Chapter 7 - Chemical Equilibrium Flashcards
what is atmospheric carbon dioxide?
a greenhouse gas
what does atmospheric carbon dioxide contribute to?
climate change
how is carbon dioxide gas released to the atmosphere?
through combustion of fossil fuels
an example of a reversible reaction involving carbon dioxide gas
carbon dioxide gas dissolves in water to produce carbonic acid H2CO3 (aq), this is reversible, carbonic acid decomposes to produce water and carbon dixoide gas
what happens when concentrations of reactants and products are stable?
there is a balance in the rates of the forward and reverse reactions
is carbon dioxide gas in the atmosphere stable and what does this cause?
no, the formation of carbonic acid increases
what does the increase of carbonic acid in oceans cause?
acidification, and has an impact on shells composed of calcium carbonate (CaCO3 (s)), which dissolves in acidic solutions, can lead to bleaching of coral reefs
what does it mean when a chemical reaction proceeds to completion
one of the reactants runs out
define chemical equilibrium
the state of a reaction in which all reactants and products have reached constant concentrations in a closed system
define dynamic equilibrium
a balance between forward and reverse reactions that are occurring stimultaneously (rates of forward and reverse reactions are equal)
what are all chemical equilibriums?
dynamic equilibriums
what happens to reversible reactions in a closed system?
reach chemical equilibrium
what does it mean when molar ratio is the same?
concentrations are the same
what does a vertical line mean for reaction progress?
equilibrium
define equilibrium position
the relative concentrations of reactants and products in a system in dynamic equilibrium
by convention, how is equilibrium position communicated in reference to?
the left hand side (reactant side) or the right hand side (the product side)
what does it mean when equilibrium position is to the far right?
almost all reactants are converted to products, but the concentrations of reactants never reach zero
define reversible reactions
a chemical reaction that proceeds in both the forward and reverse directions, setting up an equilibrium in a closed system
at dynamic equilibrium, what is the concentration of reactants?
constant
how are reversible reactions indicated?
⇌
generalization for forward and reverse reactions regarding a closed chemical equilibrium system in constant environmental conditions
the same equilibrium concentrations are reached regardless of the direction by which equilibrium is reached
when is an ICE table useful?
for chemical equilibrium systems composed of aqueous solutions or gases
define equilibrium law
the mathematical description of a chemical system at equilibrium (reversible reaction)
define equilibrium constant
the numerical value defining the equilibrium law for a given system, units are not included when giving the value of K
what is the symbol for the equilibrium constant?
K
what does not change the K value?
the initial concentrations
what change the value of K?
temperature
what does equilibrium position describe?
the relative concentrations of reactants and products in a chemical reaction system
what can the magnitude of the equilibrium constant help you find?
the equilibrium position of a chemical reaction system
if K equals the forward reaction and K’ equals the reverse reaction, how are they related
they are reciprocals, 1/k’ = k
define homogeneous equilibrium
a chemical equilibrium in which all reactants and products are in the same state of matter
define heterogeneous equilbrium
a chemical equilibrium in which the reactants and products are present in at least 2 different states
what does the equilibrium position not depend on?
pure solids or liquids concentrations are not included in the chemical law equation because they do not affect the equilibrium position
why do pure solids/liquids not affect the equilibrium position?
their concentrations cannot change, they are constants
when the equilibrium constant is much greater than 1, what 3 things does this tell us?
the equilibrium position is far to the right, it favours the products, concentration of products are greater than the concentrations of the reactants
when the equilibrium constant is close to being equal to 1, what 3 things does this tell us?
equilibrium concentration of the products is similar to that of the reactants
when the equilibrium constant is much less than 1, what 3 things does this tell us?
equilibrium position is far to the left, favours reactants, concentration of reactants is greater than those of the products
how can chemical systems at equilibrium be disturbed?
through changes in temperature, pressure, concentration or a combination of these
what was the goal behind Le Chatelier’s investigations?
to maximize the yield of products from equilibrium systems
Le Chatelier’s Principle
when a chemical system at equilibrium is disturbed by a change in a property, the system adjusts in a way that opposes the change
what does le chatelier’s principle allow chemists to do?
predict qualitative effects of changes in concentration, pressure, and temperature on a chemical reaction system at equilibrium
define equilibrium shift
a change in concentration of reactants and products in order to restore an equilibrium state
what happens when you increase the concentration of a reactant to the equilibrium
equilibrium shifts to the right
when a reaction occurs, what happens to the concentration of reactants and products
concentration of reactants decrease while concentration of products increase
when more reactant is added, what happens to the concentration of the two reactants and the products
the concentration of the reactant added spikes and then decreases because some of the ions are being used to make more product, the concentration of the other reactant decreases for the same reason, the concentration of the product increases as more product is formed
equilibrium concentrations of reactant, added reactant and product when you add reactant from original equilibrium to new equilibrium
equilibrium concentration increases for product and added reactant, equilibrium concentration decreases for other reactant
what happens when you decrease the concentration of a reactant to the equilibrium
equilibrium shifts to the left
when reactant is removed, what happens to the concentration of the reactant and the two products?
