rate of reaction
Rate of Chemical Reaction
reaction rate
instantaneous rate of reaction
instantaneous rate = d[species] / dt (slope of tangent at t)
rate curve: graphy plotting the amount of reactant or product against time
initial rate = instantaneous rate at t=0
average rate of reaction = change in amount (concentration) of a species / time taken for the change
following reaction
chemical
titration
procedures
physical
change in volume
Mg (s) + 2HCl (aq) --> MgCl2 (aq) + H2 (g)
change in pressure
Mg (s) + 2HCl (aq) --> MgCl2 (aq) + H2 (g) closed system
change in mass
CaCo3 (s) + 2HCl (aq) --> CaCl2 (aq) + H2O (l) + CO2 (g)
change in colour intensity
MnO4- (aq) + 5C2O42- (aq) --> Br- (aq) + 2H+ (aq) + 8H2O (l) + 10CO2 (g)
Br2 (aq) + HCOOH (aq) --> 2Br- (aq) + 2H+ (aq) + CO2 (g)
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change in transmittance of light
Na2S2O3 (aq) + 2HCl (aq) --> 2NaCl (aq) + H2O (l) + SO2 (g) + S (s)
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reaction rate is directly proportional to 1/ time taken
Molar Volume
gases
dm3mole-1
molar volume at 25C and 1 atm : 24.0 dm3 (r.t.p.)
molare volume at 0C and 1 atm : 22.4 dm3 (s.t.p.)
colume of gas = no. of moles x molar volume
Avogadro's Law: equal volumes of all game at same temp. and atm contain same number of molecules
volume ratio of two gases = mole ratio of the two gases
solids and liquids
cm3mol-1
depends on size of particles and closeness of packing of particles
def: the volume occupied by one mole of the substance
molare volume = molar mass / density (under same condition)
Factors affecting Rate of Reaction
simple collision theory
reactants must collide together, possess energy > Ea, orient correctly to one another to react
reaction rate is proportional to (number of effective collision) / time
concentration
increases
change of collision increases, rate increases
temperature
increases
chance of collision increases, rate increases
surface area
increases
higher collision frequency, higher rate of reaction
catalyst
lower Ea
more suitable molecules, rate increases