Equilibrium Unit 11

Why do chemist use La chatelier's principle?

so they could control the set of concentration of a reaction to favor or maximize the amount of product.

If the equilibrium constant K for a given equilibrium reaction is very much less than one, then what happens

the forward reaction is barely underway when the equilibrium is established, its numerical value may be changed by altering the reaction temperature.

physical equilibrium

the rate of both reaction is equal but it appears to have stopped, but it hasn't actually stopped it just means that you have reached equilibrium and the concentrations are equal

What happens when an irregularly shaped crystal of NaCl is placed in a saturated solution of NaCl)

the shape of the crystal becomes more regular

Meaning of shifting an equilibrium

when certain substances is added whether in the reactants or the products side so equilibrium will force a shift from left to right to reduce the concentration.

When you are trying to produce more product in an exothermic reaction what should you do?

you have to decrease the temperature so it shift right

When a state of equilibrium is reached between two chemical reaction. What happens?

1) Both reactions continue but the net change in the concentrations is zero 2) The rates of the two reactions are equal 3) the quantities of reactants and products remain unchanged

For the hypothetical reaction A+B <-> C+D an increase in the concentration of A causes.......

1) displaces the equilibrium to the right 2) causes A and B to be used up faster 3) causes C and D to be formed 4) results in a reestablished equilibrium in which the concentration of B will be lower.

What is true about chemical equilibrium?

1) is a dynamic state 2) exists when opposing chemical reactions occur at equal rates

What is true about The expression for the equilibrium constant K ?

1) may be written directly from the chemical reaction 2) may be derived from the appropriate rate laws for the forward and reverse reactions 3) may be calculated from the equilibrium concentrations of reactants and products which are determined experimentally.

What happens in equilibrium system in which gases are involved?

1) pressure changes have the effect of altering the concentration of the gases 2) pressure changes have no effect on the numerical value of the Kc 3) an increase in pressure causes a shift in equilibrium

In the synthesis of N2 + 3H2 <-> 2NH3 an increase in pressure results in a greater yield of ammonia because?

1) the formation of ammonia molecules relieves the pressure 2) there are 2 molecules of NH3 formed for every four molecules of reactants used

In the equilibrium reaction A+B <-> C+D what can happen?

1) the speed of the reverse reaction increases as A and B are used up 2) the speed of the forward reaction decreases as A and B are used up 3) the speeds of both forward and reverse reaction are equal at equilbrium

How do chemists recognize a system that has reached a state of chemical equilibrium? When writing the chemical equations how do we indicate reactions that come to a state of chemical equilibrium?

A system has reached equilibrium when no more product forms, even though significant amounts of all the needed reactants are present. This lack of further product creation indicates that the reverse process is now occurring at the same rate as the forward process that is, every time A product Molecule forms in the system, another product molecule reacts to give back the origin of reactants elsewhere in the system reaction that come to equilibrium are indicated by a double arrow

Will the rate of forward reaction exceed the rate of the reverse reaction?

Conversely, if the concentrations of the reactants are too small, the rate of the reverse reaction will exceed that of the forward reaction, and the reaction will convert some of the excess products back into reactants until the system reaches equilibrium.

chemical equilibrium

In a chemical reaction, the state in which the rate of the forward reaction equals the rate of the reverse reaction, so that the relative concentrations of the reactants and products do not change with time.

Suppose the system is already at equilibrium, and then an additional mole of a reactant is injected onto the system at constant temperature. Does the amount of product in the system increase or decrease?

Increases

What does base do in equilibrium?

It reduces the H+ so the equilibrium will shift to reactants or products side if one of them has H+

Difference between physical and chemical equilibrium?

Physical equilibrium includes the coexistence of two physical states inside the same closed system. (pure substance ex: water) Chemical equilibrium show no changes in concentrations of reactants and products that are involved in the equilibrium.

In general terms what does the equilibrium constant for a reaction represent?

Represents the rate of reactants and products when their reaction speed equals

dynamic equilibrium

Result of diffusion where there is continuous movement of particles but no overall change in concentration where the rate of both reaction is equal

What does a catalyst do in equilibrium?

The effect of a catalyst on an equilibrium is to increase the rate at which equilibrium is achieved without changing the concentrations of the equilibrium mixture

There is only one value of the equilibrium constant for a particular system at a particular temperature, but there are an infinite number of equilibrium positions. explain

The equilibrium constant is a ratio of the concentration of products to the concentration of reactants all at equilibrium. Depending on the amount of reacting to that was origin only present, different amounts of reactants and products will be present at equilibrium, but the ratio will always be the same for a given reaction at a given temperature. For example the ratios 4/2 and 6/3 involve different numbers but each of these ratios has the value two.

In an equilibrium in which the forward reaction runs well toward completion before the speed of the reverse reaction is high enough to establish equilibrium. Who is favored?

The forward reaction is favored

What is the significance of the portion of the plot where the two curves join together to form a single curve as time increases?

The two curves come together when is state of chemical equilibrium has been breached after which point the forward and reverse reactions are occurring at the same rate so that there is no further net change in concentration

What does it mean when the quotient is smaller than the equilibrium constant

Then it means the reaction will proceed in forward reaction where the products are favored so the concentration of products will go up and the concentration of reactants will go down

What does it mean when the quotient > equilibrium constant

Then it means the reaction will shift to the left where reactants is favored the concentration of products will go down and the concentration of reactants will go up

What does it mean to say that a state of chemical or physical equilibrium is dynamic?

To say that there is a dynamic equilibrium would mean that their rates are equal and the product and reactants remain constant

When you are trying to produce more product in an endothermic reaction what should you do?

You have to increase the temperature so it shift right

What is true about the rate of forward reaction and reverse reaction at equilibrium?

both rates are equal

What is true about concentrations of the reactants and products at equilibrium?

concentration of reactants and products are not necessarily equal in a dynamic equilibrium. Equilibrium occurs for a reversible reaction. Reversible means that as reactants bump into each other and become product, products eventually accumulate and bump into themselves, reacting to reform reactants. Equilibrium is reached when system is no longer visibly changing. That point is not reached when there is equal amount of products and reactants, but rather when the rate at which products are made is equal to the rate at which reactants are made.

Le Chatelier's Principle

if a change is imposed on a system at equilibrium, the position of the equilibrium will shift in a direction that tends to reduce the effect of that change

In the equilibrium reaction : [C]x [D] to [A]x[B] What is true about this reaction

is known as the equilibrium constant, Kc may be greater or less than one

What does a change in operating temperature of an equilibrium reaction do?

it always causes a change in the numerical value of the equilibrium reaction, it alters the speed of both reactions unequally.

What is a quotient?

it is the same as equilibrium except that it uses initial concentrations instead of equilibrium concentrations. IT is used to determine whether the initial reaction conditions will proceed in the forward or reverse direction.

In this reaction 2A <-> 2B + C exothermic (what happens if I increase container pressure)

it shifts left,

How does increasing temperature affect the equilibrium

it will shift the equilibrium to the left, producing more reactants and less products, thereby reducing the value of K.

less volume ____ pressure and more volume _____ pressure

more, less