reactant spikes and then decreases, the concentrations of the products increase
equilibrium concentrations of reactant and products as reactant is removed from original to new equilibrium?
increases
what happens when you decrease the concentration of a product to the equilibrium
shifts to the right
concentrations of reactant and two products when concentration of product is decreased?
reactant decreases, product spikes down and increases, other product increases
equilibrium concentrations of reactant and two products when concentration of product is decreased from original to new equilibrium
reactant decreases, product that is removed decreases, other product increases
when we add more reactant entities, what happens to equilibrium with regards to collision theory
equilibrium shifts to right because the number of successful collisions for the forward reactions increase
when we add more product entities, what happens to equilibrium with regards to collision theory
equilibrium shifts to the left because the number of successful collisions for the reverse reaction increases
what does the rate of a chemical reaction refer to?
how often entities collide, be they reactants or products
how do rates of forward and reverse reactions become equal and a new equilibrium established?
when we add a substance to an equilibrium system, the higher concentration increases the rate of the forward reaction as more entities collide, the higher rate then decreases the concentration of the substance so the rate then decreases, same occurs in reverse reaction with products until they are equal
how do we use le chatelier’s principle to increase yield of products
continuous addition of reactants or removal of products, prevents the chemical system from reaching equilibrium and favours the formation of products
3 applications of le chatelier’s principle
industrial production of aqueous nitric acid HNO3 (aq), gasification of carbon, hemoglobin binds to dissolved oxygen in a reversible reaction in your blood
explain the industrial production of aqueous nitric acid
nitric acid can be used in the synthesis of fertilizers, explosives, dyes, and perfumes. nitric oxide is not as useful, it must be removed from the chemical reaction system by reacting it with oxygen gas, this causes the equilibrium to shift to the right, this forms more product and thus more nitric acid
reaction for the industrial production of aqueous nitric acid
3 NO2 (g) + H20 (l) ⇌ 2 HNO3 (aq) + NO (g)
explain the gasification of carbon
important part of the conversion of biomass to usable hydrogen gas fuel, at high temperatures, carbon reacts with water vapour to produce hydrogen gas and carbon monoxide gas
reaction for the gasification of carbon
C (s) + H20(g) ⇌ H2 (g) + CO (g)
explain the water-gas shift reaction
as fast as the gasification reaction produces gaseous carbon monoxide, it is used up as a reactant in the water-gas shift reaction so the equilibrium is to the right, producing more products (hydrogen)
reaction for the water-gas shift
CO (g) + H20 (g) ⇌ CO2 (g) + H2 (g)
explain the reaction between hemoglobin and oxygen gas
oxygen is absorbed into lungs, concentration of the reactant, oxygen is high, so the equilibrium position is to the right, hemoglobin-oxygen complex is pumped through body cells, where oxygen (reactant) concentration is low, to compensate, equilibrium shifts to the left and as a result oxygen is released from hemoglobin and is available for use by body cells
endothermic reaction: formula and what energy does
energy is absorbed by reactants, reactants + energy ⇌ products
exothermic reaction: formula and what energy does
energy is released from reactants, reactants ⇌ products + energy
if an endothermic reaction is cooled, what happens with reactants/products, equilibrium, and bond energy
quantity of one of the reactants decrease, equilibrium shifts to the left and energy used in the bonds of the products will be released
if an endothermic reaction is heated, what happens to the equilibrium and the additional energy
equilibrium shifts to the right, additional energy is absorbed to create more product
if an exothermic reaction is cooled, what happens to the equilibrium, and what happens to counteract the change
equilibrium shifts to the right, energy stored in the reactants will be released to counteract the change
if an exothermic reaction is heated, what happens to the equilibrium and the additional energy
equilibrium shifts to left, energy is used to convert products to reactants
what changes the equilibrium position of a chemical system
changes in concentration, energy, gas volume
what is changed when you change the volume of a container of gas
the concentration of the gases
define ideal gas
a hypothetical gas of entities that have no size, travel in straight lines, and have no attraction to each other (no intermolecular forces), a gas that obeys all gas laws
what does Boyle’s law state
pressure exerted on a container by a certain amount of ideal gas held at a constant temperature varies inversely with the volume of the gas
decreasing the volume by 1/3 does what to the pressure?
