Paper 2 PPQs

Question 1

name and describe the ppt produced when copper ions react with sodium hydroxide and give the ionic equation

Answer 1

• copper hydroxide (blue)
• Cu^2+ + 2OH^- ⇒ Cu(OH)2

Question 2

name and describe the ppt produced when calcium ions react with sodium hydroxide and give the ionic equation

Answer 2

• calcium hydroxide (white and doesn’t dissolve when more NaOH added)
• Ca^2+ + 2OH^- ⇒ Ca(OH)2

Question 3

name and describe the ppt produced when magnesium ions react with sodium hydroxide and give the ionic equation

Answer 3

• magnesium hydroxide (white and doesn’t dissolve when more NaOH added)
• Mg^2+ + 2OH^- ⇒ Mg(OH)2

Question 4

name and describe the ppt produced when aluminium ions react with sodium hydroxide and give the ionic equation

Answer 4

• aluminium hydroxide (white and dissolves when more NaOH added)
• Al^3+ + 3OH^- ⇒ Cu(OH)3

Question 5

name and describe the ppt produced when iron (II) ions react with sodium hydroxide and give the ionic equation

Answer 5

• iron hydroxide (green)
• Fe^2+ + 2OH^- ⇒ Fe(OH)2

Question 6

name and describe the ppt produced when iron (III) ions react with sodium hydroxide and give the ionic equation

Answer 6

• iron hydroxide (brown)
• Fe^3+ + 3OH^- ⇒ Fe(OH)3

Question 7

name and describe the ppt produced when sulfate ions react with barium chloride and give the ionic equation

Answer 7

• barium sulfate (white)
• Ba^2+ + SO4^2- ⇒ BaSO4

Question 8

name and describe the ppt produced when chloride ions react with silver nitrate and give the ionic equation

Answer 8

• silver chloride (white)
• Ag^+ + Cl^- ⇒ AgCl

Question 9

name and describe the ppt produced when bromide ions react with silver nitrate and give the ionic equation

Answer 9

• silver bromide (cream)
• Ag^+ + Br^- ⇒ AgBr

Question 10

name and describe the ppt produced when iodide ions react with silver nitrate and give the ionic equation

Answer 10

• silver iodide (yellow)
• Ag^+ + I^- ⇒ AgI

Question 11

Suggest one reason why using solar energy is a more sustainable way of generating electricity than burning oil.

Answer 11

solar energy is a renewable source of energy

Question 12

Explain why HDPE has a higher density than LDPE.

Answer 12

in HDPE polymer chains/molecules are closer together as they are unbranched so more atoms per unit volume

Question 13

Ethene produces different forms of poly(ethene). How can different forms of poly(ethene) be produced from ethene?

Answer 13

use different reaction conditions (different pressures/temperatures)

Question 14

industrial proces:
1. React streams of ammonia solution and sulfuric acid together.
2. Evaporate the water by passing the solution down a warm column.
3. Collect dry crystals continuously at the bottom of the column.
laboratory:
1. React ammonia solution and sulfuric acid in a conical flask.
2. Evaporate water from the solution until crystals start to form.
3. Leave to cool and crystallise further.
4. Separate the crystals using filtration.
5. Dry the crystals between pieces of filter paper.
Evaluate the two methods for producing a large mass of ammonium sulfate.

Answer 14

industrial process is larger scale and is quicker and is a continuous process + reasoned judgement

Question 15

Phytomining has not been widely used to extract copper. Suggest two reasons why.

Answer 15

• high grade ores still available
• land not available
• phytomining takes a long time
• new technology

Question 16

The activation energy for the reaction between zinc and sulfuric acid is lowered if a solution containing metal ions is added.
What is the most likely formula of the metal ions added?
Al3+
Ca2+
Cu2+
Na+

Answer 16

Cu2+ - transition metals are catalysts

Question 17

Ethanol can be produced from ethene and steam. The equation for the reaction is:
C2H4(g) + H2O(g) ⇌ C2H5OH(g) The forward reaction is exothermic. Explain how the conditions for this reaction should be chosen to produce ethanol as economically as possible.

Answer 17

Rate:
* higher temperature gives higher rate because more frequent collisions
* higher pressure gives higher rate because more frequent collisions
* a catalyst can be used to give a higher rate because the activation energy is reduced
Yield:
* higher temperature gives lower yield because the reaction is exothermic
* higher pressure gives higher yield because there are more molecules on left hand side
Other factors:
* higher temperatures and pressures use more energy so costs increase
Compromise:
* chosen temperature is a compromise between rate and yield
* chosen temperature is a compromise between rate and cost (of energy used)
* chosen pressure is a compromise between rate and cost (of energy used)
* chosen pressure is a compromise between yield and cost (of energy used)