Chemistry terms and definitions

Dynamic equilibrium

Occurs when the rates of the forward reaction and the reverse reaction equal each other

Le châtelier’s principle

If a system at equilibrium is disturbed by a change in temp, reactant or product concentration, pressure, the system shifts in a direction that counteracts the disturbance.

Equilibrium constant (k)

Ratio of the concentration of products to concentration of reactants raised to their coefficients

The change in n in the Kp formula

Moles of products - moles of reactants (gases only)

Q

Réaction quotient; ratio of concentration of products to concentration of reactants at any point in time (not at equilibrium!)

coefficients multiplied by x so you

K to the power of that number

reverse the reaction so you

Reciprocal its’ K

Add reactions so you

Multiply the two K’s

Chatelier principle: adding/removing a product or reactant

Concentrations of x will change, k will not change. Adding a reactant means we need to decrease the reactant and increase product to re-establish equilibrium (original k value)

Chatelier’s principle: changing volume

K doesn’t change. will shift equilibrium towards the side with fewer moles of gas. When volume is halved gas concentrations double. Volume inversely proportional to pressure

Chatelier’s principle: changing temperature

K will change. If temperature increases in an exothermique reaction there is more heat in the products side so the equilibrium shifts to the reactants and vice versa for endothermic and opposite for all.

Acid (Arrhenius definition)

Substance that increases H+ concentration

Base (Arrhenius definition)

Substance that increases OH- ion concentration

Acid (Brønsted-Lowry)

Substance that donates an H+ to another substance

Base (Brønsted-Lowry)

Substance that accepts an H+ from another substance

Acid (Lewis)

Substance that accepts electron pair

Base (Lewis)

Substance that donates electron pair

Conjugate acid

Formed when a base accepts a proton

Conjugate base

Formed when an acid donates a proton

Strong acid

Completely dissociates in water forming H3O (complete ionization), equilibrium all the way to the right

Strong base

Completely dissociates in water forming OH-, equilibrium all the way to the right

Weak acid/base

Only partial dissociation.

Kw

Ionization constant for water (Ka x Kb)

Ka

Describes how an acid dissociates

Kb

Describes how a base dissociates

Pka

-log(Ka)

Pkb

-log(Kb)

pKa = pH/pKb = pOH when?

When it’s a strong acid/base and does full dissociation. The concentration of the acid/base dissociating is equal to [H3O], [OH]

Acidic salt

strong acid + weak base. The strong acid fully dissociates; the weak base partially dissociates

Basic salt

strong base + weak acid. The strong base fully dissociates; the weak acid partially dissociates

buffer

solution containing a weak acid/base and its conjugate that resists pH changes and neutralizes the small amounts of acid and base added.

the h-h equation

calculates the pH of a buffer solution by knowing the pKa of the weak acid and the ratio of the conjugate base to the conjugate acid

H3O

when an acid dissolves in water it releases an H+ ion which automatically needs to attach- to a water molecule making H3O

monoprotic acid/base

can only accept/donate 1 proton per molecule when dissociating in water. dissociation happens in 1 step

polyprotic acid/base

can accept/donate more than 1 proton per molecule when dissociating in water. dissociation happens in multiple steps