أكاديميا - كولنز - معاجم الجيب العلمية - الكيمياء - انكليزي - فرنسي - عربي الحرف ٢_ l

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Le Chatelier's principle
Principle m de Le Chatelier

Le Chatelier's principle. If there is a reaction in equilibrium and any of the conditions change, further reaction occurs to equalize the changes and restore equilibrium.

Examples:
Haber process:

N2 (gas) + 3H2 (gas) = ​​2NH3

If more nitrogen or hydrogen is added to a balanced mixture, more ammonia is formed and the balance is restored. Likewise, if more ammonia is added, more nitrogen and hydrogen are formed. If the pressure increases, more ammonia is formed, because the formation of more ammonia reduces the pressure as a result of a general decrease in the number of gas molecules present.

In this way, balance is restored. A change in temperature leads to a change in the proportions of the balanced mixture. In exothermic reactions (such as the Haber process, raising the temperature encourages the right-left reaction, and the ammonia reacts to form more nitrogen and hydrogen).

This is because the right-left reaction is an endothermic reaction, and therefore it is equivalent to an increase in temperature by absorption.

lime (or quicklime)
chaux f

Lime. Lime. It is calcium oxide (CO). It is produced by heating calcium carbonate. It is used to make slaked lime and to convert impurities in the blast furnace into slag. In the laboratory, it is a dilution agent for ammonia.


limestone
Pierre ƒ à chaux. calcaire m

Limestone. Common rocks containing between 50 and 90 percent calcium carbonate (CaCO3). Limestone is used in making lime and cement. It is also used as building stones and in building foundations.

limewater
eau f de chaux

Limewater is a dilute solution of a slightly soluble compound calcium hydroxide. It is an alkaline solution used to test the presence of carbon dioxide:

Ca(OH)2 + CO2 → CaCO3 + H2O
(liquid) (solid) (gas) (water)

A white precipitate that appears milky is formed in the solution. If more carbon dioxide is added to the solution, the precipitate reacts to form a soluble salt, hydrogen calcium, and the liquid becomes clear:

CaCO3 + H2O + CO2 → Ca(HCO3)2
(Water) (Gas) (Liquid) (Solid)


linear molecules
Molécules fpl linéaires

Linear particles. Straight molecules, that is, their atoms are aligned in one line. All molecules containing only two atoms must be linear, but below are some examples of more complex molecules:

dioxide
O=C=O

Etienne
H-C-= C-H

Beryllium chloride
CI-Be-CI


liquid
liquide m

A liquid is a state of matter in which it is related
Particles are weakly connected by intermolecular forces. A liquid always takes the shape of the container in which it is placed. The liquid molecules are not fixed within a specific lattice frame.
See boiling and evaporation.


lithium
lithium m

Lithium is a metal from Group A, which is the least reactive element in the group. However, it is stored under oil due to its reactivity towards air and water. This metal is soft and can be cut with a knife, revealing a silvery surface that quickly dulls. Its interaction is stable with water, but it reacts strongly with acids.

2Li+ 2H2O → 2LIOH + H₂
(gas) (water) (liquid) (solid)

This metal may become very important in the future if electricity generation through fusion reactions succeeds
nuclear fusion.

The lithium ion gives a red flame test.


litmus
tournesol m

Sunflowers. Litmus is extracted from lichen and is used as an acid-base indicator.

Alkaline solution
blue

pH
7
purple

Acidic solution
red


liter
liter m

Liter. A liter is exactly equal to 1 dm3 (1000 cm3). and he
The unit volume is used in daily life to measure fruit juice, for example, or the volume of paint, while the scientific unit of volume is the cubic decimeter (dm3).

lone pair of electrons
pair f d'electrons célibataires

Free pair of electrons. These are the pairs of outer shell electrons that are not used in bonds within the compound. But they can be used to form bonds with other compounds.

Examples:

The free pair is used here to form the ammonium ion

Three pairs of bonded electrons