rates equilibrium and pH part one
- Created by: Andrei stephen
- Created on: 21-09-14 13:33
View mindmap
- equilibrium pH and rate determining step
- the rate determining step
- this is the slowest step in a reaction this sets the rate of the reaction
- to start off it is best to write a balanced stoichiometric equation this will tell you all the reactants you will be working with
- this equation does not tell you about the reaction mechanism for the rate determining step to work this out we need to carry out some rate experiments
- the aim of these experiments is to work out the orders of the reactants as this information is needed to determine the rate determining step
- an example is NO2+CO===> NO+ CO2
- from experimentation we determine that NO2 is second order and CO is zero order
- the equilibrium constant
- the equilibrium constant is called Kc
- here is an example of how to do a basic question on this
- N2042NO2
- the kc for this would be Kc=[NO2]^2/[N2O4]
- The units are worked out like so=(mols dm^3)/mols dm^3 so your units for this can be worked out by canceling giving the unit of mols dm^3
- the kc for this would be Kc=[NO2]^2/[N2O4]
- N2042NO2
- here is an example of how to do a basic question on this
- this constant can only be calculated when a reaction is in dynamic eqaulibrium
- this can only occur in a closed system when the concentrations of the products and reactants stay the same
- the equilibrium constant is Kc= products/reactants
- for example
- the amount of moles in the equation for each reactant and product is the power of the concentration of each reactant and product
- Kc can have no units
- position of equilibrium and the equilibrium constant
- when the value for equalibrum = 1 this means that there is equilibrium halfway between the reactants and products
- if the kc is larger than one the reaction favours the products this means that the position of equilibrium is to the right
- if the kc is less than one this means that the position of equilibrium is favouring the reactants shifting equilibrium to the left
- temperature if increased will shift equilibrium in the endothermic direction
- if temperature is decreased it is shifted in the exothermic direction
- pressure has no effect on kc as the system will shift to maintain equilibrium in the system
- catalysts also don't effect equilibrium as they speed up the forward and reverse reaction equally
- the equilibrium constant is called Kc
- the equilibrium constant Kc vs the rate constant k
- large Kc= equilibrium lies to the right so more products are produced
- large k= fast rate of reaction
- pressure and concentration have no effect on Kc
- pressure and concentration cause the value of k to change
- high temperature shifts the equilibrium in the endothermic direction
- low temperature shifts equilibrium in the exothermic direction
- temperature increases the rate of reaction increasing the value for k
- this changes Kc
- low temperature shifts equilibrium in the exothermic direction
- temperature increases the rate of reaction increasing the value for k
- low temperature shifts equilibrium in the exothermic direction
- low temperature shifts equilibrium in the exothermic direction
- Kc can be worked form a balanced equation k can only be used from experimental data
- large Kc= equilibrium lies to the right so more products are produced
- acids
- three definitions for acids and bases
- arrhenius
- acid = H^+
- base = OH^-
- bronsted lowry (important need to know)
- Acid = a proton donor
- base= proton acceptor
- lewis
- acid = electron acceptor
- base=electron donor
- arrhenius
- all acids have hydrogen in them
- three types of basic acids
- monobasic acids these have only one available hydrogen
- dibasic acid these have two available hydrogens
- tribasic acids have three available hydrogens
- conjugate acid base pairings
- a typical acid base reaction
- HCL+NaOH NaCl + H2O
- this reaction is reversible in the forward reaction the HCl is an acid ans the NaOH is a base
- in the reverse reaction the H2O can give away a H^+ ion to the NaCl which will accept it as such the water molecule becomes a acid and the NaCl becomes a base
- the NaCl is the conjugate base for HCl and the H2O is the conjugate acid for the NaOH
- this reaction is reversible in the forward reaction the HCl is an acid ans the NaOH is a base
- HCL+NaOH NaCl + H2O
- another example
- HNO2+H2O====> H3O^+) +NO2^-
- in the forward reaction the HNO2 is the acid and the H2O is the base
- the conjugate base for HNO2 is NO2^-
- the conjugate acid for H2O is H3O ^+
- in the forward reaction the HNO2 is the acid and the H2O is the base
- HNO2+H2O====> H3O^+) +NO2^-
- the definition for a conjugate acid base pairing is a pair of two species that transform into each other by the loss or gain of a proton
- a typical acid base reaction
- acid reactions
- reactions with bases and alkalis
- acid + base/alkali====> salt + water
- acid and carbonate
- reactions with bases and alkalis
- three definitions for acids and bases
- the rate determining step
Comments
No comments have yet been made