2021 paper 1

Question 1

Explain why graphite is:
-a good electrical conductor
-soft and slippery
You should answer in terms of structure and bonding [6 MARKS]

Answer 1

bonds are covalent
giant structure

three covalent bonds per carbon atom
so one elctron per carbon atom is delocalised
these delocalised electrons
can move through structure
and carry charge
so can conduct

layered structure
of hexagonal rings
with weak intermolecular forces between layers
so layers can slide over eachother
so graphite is soft and slippery

Question 2

Give 2 reasons why the discovery of elements after mendeleev’s prediction, supported him to become accepted

Answer 2

-fitted a gap he had left
properties wre predicted correctly

Question 3

List observations when piece of K added to water

Answer 3

-floats
-melts
-moves around
-becomes smaller
-lilac flame
-fizzing (effervescence)

Question 4

explain why (sodium oxide) has high melting point [3 MARKS]

Answer 4

-giant ionic lattice
-oppositeky charged ions bonded by strong electrostatic forces
-take a lot of energy to ivercome

Question 5

when making crystals, how should filtrate be evaporated gently

Answer 5

water bath

Question 6

Explain the difference between the processes in electrolysis and in a chemical cell

Answer 6

-electrolysis uses electricity to produce a chemical reaction
-cells use a chemical reaction to produce electricity

Question 7

Suggest why colour of electrolyte solution fades during electrolysis

Answer 7

(coloured) ions are removed from solution

Question 8

does a lower pH mean acid or alkaline

Answer 8

acid

Question 9

List improvements of titrations

Answer 9

-swirl solution
-white tile under flask
-add acid dropwise (near endpoint)
-repeat AND calculate mean