11 Part A Energy in Reactions
this reaction is endothermic
2NH3(g) + 92.4 kj => N2 (g) + 3H2 (g)
A catalyst speeds up a reaction
by lowering the required activation energy
An inhibitor slows down a reaction
by raising the activation energy
For an Exothermic reaction, the change in enthalpy (delta H) is
negative
For an Endothermic reaction, the change in enthalpy (delta H) is
positive
Collision theory
reactions occur as a result of collisions between the reactants.
In an Endothermic Reaction, energy is ...
... absorbed
In an Endothermic reaction, the temperature inside the reaction vessel...
... becomes cooler.
In an Exothermic reaction, the temperature inside the reaction vessel...
... becomes warmer.
Activation Energy ...
... is always a positive number. D H in this reaction is positive (endothermic)
Exothermic Reaction, energy is ...
... is released.
Exothermic Reaction
Energy is a product of the reaction.
Endothermic Reaction
Energy is a reactant of the reaction.
Temperature affects reaction rate
If temperature is increased, the reaction will be quicker. Faster moving particles collide more often, and more particles will have enough energy (Ea) when they collide
Definition of Activation Energy (Ea)
The minimum amount of energy required for a reaction to occur.
5 basic ways to speed up a reaction
Increase collisions by: temperature; Surface Area; Concentration. Reduce activation energy by using a Catalyst. Nature of the reactants
Surface Area of the reactants affects reaction rate
More exposed particles causes more collisions, so there will be more collisions with the correct orientation
this reaction is exothermic
N2 (g) + 3H2 (g) => 2NH3(g) + 92.4 kj
Concentration of reactants affects reaction rate
Number of particles in a given volume affects rate of concentration - more particles, more collisions
Catalyst
Reduces the activation energy of a reaction and speeds the reaction up without being used up in the process
Activation Energy
The energy from the peak of the reaction minus the energy in the reactants.
Change in enthalpy (delta H)
The energy of the products minus the energy of the reactants.
Nature of the reactants affects reaction rate
The rate of a chemical reaction depends on the medium in which the reaction occurs. It may make a difference whether a medium is aqueous or organic; polar or nonpolar; or liquid, solid, or gaseous, reactive or non-reactive.
Activated complex (Transition state)
a short lived intermediate substance that occurs at the peak energy of the reaction. It lasts for 10 -13 seconds. It is an arrangement of the atoms somewhere between the reactants and the products.
In an Endothermic reaction, the energy of the reactants is ____ than the energy of the products
greater
In an Exothermic reaction, the energy of the reactants is ____ than the energy of the products
less
