IEB Grade 12 Energy changes, rates of reaction and chemical equilibrium notes
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Course
Physical Sciences
Institution
12th Grade
This document contains notes on energy changes, rates of reaction and chemical equilibrium from the IEB SAGS document. It includes all the IEB SAGS definitions as well as very detailed explanations on all the concepts in this section.
Collision
theory
states that in order for particles react must collide
effectively ( with
>
correct
two to .
they
orientation and sufficient energy )
>
successful collisions are collisions that result in a chemical reaction
> the greater the number of successful collisions that occur per second ,
the
greater the rate
of a chemical reaction
1. 1 Successful collisions
1. The reactant
particles must collide
2. The reactant
particles must collide with sufficient kinetic energy (activation energy EA ) .
at the
bonds and form bonds
moment of impact to break
existing new
energy required
activation chemical reaction
-
to start a
energy is the minimum
colliding molecules must have kinetic
energy equal to greater than the activation
-
a or
of reaction before the reaction can take place
energy
a
kinetic molecules collide is the principal of the
'
energy carry when they source
energy
that must be invested in a reaction to get it started
reactant
slowly bounce off
'
if particles too with too little kinetic
are
moving energy they,
one another and the collision is unsuccessful
3. The reactant particles must collide with the correct orientation
if they the correct at the moment of impact
they will bounce off
-
are not
facing way ,
each other
, ( stronger bonds require more
energy to break and release more
energy when formed )
Energy changes in reactions
> to break a bond requires the molecules to take in atoms apart which is
energy to pull ,
an
endothermic
change (energy in ) , where the atoms vibrate more until they separate
> to form a bond ,
atoms must give out energy to become combined and electronically more
(energy out )
stable this is ,
an exothermic
change
2. 1 Potential
energy profile
diagram used to describe the mechanism of reaction and show the
changing potential
> a
energy between the reactant and product that occurs
2.1.1 Exothermic reaction (energy released )
Hz (g) Clzcg , 2 HCl
+ →
(g)
> the activated complex occurs when successful
collisions take place ,
here old bonds are
being
broken and new bonds are
being formed
> activated complex is a
high energy ,
unstable ,
transition state between the
temporary
reactants and products (all the energies states )
> released product formation taken to break bonds
energy on is
greater than
energy
>
potential energy of the products is less than the potential energy of the reactants
the excess liberated in the form of thermal
is
energy
>
energy
>
exothermic reactions transfers potential energy into thermal
energy
> the heat of reaction COH ) is the net change of chemical potential energy of the
system
OH =
E -
Ereactants
products
=
416 -600 OH < 0 for exothermic
"
184 KJ MOI
=
-
.
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