Chemical Synthesis

Question 1

Chemical Synthesis

Answer 1

The synthesis of useful products using chemistry

Question 2

Fuels

Answer 2

Hydrogen, ethanol, biodiesel

Question 3

Biofuel

Answer 3

Produced from renewable sources such as plants, rather than fossil fuels

Question 4

Biodiesel

Answer 4

Esters made from vegetable oils and animal fat and oils (triglycerides). This occurs through transesterification, with the use of a base or lipase catalyst.

E.g. Triglyceride + Methanol —> Mixture of fatty esters (biodiesel) + Glycerol
Conditions: NaOH catalyst or lipase catalyst

Question 5

Transesterification

Answer 5

Uses an alcohol as a catalyst to split a triglyceride into glycerol and an ester

Question 6

Base Catalyst

Answer 6

Uses a strong base as a catalyst. Uses low temp and pressure.

Question 7

Lipase Catalyst

Answer 7

Uses lipase as a catalyst. Slow and expensive but pure products.

Question 8

Ethanol

Answer 8

Produced via hydration of ethene
Conversion rate of 5%, so is repeated

Question 9

Fermentation of Glucose

Answer 9

Glucose from renewable feedstock (corn or sugarcane) are fermented with yeast as a catalyst.

Glucose —> Ethanol + CO2
Conditions: Yeast

Question 10

Hydrogen Fuel Cells

Answer 10

Used for production of electricity
A type of galvanic cell

Question 11

Steam Reforming

Answer 11

Most common method of hydrogen production
Steam reacts with fossil fuels in the presence of a nickel catalyst. Then, carbon monoxide reacts with steam in the presence of a copper or iron catalyst.

CH4(g) + H2O(g) –> CO(g) + 3H2(g)
Conditions: Ni
CO(g) + H2O(g) –> CO2(g) + H2(g)
Conditions: Fe or Cu

Question 12

Electrolysis of Water

Answer 12

Not a widely used method for hydrogen production
2H2O(l) —> O2(g) + H2(g)
Conditions: Electricity

Question 13

In both acidic and alkaline hydrogen fuel cells

Answer 13

H2 is oxidised
O2 is reduced
H2O is produced and removed
Electrons flow from anode to cathode
Semi-permeable membrane breaks H2 and O2 gas apart

Question 14

Acidic hydrogen fuel cell

Answer 14

H2 oxidised at anode
H2 –> 2H+ + 2e-
O2 reduced at cathode (using H+ from electrolyte)
O2 + 4H+ +4e- –> 2H2O
Water produced at cathode and removed
Ions move anode to cathode
Electrolyte: Hot H3PO4

Question 15

Alkaline hydrogen fuel cell

Answer 15

H2 oxidised at anode (using OH-)
H2+ 2OH- –> 2H2O +2e-
O2 reduced at cathode (using H2O)
O2+ 2H2O + 4e- –> 4OH-
Water produced at anode and removed
Ions move from cathode to anode
Electrolyte: Hot KOH

Question 16

Haber Process

Answer 16

N2(g) +3H2(g) <—> 2NH3 (g) enthalpy -92.4kJ
Produces ammonia - NH3 used in fertilisers
35% efficiency, but can be recycled
Iron catalyst, 200atm pressure, 500 degrees temp

Question 17

Contact Process

Answer 17

1. S(s) + O2(g) —> SO2(g)
2. 2SO2(g) + O2 (g) <—> 2SO3(g) enthalpy -196kJ
3. SO3(g) + H2SO4(l) —> H2S2O7 (l)
   H2S2O7(l) + H2O(l) —> 2H2SO4(l)

3-step process to make sulphuric acid
Vanadium oxide catalyst, low pressure 2atm high temp 450 degrees