increases it 3x
what type of gases does boyle’s law apply to?
pure gas or a mixture of gas
when a container holds a mixture of gas, what must be accounted for?
each gas exerts its own partial pressure
define partial pressure
the pressure that a gas, in a mixture of gases, would exert if it alone occupied the whole volume occupied by the mixture
what is the total pressure of a mixture of gas?
the sum of the partial pressures
when volume of a gas mixture decreases, what happens to concentration and partial pressures?
concentration increases proportionally to the increase of partial pressures
when pressure increases, what happens to the equilibrium?
equilibrium shifts to the right to reduce the number of entities (if more entities are reactants), or shifts to the left (if more entities are products), to decrease the total pressure
what methods can be used to change an equilibrium system (modify amount of reactants and products) without affecting equilibrium position
using catalysts, addition of inert gas, changing state of reactants
how can we use a catalyst to change an equilibrium system?
increases rate of forward and reverse reactions equally since both reactants and products can form by the lower energy path and the reaction reaches equilibrium faster
what does a catalyst not change in an equilibrium system?
the equilibrium position and the final equilibrium concentrations of reactants and products are not altered
what is an inert gas
gas that is not reactive and will not enter into a chemical reaction
what happens when you add an inert gas to an equilibrium system involving a gas mixture and volume is kept constant?
entities in the volume and the total pressure will increase
collisions when adding inert gas
total number of collisions increase but collisions involving inert gas do not result in chemical reaction, these collisions can redirect the movement of any entity with which they collide
what does inert gas not change?
does not change frequency with which reactants/product entities collide with each other + partial pressures of reactant/product and does not change the equilibrium as long as the collision frequency for both forward and reverse reactions does not change
what happens when a chemical system involves entities in more than one state of matter
equilibrium is affected only by changes in concentration of entities that are in the same state of matter as the substances involved in the chemical reaction
does changing concentrations of reactants/products change the equilibrium constant and why?
no because the equilibrium constant is for when the reaction is at equilibrium, when you add concentrations of reactants/products, the system is no longer at equilibrium
define reaction quotient
the product of the concentrations of the products, divided by the product of the concentrations of the reactants, for a chemical reaction that is not necessarily at equilibrium
symbol for the reaction quotient
Q
what concentrations are used in the equilibrium law equation to get the reaction quotient
using instantaneous concentrations
define instantaneous concentrations
concentrations that occur together at a particular instant in time in the progress of a chemical reaction
when is it convenient to calculate concentrations for reaction quotient and why?
at the beginning of a reaction, where the concentrations of products are zero
what happens when Q is less than K with concentration of products/reactants, equilibrium shift and why
the concentration of products is less than concentration of reactants,equilibrium shifts to the right so reactants are consumed and products are formed until Q reaches K and equilibrium is reached
what happens when Q equals K with equilibrium and shift
system is at equilibrium so not shift will occur
what happens when Q is larger than K
concentration of products is larger than reactants, equilibrium shifts to the left so products are converted to reactants until equilibrium is reached
define solubility
the quantity of solute that dissolves in a given quantity of solvent at a particular temperature; the concentration of a saturated solution at a particular temperature
what are ionic compounds composed of?
ions joined by ionic bonds
what happens when a solid ionic compound dissolves in water?
ions are removed from the crystal lattice as they are surrounded by water molecules, the reverse reaction
takes place, resulting in dynamic equilibrium
two processes that occur when a solid ionic compound dissolves in an ionic compound and explain each
dissolution (ions in the solid ionic compound attract to the water molecules, the positively charged oxygen atom and the negatively charged hydrogen atom), precipitation (aqueous ions collide with each other causing them to reform)
at equilibrium, what happens to an aqueous solution with dissolved ions with regards to the solution, amount of solute, rates of reactions, and concentrations of ions
solution is saturated: contains maximum amount of solute at given temperature and pressure, the dissolution and the precipitation occur at the same rate,, concentrations of ions remain constant
defines solubility equilibrium
a dynamic equilibrium between a solute and a solvent in a saturated solution in a closed system
what kind of equilibrium system is a solubility equilibrium and what is involved
heterogeneous, solid ionic compound and its ions dissolved in a saturated aqueous solution
define solubility product constant
the value obtained from the equilibrium law applied to a saturated solution for solubility equilibriums
symbol for solubility product constant
Ksp
when do we commonly use Ksp
for substances with low solubilities
what does the solubility of an ionic compound depend on and why?
the more highly charged anions and cations are, the less soluble the ionic compound will be, because it takes more energy for a solvent to break the ionic bonds in the crystal lattice
how does the solubility of an ionic compound and the solubility product constant relate and how don’t they relate?
solubility is different that its Ksp value, you can find one if you know the other
