Managing Resources (4)

Question 1

What is the balanced equation for the fermentation producing ethanol.

Answer 1

C6H12O6 (aq) —-> 2C2H5OH (aq) + 2CO2 (aq)

Question 2

What is reverse osmosis?

Answer 2

ii. Water is pressurised and forced through a semi-permeable membrane, which allows smaller water molecules but not larger dissolved salts or ions to pass through. Water travels against the concentration gradient to an area of lower concentration.

Question 3

What is the formula for ethanol

Answer 3

C2H5OH

Question 4

Most fertilizers contain nitrogen in the form of nitrates or ammonium ions. State why nitrogen is applied in these forms.

Answer 4

Nitrate and ammonium ions are water soluble which allows them to be absorbed by plant roots from the soil solution.

Question 5

What is the formula for complete combustion?

Answer 5

Fuel + O2 —-> C02 + H2O

Question 6

What is the formula for incomplete combustion?

Answer 6

Fuel + O2 —–> (CO or C) + H2O

Question 7

What is the enthalpy change of a reaction?

Answer 7

The difference in potential energy of the reactants and the products is the enthalpy change for a reaction.

• If enthalpy change is positive (products higher than reactants) it is endothermic (heat absorbed)
• If enthalpy change is negative (reactants higher than products) it is exothermic (heat released)

Question 8

What does Q represent?

Answer 8

Quantity of heat transferred (heat energy) measured in jules (J)

Question 9

What does ^T represent?

Answer 9

Change in temp of solvent (usually water) measured in degrees

Question 10

What does m represent?

Answer 10

mass of water (or liquid) heated by combustion (1g = 1ml) measured in grams (g)

Question 11

What does ^H represent?

Answer 11

Molar enthalpy of combustion (change in enthalpy) measured in KJ mol -1

Question 12

What does n represent?

Answer 12

Moles of fuels that have undergone combustion (amount of substance) measured in moles (mol)

Question 13

What is the equation for photosynthesis?

Answer 13

6CO2 (g) + 6H2O (l) —-> C6H12O6 (s) + 6O2 (l)

Question 14

What is an oxidant or oxidizing agent?

Answer 14

A species that brings upon oxidation (and is reduced) is called an oxidant or oxidizing agent
Decrease in oxidation number

Question 15

What is a reductant or reducing agent?

Answer 15

A species that brings upon reduction (and is oxidized) is called the reductant or reducing agent
Increases in oxidation number

Question 16

What is a flow cell?

Answer 16

Are rechargeable fuel cells that can be used to store power (i.e. wind and solar)
They can be charged (electrical energy to chemical energy) and discharged (chemical energy to electrical energy) via reversible redox reactions
A redox reaction that can proceed in the forward and backward directions

Question 17

What are the steps in metal production?

Answer 17

1. Extraction - The removal of metal ore from the Earth’s crust
2. Concentration
   Ore crushed and ground
   Completed at mine site to reduce cost of transportation and rock disposal
   Removal of gangue to form mineral concentrate
   May not be required if mineral in ore was in high concentration or it is possible to remove mineral in presence of wastes
3. Conversion
   Converts mineral to a compound that can be reduced, therefore is not required if compound can already be reduced
   Chemical process e.g. roasting the sulfide mineral to produce the metal oxide or sintering
4. Reduction
   Depends on the reactivity of the metals but may include. Molten electrolysis, aqueous electrolysis and chemical reduction via a chemical reducing agent
5. Refining
   Remaining impurities can be removed by electrolysis or further chemical reactions if necessary
   Removing trace impurities (not required for Al or Zn)

Question 18

What are the 5 main factors of a Galvanic cell?

Answer 18

1. changes chemical energy into electrical energy
2. ANODE = NEGATIVE (-)
3. CATHODE = POSITIVE (+)
4. Spontaneous reaction occurs
5. Doesn’t require battery

Question 19

What are the 5 main factors of an Electrolytic cell?

Answer 19

1. Changes electrical energy into a chemical reaction
2. ANODE IS POSITIVE (+)
3. CATHODE IS NEGATIVE(-)
4. Non-spont reaction occurs
5. Battery is required

Question 20

What are the two main types of recycling polymers?

Answer 20

There are two main methods of recycling polymers:

• Physical (broken down by shredding or melting)
• Chemical (broken down to be reused to make new polymers or used as fuels)

Question 21

What are the names of the 2 materials which composite materials are made of?

Answer 21

Composite materials consist of two materials: a matrix and a reinforcement.
Matrix: the bulk material e.g. metal, polymer, ceramic.
Reinforcement: material embedded throughout the matrix e.g. fibres, particles.

Question 22

What do you call water that is safe to drink?

Answer 22

Potable water

Question 23

What are the 6 steps of water treatment?

Answer 23

1. Coagulation is the chemical process of neutralizing the surface charge of particles
2. Flocculation is the physical process of clustering (aggregation) of impurity particles

3.Sedimentation is the settling of the floc aggregates

4. Filtration is the removal of solid impurities
   Done through passing dirty water through layers of sand and charcoal
5. Disinfection is the removal of any biological contaminants

6.Fluoridation is the controlled adjustment of fluoride content within water

Question 24

Explain how reverse osmosis produces potable water from saline water.

Answer 24

Desalination is a process used to remove minerals from saline water to produce fresh potable water. Reverse osmosis and thermal distillation are two widely used methods for desalination.
Describe the disadvantages of using desalination for the production of potable water.

Question 25

Explain natural nitrogen fixation with the aid of equations.

Answer 25

Lightning, volcanic activity and forest fires provide sufficient energy (high temperatures) to break the strong N2 covalent triple bond, allowing it to react with atmospheric oxygen and form nitrogen oxides.

N2 + O2 → 2NO (nitric oxide)

2NO + O2 → 2NO2 (nitrogen dioxide)

Nitrogen dioxide then dissolves in water vapour in the atmosphere forming nitrous acid (HNO2) and nitric acid (HNO3).

2NO2 + H2O → HNO2 + HNO3

Both acids ionise, producing soluble nitrate ions (NO3-) and nitrite ions (NO2-) which are deposited into the soil during rain fall.

Question 26

What is the equation for respiration?

Answer 26

C6H12O6 + 6O2 —-> 6CO2 + 6H2O

Question 27

What is eutrophication?

Answer 27

1. Excess nitrogen and phosphorus from fertilisers, detergents (contain phosphate groups) or sewage can be leached from soils into waterways e.g. rivers and lakes causing eutrophication.
2. The increase in available nutrients promotes the excessive growth of aquatic plants including photosynthetic microbes including; algae and bacteria. These microbes form a bloom (thick mat on the surface of the water) which prevents sunlight from reaching into the waterway.
3. Aquatic plants underneath the bloom do not receive sunlight and are unable to photosynthesise causing them to die.
4. Aerobic bacteria decompose the dead plant matter, further depleting the oxygen supply in the water and causing the death of aquatic organisms (plants, fish etc.).
5. When the oxygen supply is fully depleted, anaerobic bacteria decompose the plant and animal remains generating products that are toxic to the water, making the water even less habitable for the remaining organisms.