Random Chem past paper questions

Describe a test to show that the white powder in an unlabelled bottle is lithium carbonate (5)

1) Flame test

2) Burns with red flame

3) Add dilute hydrochloric acid

4) Bubble carbon dioxide through limewater

5) Limewater turns cloudy

Describe what a student should do to make sure that all the water is removed from hydrated sodium sulphate (2)

1) Heat sodium sulphate

2) Until there is no further change in mass

Describe how a catalyst works (2)

1) Provides alternate pathway

2) With a lower activation energy

State what is meant by the term ionic bonding (2)

1) Electrostatic attraction

2) Between oppositely charged ions

Explain why the structure of most metals makes them good conductors of both electricity and heat (2)

1) Metals have delocalised electrons which are free to move
2)These delocalised electrons can carry both heat energy and charge through the structure of the metal

Describe the differences in the reactions of ethane and ethene with bromine. Refer to the conditions, the products and the types of reaction involved (5)

1) Ethane needs UV (radiation) to react

2) Ethane produces bromoethane

3) Ethane produces hydrogen bromide

4) Ethene produces dibromoethane

5) Reaction with ethane involves breaking C-H bond / reaction with ethene involves breaking C=C bond

6) Ethane reaction is substitution

7) Ethene reaction is addition

Explain, in terms of particle collision theory, how increasing the temperature affects the rate of reaction (3)

1) Particles gain more kinetic energy

2) More collisions are successful

3) Collision frequency increases/rate of reaction increases

Explain why C60 fullerene has a much lower melting point than diamond and graphite (4)

1) C60 fullerene has weak intermolecular forces

2) Less energy needed to overcome the forces

3) diamond and graphite have strong covalent bonds

4) More energy needed to overcome the covalent bonds

Describe how a student can obtain pure dry crystals of salt from salt solution (5)

1) Filter to remove excess

2) Heat solution

3) Evaporate some of the water

4) Leave the remaining solution to crystallise

5) Filter to obtain crystals by removing excess liquid

6) Place crystals in oven to dry

Give the formula for rust (1)

Fe2O3

Describe a test for ammonium ions (3)

1) Add sodium hydroxide solution

2) Test with damp red litmus paper

3) Red litmus turns blue

Give 3 ways the rate of reaction could increase (3)

• Temperature increases

• Concentration of dissolved reactants increases

• Pressure of gases increases:

• Solids reacting are in smaller pieces with bigger surface area

• Catalyst

Give a reason why universal indicator is not suitable for use in a titration (1)

No clear end point

Explain the different ways that magnesium and magnesium chloride conduct electricity (4)

1) Magnesium has delocalised electrons

2) Electrons can move

3) Magnesium chloride can only conduct when molten/in solution OR

4) Ions are free to move

Describe how crude oil is separated into fractions in a fractionating column

1) Heat to turn the crude oil into vapour/gas

2) Gases rise up column

3) Column hotter at the bottom than at the top

4) They condense when they reach their boiling point

5) Big molecules at the bottom, small molecules at the top

Describe a test to show that ammonium chloride contains ammonium ions (3)

1. Add sodium hydroxide solution

2. (test gas with damp) red litmus

3. Turns blue

Describe tests to show that an aqueous solution of calcium chloride contains calcium ions and chloride ions (4)

1. (Ca2+)flame test

2. orange/red flame colour

3. (Cl-)add silver nitrate

4. white precipitate

The four solutions are

• potassium carbonate

• potassium chloride

• potassium iodide

• sodium chloride

Describe a method to identify each solution. (6)

• M1 do a flame test

• M2 sodium chloride produces a yellow flame

• M3 add acid

• M4 potassium carbonate effervesces / bubbles

• M5 add dilute nitric acid

• M6 add silver nitrate (solution)

• M7 potassium chloride gives a white precipitate

• M8 potassium iodide gives a yellow precipitate