Unit 4 - equilibroum

What is the difference between static equilibrium and dynamic equilibrium

• static equilibrium

  • Static equilibrium occurs when all forces are balanced and the system is at rest

• dynamic equilibrium

  • Dynamic equilibrium occurs when a system is in motion but the opposing forces are balanced, resulting in constant velocity or continuous but equal rates of forward and reverse reactions

What is chemical equilibrium

• the state of a reaction in which all reactants and products have reached constant concentrations in a closed system

WHat are the 3 characteristics of equilibrium

1. Observable properties do not change with time; constant macroscopic properties

2. the system is closed and temperature and pressure and kept constant

3. opposing internal processes proceed at equal rates (the reaction is reversible)

Graph the equilibrium

WHat happens if the equilibrium constant, Keq is large? WHat happens if its small?

• if Keq is large

  • ratio of product/reactant is large

  • the reaction happens to a large extent (more products than reactants at equilibrium)

• If Keq is small

  • ratio of products/reactant is small

  • the reaction happens to a small extent and there are more reactants than product at equilibrium

write k and k¹ for the following

What does Le Chatelier’s Principle state

• when a change is imposed on a system in equilibrium, the system will shift in the direction which counteracts the imposed change

What happens if an inert gas is added to a reaction? What way does the direction go toward

• nothing

• if an inert gas is added, it does not react with anything

What happens when a catalyst is added

nothing happens it just speeds up the reaction on both sides

Identify A B and C and describe what's happening in the graph

Use le chatlier principle to describe what's appening

Use le chatlier principle to describe what's appening

Use le chatlier principle to describe what's appening

describe the effect on the concentration of the bold substance by the following changes. Write INC for increase, DEC for decrease, and NC for no change

describe the effect on the concentration of the bold substance by the following changes. Write INC for increase, DEC for decrease, and NC for no change

Interpret the following graph in terms of the changes which musth ave been imposed on the equilibrium

The equilibrium us:

H_2(g) + I_2(g) → 2HI_(g) + 52 kJ

Interpret the following graph in terms of the changes which musth ave been imposed on the equilibrium

The equilibrium us:

H_2(g) + I_2(g) → 2HI_(g) + 52 kJ

Interpret the following graph in terms of the changes which musth ave been imposed on the equilibrium

The equilibrium us:

H_2(g) + I_2(g) → 2HI_(g) + 52 kJ

Interpret the following graph in terms of the changes which musth ave been imposed on the equilibrium

The equilibrium us:

H_2(g) + I_2(g) → 2HI_(g) + 52 kJ

The graph below shows the number of moles of all three species of the system plotted against time under a given set of conditions

CO_(g) + Cl_2(g) → COCl_2(g)

a) How much time was required for the system to reach equilibrium

b) Approximate the value of K using the concentration at t = 17s

c) Explain the changes 20 seconds after the initiation of the reaction

d) What change in conditions might have been imposed on the system 30 seconds after the initiation of the reaction?

e) are any events taking place between the interval of 15s and 20s? Explain.

f) what changes may have taken place at t = 45s

g) What differences would you have noted if a catalyst had been present during the entire course of this reaction?

h) List the changes you might impose on this system if you wanted to produce a maximum amount of COCl₂?

i) How could you account for the differences in the value of K at different points on the graph?

h) increase the concentration of reactants (Co and Cl2)

• increase the pressure

i) change in temperature

The equation represents a gaseous system at equilibrium

2SO_2(g) + O_2(g) → 2SO_3(g) + heat

Indicate the direction in which the equilibrium shifts when these changes are made. Briefly justify your answer

a) The concentration of SO₂ is increased

b) The partial pressure of SO₃ is decreased

c) The temperature of the system is decreased

d) The volume of the container is increased

e) Helium gas is added at constant volume so that the total pressure is increased

f) Helium gas is added. but the total pressure is kept constant

g) a catalyst is added 

a) right

b) right

c) right

d) left

e) no shift

f) left (inert gas at constant pressure affects equilibrium while intert gas at constant volume doesn't)

• increases volume

• decreases pressure

g) no shift

The equation represents a gaseous system at equilibrium

heat + 2H₂O_(g) → 2H_2(g) + O_2(g)

Indicate the direction in which the equilibrium shifts when these changes are made. Briefly justify your answer

a) The concentration of H₂ is increased

b) The partial pressure H₂O is increased

c) The concentration of O₂ is decreased

d) The temperature is increased

e) The volume of the container is decreased

f) Helium gas is added at constant volume so that the total pressure is increased

g) Helium gas is added, but the total pressure is kept constant

h) A catalyst is added

• 3

• A2 = 1..0M

• B2 = 4.0M

• AB = 2.8 × 10^-3 M

Who made the equilibrium law

• Guldberg and Wage

• Norwegian chemists

What is the difference between the Arrhenius acid-base theory and the bronsted-lowry acid-base theory

• The Arrhenius acid-base theory states that an acid is a substance which produced H+ when dissolved in water and a base is a substance that produces OH- when dissolved in water

• The bronsted-lowry acid-base theory states that acids are hydrogen ion (proton) donors and bases are hydrogen ion (proton) acceptors

• B-L is more accurate

Give a definition of Amphiprotic. Give a common example

• amphiprotic is a substance that can act as a substance or a base

• an example is water

what is a conjugate base and conjugate acid

• A conjugate base is a B-L acid that loses a proton

• A conjugate acid is a B-L base that gains a proton

• NH3 base → NH4+ conjugate acid

• H2O acid → OH- conjugate base

• NH3

• HPO4(2-)

• CO3(2-)

• HPO4(2-)

• H3PO4

• H2CO3

What are strong acids and weak acids

Whats the difference between them

• strong acids react with water and ionize to produce a high concentration of hydronium (H3O+)

• weak acids react with water and ionize to produce a low concentration of hydronium ions

  • all organic acids are weak acids

• While strong acids ionize to a large extent, with equilibrium favouring the product side, weak acids ionize to a small extent, favouring the reactant side

What are strong bases and weak bases

What is the difference between them

• strong bases dissociate in water to produce a high concentration of hydroxide ions

• weak bases- dissociate in water to produce a low concentration of hydroxide ions

• While strong bases dissociate completely, weak bases- ionize to a small extent, with equilibrium favouring the reactant side

What side does the equilibirum favor when it comes to weak acids and weak bases. Why?

• the reactant side, as weak acids and bases only ionize to a small extent to produce little products and keep more reactants

What side does equilibrium favor when it comes to strong acids and strong bases. Why?

• equilibrium favors the product side as strong acids and bases ionizes to a large extent so that more product is produced while little reactants remain

What is the general rule to tell if a base or an acid is strong or weak

• if k is »» 1, the acid or base is strong

• if k is ««« 1, the acid or base is weak

a) 2.8 × 10^-3M

b) 6.0 × 10^-6M

c) 4.7 × 10^-10M

d) 0.60

e) 2.00

f) 1.08

g) 12.11

h) 12.04

What is Kw of water

• 10^-14

What is the conjugate relationship

• Kw = Ka x Kb

What is wrong with the Arrhenius theory

• only considered aqueous systems

• could not explain why some molecular substances that lacked a hydroxide ion were basic

• also the theory suggested some ionic compounds (salts) that were made from neutralization reactions were neutral but they aren't