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Chem 116 Exam 2

All reactions are ____ and reach a state of ____ where concentrations of reactants and products will no longer change reversible; equilibrium
Formula for equilibrium constant (K) K=(Kfwd)/(Krev)
Define the law of chemical equilibrium/ Law of mass action At a given temperature, a chemical system reaches a state in which a particular ratio of reactant and product concentrations has a constant value
What is the ration of concentration terms for a given reaction Q
For multiple reactions, Q(overall) = what? K(overall)= what? Q(overall) = Q1 X Q2 X Q3... K(overall) = K1 X K2 X K3...
At what point does K=Q Equilibrium
If Q<K, what is the reaction shift? right, towards the products
If Q>K, what is the reaction shift? left, towards the reactants
Define Le Chatelier's Principle When a chemical system at equilibrium is disturbed, it retains equilibrium by undergoing a newt reaction that reduces the effect of disturbance
What are the three common disturbances to a reaction at equilibrium? Change in concentration Change in Pressure (volume) Change in temperature
If the concentration of A increases, the system will react to _____ some of A consume
If the concentration of A decreases, the system will react to _____ some of A produce
What is the effect of adding an inert gas to an equilibrium system? There is NO effect
If volume decreases, pressure _____ and the reaction shifts to _____ the number of gas molecules increases; decrease
Does a change in volume/pressure alter K? NO
Does a change in temperature alter K? YES
What is the effect of a catalyst on equilibrium position? There is NO effect
An Arrhenius acid contains a ___ molecule, an Arrhenius base contains a ___ molecule H+; OH-
The process in which water dissociates slightly into ions in an equilibrium process is defined as what? autoionization
According to the Bronsted-Lowry Acid Base definition, an acid is a _____ and a base is a _____ proton donor; proton acceptor
For a conjugate acid base pair, the reaction will process to the greater extent in the direction in which a ____ acid and a ____ base will form a ____ acid and a ____ base strong; strong; weak; weak
K(w)= K(a)*K(b)
According to the Lewis Acid Base definition, a base is any species that _____ and an acid is any species that _____ donates and electron pair; accepts an electron pair
The product of a Lewis Acid Base reaction is a single species that contains a new covalent bond defined as an ____ adduct
Define an acid base buffer a solution that lessens the impact on pH from the addition of an acid or base
What are the general components of a buffer A conjugate acid base pair
What is the common ion effect that causes buffers to be effective? When a given ion is added to an equilibrium mixture that already contains that ion and the position of equilibrium shifts away from forming it
What is the measure of the strength of a buffer? Buffer capacity
What does buffer capacity depend on? concentrations
What is buffer range? The pH range over which a buffer is effective
What is an acid-base titration cure a plot of pH vs. volume of titrant added
What is an acid base indicator? a weak organic acid whose color differs from the color of its conjugate base and color changes over a specific narrow pH range
When the number of moles of OH- added is equal to the number of moles of H3O+ originally present is referred to as the ____ equivalence point
The end point of a titration is when ____ the indicator changes color
Kinetics is the _____ of a reaction while equilibrium is the ____ of a reaction speed; extent
Once a reaction reaches equilibrium what happens? It continues to react both forward and reverse equally
Does the concentration of solids and liquids change as the volume changes? NO
If K(eq) = 5e-5, would you expect more reactants or products at equilibrium? reactants
If a reaction is exothermic (-), treat heat as a ____. If a reaction is endothermic(+), treat heat as a _____. product; reactant
For a reaction to respond to a change in pressure what must be true? The number of moles of gas must change in the reaction
Strong acids are ____ favored while weak acids are ___ favored product; reactant
The strength of an acid refers to the extent o f_____ of its proton in H2O at equilibrium dissociation
Buffers generally consist of a solution of _____ and its ______ (or vise-versa) weak acid; conjugate base
To prepare a buffer: 1. Mix weak acid and conjugate base (Pick acid with pK(a) apptox. = to desired pH) 2. Start with weak (acid/base) and conjugate (base/acid) to half-way point of titration
How can you simplify finding equilibrium quantities? assume the change in concentration, x, is relatively small
A conjugate acid-base pair differs by what? One proton
What is the pH at the end point of the addition of a strong acid to a strong base? 7
How does the pH of a .1M acetic acid solution compare to that of a .1M HCl solution? It is lower
Created by: jkmccord11