C4: ACIDS AND ALKALIS

Question 1

What is an acid?

Answer 1

a substance that
-forms aqueous solutions with a pH less than 7
-forms H+ ions in water

Question 2

What’s the difference between a strong acid and a weak acid?

Answer 2

-a strong acid fully ionises in solution
-a weak acid only partially ionises in solution

Question 3

What is a base?

Answer 3

a substance with a pH greater than 7

Question 4

What is an alkali?

Answer 4

a base that
-dissolves in water to form a solution with a pH less than 7
-forms OH- ions in water

Question 5

What is a neutralisation reaction?

Answer 5

acid + base –> salt + water
or
H+ (aq) + OH- (aq) –> H2O (l)

Question 6

Titrations

Answer 6

-using pipette and pipette filler measure 25 cm^3 of alkali into the conical flask
-add a few drops of methyl orange indicator to the flask
-place a white tile under the conical flask
-fill burette with acid of known conc. and record initial volume
-add acid from the burette slowly and swirl the flask constantly
-as soon as there is a colour change sop adding acid
-calculate volume of acid added
-repeat titration and calculate mean

Question 7

Reaction of an acid with metal

Answer 7

(metal) + (acid) –> (salt) + hydrogen

Question 8

Reaction of an acid with metal oxide

Answer 8

(metal) oxide + (acid) –> (salt) + water

Question 9

Reaction of an acid with metal hydroxide

Answer 9

(metal) hydroxide + (acid) –> (salt) + water

Question 10

Reaction of an acid with metal carbonate

Answer 10

(metal) carbonate + (acid) –> (salt) + carbon dioxide + water

Question 11

RP crystallisation (copper sulfate crystals)

Answer 11

-measure 30cm^3 of sulfuric acid into a beaker
-gently heat
-add copper oxide in excess using a spatula
-filter out excess copper oxide using funnel and filter paper
-pour into an evaporating basin, put over water bath and heat
-remove from heat and allow crystals to cool and dry