unit 4 section 2 rate equations and Kp Flashcards
how do you work out the rate of reaction of a straight line graph
gradient = change in y /change in x
how do you work out the rate of reaction of a curve
you draw a tangent to the curve and then work out the gradient of the tangent
what is the rate reaction for this general equation A + B = C + D
rate = K[A]^m[B]^n
[A]- concentration of A
[B]- concentration of B
K- rate constant
m&n - the order of reaction
what is m & n restricted to
it is restricted to 0,1 and 2
what is the arrhenius equation
k = Ae^(-Ea/RT)
k = rate constant
A= arrhenius constant
Ea= activation energy (j mol-1)
R= gas constant (8.31)
T= temperature (K)
what does higher Ea mean in the arrhenius equation
the higher the Ea the smaller the value of K therefore the slower the reaction.
what is the other way the arrhenius equation can be written
lnk = -Ea / RT + ln A
what is partial pressure
each individual gas exerts its own pressure
what is a mole fraction
it is the proportion of gas mixture that is made up of a particular gas
what is the equation for mole fraction
mole fraction of a gas in a mixture = number of moles of gas in a mixture / total number of moles of gas in a mixture
what is the equation for the partial pressure of gas in a mixture
mole fraction of gas x total pressure of the mixture
what is Kp
it is the equilibrium constant for a reversible reaction where some, or all , products and reactants are gases
give the equation for Kp using this general equation aA(g) + bB(g) = cC(g) + dD(g)
it is the same equation as Kc however you use the partial pressure instead of the concentration (this is done by adding pp in front of the molecule) and the brackets are normal brackets and not square brackets
what happens when you change the temp on equilibrium in gases
-if increase -the equilibrium will shift in the endothermic direction
-if decrease - the equilibrium will shift in the exothermic direction
what happens when you change the pressure of equilibrium in gases
the position of equilibrium shifts in such a way the partial pressure of the reactants and products at the new equilibrium position keeping Kp constant.
what effect does a catalyst have on the Kp
it has no effect as it speeds up the rate of reaction of both the forward reaction and the backward reaction
what is the arrhenius equation used for
it is used to determine the effect of a temperature change on the rate constant
how is a zero order reaction presented on a graph
it is presented as a horizontal straight line.
it has the equation: rate = k
the graph would look like a y=1 graph
how is a first order reaction presented on a graph
it is present as a straight line graph
it has the equation: rate = k[A]
it would look like the graph y=x
how is a second order reaction represent on a graph
it is presented as curved line
it has the equation: rate = k[A]^2
it would look like the graph y = x^2
Rate = k [E]
Explain qualitatively why doubling the temperature has a much greater effect on the rate of
the reaction than doubling the concentration of E
(3)
reactions occur when the molecules have the required activation energy. by doubling the temperature it causes many more molecules to have the required activation energy. whereas doubling the concentration of E only doubles the amount of particles with the activation energy.
State how the initial rate is obtained from a graph of the concentration of the product
against time
(2)
-(Calculate) gradient (of tangent/curve/graph)
-at t=0 or at start of graph/curve
how do you convert kpa to pa
x1000
what is the iodine clock experiment
it is a reaction where you can time how long it takes for a colour change