Unit five JT Flashcards
define rate of reaction
the change in concentration of a reactant or product per unit time
define initial rate of reaction
the change in concentration of a reactant or product , per unit time at the start of the reaction when T=0
how would an increase in temperature effect rate of reaction?
particles would have more kinetic energy, this increases frequency of collisions. A greater proportion of molecules will have the activation energy or greater to react
how would an increase in pressure/concentration effect rate of reaction?
more particles in the same volume increases the frequency of collisions
how would the presence of a catalyst effect rate of reaction?
catalysts reduce activation energy so a greater proportion on particles will have enough energy to react
how would an increase in surface area effect rate of reaction?
as surface area increases, the rate of reaction generally increases
equation for rate of reaction
change in concentration (or moles) of product / time
catalyst definition
an enzyme that lowers the activation energy of the reaction by providing an alternate lower energy pathway for the reaction to follow
homogenous catalyst definition
the catalyst is in the same physical state as the reactants
e.g. making esters with sulfuric acid as a catalyst
heterogenous catalyst definition
the catalyst is in a different physical state than the reactants
e.g. the Haber process
the Haber process
H2(g) + 3h2(g) –>
the Contact process
2SO2(g) + O2(g) –>
what is the catalyst in the contact process?
vanadium oxide (V2O5)
list three advantages of using a catalyst
lower energy demands, less carbon dioxide produced, less environmental impact
convert 1cm3 into dm3
divide by 1000
0.001dm3 = 1cm3
Le Chatelier’s Principle
When a system in dynamic equilibrium is subject to change, the position of the equilibrium will shift to minimise the effect
Whats happens to the equilibrium when you increase pressure?
It will shift to the side with the fewest moles of gas as the system will oppose the change by trying to decrease the pressure
Whats happens to the equilibrium when you increase temperature?
It will favour the endothermic reaction as the system will try to oppose the change by trying to reduce the temperature
what is the reaction if delta H is positive?
endothermic
what is the reaction if delta H is negative?
exothermic
Whats happens to the equilibrium when you add a catalyst?
the position of the equilibrium will not change as the catalyst will increase the rate of both the forwards and reverse reactions equally
what does Avogadro’s number represent?
The number of atoms per mole of the carbon-12 isotope
6.023 x 10^23
Heterogeneous equilibrium definition
A reaction equilibrium in which some of the reactants and products are in different states
Homogeneous equilibrium definition
A reaction equilibrium in which the reactants and products are all in the same state
Kc=
[C]c x [D]d
[A]a x [B]b
What does the capital letter represent in the Kc equasion
concentration (moldm-3)
What does the lowercase letter represent in the Kc equasion
number of moles
What is the equilibrium constant?
A measure of the position of the equilibrium in dynamic equilibrium
Where is the equilibrium of Kc = 1
halfway between the reactants and products
Where is the equilibrium of Kc < 1
right hand side, backwards reaction and reactants are favoured
What is the temperature in the Haber process?
450C
What is the pressure in the Haber process?
200 atmospheres
What is the catalyst in the Haber process?
Iron
X axis on the boltzmann distribution diagram
Number of molecules with a given energy
Y axis on the boltzmann distribution diagram
energy
