rates of reactions. Flashcards
how are reaction rates measured?
by observing the changes in quantities of reactants and products over time.
how do you measure rates of reactions?
rate= change in concentration/change in time
what is the rate of reaction proportional to?
the concentration of a particular reactant raised to a power.
what is the rate constant?
the constant that links the rate of reaction with the concentrations of the reactants raised to the powers of their orders in the rate equation.
how can orders NOT be found?
directly from the chemical equation
where can orders be found?
by monitoring how a physical quantity changes over time.
how are concentration-time graphs plotted?
from continuous measurements taken during the course of a reaction.
what are methods for continuous monitoring?
monitoring by gas collection
monitoring by mass loss
colorimeter
How do you monitor with a colorimeter?
the wave length of light passing through a coloured solution is controlled using a filter. The amount of light absorbed by a solution is measured.
how do you know the order with respect to a reactant from a concentration-time graph.
straight line going downwards from the initial rate- zero order
decreasing line going downwards from the initial rate- first order.
second order- more steeper
what is half life?
the time taken for half of a reactant to be used up.
what order has a constant half life?
first order.
what is the pattern called?
exponential decay.
what are the two methods for determining the rate constant from a concentration time graph?
calculating the rate constant from the rate.
calculating the rate constant from the half life.
how do you calculate the rate constant from the rate?
draw a tangent,
rate= gradient= concentration/time
k=rate/concentration at point.
