IA1 - Data Test Flashcards
define the term equilibrium?
- when physical changes and reversible chemical reactions reach a state of dynamic equilibrium in a closed system
- dynamic equilibrium: the rate of the forward reaction is equal to the rate of the reverse reaction
how are reactions reversible/irreversible?
- physical change: reversible (only need to overcome weak intermolecular forces and only altering states)
- chemical change: irreversible (stronger forces need to be broken - covalent, ionic, metallic)
what is the enthalpy of reverse reactions?
- the same value as forward reaction (either endo/exo) but the opposite charge
how can reactions be exothermic or endothermic?
exothermic:
- negative delta H value
endothermic:
- positive delta h value
how do you analyze concentration graphs to show how systems respond to change?
- Increasing at a decreasing rate
- decreasing at a decreasing rate
- we have reached equilibrium:
- the relative concentrations of the reactants and products is constant at this point in time
- the rate of the forwards and reverse reactions are equal - equilibrium
explain and identify how temperature affects a reaction at equilibrium
- increasing temperature
TEMPERATURE INCREASE:
1. Identify the stress
- there has been an increase in the temperature
- Connect to enthalpy
- the enthalpy indicates the forwards direction is exothermic (deltaH is negative) - Determine the shift in the reaction
- results in the reverse direction as a increase will always shift in the endothermic direction causing a shift to the left/reactants - Identify the results
- causing the equilibrium position to shift to the right
- decreasing [NH3]
- increasing [N2] and [H2]
explain and identify how temperature affects a reaction at equilibrium
- decreasing temperature
- Identify the stress
- there has been a decrease in the temperature - Connect to enthalpy
- the enthalpy indicates the forwards reaction is exothermic (delta H is negative) - determine the shift in the reaction
- results in the forward direction as a decrease will always shift in the exothermic direction causing a shift to the right/products - Identify the results
- causing the equilbrium position to shift to the right
- increasing [NH3]
- decreasing [N2] and [H2]
explain and identify how concentration affects a reaction at equilibrium?
- increasing concentration
- Identify the stress
- there has been an increase in [element] concentration - connect to collision theory
- causing increased successful collisions between reactants/products (depending on where stress [element] is) - determine the shift in the reaction
- causing a shift away from the increase and thus towards the reactants/products (depending on where [element] is) - Identify the results
- moving to reactants will increase reactants and decrease products
- moving to products will decrease reactants and increase products
explain and identify how concentration affects a reaction at equilibrium?
- decreasing concentration
- Identify the stress
- there has been a decrease in [element] concentration - connect to collision theory
- causing decreased successful collisions between reactants/products (depending on where stress [element] is) - determine the shift in the reaction
- causing a shift towards the decrease and thus towards the reactants/products (depending on where [element] is) - Identify the results
- moving to reactants will increase reactants and decrease products
- moving to products will decrease reactants and increase products
explain and identify how pressure affects a reaction at equilibrium?
- increase in pressure
- Identify the stress
- there has been an increase in pressure (due to a decrease in volume) - connect to collision theory
- causing an increase in successful collisions in both reactants and products - determine the shift in the reaction
- reaction will shift to the side with less moles, which is the reactants/products - identify the results
- moving to reactants will increase reactants and decrease products
- moving to products will decrease reactants and increase products
explain and identify how pressure affects a reaction at equilibrium?
- decrease in pressure
- identify the stress
- decrease in pressure (due to increase in volume) - connect to collison theory
- causing a decrease in successful collisions in both reactants and products - determine the shift in the reaction
- reaction will shift to the side with more moles, which is the products/reactants - identify the results
- moving to reactants will increase reactants and decrease products
- moving to products will decrease reactants and increase products
Use Le Chatelier’s principle to predict the effect of changes to temperature on the position of equilibrium
refer to photo
Use Le Chatelier’s principle to predict the effect of changes to concentration on the position of equilibrium
refer to photo
Use Le Chatelier’s principle to predict the effect of changes to pressure on the position of equilibrium
refer to photo
what is the effect of a catalyst on equilibirum position?
- lowers the activation energy of both the forward and reverse reactions
- no effect on the equilibrium
- allows the system to achieve equilibrium faster
how can you use Kc to determine if the system contains more reactants or products?
- if K>1
- products are bigger than reactants
- product predominates at equilibrium - if K<1
- reactants predominate at equilibrium
- reactants are bigger than products
what is the effect on Kc from changes to equilibirum?
- the ONLY variable that can change the equilibrium constant (Kc) is the TEMPERATURE
- all variables (concentration, pressure/volume and temperature) can alter the equilibrium position but only temperature alters the Kc
what does Q mean?
- reactant quotient
- used to determine if a system is at equilibirum
- calculated same way as Kc
1. if Q = Kc - the system is at equilibrium
2. if Q doesn’t = Kc - the system is not at equilibrium
how do you use Q and Kc to determine if the reaction will proceed in the forwards or reverse reaction to reach equilibrium?
- if Q < Kc
- the system will shift to increase the Q (to the products)
- i.e. the value gets bigger - if Q > Kc
- the system will shift to decrease the Q (to the reactants)
- i.e. the value gets smaller
do you feel confident in being able to answer questions relating to equilibrium?
try questions in photo
do you feel confident in being able to answer questions relating to equilibrium?
try questions in photo
Do you know how to look at data and determine if an acid/base is strong or weak?
the strength of dissociation
- strong acids completely dissocate
- weak acids partially ionise
Do you know how to look at data and determine if an acid/base is strong or weak?
- ph 0-2 strong acid
- pH 2-4 weak acid
- pH 10-12 weak base
- pH 12-14 strong base
Do you know how electrical conductivity can be used to determine the strength of an acid/base?
ACID:
- high electrical conductivity = strong acid/low pH
- low electrical conductivity = weak acid/mid-low pH
BASE:
- high electrical conductivity = strong base/high pH
- low electrical conductivity = weak base/mid-high pH
how do you solve for pH?
refer to photo
How do you solve for H+ ion concentration?
refer to photo for formula’s
how do you solve for OH- ion concentration?
refer to photo
How do you solve for pOH?
refer to photo
how do you solve for Kw?
refer to photo
answer the examples [H+] and [OH-] questions in the picture
refer to photo
how do you solve for Ka?
how do you solve for Kb?
how do you solve for pKa?
how do you solve for pKb?
how do you identify BL acid base pairs and conjugate acids and bases?
- acids = proton donors
- bases = proton acceptors
how do you answer the following BL questions?
How do you select the strength of an acid and base on a titration curve?
pH 0-2 = strong acid
pH 2-7 - weak acid
pH 7-12 = weak base
pH 12-14 = strong base
- acids are always on bottom half on curve
- bases are always on top half of curve
what are the appropriate indicators for reaction of weak acid/strong base ?
what are the appropriate indicators for reaction of weak base/strong acid?
what are the appropriate indicators for strong acid/strong base?
how do you find pKa from pH?
- the pH at the half-equivalence point = the pKa
- ie. half the volume of the equivalence point and then trace up to where intersects with pH on curve
what formula do you use to find concentration from titration curves?
- general stoichiometric equations:
1. c = n/v
2. c1v1=c2v2 (for dilution calculations)
