Acids Flashcards
Give the definition of an acid
Acid – A compound that dissolves in water to produce hydrogen ions (H+)
Give the definition of a base
Base – A substance that reacts with acid producing a salt and water.
Give the definition of an alkali
Alkali – Soluble bases which dissolve in water to produce hydroxide ions OH-
Give the definition of neutralisation
Neutralisation - H+ (aq) + OH-(aq) -> H2O(l)
Give the definition of monoprotic
Monoprotic – 1 mole of acid produces 1 mole of H+ ions.
Give the definition of diprotic
Diprotic – 1 mole of acid produces 2 moles of H+ ions.
Give the definition of a Hydonium ion or hydroxonium ion or oxonium ion.
Hydonium ion or hydroxonium ion or oxonium ion – H3O+. It is the ion formed when acids react with water.
Give the definition of a buffer
Buffer – solutions that can resist changes in pH when small quantities of acid or base are added.
Give the definition of a Bronsted-Lowry acid
A Bronsted-Lowry acid is a proton donor.
Give the definition of a Bronsted-Lowry base
A Bronsted-Lowry base is a proton acceptor.
What happens to strong bases in aqueous solution?
Strong acids (HCl, H2SO4, HNO3) and bases (NaOH, KOH) completely dissociate in aqueous solution.
What happens to weak bases in aqueous solution?
Weak acids and bases are slightly dissociated in aqueous solution.
How do you calculate the new concentration of a solution?
New concentration of a solution = amount in moles of
What is the equation for pH?
pH = -log10[H+]
What is the equation for [H+]?
[H+] = 10(-pH)
What is the equation for Kw?
Kw=[H+] [OH-] units mol2dm-6
At 25oC what does Kw equal?
At 25oC Kw = 1.00 x 10-14
In pure water how would you calculate [H+]?
In pure water [H+] = √Kw
What is the equation for pKw?
pKw = -log10Kw (14 at 25oC)
What is the equation for pOH?
pOH = log10 [OH-]
What is the link between pOH and pH?
pOH + pH = pKw
Give the equilibrium equation for the dissociation of HA.
HA H+ + A-
What is the equation for Ka?
Ka = [A-] [H+] /[HA]
What is the equation for pKa?
pKa = -log10[Ka]
How do you work out the concentration of a weak acid?
[Weak acid]=[H+]2 / Ka
What is an acidic buffer formed from?
Formed from weak acid and its salt
What happens when you add acid to an acidic buffer solution?
When small amount of acid is added extra H+ ions are added.
What happens to the position of equilibrium of an acidic buffer solution?
The position of equilibria moves to the LEFT to remove the H+ ions.
What happens to the pH of an acidic buffer solution?
This keeps the pH almost constant.
What happens to a buffer when a base is added?
When a small amount of base is added extra hydroxide OH- ions are added.
How are the hydroxide ions removed?
The hydroxide ions react with the hydrogen ions removing some of the H+ ions.
What happens to the position of equilibrium if bases are added and why?
The position of equilibrium moves to the RIGHT to replace the H+ ions.
What happens to the pH of a buffer when bases are added?
This keeps the pH almost constant.
What is an acidic buffer formed from?
Basic buffers
Give the equation for the dissociation of a basic buffer.
B + H+ BH+
What happens when you add acid to a basic buffer solution?
When small amount of acid is added extra H+ ions are removed as they react with the base B.
What happens to the position of equilibrium of a basic buffer solution?
The position of equilibrium moves to the RIGHT.
What happens to a basic buffer when a base is added?
When a small amount of base is added extra hydroxide OH- ions are added.
How are the hydroxide ions removed?
The hydroxide ions react with the hydrogen ions in the buffer removing some of the H+ ions.
What happens to the position of equilibrium if bases are added to a basic buffer and why?
The position of equilibrium moves to the LEFT to replace the H+ ions
What pH range does Thymol blue work over and what is the colour change in acid and in alkali?
Thymol blue 1.20-2.80 red – yellow (acid – alkali)
What pH range does Methyl orange work over and what is the colour change in acid and in alkali?
Methyl orange 3.10-4.40 red – yellow
What pH range does Methyl red work over and what is the colour change in acid and in alkali?
Methyl red 4.40-6.20 red – yellow
What pH range does Bromothymol blue work over and what is the colour change in acid and in alkali?
Bromothymol blue 6.00-7.60 yellow – blue
What pH range does Phenolphthalein work over and what is the colour change in acid and in alkali?
Phenolphthalein 8.30-10.00 colourless – pink.
