A-level Acids

What is the definition of a Bronsted-Lowry acid?

• A substance that reacts with hydroxide ions

• Anything that contains H⁺ ions

• A proton donor

• An acceptor of a lone pair of electrons

What is the correct expression for the ionic product of water and its unit?

• K_w = [H⁺][OH^-] mol/dm³

• K_a = [H₃O⁺][OH^-]/[H₂O] mol/dm³

• K_a = [H⁺][OH^-] mol²/dm⁶

• K_w = [H₃O⁺][OH^-] mol²/dm⁶

What is a strong acid?

• Any acid with a concentration above 1 mol/dm³

• Sulphuric acid

• An acid that is totally dissociated into ions

• An acid that can react with carbonate bases

What happens to K_w and pH when pure water is heated?

• K_w increases and pH decreases

• Nothing, pure water is neutral

• K_w and pH both increase

• K_w and pH both decrease

• K_w decreases and pH increases

What is the definition of pH?

• -Ln[H⁺]

• Log[H⁺]

• The negative logarithm to base 10 of the hydrogen ion concentration

• A measure of acidity from 1 to 14

What is a weak acid?

• Any acid with a concentration below 0.1 mol/dm³

• An acid that has only slightly more positive H⁺ ions than negative ions

• An acid with a pH between 4 and 6

• An acid that has only partially dissociated into ions

What is a conjugate base?

• A proton acceptor

• A proton acceptor produced when an acid loses a proton

• A particle that can join with a base

• A particle produced when a base has joined to a proton

What is a buffer?

• A small amount of substance that resists a change in pH when acid or alkali is added

• A substance that keeps the pH constant

• A substance that maintains a neutral pH when a small amount of acid or alkali is added

• A substance that resists the change in pH when a small amount of acid or alkali is added

Which of the following mixtures would form a buffer solution?

• 25cm³ of 1mol/dm³ NaOH and 25cm³ of ethanedioic acid

• 25cm³ of 1 mol/dm³ NaOH and 25cm³ of ethanoic acid

• 50cm³ of 1 mol/dm³ NaOH and 25cm³ of ethanoic acid

• 50cm³ of 1 mol/dm³ NaOH and 25cm³ of ethanedioic acid

At the half-neutralisation point in a titration the pKa is equal to…

• -Log[H⁺]

• 14-pH

• 7

• -LogK_a