium
3. what concentrations of reactants and products are present at equilibrium?

Front 8

The only concentrations that do appear in an equilibrium constant equation are:

Back 8

Gases and solute in dilute solutions

Front 9

Concentrations that do *NOT* appear in an equilibrium constant equation are:

Back 9

Pure solids, pure liquids and solvents in dilute solutions

Front 10

Equilibrium constant expression (formula)

Back 10

Kc = [C]^c[D]^d / [A]^a[B]^b

where C & D are products (A & B are reactants) and exponents are stoichiometric coefficients.

Front 11

Whenever the __________ ___________ of a balanced equation are multiplied by some factor, the equilibrium constant for the new equation is the old constant _____ ____ ___ _____ of the multiplication factor

Back 11

Whenever the _stoichiometric_ _coefficients_ of a balanced equation are multiplied by some factor, the equilibrium constant for the new equation is the old constant _raised_ _to_ _the_ _power_ of the multiplication factor

Front 12

The equilibrium constant for a reaction and that for its reverse reaction are _______

Back 12

The equilibrium constant for a reaction and that for its reverse reaction are _reciprocals_

Front 13

If two chemical equations can be summed to give a third, the equilibrium constant for the overall reaction equals:

Back 13

the product of the two equilibrium constants for the equations that were summed

Front 14

Equilibrium constant in terms of partial pressures (formula)

Back 14

Kp = Product pressures raised to powers of coefficients divided by reactant pressures raised to powers of coefficients

Front 15

Equilirbrium constant, in terms of partial pressure (formula)

Back 15

Kp = Kc(RT)^(Δn)

Front 16

To calculate Equilibrium constant

Back 16

1. Write a balanced equation and derive Kc ([prod]/[reac])
2. set up a table of initial concentrations, change in concentrations and equilibrium concentrations for each substance
3. Use x to represent the change inconcentration of one substance. Use stoich. coeffs in the balanced equation to calc other changes in terms of x
4. calculate the equilibrium concentrations in terms of x
5 Use the simplest equation to solve for x

Front 17

if Kc >> 1 . . .

Back 17

. . . Reaction is strongly product-favored

Front 18

If Kc << 1 . . .

Back 18

. . . Reaction is strongly reactant-favored

Front 19

IF Kc ~= 1 . . .

Back 19

Equilibrium concentrations must be calculated

Front 20

Q

Back 20

Reaction Quotient

Front 21

Reaction Quotient

Back 21

Ratio of actual concentrations in the mixture, instead of equilibrium concentrations

Front 22

if Q = Kc

Back 22

Reaction is at equilibrium

Front 23

If Q is less than Kc . . .

Back 23

. . . the concentration of products is not as large as they would be at equilibrium

Front 24

If Q is greater than Kc . . .

Back 24

. . . the concentration of products is more than they would be at equilibrium

Front 25

Le Chatelier's Principle

Back 25

If a system is at equilibrium and the conditions are changed so that it is no longer at equilibrium, the system will reach a new equilibrium in a way that partially counteracts the change.