Chem 140 Unit 1 Study Guide

Chapters 15 + 16A: Chemical Kinetics and Equilibrium

Mathematical Definition of rate

Rate= (𝚫 concentration) / (𝚫time)

Units of Rate

Molarity/ second

Rate of reaction

Speed of the chemical reaction

Rate of appearance

Speed that products form

Rate of disappearance

Speed that reactants break

Reaction Order

How reactant concentration affects rate of reaction

How to calculate reaction order of a reactant

See how much the rate changes when reactant doubles (none: 0, doubles: 1, quadruples: 2, etc.)

How to calculate overall reaction order

Add reaction orders of reactants together (no exponent= 1)

Rate law for 0 order

Rate=k\[A\]^0 or rate=k

Units for k for 0 order

M/s^-1

Integrated rate law for 0 order

\[A\]t=-kt + \[A\]0

half life equation for 0 order

t1/2= \[A\]0/2k or t1/2= (1/k) (\[A\]0/2)

x and y axes, slope, and y-intercept of 0 order graph

x axis: time

y axis: \[A\]

Slope: -k

y- intercept: \[A\]0

rate law for 1st order

rate= k\[A\]

units for k for first order

s^-1

integrated rate law for 1st order

ln\[A\]t= -kt + ln\[A\]0

half life equation for 1st order

t1/2= ln(2)/k

x and y axes, slope, and y-intercept for 1st order graph

x axis: time

y axis: ln\[A\]

slope: -k

y intercept: ln\[A\]0

Rate law of 2nd order

Rate=k\[A\]^2

Units of k for 2nd order

M^-1 s^-1

Integrated rate law for 2nd order

1/\[A\]t=kt + (1/\[A\]0)

x and y axes, slope, and y intercept for 2nd order graph

x axis: time

y axis: 1/\[A\]

Slope: k

y intercept: 1/\[A\]0

Half life equation for 2nd order

t1/2= 1/(k\[A\]0)

Factors affecting rate law

temperature, catalysts, concentration of reactants, nature of reactants

Basic Arrhenius equation

k= Ae^(-Ea/RT)

k= rate constant

A= frequency factor

Ea= activation energy

R= gas constant (8.314 j/mol\*K)

T= temperature (K)

Linear Arrhenius equation

ln(k)=(-Ea/R) (1/T) + ln(A)

x value: 1/T

y value: ln(k)

k= rate constant

Ea= activation energy

R= gas constant (8.314 j/mol\*K)

T= temperature (K)

A= frequency factor

Two point Arrhenius equation

ln(k2/k1)= (Ea/R) (1/T1)-(1/T2)

k= rate constant (first and second values)

Ea= activation energy

R= gas constant (8.314 j/mol\*K)

T= temperature (first and second values) (K)

Catalyst

molecules that affect the speed of a reaction without being permanently consumed. Used in an early step and replaced later. Can speed up or slow down reactions.

Equation for equilibrium constant of aA+bB ⇌ cC+dD

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

Liquids and solids omitted

Meaning of K

Position of equilibrium

If K>1

Reaction favors products

If K=1

Reaction doesn’t favor a side

If K<1

Reaction favors reactants

Kc vs Kp (states)

Kc= aqueous

Kp= gases

Kc vs Kp (equation)

\-Kp= Kc (RT)^Δn

Kp= position of a gas molecule

Kc= position of an aqueous molecule

R= .0821 L** atm / K * mol*

T= temperature (Kelvin)

Δn= # moles gas products- # moles gas reactants

Le Chatelier’s Principle (general summary)

when stress is applied to the equilibrium, the reaction will shift to relieve the stress

Le Chatelier’s Principle when a reactant is added

Shift to the right/ favors products

Le Chateliers Principle when a reactant is removed

Shift to the left/ favors reactants

Le Chatelier’s Principle when a product is added

Shift to the left/ favors reactants

Le Chatelier’s Principle when a product is removed

Shift to the right/ favors products

Le Chatelier’s Principle for exothermic reactions (increase and decrease in temp)

Increase in temp: shift to the left/ favors reactants

Decrease in temp: shift to the right/ favors products

Le Chatelier’s Principle for endothermic reactions. (Increase and decrease in temp)

Increase in temp: shift to the right/ favors products

Decrease in temp: shift to the left/ favors reactants

Le Chatelier’s Principle for the use of a catalyst

No affect on position, helps reach equilibrium if not at it

Le Chatelier’s Principle for an increase in volume

shifts to the side with more moles

Le Chatelier’s Principle for a decrease in volume

shifts to the side with fewer moles

How does adding an inert gas affect the pressure and partial pressure

Increase in pressure but no change in partial pressures

Le Chatelier’s Principle for an increase in pressure

Shifts to the side with fewer moles

Le Chatelier’s Principle for a decrease in pressure

Shifts to the side with more moles