3.1.9 Rate Equations Flashcards
Define Rate of reaction.
Change in concentration per unit time.
What are the units of rate?
mol dm-3 s-1
Define activation energy.
Minimum energy required for a reaction to occur.
How does a rate change when the concentration of a zero order species is doubled?
Rate would stay the same.
How does a rate of reaction change when the concentration of a first order species is doubled?
Rate would also double.
How does a rate of reaction change when the concentration of a second order species is doubled?
It would multiply by 4.
What are the two experimental methods for measuring a rate of reaction.
Continuous monitoring method and initial rates method.
How can a continuous monitoring practical be tracked?
Measure the concentration of reactants at regular time intervals.
What graph can be plotted from a continuous monitoring practical?
A concentration time graph.
How can a an initial rate be found on a concentration time graph?
draw a tangent at t=0 and calculate gradient.
Which equation is used to calculate a gradient?
dy/dx
Complete the missing spaces with changes in concentration, rate, and order of reaction.
Complete the missing spaces with changes in concentration, rate, and order of reaction.
Complete the missing spaces with changes in concentration, rate, and order of reaction.
Complete the missing spaces with changes in concentration, rate, and order of reaction.
Complete the missing spaces with changes in concentration, rate, and order of reaction.
How is an initial rates practical carried out?
Vary the concentration of 1 of the reactants and measure the time taken to react the endpoint.
How is rate of calculated the initial rates method.
rate = 1/t
why is rate 1/t in the initial rates method?
As the concentration of the product formed at the end point of the reaction is
fixed, it
can be taken as a constant.
What does a rate concentration graph looks like for a zero order reaction?
What does a rate concentration graph looks like for a zero order reaction?
What does a rate concentration graph looks like for a zero order reaction?
During an experiment, How can the order of a reactant be changed to be come zero order?
Use a large excess of that reactant as the concentration change would be negligible so its concentration can be taken as constant.
What is the rate equation if the units of k are s-1?
r = k [A]
What is the rate equation if the units of k are mol -2 dm 6 s-1?
r = k [A]^3
What are the units of k if the rate equation is r = k [A]
s-1
What are the units of k if the rate equation is r = k [A][B][C]?
mol -2 dm 6 s-1
What is the Arrhenius equation for the rate constant k?
What is the natural log form of the Arrhenius equation?
How does the Arrhenius equation match the general equation for a straight line?
Draw a sketch of a typical Arrhenius equation graph. Include the axes, the intercept and what the gradient of the line is equal to.
How do you work out the activation energy (Ea) from this graph?
- Gradient = negative Ea/R (Ea is ALWAYS a POSITIVE number)
- Gradient x R = Ea
- R has units of J mol−1 K−1 so Ea calculated from gradient will be in J mol−1
- Divide by 1000 to convert Ea to kJ mol−1
