chapter 14

Question 1

what does a single arrow indicate

Answer 1

A single arrow indicates essentially all the reactant molecules are converted to product molecules at the end

Question 2

what does a double arrow indicate

Answer 2

A double arrow indicates reaction stops when only some off the reactant molecules have been converted into products

Question 3

arrow length indications

Answer 3

top longer= mostly product
bottom longer = mostly reactants
middle/even = substantial amounts
of product and reactants

Question 4

what happens to rate as reactant concentration decreases?

Answer 4

as reactant concentration decreases, the forward reaction rate decreases
as reactant concentration increases, the reverse reaction rate decreases

Question 5

what can the products react to reform?

Answer 5

Eventually, the products can react to re-form some of the reactants
assuming the products are not allowed to escape

Question 6

what are reversible processes?

Answer 6

Processes that proceed in both the forward and reverse direction are said to be reversible
Reactants products

Question 7

hypothetical reaction

Answer 7

slide 4 in notes
At some time between 100 and 110 sec,
the concentrations of both the Red and
the Blue molecules no longer change –
equilibrium has been established.
Notice that equilibrium does not mean
that the concentrations are equal!
Once equilibrium is established, the rate
of Red molecules turning into Blue is the
same as the rate of Blue molecules turning
into Red

Question 8

when is equilibrium established?

Answer 8

Eventually, reaction proceeds
in reverse direction as fast as
it proceeds in forward 
- Equilibrium established
reactant concentration decreases, 
forward reaction slows. As products 
accumulate, reverse reaction goes

Question 9

what happens once equilibrium is established?

Answer 9

Once equilibrium is established, the forward and reverse reactions proceed 
at the same rate, so the concentrations 
of all materials stay constant
Initially, only the forward
reaction takes place
As the forward reaction proceeds
it makes products and uses reactants

Question 10

what is a dynamic equilibrium?

Answer 10

Dynamic equilibrium is the condition wherein the rates of the forward and reverse reactions are equal
Once the reaction reaches equilibrium, the concentrations of all the chemicals remain constant
because the chemicals are being consumed and made at the same rate

Question 11

do they have equal rates at equilibrium?

Answer 11

The rates of the forward and reverse reactions are equal at equilibrium
But that does not mean the concentrations of reactants and products are equal

Question 12

when are products favored?

Answer 12

Some reactions reach equilibrium only after almost all the reactant molecules are consumed – we say the position of equilibrium favors the products

Question 13

when are reactants favored?

Answer 13

Other reactions reach equilibrium when only a small percentage of the reactant molecules are consumed – we say position of equilibrium favors the reactants

Question 14

what is the law of mass action?

Answer 14

The relationship between the chemical equation and the concentrations of reactants and products is called the Law of Mass Action
For general equation aA(aq)+bB(aq) cC(aq)+dD(aq),
the Law of Mass Action gives the relationship below
the lowercase letters represent the coefficients of the balanced chemical equation
always products over reactants (for reaction as written)

Question 15

what is K?

Answer 15

K is called the equilibrium constant

Unitless

Question 16

when do we use kc?

Answer 16

For reactions with only aqueous (aq) components

K = Kc (all in concentration units mol/L)

Question 17

when do we use kp?

Answer 17

For reactions with only gaseous (g) components

K = KP (all in pressure units of bar)

Question 18

what about reactions with both?

Answer 18

For reactions with both aqueous (aq) and gaseous (g) components
K is not Kc or KP (aqueous in mol/L and gases in pressure units of bar)

Question 19

what happens when k is larger than 1?

Answer 19

When the value of Keq&raquo_space; 1, we know that when the reaction reaches equilibrium there will be many more product molecules present than reactant molecules
the position of equilibrium favors products

Question 20

what happens when k is smaller than 1?

Answer 20

When the value of Keq &laquo_space;1, we know that when the reaction reaches equilibrium there will be many more reactant molecules present than product molecules
the position of equilibrium favors reactants

Question 21

what happens when the reaction is written backwards?

Answer 21

When the reaction is written backward, the equilibrium constant is inverted

Question 22

what happens when the coefficients ARE MULTIPLIED?

Answer 22

When the coefficients of an equation are multiplied by a factor, the equilibrium constant is raised to that factor

Question 23

when does kc = kp?

Answer 23

Kp = Kc when Dngas = 0 (unitless value)

The relationship between them is kp= kc x (RT) ^delta n gas

Question 24

what is delta n

Answer 24

the difference between the number of moles of

gas reactants and moles of gas products