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Chemistry Unit 4 > Kinetics > Flashcards

Flashcards in Kinetics Deck (12):

Define rate of reaction

Change in concentration of any reactant or product per unit time.


How do you find rate from a concentration-time graph?

Draw a tangent to the graph at the time you wish to find the rate, and find the gradient of that tangent.


What is the rate equation?

rate = k[A]^m[B]^n


What is the unit for rate?

mol dm^(-3)


In the rate equation, what do the powers represent?

The order of reaction with respect to the reactant it is the power of.


What is the overall order of reaction?

The sum of the powers.


What are the units for the rate constant?

You have to work it out each time you calculate it.


What happens to the rate constant if you increase the temperature of a reaction, and why?

Increasing the temperature of a reaction gives the reactants more energy. This means there are more successful collisions per unit time, causing the rate of reaction to increase. The concentrations and orders of reaction stay the same, so rate constant (k) increases to keep the equation balanced.


Explain what 'zero order' means.

If a order with respect to a reactant is 0, this reactant has no effect on the rate of the reaction.


What is the rate-determining step?

The slowest reaction in a multi-step reaction.


How we can figure out which step in a reaction is the rate-determining step?

Comparing the orders of reaction (from the rate equation) and the reaction mechanism.


Which reactants appear in the rate equation?

Only those that are involved in the rate-determining step of the reaction.