Acid and Bases Flashcards
What is the Arrhenius definition of an acid?
A substance releasing hydrogen ions in water
What is the Arrhenius definition of an base?
A substance releasing hydroxide ions in water
Give an example of a limitation of the Arrhenius definition of acids and bases.
NaHCO3 (baking soda) is a base but does not release hydroxide ions
What is the Bronsted-Lowry Theory of an acid?
Substance that donates a proton
What is the Bronsted-Lowry Theory of a base?
A substance that accepts a proton
What do conjugate acid-base pairs differ from? Give an example.
By a single proton.CH3COOH/CH3COO-
What is self-ionisation?
When a molecule reacts with itself to give ions
What is the equilibrium constant (Kc)?
The concentration of the products divided by the concentration of the reactants
What is the ionic product of water?
Kw= [H30+]x[OH-]=10-14 at 25 oC
What is a Bronsted acid?
Proton donors and they increase the concentration of H+
What is a Bronsted base?
Proton acceptors and they decrease the concentration of H+
How can the acidity or basicity of a solution be measured?
By its hydronium ion concentration
What is the equation for pH?
pH= -log10[H30]
What is the equation for [H30]?
[H30]= antilog10(-pH)=10-pH
What are weak acids ( or weak bases)?
Weak electrolytes: partially ionised
What does the higher the value of Ka mean?
The stronger the acid
What does the higher the value of pKa mean?
The stronger the acid
What does the lower the value of pKa mean?
The stronger the acid
What are polyphonic acids?
Acids that can donate more than one proton e.g. phosphoric acid is triprotic acid
What does the higher the value of Kb mean?
The stronger the base
What does the lower the value of pKb mean?
The stronger the base
What are salts?
Salts are ionic species which can be produced by reaction of an acid with a base
Give a example of a neutral salt
NaCl, LiBr
Give a example of a acidic salt?
NH4Cl, NH4Br
Give a example of a basic
NaCN , CH2COONa
What is the cation of the salt?
The conjugate acid of the weak base. The salt hydrolysis to give an acidic solution
NH4Cl-NH4+ + CL-
What is the anion of the salt?
The conjugate base of the weak acid. The salt hydrolyses to give a basic solution.
CH3COONa- Na+ + CH3COO-
What is percentage ionisation?
Ratio of the concentration of ionised molecules to the concentration of all molecules put into the solution
