Rate Equations Flashcards
What does a rate equation show
How changes in the concentrations of reactants affect the rate of reaction
What does each letter stand for in rate=k[A]^x[B]^y
-constant k is rate constant
-[A] and [B] represent the concentrations of reactants in mol/dm3
-powers x and y are the reaction orders with respect to A and B in equation
What is the overall order of a reaction
The sum of the orders for all the substances that appear in the rate equation
What does factor does rate constant (k) vary with
Temperature
What is a first order reaction
Reaction is first order with respect to a reactant if the rate of reaction is proportional to concen of that reactant, raised to power one in the rate equation
What type of line is on graph for first order reaction
Straight line passing through the origin
What is the half-life of a reaction
The time for the concentration of one of the reactants to fall by half
What is a second order reaction
If the rate of reaction is proportional to the concentration of that reaction squared, raised to the power two in the rate equation for that reactant
What does doubling concentration of X raised to power 2 in rate equation do to rate
Increases rate by factor of four
What does concentration-time graph look like for second order reaction and how to find gradient
Curve, draw tangents to curve to find gradient
What is a zero order reaction and what does concentration-rate graph look like
When rate of reaction is unaffected by changes in the concentration of that reactant, raised to the power zero
-graph is straight line
What do the units of the rate constant depend on
The overall order of the reaction
Does the half-life of a first order reaction change depending on starting concentration
No it is the same whatever the starting concentration
How to find the half-life of a second order reaction
Half-life is inversely proportional to the starting concentration
If reactant involved in mechanism after rate determining step what is its order and what about before
Zero, if before either first or second
Units of rate constant for zero order reaction
mol dm^-3 s^-1
Units of rate constant for first order reaction
s^-1
Units for rate constant for second order reaction
Mol^-1 dm^3 s^-1
Units for rate constant for third order reaction
Mol^-2 dm^6 s^-1
How to get units for rate constant
Rearrange to get rate/concens and unit for rate is moldm^-3 s^-1
What do concentration time graphs look like for first and second order reactions
Curved
Is half life constant throughout first order reaction
Yes
