Chapter 4- Chemical Equilibrium

Question 1

How do we determine whether the reactants or products are favoured on a graph of the two?
(Page 184)

Answer 1

Products start at zero and which ever equilibrium line is higher on the graph is favoured

Question 2

What exactly is equal at equilibrium?

Answer 2

The rates of the reactions

NOT the concentrations

Question 3

What is the equation for the equilibrium constant (K) for the reaction:
aA + bB cC + dD

Answer 3

K= ([C]^c [D]^d)/([A]^a [B]^b)

[ ] means molar concentration of element

Question 4

What is the law of mass action?

Answer 4

The relationship between the balances chemical equation and the expression of the equilibrium constant

Question 5

Which direction of the reaction is favoured when the equilibrium constant (K) is much larger than 1?
Roughly equal to 1?
Much less than 1?

Answer 5

Larger- forward reaction is favoured
Roughly equal- neither reaction is favoured, forward proceeds about halfway
Smaller- reverse reaction favoured

Question 6

What happens the the equilibrium constant (K) equation when you:

a) reverse the equation?
b) multiply the coefficients in the equation by n?
c) add two or more chemical equations to obtain an overall equation?

Answer 6

a) invert the K equation
b) put the K equation to the power of n, (…)^n
c) multiply the corresponding equilibrium constants by eachother to obtain overall constant
Ex: K1= A 2B
K2= 2B 3C
Koverall= K1 (K2)

Question 7

What are the two ways we can express the equilibrium constant in terms of?

Answer 7

Concentration- Kc (moles/litre)
Partial pressures of gases- Kp (atm)

They are not unitless since those units cancel

Question 8

How do you find the concentration of an ideal gas A given the number of moms and the volume in litres?

Answer 8

[A]= n/V

PV=nRT
P=n/V (RT)
P=[A]RT

Question 9

What is the equation that connects Kc to Kp?

Answer 9

Kp= Kc(RT)^(c+d-(a+b))

Question 10

What states of matter are not included in the equilibrium expression?

Answer 10

Solids, liquids

Question 11

If given the concentration of one compound in an equilibrium, how do you find the other concentrations?

Answer 11

Use stoichometry

Question 12

If no initial concentration is given for an element in an ICE question, what do we assume it’s concentration is?

Answer 12

0 M

Question 13

What is the reaction quotient (Qc)?

Answer 13

The ratio at any point in the reaction of the concentrations of the products raised to their stoichiometric coefficients divides by the concentrations of the reactants raised to their stoichiometric coefficients
Qc= ([C]^c [D]^d) / ([A]^a [B]^b)

This is used to determine how close a reaction is to equilibrium

Question 14

What is the reaction quotient with a reaction mixture containing only reactants?
Only products?
Perfect equilibrium?

Answer 14

Only reactants- 0
Only products- infinity
Equilibrium- it will equal the exact value of K
QK- goes to left

Question 15

How do you find equilibrium concentrations when giving the equilibrium constant and all but one of the equilibrium concentrations?

Answer 15

Use the Equation for K of products over reactants and re arrange to solve for concentration of missing element

Question 16

Do example questions on finding equilibrium concentrations from initial concentrations and the equilibrium constant.
Page 215-217

Answer 16

Aight

Question 17

What does it mean to approximate an equilibrium problem?

How do we check the validity?

Answer 17

Mean to cross out any x that will result in a small change when added or subtracted to a bigger value
Ex: 1-x would be small because we know x is small so it would barely affect 1

We check this by taking the ration of x divided by the number it was subtracted from and timesing it by 100, if it’s less than 5% you good

Question 18

What is Le Chatelier’s Principle?

Answer 18

States that when a chemical system or equilibrium is disturbed, the system shifts in a direction that minimizes the disturbance

Question 19

What happens if we increase the concentration (add more) of the reactants of an equilibrium reaction?

Answer 19

The reaction will shift right

Question 20

What states of elements will not be affected when increasing concentration, volume, or pressure?

Answer 20

Solids

Liquids

Question 21

What happens to an equilibrium reaction when the volume of reactants is increased?

Answer 21

Increase in volume=decrease in pressure

The reaction will shift to the side with more moles of gas

Question 22

What happens to an equilibrium reaction when the volume of reactants is decreased?

Answer 22

Decrease in volume= increase in pressure

The reaction will shift to the side with less moles of gas

Question 23

How do catalysts or inert gases at constant volume change the equilibrium?

Answer 23

They do not change the equilibrium

Question 24

How does the temperature change affect the equilibrium shifting?

Answer 24

Temperature=heat
Exo- heat in products
Endo- heat in reactants
The reaction will shift to the side opposite of where heat was added