Chapter 6: Rates and Equilibrium Flashcards
1
Q
Collision Theory
A
- Reacting particles must collide
- Must collide w/ sufficient energy to react (activation energy)
- On collision particles must have correct orientation
2
Q
Activation Energy
A
The minimum energy with which particles must collide to react
3
Q
What happens when two molecules react
A
- Bonds are broken and new bonds are formed.
- When the reactant particles collide, it is transformed into potential energy due to bond breaking.
- > Potential energy of the system increases
- potential energy decreases as new bonds formed
- > If there is sufficient energy, bonds in colliding particles will break and new bonds begin to form
- > max potential energy state reached
- > species existing at this state is transition state
4
Q
Transition State
A
- Highest potential energy state for reacting system
- Corresponds to some stage in reaction at which bond breaking and bond formation is taking place
- exists temporarily
5
Q
Exothermic Reaction
A
- products have LESS potential energy than reactants
- heat is RELEASED during reaction
- temperature of outside is INCREASED
- produces heat
6
Q
Endothermic Reaction
A
- Products have MORE potential energy than reactants
- Change H is positive
- Heat energy is absorbed
- Decrease in temperature of surroundings
- absorbs heat
7
Q
Factors Affecting Reaction Rate
A
Nature of Reactants
- > High low activation energy depending on the strength of bonds
- > Weak bonds, i.e ions in soln, reaction occurs fast.
Concentration of Reactants
- > Increase partial pressure or concentration of a gas can increase reaction rate.
- > Decrease does the opposite.
- > Greater chance of reactant particles colliding and reacting if concentration increases.
State of subdivision of the reactants
- > Greater the surface area of one reactant that is exposed to the second reactant, the greater the reaction rate.
- > Powdered state will react quicker.
Temperature
-> High temp. increase in average kinetic energy therefore greater number of reactant particles have sufficient activation energy.
Catalyst
- > Increase rate of reaction
- > Provide alternative reaction pathway w/ smaller activation energy
- > More collisions as more particles have sufficient energy to react
8
Q
When chemical reaction system is at equilibrium…
A
- Concentration of reactants and products remain constant w/ time
- Macroscopic properties (i.e colour) remain unchanged w./ time
- Rates of forward and reverse reactions are equal
- chemical equilibrium is dynamic.
9
Q
Equilibrium Vapour Pressure
A
- Liquid in closed container,
- > some evaporates to produce vapour above liquids
- > Some vapour condenses to re-form liquid
- At equilibrium, liquid evaporating = rate of vapour condensing
Pressure exerted by vapour will be constant - Amount of liquid and vapour pressure will remain constant w/ time.
10
Q
Solution Equilibria
A
- Solid placed in liquid.
- > Solid dissolves as particles break away from lattice and mix w/ solvent’s aprticles
- > dissolved particles also crystallise out of solution to reform solid
- Equilibrium established if sufficient solid present
- Particles are dissolving at the same rate they are crystallising
- Amount of solid present remain constant, amount of dissolved substance also constant.
11
Q
Equilibrium Law K: Characteristics
A
- Constant value for particular reaction representing reaction at given temperature.
- Changes when temperature of reaction changes
Indicates relative proportions of reactants and products in equilibirum mixture
Large value = large conc. of products and small conc. of reactants
Small value: large conc. reactants, small conc. products
- Does not include substances that are solids or pure liquids, concentrations do not vary from one reaction to next.
12
Q
Change in concentration: LCP
INCREASE CONCENTRATION OF REACTANT
A
- Increase concentration of REACTANT
- LCP: new substance will be consumed.
- Causes in increase in the rate of the forward reaction.
- When equilibrium is re-established, the forward and reverse reaction rates are GREATER than previous
- > Due to greater concentration.
- > Results in more of the products being present in the new equilibrium mixture.
- > Change made to system is not completely opposed.
13
Q
Change in Concentration: LCP
DECREASE CONCENTRATION OF REACTANT
A
- system will re-establish in a way that will lead to an increase in concentration of the removed substance.
- Causes an increase in the rate of a reverse reaction
- Causing reverse reaction to be favoured
- rate of the forward and reverse reaction are equal but less than they were in the original mixture.
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