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20 Cards in this Set

  • Front
  • Back
Reaction Rate
Collision Model
For a reaction to take place...
1. Particles must collide with a certain amount of energy
2. Particles must collied with the correct orientation
Factors that affect the reaction rate
1. Temperature
2. Concentration
3. Particle size
4. Pressure (only gases)
How do those factors affect the reaction rate?
1. When T rises, Rate rises, causing particles to move faster, creating more collisions per time with a higher average KE
2. When [] rises, Rate rises, because more particles are in the same place, creating more collisions per time and more of a chance of agreeing with the collision model
3. When PS lowers, Rate rises, because there is more surface area for reactions to take place, so there are more collisions per time
4. When P rises, Rate rises, because the particles have less space to react in and are closer together, so there are more collisions per time
What is a catalyst? How does it affect a chemical reaction?
A substance facilitating a reactions without being consumed by reducing the activation energy
What is the transition state, and what happens there?
The most unstable state of a chemical reaction where some bonds are breaking and some are forming at the same time. From here, the reaction could potentially go backwards or forwards
Is every chemical reaction reversible?
In theory, every reaction is reversible, but this is not true in practice, for some activation energies are too high
Equilibrium can only occur when... is occuring in a closed system, where nothing can get in or out
Equilibrium is reached when...
...the forward reaction rate = the reverse reaction rate
What is an equilibrium expression? Then use example reaction: aA+bB->cC+dD
Keq = [Products] / [Reactants]
Keq = ([C]^c)([D]^d) / ([A]^a)([B]^b)
What can be written in the equilibrium equation? Why?
Only gases and aqueous solutions can be used in the equation because pure solids and liquids have constant densities, and that won't change throughout a reaction
What is an equilibrium position?
A set of equilibrium concentrations at a given temperature that can change as long as T and Keq are constant
What does it mean to have "equilibrium favoring one side"?
The concentration of one side is greater than the other, but the reaction is still at equilibrium
How can you use the Keq to see which side the equation favors?
Keq > 1 = Favors products (Denominator is smaller)
Keq < 1 = Favors reactants (Denominator is bigger)
Le Chatelier's Principle
If an equilibrated system is distrubed by an outside force, the equilibrium position will shift to minimize the impact of the change, and Keq is still constant unless T changes - the total is the same, but there is relatively more of each reactant or product
Factors that affect equilibrium position
1. Concentration
2. Pressure (only gases)
3. Temperature
How do those factors affect equilibrium position?
1. Shifts to the side opposite where moles were added - fewer collisions occur on the side with fewer moles
2. When pressure rises and volume gets smaller, position shifts in the direction of fewer moles of gas
3. Temperature can shange the value of Keq and the position, so adding heat shifts in the direction of the endothermic reaction, or away from wehre you add heat
What cannot affect equilibrium position?
Particle size, because solids are not included in the equilibrium equation (though it does affect reaching equilibrium), and a catalyst lowers activation energy for both sides, so it only affects reaching equilibrium rather than the reaction at equilibrium
Solubility Equilibrium
No real chemical reaction takes place - just dissolving in water
A higher Ksp means that more moles were dissolved
Though the two are pretty much the same, what is the difference between Ksp and Keq?
Ksp is a physical process of an aqueous solution being created (solubility product constant), while Keq represents a equilibrium in any system