IB Docs (2) Team MC test: Biochemistry & the environment
Multiple choice test on B.6 Biochemistry & the environment
Use the following 'quiz' to test your knowledge and understanding of this sub-topic. As this relates to a sub-topic on the options you may need access to the IB data booklet.
If you get an answer wrong, read through the explanation carefully to learn from your mistakes.
Which class of compounds does the substance below belong to?
2,3,7,8-tetrachlorodibenzodioxin is one of the most toxic tetrachlorinated dioxins.
Which are xenobiotics?
I. PCBs
II. Antibiotics
III. Mercury
Antibiotics are natural xenobiotics whereas PCBs and the heavy metal mercury are pollutants that can be absorbed by organisms.
The production and use of dioxins is tightly controlled. Which describes the main way in which dioxins can still be released into the environment?
Most dioxin emissions come from burning household waste containing plastics under conditions that are not properly controlled.
Which substance can be used as a starting material to make a biodegradable plastic?
Bioplastics made from corn starch possess glycosidic bonds which can be broken down by organisms - the other three compounds are the starting materials for addition polymers which cannot be degraded naturally unless certain additives are added to aid decomposition.
Which forces of attraction can exist between the host and the guest in a host-guest complex?
I. covalent bonds
II. hydrogen bonds
III. dipole-dipole interactions
There are no covalent bonds as these would be too strong to allow the guest molecule to bond transiently to the host.
In the twentieth century over 1000 people died in Japan due to 'Minamata disease'. This occurred near the town of Minamata where industrial waste containing mercury was released into the sea and accumulated in shellfish and fish which was then eaten by humans and domestic animals. What term is given to describe this phenomenon?
The concentration of xenobiotics caused by moving up the food chain is known as biomagnification.
Which is the correct expression for atom economy?
The atom economy is not the percentage yield, which is based on the actual mass of the desired product(s) obtained. It is based on the mass of all the atoms in the desired product(s) divided by the total mass of all atoms present in all the products( which is is also equal to the mass of all the atoms present in the reactants) according to the stoichiometric equation, expressed as a percentage.
Which are aspects of green chemistry?
I. It aims to reduce consumption of non-renewable substances.
II. It focuses on the effects of pollutants on the environment.
III. It aims to minimise the use and generation of hazardous substances.
Green chemistry is concerned with minimising the use and production of hazardous substances and minimising the use of energy. Environmental chemistry is concerned with the effects of pollutants.
Hydrogen gas can be obtained by reacting steam with coal. Assuming coal is 100% carbon the equation is:
C(s) + 2H2O(g) → CO2(g) + 2H2(g)
What is the atom economy for the production of hydrogen by this method?
The atom economy = 4/48 x 100 = 8.33%. 'Synthesis gas' is the production of carbon monoxide and hydrogen from coal and steam. This has an even lower atom economy (6.67%) and also produces poisonous carbon monoxide. By a process known as 'water gas shift' carbon dioxide can be formed in the reaction instead of carbon monoxide. If the carbon dioxide can be trapped and stored as a solid this method provides a clean way to produce hydrogen from coal.
What is meant by biodegradation?
Although the syllabus states "Biodegradable/compostable plastics can be consumed or broken down by bacteria or other living organisms." technically compostable is more specific as it means can be consumed or broken down only under composting conditions whereas biodegradable refers to any conditions.
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