Module Five - Equilibrium and Acid Reactions Flashcards
open system
one which reacts with its environment meaning that both energy and matter can move in and out of the system. Energy and Matter are constantly moving between the system and the environment
closed system
energy may still be able to flow in and out between the system and the environment, but matter cannot enter or leave the system. When a system reaches equilibrium, no energy enters or leaves the system
characteristics of an equilibrium system
closed system, rate of forward reaction = rate of reverse reaction, macroscopic properties stay constant, concentrations of all reactants and products stay constant, continuous changes occur at atomic level, equilibrium can be approached from either direction
dynamic equilibrium
a system in which the forward and reverse reaction are occurring at the same rate and the same time, so that there is no net change
static equilibrium
occurs when nothing is happening in the reaction
enthalpy
total energy in a system. exothermic reactions have negative enthalpy changes, endothermic reactions have positive enthalpy changes
entropy
measure of the possible ways in which energy can be distributed in a system of molecules
combustion reaction
irreversible and does not form and equilibrium system. all are exothermic
photosynthesis
irreversible endothermic reaction, enthalpy is positive. goes to completion and is not an equilibrium system
Le Chatelier’s Principle
If a system is in equilibrium, and it is disturbed or changed in any way, then the system will adjust itself to minimise the amount of change
Factors that Affect equilibrium
temperature, concentration, volume/pressure, catalyst
How temperature affects equilibrium
Increasing temperature will shift equilibrium towards the endothermic reaction. Decreasing temperature will shift equilibrium towards the exothermic reaction
How concentration affects equilibirum
Increasing the concentration of reactants will favour the reaction forming products. Increasing the concentration of products will favour the reaction forming reactants
How volume/pressure affects equilibrium
Increase in pressure will shift equilibrium towards the side of reaction with fewer gas molecules. Decrease in pressure will favour the side of reaction with more molecules of gas
Note gases must be present for pressure to have an effect
How a catalyst affects equilibrium
Reaction will reach equilibrium faster, or no effect if the reaction has already reached equilibrium
Keq
Keq= [products]/[reactants] *solids and pure liquids are not included in equilibrium expressions
RICE tables
Ratio : molar ratio of reactants and products
Initial : concentration of each reactant and product at the start
Change : change in concentration, according to molar ratio
Equilibrium : Concentration of each reactant and product at equilibrium
effect of temperature on equilibrium constant
If a temperature change increases the concentration of reactants, Keq will decrease
If a temperature change increases the concentration of products, the Keq will increase
dissolution of ionic compounds
a solute dissolves when the energy of the bonds it forms with water is lower than the energy of the bonds between water molecules or between the ions of the substance being dissolved
solubility
the maximum mass in grams that can dissolve in 100g of the solvent at a given temperature
soluble ions
NO3, All group 1 cations and NH4, Cl-, Br-, I-, (SO4)2-
insoluble ions
(SO3)2-, (CO3)2-, (PO4)3-, S2-, O2-, OH-
Exceptions for solubility for Cl- Br- I-
Ag, PB, Hg
Exceptions for solubility for SO4
Ba, Pb, Ca, Hg
Exceptions for insolubility (SO3)2-, (CO3)2-, (PO4)3-
All group 1 cations and NH4
Exceptions for insolubility S2-
All group 1, 2, NH4
Exceptions for insolubility O2-
All group 1, Ba 2+, Ca2+
Exceptions for insolubility OH-
All group 1, NH4+, Ba2+, Ca2+
precipitate
an insoluble ionic compound
