Topic 13 (insert EXAM style questions)

Term
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RECAP:
what does exothermic and endothermic mean
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Terms in this set (27)
RECAP:
what does exothermic and endothermic mean
exothermic - RELEASES heat (exit)
endothermic - takes in heat (temperature goes down)
IMPORTANT RULES for eNdothermic reaction
(in terms of equilibrium shifting)
hotter = eq moves to the right (more products)
colder = eq moves to the left
What do K values mean?
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How do you know what units are for Kc?
prod/reac units
What are some features of dynamic equilibrium (there are 3)
1. Concentration of reactants and products remain constant
2. Speed of forward and backward are equal
3. Catalyst will not affect equilibrium
IMPORTANT RULES for eXothermic reaction
(in terms of equilibrium shifting)
hotter = eq moves to the left (more REACTANTS)
colder = eq moves to the right
What is LeChatelier's Principle?
If there is stress, or change in temperature/concentration/pressure inflicted on the equilibrium, the reaction will SHIFT to reduce the change
dynamic equilibrium
a state of balance between continuing processes
Position of equilibrium in terms of pressure
increased pressure = eq moves to the are with less moles
explain how increasing the temperature affects the value of △S total of this reaction (doesn't affect △S system)
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△S total = RlnKR = 8.31 K = Kc or Kp (ln is on the calculator)How does increasing the temperature of an endothermic reaction affect △Ssurr and △S total?increasing the temperature, increases △surr and therefore increases △S total (what is "K"K can be Kc or KpWhat is Qc? How do you calculate?anytime K is NOT at equilibrium, n1/v1 = n2/v2 (Kc: Qc)Steps to find Kp1. find equilibrium moles 2. calculate total moles 3. mole fraction = mol of X/total mole 4. Partial pressure = mole fraction x eq mixture at ? atm 5. Kp equation (pressure of product/reactant)equation for △S total= △Ssurr + △Ssystem△S surr== -△H/T (T is in Kelvin)△S system= total S product - total S reactantWhat do you need to remember for△S surr = -△H/T-△H is in JOULES (the question usually gives it as kJ)IMPORTANT CONCEPT if a solution in a syringe is at 50cm3 at rtp, what will it be at ice cold vs hot waterice cold - 20cm3 hot water - 70cm3 (the molecules have expandedIMPORTANTSolids do NOT count in Kp or Kc calculations because their concentration stays constant throughout the reactionWhat is Kc?product/reactantHow to calculate Kc when only moles are given*How does Kc change when temperature is changed?EXO/ENDO *Use the Kc equation logic, aka more prod/reac = INCREASE in Kc less prod/more reac = DECREASE KcHow does Kc change in an endo reaction?ENDO hotter = eq moves to right = Kc increases . colder = eq moves to the left = Kc decreasesEXO hotter = eq moves to left = Kc decreases . colder = eq moves to the right = Kc increasesunderstand how, if at all, a change in temperature, pressure or the presence of a catalyst affects the equilibrium composition in a homogeneous or heterogeneous system How does a change in temperature, pressure or presence of catalyst affect equilibrium?Position can ONLY be changed by temperature