Rate= [A]m[B]n -m&n are orders or reaction (1,2 or 0) -A & B are Reactants -K is Rate Constant
- If [A] changes and the rate stays the same ---> 0 order -If the rate is proportional to [A] ---> 1st order -If the rate is proportional to [A]2 (if [A] doubles, the rate will double) ----> 2nd order
Overall order is m + n
Rate Equations e.g. CH3COCH3 (first) + I2 (zero) -- H+ (first)----> CH3COCH2I + H+ + I- Rate = K[CH3COCH3}1[H+]1[I2]0 ----> Rate = K[CH3COCH3][H+]
Rate Constant -Write out equations -Insert the numbers that you have -Rearrange the quation to calculate what you want -work out the units.
Initial Rate -Find using a concentration-time graph, calculate the curve of the graph by using a tangent. -Then divide the reactant part of the tangent by the time part.
Rate Determining step -Mechanisms have one or a series of steps. -In a series of steps the overall rate is determined by the step with the slowest rate ----> Rate determining step.
Orders of reaction and rate determining step: -Order of reaction with respect to a reactant shows the number of moleccules that reactant are involved in the rate determining step. -So if a reaction is second order with respect to X, there wil be 2 molecules of X in the rate-determining step.
Reversable Reaction Symbol:
As reactants are used up the forward (-->) reaction slows down. When more products are formed the reverse (<--) reaction speeds up. Dynamic equilibrium is when the forward and backwards reaction are the same rate. (this only happens in a closed system and at a constant temperature)
Equilibrium constant = Kc
aA + bB dD + eE
Kc= [D]d [E]e
Calculating Kc -Put numbers in the equation. -Work out units, they may vary. -Might have to work out equilibrium concentrations: 1. Work out moles at equilibrium 2. divide moles by volume of container 3. Put numbers in Kc.
Changing the Equilibrium
Changing the temperature, Concentration and pressure alters the position of the quilibrium. <---more reactants or ---> more products
Le Chateliers Principle: The position of equilibrium will shift to conteract a change in temperature, concentration or pressure.
TEMPERATURE: -If it increases, equilibrium will shift to the endothermic (+) direction. -If it decreases equilibrium will shift exothermic (-) direction. -Affects the value of Kc.
CONCENTRATION: -Kc is fixed at a given temperature. -If concentration of one thing changes, the concentration of others must change to keep the value of Kc the same.
CATALYST: -No effects on the position of equilibrium or Kc. -It only increases the forward and backwards rate by the same amount. -Equilibrium is reached faster.