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

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peroxide m

Superoxide. Superoxide contains the anion -ion-2/2 or group O-2/2. The best example is hydrogen peroxide (H2O2). They are also known as alkali metal peroxides. Hydrogen peroxide can be made by the action of the following acid:

Na2O2 + 2HCl → 2NaCl + H2O2
(aqueous) (aqueous) (aqueous) (solid)

or

O-2/2 (solid) + 2H+ (aqueous) → H2O2 (aqueous)

Hydrogen peroxide can be used in a diluted solution as a disinfectant and shortening agent. See hydrogen peroxide. Peroxides are powerful oxidizing agents.


petrochemical
The petrochemical mat

Petroleum chemical. A chemical substance derived from petroleum. Examples include ethene and proin. These chemicals are used in making other chemicals, such as poly(ethene) or poly(propene). Petroleum chemicals are intermediate materials from which final products are produced.


petro
essence f

Gasoline is a mixture of hydrocarbons
It is used as fuel in internal combustion engines, produced from petroleum in refineries. It is basically a mixture of 10C - 5C alkanes obtained either by direct fractional distillation or by cracking and reforming.
See octane rating.

Gasoline has other names in English, such as gasoline and motor spirit.


petroleum
petrole m

oil. A term that describes a mixture of hydrocarbons found in the Earth's crust, such as natural gas and crude oil. These materials were produced over millions of years from the remains of marine animals and plant organisms. It is the raw material for petroleum chemicals and the source of the gasoline we use in our cars, diesel fuel, and supplies of fuel oil and gas. There are extensive oil reserves in the Middle East, the United States, the Soviet Union, Central America, and the North Sea.

Oil has replaced coal as the main source of raw materials in the chemical industry. But oil resources will not last forever, and the search is already underway for the substance that will replace it in our lives.

In the refining entry there is an explanation of how oil is converted into useful products. See also fractional distillation.


pewter
potin m

Pewter. Tin mixture. The alloy was made from lead, tin (80-90%), and small amounts of antimony. It was widely used in making dishes and jugs, and is now used in making jewelry. The pewter that is manufactured today does not contain any lead due to the risk of it entering solutions or contaminating food. Copper and antimony replaced lead.


P.H
pH

pH.

Increasing acidity → neutral → increasing alkalinity
14 ----- 10 --------- 7 ----------3 ---------- 0

pH scale measures the acidity or alkalinity of a solution. The lower its value, the greater the acidity of the solution, that is, the greater the concentration of oxonium ions in it. The neutral solution, in which the oxonium and hydroxide ions are equal, has a pH of 7 at a temperature of 25°C.

pH = - log10 [H3O+]

The pH of the solution is the negative logarithm (base 10) of the concentration of oxonium ions.
Mol/dm³ mol/dm³.

Example :

The pH of a solution with a concentration of 0.1 3 mol/dm3 is log (0.1) = 1.

Hydrogen basis for common substances

A substance with a concentration of 1 mol/dm3

strong acid (HCI)
Mild acid (CH3COOH)
water
Ammonia solution
Strong alkali (NaOH)

pH

0
4
7
10
14


phase change (or change of state)
change m d'état

Phase change (or state change). A phase change occurs
When a substance moves from one physical state to another.
The possible phases in the chemical system are shown below:

liquid

condensate = a
freeze = b
Evaporation = d
fusion = e
Sublimation = C + F