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

Academia - Collins - Pocket Scientific Dictionaries - Chemistry - English - French - Arabic Letter 2_ R


recrystallization
recrystallization f

Recrystallization. A process aimed at purifying impure crystalline materials. These materials are dissolved in a solvent, filtered, then allowed to crystallize and impurities are removed in this way.


redox
oxydoreduction f

Reduction and oxidation reaction that includes both reduction and oxidation. Any reaction that involves oxidation must also include reduction.

Examples of reduction and oxidation reactions:

oxidation

(solid) C + (solid) Mgo → (solid) Cuo + (solid) Mg

return


oxidation

Cu2+ (aqueous) +zn (solid) → Cu (solid) + zn2+ (aqueous)
return


reducing agent
agent m ducteur

Reference factor. Return operator. The reducing agent achieves the reduction of the substance, and it is always oxidized in this
Interaction. Common return factors include:

Hydrogen H2
Carbon C
Carbon monoxide CO
Sulfur dioxide SO2
Hydrogen sulfide H2S

Return operators in action:

Fe2O3 + 3CO → 2Fe + 3CO2
(gas) (solid) (gas) (solid)

CuO + H2 → Cu + H2O
(gas) (solid) (gas) (solid)

ZnO + C → Zn + CO
(gas) (solid) (solid) (solid)

.
reduction f

return . The item is subject to return if:

I lost oxygen

PbO + C → Pb + CO
(hard) (hard) (hard)

I gained hydrogen

Cl2 + H2 → 2HCI
(gas) (gas) (gas)

I gained an electron

Na+ + e- → Na
(liquid) (liquid)

See redox, reducing agent, and oxidation.


refining
affinage m. raffinage m

Refining. Purification. This expression includes removing impurities from a substance or removing components from a mixture.

(A) In minerals: When a metal is extracted from its metals, it is often not completely pure. This may be acceptable for certain uses, as pig iron contains impurities, for example. But other uses require a more pure product, and then the metal is refined until the correct purity is reached.

(b) Oil is a complex mixture of hydrocarbons. To make the oil more useful, it is separated into sections called fractional by fractions distillation. Each part is a mixture, but a less complex mixture. The parts contain compounds whose boiling points range within a certain range.

Conditions vary from one refinery to another and depend on the products required. The main output required may be gasoline (petrol), or it may be a petroleum chemical feedstock (petrochemicals) that are then converted into alkanets and other materials to produce ionomers.
See reforming and cracking.


reforming
reforming m

Improving an important process used in oil refineries and chemical facilities, where molecules are taken and converted into more useful products without any change in the size of the molecule. One example of this is the conversion of unbranched alkanes into branched alkanes, giving petrol a higher octane rating:

Actan
methyl heptane

Another example is the production of aromatic compounds from alkenes.


C7H14- → CH7H8 + 3H2
Hydrogen-methylbenzene-heptene

relative atomic mass (R.A.M.)
Masse f atomique relative

Relative atomic mass. The relative atomic mass of an element is the mass of an average atom of the element compared to the isotope of a carbon atom 12/6C given a value of exactly 12.
See Ar.