4.6 Rate and Extent of Chemical Change Flashcards
Rate of reaction 1
= Amount of reactant used/Time
Rate of reaction 2
=Amount of product formed/Time
The quantity of reactant or product can be measured by
mass in grams or by a volume in cm3 g/s or cm3/s.
Where the slope is steepest in the graph the…
the reaction rate is fastest
how do you find gradient?
Gradient= difference in y
difference in x
Common ways of measuring rate:
- the loss in mass of reactants
- the volume of gas produced
- the time for a solution to become opaque or coloured.
Factors which affect the rates of chemical reactions
include:
- the concentrations of reactants in solution,
- the pressure of reacting gases,
- the surface area of solid reactants,
- the temperature
- the presence of catalysts.
what is collision theory
Collision theory explains how various factors affect rates of reactions. According to this theory, chemical
reactions can occur only when reacting particles collide with each other and with sufficient energy.
The minimum amount of energy that particles must have to react is called…
the activation energy
what happens while Increasing Temperature
Increasing the temperature means the particles gain
energy increases the speed of the reacting particles so
that they collide more frequently and more
energetically. More of the collisions are successful as
more have energy greater than the activation energy.
This increases the rate of reaction.
what happens while increasing concentration
Increasing the concentration of reactants in
solution, increases the number of particles in the
same volume and so increases the frequency
of collisions and therefore increases the rate of
reaction.
what happens while increasing volume of mass
Increasing the pressure of reacting gases, is the
same as increasing concentration. It increases
the number of gas molecules in the same volume
and so increases the frequency of collisions
and therefore increases the rate of reaction.
what happens if solid reactants have smaller pieces
the smaller pieces have larger surface area
what happens if you inrcease the surface area of a solid
Increasing the surface area of solid reactants increases
the frequency of collisions and so increases the rate of
reaction.
about catalysts:
Catalysts change the rate of chemical reactions but are
not used up during the reaction
Different reactions need different catalysts. Enzymes act
as catalysts in biological systems.
Catalysts increase the rate of reaction by providing a
different pathway for the reaction that has a lower activation
energy.
