Studied by 5 people
How is initial rate of a reaction calculated
Draw a tangent at t = 0
It is where the rate is greatest due to having the highest concentration of reactants
How can rate of reaction be calculated by volume of gas produced
Collecting the gas and measuring the change in volume.
This can be used using a gas syringe or an inverted burette, measuring water displacement
A data logger can also be used
How can rate of reaction be calculated by change in mass
Perform the experiment on a balance, if the mass change is significant, if not it will not work.
How can rate of reaction be calculated by change in transmission of light
If one of the reactants is coloured, so absorbed in the visible light spectrum. A colorimeter or spectrophotometer can be used which passes light of a specific wavelength through the studied solution, and measured the intensity of light transmitted by the components.
What does the Maxwell Boltzmann distribution curve show
The particles in a gas at a particular temperature show a range in their values of kinetic energy which is expressed in the curve.
What does the “successfulness” of a reaction depend on
The energy of the collision
The geometry of the collision
How does particle size affect the rate of reaction
Decreasing particle size increases rate of reaction
This is because increased surface area increases contact and probability of a collision
What is the rate equation
Rate = k[A]^m[B]^n, where k is the rate constant, [A] and [B] are the concentrations of reactants, and m and n are the reaction orders with respect to A and B
What is the overall order of a reaction
The sum of all individual orders
What are the units of k in a zero order reaction
mol dm-3 s -1
What are the units of k in a first order reaction
s-1
What are the units of k in a second order reaction
mol-1 dm3 s -1
What are the units of k in a third order reaction
mol-2 dm6 s -1
What does the graph of a zero order reaction look like
Conc-time graph = straight diagonal line showing constant rate
rate-conc graph = horizontal line
What does the graph of a first order reaction look like
Conc-time graph = curve showing rate decreasing with conc
Rate-conc graph = straight line passing through the origin with gradient k
What does the graph of a second order reaction look like
Conc-time graph = steeper at start than 1st order and levels off more but is still a negative curve
Rate-conc graph = parabola, rate is initially zero.
How can we deduce that a reaction is zero order
If changing the concentration of A has no effect on the rate, A is zero order
How can we deduce that a reaction is first order
If changing the concentration of A directly proportionally changes the rate. eg. doubling conc of A doubles rate of reaction then A is first order
How can we deduce that a reaction is second order
If changing the concentration of A lead to a square in rate. Eg. if doubling the conc of A quadruples the rate. Then A is second order
What is the rate determining step
The slowest step in a reaction mechanism, it determines the overall rate of reaction.
How do we determine a rate expression from a reaction mechanism
If there is a coefficient before a reactant then that is of that order. eg. 2A means A to the second order.
How do zero order reactants affect the rate determining step
They don’t as they don’t take part in the step
What is the Arrhenius equation
Arrhenius equation relates rate constant with temperature for chemical reactions. It is k = A * e^(-Ea/RT)."
k = rate constant
A = Arrhenius constant
Ea = Activation energy
T = temperature
R = gas constant (8.31)
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