Change in concentration of reactant or product per unit time.
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Define order wrt a reactant
The power in which concentration of a reactant is raised to in the rate equation.
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What is the overall order?
Sum of the individual orders.
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What is the rate constant, k?
The constant that links rate of reaction with concentration of reactants raised to the powers of their orders in the rate equation.
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Define half life
The time taken for the concentration of a reactant to reduce by half, t1/2.
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What is the rate determining step, RDS?
The slowest step in the reaction mechanism of a multi-step reaction.
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What is the rate equation?
rate=k[A]^m[B]^n (moldm^-3s^-1 dependent on reaction)
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How do you calculate the rate constant, k?
k=rate/[A]^m[B]^n
8 of 20
Describe a concentration-time graph for zero order and what this tells us.
As concentration decreases, rate stays constant and therefore tangents stay constant. T1/2 decreases with time so therefore rate=k.
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Describe a concentration-time graph for first order and what this tells us.
As concentration decreases by a factor of 2, rate decrease by a factor of 2 and therefore tangents decrease. T1/2 remains constant so k=ln2/t1/2
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How can you plot concentration-time graphs?
Using continuous measurements taken during a reaction such as pH changes, gas volumes, pressure changes and colour changes.
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Describe a rate-concentration graph for zero order.
Changing the concentration has no effect on rate.
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Describe a rate-concentration graph for first order and what this tells us.
Doubling the concentration, doubles the rate of reaction so therefore k=rate/[A].
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Describe a rate-concentration graph for second order.
Doubling the concentration, quadruples the rate of reaction.
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How can a rate-concentration graph be plotted?
Using continuous monitoring or the initial rates method, a clock reaction using time, where rate is directly proportional to t1/2.
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Define reaction mechanism.
A series of steps that together make up an overall reaction, with as many particles of each reactant as there is in the RDS.
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What effect does temperature have on k?
Raising the temperature, increases rate of reaction by increasing k. Typically doubling rate, doubles k.
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What is the Arrhenius equation?
The exponential relationship between k and temperature, where A= pre-exponential factor, Ea= activation energy, R= gas constant and T= temperature (in k 273k=0)
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How to use alternative forms of the Arrhenius equation to determine Ea graphically.
-Ea/R in the gradient of the line. -Ea/E=x so Ea=-Rx.
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How to use alternative forms of the Arrhenius equation to determine A graphically.
lnA gives you the y intercept. lnA=x so A=e^-x.
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Other cards in this set
Card 2
Front
Define order wrt a reactant
Back
The power in which concentration of a reactant is raised to in the rate equation.
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