Unit 2: Equilibrium, Acids & Bases, Buffers Flashcards
What do the different relationships between Q (reaction quotient) and K (equilibrium constant) mean?
(<, >, and =)
- If Q > K, the reaction proceeds leftward toward reactants because product concentration is higher than at equilibrium.
- If Q < K, the reaction proceeds rightward toward products because product concentrations are lower than at equilibrium.
- If Q = K, equilibrium has been reached and the reaction remains stable.
What is chemical equilibrium?
- A state that occurs when the forward and reverse rates of a reaction are equal and concentrations of reactants and products are no longer changing with time
Quadratic Formula

Homogeneous Equilibrium
- all species are in the same phase
What is Kp?
- the equilibrium constant with respect to pressure of gases
- it is only expressed in terms of gases, SOLIDS AND LIQUIDS DO NOT COUNT towards Kp
- it equals the partial pressures of products over the partial pressures of reactants, at equilibrium and raised to their stoichiometric coefficients

What is the equation for the relationship between Kp and Kc?
- Kp is equal to Kc times the product of the ideal gas constant and temperature (Kelvin) raised to the power of the difference in moles between products and reactants
the picture shows the inverse:

Heterogeneous Equilibrium
- a reversible reaction in which the chemical species of reactants and prodcuts are in different phases
- pure solids and liquids DO NOT COUNT in the equilibrium expression (their values remain constant at a given temperature)
Le Châtelier’s Principle
If external stress is applied to a system at equilibrium, the system adjusts such that the stress is offset and equilibrium is re-established.
Factors that affect equilibrium
- temperature
- pressure
- volume
- concentration
How does temperature affect equilibrium?
- Depending on the ΔH of the reaction, heat is either a reactant or a product
- ΔH > 0, reaction is endothermic, heat is reactant, raised temperature drives reaction productsward
- ΔH < 0, reaction is exothermic, heat is a product, raised temperature drives reaction reactantsward
How does pressure affect equilibrium?
- An increase in pressure drives a reaction towards whichever side has fewer moles
How do catalysts affect equilibrium?
They DO NOT. They only affect the rate at which it is reached.
What are standard state conditions?
1 atm pressure and 1 M concentration
How is ΔG related to the equilibrium constant?
- By a proportionality constant R x T, with R being the constant 8.314 J/(mol K) and T being temperature (Kelvin)
ΔG (standard state) = - RT x ln K
or for any conditions
ΔG (any conditions) = RT x ln Q + ΔG (standard state)
What’s a Bronsted-Lowry Acid/Base?
- acid is capable of yielding an H+ ion and is therefore a “proton donor”
- base yields OH- ion and is a “proton acceptor”
What are conjugate acids/bases?
A conjugate acid or base is produced from the gain or loss of H+ ions, respectively.

What are the 7 strong acids?
And what makes them “strong”?
- HBr (Hydrobromic Acid)
- HI (Hydroiodic Acid)
- HCl (Hydrochloric Acid)
- HClO3 (Chloric Acid)
- HClO2 (Chlorous Acid)
- H2SO4 (Sulfuric Acid)
- HNO3 (Nitric Acid)
- They completely dissociate in solution.
What are the strong bases? And what makes them strong?
- Group I and II Metal Hydroxides ( ex: NaOH, Ca(OH)2 )
- Group I and II Metal Oxides ( ex: MgO, CaO )
- They dissociate completely in solution to produce H+ accepting compounds.
What is a weak acid?
- Any acid not within the 7 strong acids which dissociates only partially in solution
What are the weak bases?
Amines - contain N with a lone electron pair
Carbonates - CO32- + H20 <—> HCO3- + OH-
What determines the strength of an acid bond?
- smaller atoms bond more tightly to their H+s and therefore produce weaker acids (because they give off their H+ ions less readily)
- within a group, elements closer to the top of the table (smaller atoms) produce weaker acids, whereas elements further down the table (bigger atoms) produce stronger acids
Determining strength of oxy acids with different central atoms, but same # of oxygens.
- the more electronegative central atom inductively draws electron density from H-O bond, weakening it and therefore strengthening the acid
- ex: HClO4 is stronger than HBrO4
Determining strength of oxy acids with same central atoms but different #s of oxygens.
- more oxygens inductively weaken the O-H bond, strengthening the acid
ex: HClO3 is stronger than HClO2
Lewis Acids and Bases
- Acid accepts a pair of electrons
- Base donates a pair of electrons

