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Chem 116 Exam 2
| Question | Answer |
|---|---|
| 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
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