Chemistry - Calcium Carbonate (AQA)
Calcium carbonate is the main chemical in chalk and limestone.

Chemistry - Calcium Carbonate (AQA)

The various different building materials, such as limestone and metals, is one of the topics looked at in GCSE Science. This is the first of seven quizzes on that subject and it looks in particular at calcium carbonate, commonly found in limestone and chalk.

Calcium carbonate is a really important chemical that is used in the manufacture of lots of everyday items. Luckily, there is plenty of it just lying around - it is the main chemical in chalk and limestone. It is used to make many objects that you see all the time and it is unlikely that you will ever go for one whole day of your life without coming across something that needs calcium carbonate for its manufacture.

The name tells you its chemical composition - it contains calcium, carbon and oxygen. A lot of the calcium carbonate is made by shell-building organisms (such as corals) and plankton . After the organisms die, they sink to the seafloor. Over time, layers of shells and sediment are cemented together and turn to rock, storing carbon in stone for millions of years in the form of limestones and chalk. Some limestones are made by chemical reactions in the sea, when the conditions are just right.

Quarrying of both limestone and chalk is carried out on a large scale in Britain. Some of the limestone and chalk is used for building but a lot of it goes to the manufacture of cement. There are a lot of environmental issues with both the quarrying and the processing of limestone and chalk but without the calcium carbonate that it provides, our world would be an incredibly different place. Test your knowledge of the chemistry and uses of this versatile and important chemical ...

Which of the following statements about limestone is false?
It reacts with acid rain and is gradually eroded
It is used for making the foundations of roads
It is used in the manufacture of cement
It is not used in agriculture
Farmers use it to neutralise slightly acidic soil
Some students heated pieces of limestone in a roaring flame of a bunsen burner. What would they have observed as the reaction was taking place?
The limestone spitting and popping
The limestone glowing red hot
The limestone expanding at first, then going smaller
The limestone glowing with an intense white light
This is called 'limelight' and was once used to provide lighting for the stages in theatres, hence the expression 'being in the limelight'
A student added some nitric acid to a small quantity of powdered calcium carbonate in a large beaker. Which of the following would not have been observed during the experiment?
Brown fumes of nitric oxide
The calcium carbonate frothed up
The calcium carbonate disappeared
A fizzing noise was heard
Calcium carbonate reacts with the common laboratory acids. It neutralises the acid and gives off carbon dioxide
Calcium carbonate is heated with which of the following substances to make cement?
Aggregate (gravel and small pebbles)
All of the above
The catch here was to include sand and aggregate. Often in everyday life, people talk about cement when they really mean mortar (sand and cement) or concrete (sand, cement and aggregate)
Which of the following terms best describes calcium oxide?
Calcium oxide is an acid
Calcium oxide is a base
Calcium oxide is neutral
Calcium oxide is a salt
Oxides of metals are usually bases. If a base dissolves in water, it forms an alkali
Calcium oxide is slightly soluble in water and can be used for testing for a gas. What is the gas and what happens to the solution if the gas is present?
Hydrogen is the gas and the solution goes blue
Oxygen is the gas and the solution gives a green precipitate
Nitrogen is the gas and the solution turns a pale straw colour
Carbon dioxide is the gas and the solution goes cloudy
An easy question, but, if we had said the solution was limewater, the question would have been just too easy
What are the products when calcium carbonate thermally decomposes?
Calcium and oxygen.
Calcium and carbonate.
Calcium oxide and oxygen.
Calcium oxide and carbon dioxide.
This is the basis of the cement making process
Heated limestone was left to cool and when it was cold a few drops of water were added to it. Then a piece of moist litmus paper was touched against it. What was observed?
The piece of heated limestone hissed, crumbled and became hot. The litmus paper turned red.
The piece of heated limestone hissed, crumbled and became hot. The litmus paper turned blue.
The piece of heated limestone turned pale yellow and the litmus paper stayed the same.
Nothing happened and the litmus paper stayed the same.
This process of adding water to calcium oxide is called 'slaking'
When calcium carbonate is strongly heated what does it do?
It thermally decomposes
It optically decomposes
It mentally decomposes
It does nothing
When a chemical is heated on its own and breaks down to form new materials, it is always called 'thermal decomposition'
What is the formula of calcium carbonate?
We know from its name that calcium carbonate contains calcium, carbon and oxygen, so we can rule out option 1. Limestone and chalk are mainly CaCO3
You can find more about this topic by visiting BBC Bitesize - Atoms, elements and compounds - AQA

Author:  Kev Woodward

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