rates of reactions Flashcards
what are the 2 ways to find rate of reaction
quantity reacted or produced/ time
change in concentration/time
what is rate of reaction proportional to
concentration of a reaction raised to a power ( order of reaction)
what is a zero order reaction
concentration of a reactant has no effect on rate of reaction.
Any number to the power of zero is 1
what is a first order reaction
if concentration of reactant is double, rate also doubles
if concentration of reactant triples, rate also triples
what is a second order reaction
if concentration of reactant double, rate multiplies by 2 to the power of 2 = 4
If concentration of reactant triple, rate multiplied by 3 to the power of 2 = 9
what is the rate equation?
rate = k x [A]^m x [B]^n
how do you work out the overall order?
add up the orders ( m + n )
what is half-life
time taken for half of a reactant to be used up
first-order reactions have a constant half-life with the concentration halving every half life. What is this pattern called?
exponential decay
how do you calculate rate constant from the constant half-life with exponential decay
k = Ln2/ half-life
what factors affect rate constant?
1)increasing temperature as it shifts boltzmann distribution to the right increasing proportion of particles that exceed activation energy
2) as temperature increases, particles move faster and collide more frequently
what is the arrhenius equation>
k = A x e^-Ea/RT
K = rate
A = pre-exponential factor ( frequency)
e^-Ea/RT = exponential factor ( linked to activation energy and temperature_
R= gas constant = 8.31
T= temperature in kelvin
what does the exponential factor ( e^Ea/RT) represent?
proportion of molecules that exceed Ea
what does pre-exponential factor represent?
frequency of collisions with the correct orientation
what is the arrhenius equation in logarithmic form?
k = - Ea/RT + LnA
