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Academia - Collins - Pocket Scientific Dictionaries - Chemistry - English - French - Arabic Letter 3_ D


disaccharide
disaccharide m

Disaccharide. A sugar molecule composed of...
Two monosaccharide molecules undergo a condensation reaction with the removal of a water molecule.
Examples:
Monosaccharides

Glucose + fructose
C6H12O6 +C6H12O6

Glucose + glucose
C6H12O6 C6H12O6

Disaccharides

Maltose
C12H22O11


Sucrose
C12H22O11


disinfectant
desinfectant m

Disinfectant. A substance capable of eliminating harmful germs, and it is often based on the compound phenol. In the picture above are two examples of household disinfectants.

It is used in Dettol
It is used in T.C.P


displacement reactions
Reactions fpl deplacement

Displacement Reactions In a displacement reaction, a less reactive element is displaced by a more reactive element. And this
Reduction and oxidation reactions of redox. For example:

(solid) Cu + (aqueous)Zn SO4 <- (solid) Zn (aqueous) CuSO4

2NaBr + Cl2 → 2NaCl + Br2
(aqueous) (aqueous) (gas) (aqueous)


dissociation
dissociation f

fell apart. When a compound disintegrates, it is divided into smaller, simpler molecules or ions, and the disintegration is sometimes reversible.

NH4 CI (solid) heat/cold NH3 (gas) + HCI (gas)

Hydrogen chloride Ammonium chloride (aqueous) -CI + (aqueous) +H (aqueous) HCI


dissolve
dissoudre

It dissolves. decay. When a solute dissolves in a solvent to form a solution, it is distributed throughout the solvent. The structure of the dissolved substance is disintegrated.


distillation
distillation f

Distillation. This is the process by which a solvent can be recovered from a solution or mixture. The solution is heated and the solvent turns into vapor. The vapor is led away from the hot flask to a condenser where it cools and condenses, turning into a pure liquid, and is collected. In this way the pure solvent can be recovered. In the drawing below, a traditional distillation group is shown.
See fractional distillation.

.
distilled water
water distillée

Distilled water. Tap and rain water is not pure, but contains salts and gases dissolved in it. Water is often distilled to increase its purity. Most of the salts precipitate out, but the water still contains dissolved gases.

The presence of carbon dioxide reduces the pH of water to a significant extent.


dm³
dm³

dm3 is the symbol for cubic decimetres, 1000 cm1 = 3 dm3.


DNA (deoxyribonucleic acid)
ADN

DNA (deoxyribonucleic acid). A highly complex chemical substance that controls the system by which amino acids combine to produce proteins.


double bond
liaison f double

Double bond. A chemical bond containing two shared pairs of electrons. Carbon-carbon double bonds are found in alkene molecules. The presence of excess electrons makes alkenes highly reactive. Compounds that contain double (or triple) bonds are called compounds.
Unsaturated compounds.
Compounds and elements that contain double bonds:

Oxygen O = O
Etn C = C
Carbon dioxide O = C = O