Chemistry (Kinetics) Flashcards
Rate and factors affecting it
Measured in M (molarity) / s (seconds)
1) Rate: how fast a reaction goes
2) Factors affecting rate:
a. Temperature
b. Activating energy (Ea)
c. Catalyst
Reaction constant
K= Ae^-Ea/RT
A: frequency factor how often molecules collide
-Ea: bigger value means smaller K
T: higher means more energy and faster reaction.
Rate Law
Concentration of reactants
Rate= K [reactants]^x
Forgives out by mechanism or data.
Rate order
1) Zero order:
a. Rate: K[A]^0= K
b. Units: M/s
c. [A] vs Temp graph: downward slope
2) First order:
a. Rate: K[A]^1
b. Units: M/s
c. ln[A] vs Temp graph: downward slope
3) Second order:
a. Rate: K[A]^2, K[B]^2, K[A] [B]
b. Units: 1/M•s
c. 1/[A] vs Temp graph: upward slope
4) Mixed order
a. Rate: K[A]^ 0.5 (non integer)
b. Units: M•s/s
Equilibrium and equilibrium constant (k)
Reaction goes back and forth and when rates are equal equilibrium is reached
Equilibrium constant: k= [products]/ [reactants]
Three types: K>1 (products favored), K~1 (same), K<1 (reactants favored)
Law of mass action
K= [products]^x/ [reactants]^x
Only gases and aqueous included
How to change value of equilibrium constant (k)
Changing temperature
- exothermic: Increasing T, Decreases K
- endothermic: Increasing T, increases K
How to change value of equilibrium constant (k)
Changing temperature
- exothermic: Increasing T, Decreases K
- endothermic: Increasing T, increases K
How to change [reactants] and [products]
- Add/remove either reactants or products
- Change volume/pressure.
- Affect concentration of reactants and products, BUT DOESNT CHANGE K
Reaction Quotient: Q
Are we at equilibrium?
Q too small equilibrium shifts to products. Too big shifts to reactants.
Equilibrium constant and ΔG
ΔG (spontaneity)= -R•T•ln(k)
Spontaneous (+): mostly reactants. K<1. ln= -
Non-spontaneous (-): lots of reaction happening. K>1. ln= +
Le chatlier’s Principle
System will try to fix whatever change is done to it
1) too much reactants shifts to products and vice versa.
2) Pressure
a. Decrease P| Need more P|Shift to side with more moles of gas.
b. Increase P| Need less P|Shift to side with less moles of gas.
3) Temperature
a. Increase T|Adding heat (endothermic)| shift
reaction to right
b. Decrease T| Take heat away(exothermic)| shift reaction to left
Le chatlier’s Principle
System will try to fix whatever change is done to it
1) too much reactants shifts to products and vice versa.
2) Pressure
a. Decrease P| Need more P|Shift to side with more moles of gas.
b. Increase P| Need less P|Shift to side with less moles of gas.
3) Temperature
a. Increase T|Adding heat (endothermic)| shift
reaction to right
b. Decrease T| Take heat away(exothermic)| shift reaction to left
How to change [reactants] and [products]
- Add/remove product or reactant
- change volume/ pressure
What will NOT change [reactants] and [products]
- Addition of a catalyst=> because it just helps get to equilibrium faster.
- Addition noble gas elements.
