module 3: 10.1 reaction rates Flashcards
3.2.2, 2.1.3 reaction rates
what does the term rate of chemical reaction measure
what is the equation for the rate
the rate of chemical reaction measure how fast a reactant is being used up or how fast a product is being formed.
rate = mol dm^-3 s^-1
rate = change in conc (mol dm^-3)
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time (s)
describe the rate of reaction (RoR) graph
- RoR is fastest at the start of the reaction, as each reactant is at its highest conc
- RoR slows down as the reaction proceeds because the reactants are being used up and their concentrations decrease
- once ONE of the reactants has been completely used up, the concentrations stop changing and the RoR is 0
what can cause the RoR to vary
- concentration (or pressure)
- temperature
- use of a catalyst
- SA of solid reactants
what does an effective collision require
- collision with the correct orientation
- particles having sufficient energy to overcome the activation energy barrier
what does increasing the concentration do to the Rate of reaction, RoR
An increase in concentration increases the number of particles in the same volume. As the particles would be closer together, they would collide more frequently. In a given period of time, there will therefore be more effective collisions and an increased rate of reaction.
what does increasing the pressure do to the rate of reaction, RoR
when a gas is compressed into a smaller volume the pressure of a gases increases and the RoR increases. The concentration of the gas molecules increases as the same number of gas molecules occupy a smaller volume. Closer gas molecules = more collisions, leading to more effective collisions
methods for following the progress of a reaction
- monitoring the removal (decrease in concentration) of a reactant
- monitoring the formation (increase in concentration) of a product
- monitoring the volume of gas produced at regular time intervals using gas collection
- monitoring the loss of mass of reactants using a balance
