DSE Chemistry
DSE Chemistry: Planet Earth — Practice Questions & Answers
The chemistry of Earth's atmosphere, the oxygen and nitrogen cycles, sea water as a resource, rocks and minerals, and the extraction of metals.
30 practice questions available for this topic — here are 10 with full answers and explanations.
Start an interactive quiz on Planet Earth →
Practice questions with answers
1
Multiple choice · Easy
Argon is obtained from the atmosphere by
- fractional distillation of liquid air
- electrolysis of sea water
- reduction of an ore by carbon
- decomposition of limestone
Tap an answer to check it.
WhyFractional distillation of liquid air separates argon from nitrogen and oxygen.
2
Multiple choice · Medium
Chlorine is extracted from sea water (an abundant source of chloride ions) by
- electrolysis of concentrated sodium chloride solution
- fractional distillation
- heating with carbon
- adding dilute acid
Tap an answer to check it.
WhyElectrolysis of concentrated brine oxidises Cl- to Cl2.
3
Multiple choice · Hard
Argon is unreactive and so is found uncombined in air. This is because an argon atom has
- a stable, full outermost electron shell
- a single outer electron
- seven outer electrons
- an incomplete d-subshell
Tap an answer to check it.
WhyA full outer shell makes argon chemically inert.
4
Fill in the blank · Easy
The noble gas argon is separated from the other components of air by the of liquid air.
Answer:
fractional distillation
WhyArgon has a boiling point between those of oxygen and nitrogen.
5
Fill in the blank · Medium
The natural source of the chlorine extracted on an industrial scale is (sea water / brine).
Answer:
sea water / seawater / brine / the sea
WhyChloride ions are abundant in sea water.
6
Fill in the blank · Hard
Argon makes up about % by volume of dry air, the third most abundant gas after nitrogen and oxygen.
Answer:
0.9 / 1 / about 1
WhyArgon is roughly 0.9% (about 1%) of air.
7
Multiple choice · Easy
Sea water is an important natural source of which substance?
- Sodium chloride
- Petroleum
- Aluminium
- Limestone
Tap an answer to check it.
WhyDissolved sodium chloride makes sea water a major source of common salt.
8
Multiple choice · Medium
In salt pans, how is solid sodium chloride obtained from sea water?
- Evaporation of the water followed by crystallisation
- Electrolysis of the sea water
- Filtration of the sea water
- Cracking of the sea water
Tap an answer to check it.
WhySunlight and wind evaporate the water, leaving the salt to crystallise.
9
Multiple choice · Hard
Apart from sodium chloride, sea water is also the main industrial source of which element?
- Bromine
- Iron
- Carbon
- Sulfur
Tap an answer to check it.
WhyBromine is extracted commercially from sea water (and brines).
10
Fill in the blank · Easy
The most abundant dissolved salt in sea water is sodium .
Answer:
chloride
WhySodium chloride (common salt) is the chief solute in sea water.
Key terms in Planet Earth
Lithosphere: The solid rocky outer layer of the Earth that contains minerals, ores and rocks.
Hydrosphere: All the water on Earth including the oceans, which act as a vast store of dissolved salts.
Atmosphere: The layer of gases surrounding the Earth, consisting mainly of nitrogen and oxygen.
Mineral: A naturally occurring solid with a definite chemical composition found in the Earth's crust.
Ore: A naturally occurring rock or mineral from which a metal can be extracted economically.
Seawater: The salty water of the oceans containing dissolved ions such as Na+, Cl-, Mg2+ and SO4^2-.
Sodium chloride: The main dissolved salt in seawater, NaCl, which can be obtained by evaporation or as rock salt.
Crystallisation: The process of forming solid crystals from a saturated solution as the solvent evaporates.
See the full study notes and flashcards for this topic.
Practise other DSE Chemistry topics