What does powdered limestone do to water


Lime - chemistry

The term lime can have different meanings in practical areas such as the construction industry. The term either refers to the limestone, the Quicklime or the Slaked lime. You will soon understand which lime is meant in which context.


limestone is mostly Sedimentary rockthat formed from the deposits of microorganisms on the sea floor. Limestone is chemically speaking Calcium carbonate ($ \ ce {CaCO3} $).

An experiment with limestone
You grind some limestone into a powder and add water. A white paste forms because calcium carbonate dissolves poorly in water. If you add an acid, for example acetic acid, a chemical reaction starts with foaming. The calcium carbonate reacts with the hydrogen ions ($ \ ce {H +} $) of the acid to form calcium ions ($ \ ce {Ca ^ {2 +}} $) and carbonic acid ($ \ ce {H2CO3} $). The unstable carbonic acid immediately breaks down further into water ($ \ ce {H2O} $) and carbon dioxide ($ \ ce {CO2} $), which escapes with foaming:

$ \ ce {CaCO3 + 2 H + -> Ca ^ {2+} + H2CO3} $
$ \ ce {H2CO3 -> H2O + CO2} $

Use of limestone
As we shall see in a moment, limestone is needed to make Quicklime. Limestone is also used in the production of cement and Colours second hand. It also serves as a fertilizer, as filler and as a means of Deacidification of water and acidic soils.


The second type of lime is that Quicklime. From a chemical point of view, quicklime is calcium oxide ($ \ ce {CaO} $).

Manufacture of quicklime
Quicklime is extracted from limestone Lime burning. The limestone is not burned, but only heated to temperatures of around $ \ pu {1000 ° C} $. Quicklime and carbon dioxide are formed:

$ \ ce {CaCO3 -> [{1000 ° C}] CaO + CO2} $

Quicklime is a white to gray powder that appears on mucous membranes and in the eyes very corrosive works.

Use of quicklime
In the construction industry, quicklime is used for the manufacture of mortar and for the production of Sand-lime brick, Cement clinker and Lime paint.
In chemistry, calcium oxide is the starting material for the production of Calcium carbide ($ \ ce {CaC} $). It also serves as a drying agent for gases and as a neutralizing agent.

Slaked lime

At Slaked lime from a chemical point of view it is Calcium hydroxide ($ \ ce {Ca (OH) 2} $), which arises from the chemical reaction of quicklime with water:

$ \ ce {CaO + H2O -> Ca (OH) 2} $

Slaked lime works like quicklime very corrosive on eyes and mucous membranes. It is rather poorly soluble in water, but it reacts strongly basic or. alkaline.

Use of slaked lime
Slaked lime is used in the construction industry to produce mortar. By the way, when laying or plastering with mortar, a special process takes place, which is called Setting is known. The calcium hydroxide in the mortar reacts with the carbon dioxide in the air to form calcium carbonate.

The same reaction is used in school as Detection of carbon dioxide! Do you want to z. B. to prove the carbon dioxide in the breath, then you only need to use a straw through something Lime water - this is an aqueous solution of calcium hydroxide - to blow. The lime water becomes cloudy as the insoluble calcium carbonate is formed.

$ \ ce {Ca (OH) 2 + CO2 -> CaCO3 v + H2O} $

Notes on the video

This video is about the term lime, under which depending on the application Limestone, quicklime or slaked lime is meant. You should already be familiar with the chemistry of acids and bases, the formation of salts and the setting up of reaction equations.

Exercises and worksheets
You will also find exercises and worksheets on the topic here.