UNIT 1 Section 8 - Rate Equations Flashcards
what is the rate equation
rate= K[A]a[B]b
what are the units of concentration
moldm-3
what are the units of rate
moldm-3s-1
what is a reaction order
the power to which a concentration is raised in the rate equation
what does order of reaction tell us about a reaction
how changing the concentration will affect rate
how do you determine the order of reaction
by doing an experiment and plotting the data on a graph
what happens if you change the concentration of a reactant with order 0
no affect/ doesnt change
what happens if you change the concentration of a reactant with order 1
the rate changes proportionally to the change in concentration
what happens if you change the concentration of a reactant with order 2
the rate changes square proportionally to the change in concentration
what happens to the rate constant if you increase the temperature
when the temp increases the rate constant increases as there is more kinetic energy in the particles and therefore more successful collisions
what is initial rate and how can we work it out
the rate of the reaction at 0 and we can work it out by finding the gradient using a tangent or straight line
why do we find the initial rate of a reaction
we can use initial rates to work out the rate equation by figuring out the orders of reactants
how would we find out the rate equation experimentally
- repeat experiment multiple times changing the concentration of A, B and C one at a time
2, work out the initial rate for each experiment of each A, B and C - work out orders and then the rate equation
What is the process of the Iodine Clock reaction
when we add hydrogen peroxide and iodine in solution together in the presence of starch the starch goes blue/black due to iodine and water being the products
- add sodium thiosulfate and starch and time how long the colour change is
- when you vary the concentration of iodine solution or hydrogen peroxide and keep all of the others constant you will be able to find out the order of the reactants by the changes in time taken and therefore initial rate according to the change in concentration
what ways can you measure the rate of reaction
- change in pH using a pH meter
- Amount of gas lost using mole equations
- volume of gas produced using gas syringe
- colorimeter using calibration curve
what is the rate determining step
the slowest step in a multistep reaction and appears in the rate equation
how do we know all reactants in the rate equation affect rate
if they didn’t affect the rate then their order would be 0 and therefore wouldn’t appear
other then reactants what else can appear in the rate equation
catalysts
what is the arrhenuius equation
K = A x e to the power of -Ea/RT
what does A stand for the in the Arrhenius equation
the arrhenuis constant
what does R and T stand for the in arrhenius equation
R = gas constand
T = temperature in kelvin
what does Ea stand for in the arrhenius equation
activation energy
what is the simplified version of the Arrhenius equation that doesn’t involve e
ln(K) = ln(A) - (Ea/RT)
how do you use an Arrhenius plot to work out activation energy
- plot the graph of ln(K) over 1/t
- draw a line of best fit
- work out gradient which represents -Ea/R
- gradient = -Ea/R then the gradient x R= -Ea
what is the Arrhenius equation in the form of y=mx + c
ln(K) = (-Ea/R) x 1/T ln(A)
y = m x + c
define the rate of reaction
change in conc per unit time measuring either products made of reactants used up
equation for rate of reaction
change in concentration/time
how do you measure the rate of reaction of really fast reactions
use a flash light to break bonds
use probs flashes to record amount of light absorbed by a species
what is the overall order of reaction
all of the orders added together
how could you tell that a second order graph really is second order reaction
draw concentration squared over rate graph and should be a straight line through origin
