Module 5: Equilibrium and Acid reactions Flashcards
(43 cards)
Practical of cobalt (II) chloride hydrate
Red-pink cobalt chloride hydrate gets dried on filter paper to produce blue cobalt chloride.
Reversible reaction
Practical of burning magnesium and steel wool
Irreversible - As the forward reaction is highly exothermic (low activation energy), the reverse reaction will likely not occur as there is high activation energy.
What is required of a chemical reaction for it to be reversible?
The activation energies of both the forward and reverse reactions must be low enough so that sufficient particles will have enough energy for a successful collision.
Two types of equilibriums?
Static equilibrium is when there is no net movement between the reactants and the products.
Dynamic equilibrium is when the rate of the forward and reverse reactions is equal - continuous exchange of reactants and products
Difference between open and closed system and relation to equilibrium?
A closed system does not allow any interaction with the environment.
An open system allows interaction with the environment and prevents equilibrium from being reached.
Two examples of non-equilibrium systems
Combustion and photosynthesis
Relate Gibbs Free Energy to reversibility.
As the forward and reverse Gibbs Free Energy values are negatives of each other, the closer the values are to zero, the more likely the reactions are to be reversible. Reactions need to have a Gibbs Free Energy value close to zero to be somewhat spontaneous.
Give the Gibbs Free energy formula
Don’t forget to have units in J/mol
Relate collision theory and equilibrium.
Therefore, as reactants react to form products, reactant concentration is decreasing while product concentration is increasing. Thus, reaction rate between reactants slows down over time while reaction rate between products speeds up, eventually reaching equilibrium.
- Collision theory def:
Particles react with sufficient kinetic energy and correct orientation
- Thus reaction rate increase as conc. increase
- As reactants get used up to form products, reactant conc decreases while product conc is increasing.
- Eventually reach a state of equilibrium.
Define Le Chatelier’s Principle
For a system at dynamic equilibrium, if there is a change in conditions, it will shift to counteract this change.
Using LCP, explain what will happen when cobalt chloride hydrate is heated.
The forward reaction is endothermic, while the reverse reaction is exothermic. If the system is heated, the system will work to counteract this change, thus favouring the endothermic reacion, shifting to the right.
What do vertical spikes or drops on conc/time graphs indicate?
Vertical and smooth
All smooth
All vertical
Vertical and smooth changes in concentration indicate an added change in concentration to the vertical changes.
All smooth indicates a change in temperature.
All vertical in the same direction indicates a change in pressure.
What do steeper smooth curves indicate on conc/time graphs?
They indicate a relatively higher molar ratio. The higher the molar ratio, the faster the rate of production following a disturbance to equilibrium.
Using collision theory, explain how an increase in temperature will affect a reversible reaction.
As increasing the temperature of a system reduces the activation energy of a reaction, the reactants of an endothermic reaction will be affected to a greater extent than the reactants of an exothermic reaction. This is because there is a larger proportion of particles that do not have sufficient energy to perform the reaction.
What is the equilibrium constant expression?
Allows us to make precise calculations of equilibrium processes such as equilibrium shifts.
How do you calculate the equilibrium constant?
Concentration of products ^ coefficients /Concentration of reactants ^ coefficients
What does the size of the equilibrium constant mean?
Big value: Higher concentration of products.
Small value: Higher concentration of reactants.
What is the reaction quotient? (Q)
A value that can be calculated at any point of a chemical reaction that is used with the equilibrium constant to determine which direction a reaction will proceed.
Relationship between Q and Keq?
Q > Keq: The reaction will proceed left to equilibrium.
Q < Keq: The reaction will proceed right to equilibrium.
Q = Keq: The reaction is at equilibrium.
What effect do different conditions have on the equilibrium constant?
A change in temperature will result in a different equilibrium constant.
What is required for dissolution to occur?
Similar strength intermolecular forces in solute and solvent
Solubility rules:
Soluble:
All group 1, ammonium (NH4) and nitrates are soluble in everything.
Chloride, bromide and iodide and soluble in all except Ag, Pb.
Sulfate soluble in all except Ag, Pb, Ca, Ba, Sr.
Insoluble:
Insoluble:
Carbonates, phosphates and sulfites insoluble in all.
Sulfides insoluble except for group 2.
Oxides and hydroxides insoluble except in Ca, Ba.
Enthalpy of solution formula
Energy absorbed - Energy released.
Energy of bonds breaking - energy of bonds forming.
If positive, energy absorbed to greater, and is endothermic and vice versa.
Endothermic means new bonds are weaker than the old bonds.
What is the solubility product?
Ksp is the equilibrium constant for a solid substance dissolving in an aqueous solution. We use it in calculations with solids in equilibrium.
