Year 11 Chemistry - Acids and Bases

what is an amphoteric/amphiprotic substance

a substance which can act as both an acid and a base

name the properties of an acid

sour taste

generally good electrical conductors

turns universal indicator red

turns blue litmus paper red

phenolphthalein remains colourless

name the properties of a base

taste bitter

generally good electrical conductors

turns universal indicator deep purple

turns red litmus paper blue

phenolphthalein turns pink

what do we typically call neutral

a substance with pH 7

how does the pH scale work

each number ’n’ means 1 x 10^-n

anythign below 7 is acidic and anything above 7 is basic

what is the formula for pH

pH = - log x (H+ concentration)

what does pH stand for

potential of hydrogen

what is the arrhenius definition of an acid

substances which ionise in solution to release hydrogen ions

what is the arrhenius definition of a base

substances which either ionise or dissociate in solution to release hydroxide ions

what are limitations of the arrhenius definitions

* not all substances can be shown to release hydroxide ions
* only applicable in aqueous solutions
* salts can be acidic or basic
* H+ has limited tendency to exist as free ions

how does H+ exist in water

as H+ is a strongly positively charged ion in a small volume, it has a tendency to attract water molecules and form H3O+ (hydronium)

what is the bronsted - lowry defintion of an acid

a proton/H+ donor

what is the bronsted lowry definition of a base

a proton/H+ acceptor

what is a conjugate acid base pair

an acid and a base which differ by only the presence or absence of a hydrogen ion/proton

what is the trend for conjugate acid base pairs

the stronger the acid, the weaker the conjugate base

the stornger the base, the weaker the conjugate acid

how do we know if an acid base reaction will ionise completely or partially

if the products are stronger, it will only partially ionise

if the reactants are stronger it will completely ionise

name the strong acids

Hydrochloric acid, sulfuric acid, nitric acid, Hydrogen Bromide, hydrogen iodide

name the weak acids

hydrogen fluoride, ethanoic acid, carbonic acid, phosphuric acid, sulfurous acid

name the strong bases

Usually group 1 + 2 Hydroxides amd oxides

name the weak bases

carbonates, ammonia, hydrogencarbonates (often), phopshates (often), ethanoates

what do strong acids do in solution

completely ionise

what do weak acids do in solution

partially ionise

what do strong bases do in solution

dissociate to release ions

what do weak bases do in solution

initially dissociate and then partially ionise