5.1 Rates, equilibrium and pH Flashcards
rate of reaction definition
change in concentration (of product or reactants) over time
order definition
power to which a concentration (of a reactant) is raised
overall order definition
sum of powers in the rate equation
rate constant definition
probability constant
half-life definition
time taken for concentration of a reactant to halve
rate-determining step definition
slowest step in a reaction mechanism
zero order
concentration of that reagent doesn’t affect the rate
first order
concentration of that reagent is proportional to the rate of reaction
second order
rate of reaction is proportional to the square of concentration of this reagent
rate constant relationship with constant half-life
kt1/2 = ln2 = 0.693
t1/2 = constant half-life
only for first order reactions where half-life is constant
plotting concentration against time
0 order = linear, negative gradient (decreasing half-life)
1st order = curved, negative gradient becomes less steep (constant half-life)
2nd order = curved, steeper but becomes less steep faster (increasing half-life)
plotting rate against concentration
0 order = flat horizontal line
1st order = linear line
2nd order = exponentially increased curved line
how to determine number of and what molecules are in rate determining step
0 order = not involved
1st order = 1 molecule of this reactant
2nd order = 2 molecules of this reactant
etc.
what number of different reactants in rate determining step means
1 = decomposition 2 = collision
why Arrehenius is important
standard rate equation doesn’t take into account temperature
Arrehenius units
T = temperature (Kelvin) R = gas constant (8.314 J K^-1 mol) EA = activation energy (J mol^-1) A = pre-exponential factor, takes into account number of molecules that exceed activation energy k = rate constant
why Arrehenius is important
standard rate equation doesn’t take into account temperature
Arrehenius units
T = temperature (Kelvin) R = gas constant (8.314 J K^-1 mol) EA = activation energy (J mol^-1) A = pre-exponential factor, takes into account number of molecules that exceed activation energy k = rate constant
mole fraction formula
mole fraction = number of moles/total number of moles of gas
factors affecting Kc
only temperature
partial pressure formula
partial pressure = mole fraction x total pressure
formula of Kp
exact same as formula of Kc but with partial pressures
only gaseous reactants/products