Acid and base reactions term 2 wace Flashcards
Define amphiprotic substance and examples
Substance that can donate or accept protons depending on what they are reacting with. Therefore can behave as acids/bases.
e.g. H2O, HCO3, H2PO4, HPO4,HSO4
Define monoprotic acids and examples
Can donate only one proton (acidic proton) per molecule
e.g. HCL, HF, HNO3, CH3COOH (can only donate proton part of highly polar O-H bond)
Define polyprotic acids.
Donate more than one proton from each molecule depending on the acids structure.
Examples of di and triprotic acids
Di: donate two protons
e.g. H2S04 and H2CO3
Tri: donate 3
e.g. H3PO4
How is the strength of an acid determined
Its ability to donate hydrogen ions to a base
strong acids donate a proton more readily than weak acids
how is the strength of a base measured
its ability to accept hydrogen ions from an acid
strong bases accept hydrogen more readily than weak bases
Strong acids examples
HNO3, HCL, H2S04, HBR, HI,
Weak acids examples
CH3COOH, H2CO3, H3PO4, NH4
Strong base examples
NaOH, KOH, Ca(OH)2
Weak base examples
NH3, CH3COO-, CO3
Explain the relative strength of conjugate acid-base pairs
The stronger an acid is, the weaker the conjugate base. The stronger the base, weaker the conjugate acid.
Define what occurs in a reaction with a weak acid
double arrows
the reaction is reversible as the acid has only partially ionised
Excluding their ability to donate/accept H+ ions, how else is the strength of acids/bases described?
In terms of the position of eqm when the substance donates/accepts a hydrogen ion to/from water
called hydrolysis reaction
Define Ka (write the formula)
-acidity constant
eqm constant for hydrolysis reaction of an acid
Why does waters conc not appear in constant formula?
What is it’s use in hydrolysis
It’s concentration is virtually constant=1
It is a weak electrolyte
Define Kb (write the formula)
-basicity constant
eqm constant for hydrolysis reaction of a base
Define dilution
adding more solvent to a solution
What is the ionisation constant of water
Kw=1.00x1^-14]=[OH][H3O]
Define salts and their formation
Formed in neutralisation reactions resulting in a compound whose positive ions come from a base and negative ions from an acid
Describe the pH of salts of strong acid/strong base reaction e.g.
neutral salt
e.g. NaNO3
-Na can not hydrolyse=neutral
-NO3 from strong acid therefore a weak base so cannot react
Describe the pH of salts of strong acid/weak base reaction e.g.
salts are acidic
weak base forms a conjugate acid which can hydrolyse
e.g. NH4Cl
-NH4 is acid from weak base can hydrolyse
-Cl cannot hydrolyse (neutral)
Describe the pH of salts of weak acid/strong base reaction e.g.
basic salt
anions from weak acid hydrolyse with water=hydroxide ions
e.g. CH3COONa
-CH3COO can hydrolyse as conjugate base from weak acid
-Na cannot hydrolyse
Describe the pH of salts of weak acid/weak base reaction e.g.
hard to predict
resulting pH depends on extent to which each reaction occurs
Define neutral ions=neutral pH
-group 1 and 2 ions (Na K Ca Mg)
-Conjugate neg ions of strong acids
Define ions form acidic solutions
-conjugate pos. ions of weak bases (NH4)
-Group 13 and transition metals (Al and Fe)
-HSO-4 H2PO4-
Define ions form basic solutions
-conjugate neg ions of weak acids (CH3COO F CN)
-HCO3 CO3
-HPO4 PO4
-SO4
Define and compare the acid/base models that have been used: Arrhenius and Bronsted-Lowry.
Bronsted-Lowry: acids are proton donators while bases are proton acceptors.
Arrhenius: acids dissociate and ionise in water to produce H+ ions
bases dissociate in water to produce OH- ions
Provide an examples of dissociation reaction vs hydrolysis of HCl
dissociation:
HCl(g)+H2O(l)–>H3O+(aq)+Cl-(aq)
hydrolysis:
HCl(q)–>H+(aq)+Cl-(aq)
