Lectures 12-15

Question 1

Reaction Mechanism

Answer 1

A series of elementary steps that add up to the balanced chemical equation

Question 2

Molecularity

Answer 2

Number of molecules that react in an elementary step (a single step in the equation)

Question 3

Unimolecular

Answer 3

One molecule is reacting

Question 4

Bimolecular

Answer 4

Two molecules are reacting (even if they are the same molecule)

Question 5

Termolecular

Answer 5

Three molecules are reacting (this is uncommon)

Question 6

Dynamic Equilibrium

Answer 6

A chemical reaction that has no tendency for the products and reactants to change at different rates (equilibrium), but the direction in which we write the chemical equation is arbitrary (which means that the reaction can be reversed)

Question 7

Chemical Equilibrium

Answer 7

Occurs when a reactions and its reverse reaction proceed at the same rate

Question 8

Kc

Answer 8

Equilibrium constant in relation to concentrations
Kc = Keq = [C]^c [D]^d / [A]^a [B]^b
The equation above is products over reactants raised to whatever the concentration of either is when given this chemical equation: aA + bB <-> cC +dD
Kp and Kc are related like this:
Kp = Kc (RT)^∆n
R = 0.0821
T = Temperature
∆n = moles of gaseous products - moles of gaseous reactants

Question 9

Kp

Answer 9

Equilibrium constant in relation to partial pressures
Kp = (PC)^c (PD)^d / (PA)^a (PB)^b
The equation above is exactly the same as the equation for Kc, but with partial pressures instead of concentrations (the chemical equation is the same as well)
Kp and Kc are related like this:
Kp = Kc (RT)^∆n
R = 0.0821
T = Temperature
∆n = moles of gaseous products - moles of gaseous reactants

Question 10

Q

Answer 10

Measures the relative amounts of products and reactants present in a reaction at a given time (basically would just let you know if the reaction is in equilibrium or not)
Q = [C]^c [D]^d / [A]^a [B]^b
Again with reactants over products
Keq > Q –> Reaction will shift to the right
Keq = A –> Reaction is at equilibrium
Keq < Q –> Reaction will shift to the left

Question 11

Le Chatlier’s Principle

Answer 11

When a system in equilibrium is placed under stress, the system will undergo a change in such a way as to relieve that stress
Adding to one side causes a shift to the opposite side
Removing from one side causes a shift to that side
Increasing pressure causes a shift towards fewer moles of gas
When changing temperature, look at enthalpy to determine if heat can be considered a reactant or product