Rates of reactions
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Calculation for average rate of reaction
average rate = change in value / time taken
What is needed for a reaction to occur
the reactant particles need to collide with a certain amount of energy
What can be done to increase the number of collisions between reactant particles and the certain amount of energy?
increasing the concentration increasing the surface area increasing the temperature adding a catalyst, speeds up reactions without getting used up itself. They can be recovered unchanged at the end of a reaction
How can the rate of a reaction be increased?
increasing the number of collisions with this energy will speed up a reaction
What unit should be used when calculating the rate of reaction when measuring the volume of a gas?
cm3s-1
How can one tell a reaction has finished on a line graph?
The line that is plotted becomes horizontal, indicating that even though time is progressing, there is no increase in the mass of gas that is produced
What unit is used in the reaction rate formula
gs-1
What is the test for CO2?
Co2 turns lime water cloudy
What is the test for oxygen?
oxygen should relight a glowing splint
What is the test for hydrogen?
hydrogen burns with a pop
Why does increasing the concentration of the reactant particle increase the rate of collisions between reactant particles and the certain amount of energy?
as there is more reactant particles in a given volume of space
Why does increasing the surface area increase the rate of collisions between reactant particles and the certain amount of energy?
as more of the reactant particles are exposed
Why does increasing the temperature increase the rate of collisions between reactant particles and the certain amount of energy?
reactant particles have more energy and more speed so a greater number will collide more often and with greater energy
What effect does increasing the particle size have on the rate on a reaction?
As the particle size inceases (i.e. from powder to lumps) the reaction slows down.
An experiment to do with gas. During a reaction the mass of the reacting mixture decreases, explain why the mass loss decreased?
loss of gas reaction vessel not sealed so gas can escape thus mass decreases
The rate of a reaction decreases with time, explain why.
the concentration of reactants decrease the reactant particles are used up as the reaction proceeds thus the rate of reaction decreases
what is a catalysts
Catalysts speed up chemical reactions without being used up in the reaction. Enzymes are biological catalysts. (enzymes)