IC71.4.3 Student book questions
Student book questions
© Oxford University Press 2011
IC71.4.3 Student book questions
C71 Lesson 4 Green chemistry: catalysts
1.
Classify these raw materials as ‘renewable’ or
’non-renewable’:
a
salt (sodium chloride)
b
crude oil
c
wood chippings
d
limestone
e
sugar beet.
© Oxford University Press 2011
IC71.4.3 Student book questions
2.
Which of the ways of making industry ‘greener’ are
illustrated by the development of Sorona?
3.
16 g of methane (CH4) was burned in the air. 32 g of
carbon dioxide was collected during the reaction. During
the reaction, some sooty deposits were noticed. The
equation for the combustion of methane is:
CH4 + 2O2
CO2 + 2H2O
a
What was the percentage yield of carbon dioxide?
b
Why do you think the percentage yield was so low?
c
Calculate the atom economy for the reaction.
© Oxford University Press 2011
IC71.4.3 Student book questions
4.
5.
Heating with a catalyst converts cyclohexanol, C6H11OH,
to cyclohexene, C6H10.
a
What is the percentage yield if 20 g of cyclohexanol
gives 14.5 g of cyclohexene?
b
What is the atom economy, assuming that the
catalyst is recovered and reused?
The reaction involving cyanide in the older process for
making the active ingredient for Roundup was
exothermic. The replacement reaction in the newer
process is endothermic. Suggest why this difference
contributes to safety.
© Oxford University Press 2011
IC71.4.3 Student book questions
6.
7.
a
Write a short paragraph to explain why the
biosynthetic route to vanillin is ‘greener’ than the
petrochemical route.
b
Explain why it may not be a good idea to try and
speed up the biosynthetic route by heating the
reaction mixture.
a
Explain in a short paragraph the difference between
open-loop and closed-loop recycling.
b
Suggest one possible advantage and one possible
disadvantage of each of these approaches to
recycling.
© Oxford University Press 2011
IC71.4.3 Student book questions
8.
Why is it important to carefully control waste from
industrial processes?
9.
Compare sustainable development and green chemistry.
What is the difference?
10. What is the molecular formula for ibuprofen?
11. a
b
What is the atom economy for making ibuprofen:
• by the Boots process?
• by the Celanese Corporation process?
Calculate a new value of the atom economy for the
Celanese process, if the ethanoic acid (CH3COOH)
formed as a by-product in one step is recycled and
does not go to waste.
© Oxford University Press 2011
IC71.4.3 Student book questions
1.
Classify these raw materials as ‘renewable’ or
’non-renewable’:
a
salt (sodium chloride)
non-renewable
b
crude oil
non-renewable
c
wood chippings
renewable
d
limestone
non-renewable
e
sugar beet.
renewable
© Oxford University Press 2011
IC71.4.3 Student book questions
2.
Which of the ways of making industry ‘greener’ are
illustrated by the development of Sorona?
The raw material is renewable plant material. The
production of the main feedstock happens at low
temperature with enzymes.
3.
16 g of methane (CH4) was burned in the air. 32 g of
carbon dioxide was collected during the reaction. During
the reaction, some sooty deposits were noticed. The
equation for the combustion of methane is:
CH4 + 2O2
CO2 + 2H2O
© Oxford University Press 2011
IC71.4.3 Student book questions
a
What was the percentage yield of carbon dioxide?
16 g of methane gives a theoretical yield of 44 g of
carbon dioxide.
Percentage yield = 32/44 × 100% = 73%
b
Why do you think the percentage yield was so low?
Sooty deposits were noticed showing some carbon
was formed in the reaction. The combustion was
incomplete.
c
Calculate the atom economy for the reaction.
Atom economy = 44/80 × 100% = 55%
© Oxford University Press 2011
IC71.4.3 Student book questions
4.
Heating with a catalyst converts cyclohexanol, C6H11OH,
to cyclohexene, C6H10.
a
What is the percentage yield if 20 g of cyclohexanol
gives 14.5 g of cyclohexene?
100 g cyclohexanol gives a theoretical yield of 82 g
cyclohexene.
Theoretical yield from 20 g cyclohexanol =
0.2 × 82 g = 16.4 g
Percentage yield = 14.5/16.4 × 100% = 88%
b
What is the atom economy, assuming that the
catalyst is recovered and reused?
Atom economy = 82/100 × 100% = 82%
© Oxford University Press 2011
IC71.4.3 Student book questions
5.
The reaction involving cyanide in the older process for
making the active ingredient for Roundup was
exothermic. The replacement reaction in the newer
process is endothermic. Suggest why this difference
contributes to safety.
An exothermic reaction heats the reaction mixture. A
hotter mixture reacts faster – thus giving out energy
faster and heating the mixture faster. If uncontrolled this
could rapidly become dangerous.
© Oxford University Press 2011
IC71.4.3 Student book questions
6.
a
Write a short paragraph to explain why the
biosynthetic route to vanillin is ‘greener’ than the
petrochemical route.
Points to include in the paragraph about the
biosynthetic route: uses a renewable feedstock;
avoids hazardous chemicals; operates at a little
above room temperature and at atmospheric
pressure, which saves energy and makes the
process safer.
© Oxford University Press 2011
IC71.4.3 Student book questions
b
Explain why it may not be a good idea to try and
speed up the biosynthetic route by heating the
reaction mixture.
Enzymes are denatured above a certain temperature
and no longer work. The reaction will no longer be
catalysed.
© Oxford University Press 2011
IC71.4.3 Student book questions
7.
a
Explain in a short paragraph the difference between
open-loop and closed-loop recycling.
A paragraph that distinguishes:
Open loop – recycling that recovers a polymer as
flake, which can be remoulded by heat and pressure
to make new articles.
Closed loop – recycling by converting the waste
polymer into chemicals that can be used to make
new polymers.
© Oxford University Press 2011
IC71.4.3 Student book questions
b
Suggest one possible advantage and one possible
disadvantage of each of these approaches to
recycling.
Advantage
Disadvantage
Open loop
relatively simple
because there are
no chemical
changes
product quality lower
than the quality of the
original polymer
Closed loop
recycled polymer as
good as new
because it is made
from pure monomer
can only work for
polymers that can be
reconverted to the
monomer; a relatively
complex process
© Oxford University Press 2011
IC71.4.3 Student book questions
8.
Why is it important to carefully control waste from industrial
processes?
Wastes may contain harmful chemicals which could be
hazardous if released into the air, water, or landfill. Treating
wastes can convert these chemicals into less harmful
materials.
9.
Compare sustainable development and green chemistry.
What is the difference?
Sustainable development is about meeting the needs of the
present without compromising the ability of future
generations to meet their own needs. Green chemistry is
more specifically about reducing the impact of the chemical
industry on our health and the environment by using safer
and more sustainable processes.
© Oxford University Press 2011
IC71.4.3 Student book questions
10. What is the molecular formula for ibuprofen?
C13H18O2
11. a
What is the atom economy for making ibuprofen:
• by the Boots process?
• by the Celanese Corporation process?
Boots process:
Relative mass of atoms in reactants = 514.5
Relative mass of product = 206
Atom economy = 206/514.5 × 100% = 40%
Celanese process:
Relative mass of atoms in reactants = 266
Relative mass of product = 206
Atom economy = 206/266 × 100% = 77%
© Oxford University Press 2011
IC71.4.3 Student book questions
b
Calculate a new value of the atom economy for the
Celanese process, if the ethanoic acid (CH3COOH)
formed as a by-product in one step is recycled and
does not go to waste.
Assuming recycling of ethanoic acid:
atom economy = 100%
© Oxford University Press 2011