What is 1 mole of electrons

Mole

This article deals with that Unit of measurement Mole; for other terms, see Mol (disambiguation).

The Mole (Unit symbol: mol) is the SI base unit of the amount of substance. The mole is important for quantitative information in chemical reactions.

definition

In the SI system of units, the mole is a basic unit and is defined as follows:

The mole is the amount of substance in a system that consists of as many individual particles as there are atoms in 12 grams of the nuclide carbon-12 (12C) are included; its symbol is "mol".
If the mole is used, the individual particles used must be specified; it can be atoms, molecules, ions, electrons, photons, other particles or specified groups of such particles.[1]

In other words, 12 grams of carbon-12 have exactly the amount of substance one mole. One mole of atoms of natural carbon, on the other hand, has a mass of 12.0107 grams due to the isotope mixture can serve others.

The number of particles per one mole of substance (Avogadro's constant) has the value:[2]

$ 6 {,} 022 \; 141 \; 29 \; (27) \ cdot 10 ^ {23} \ \ mathrm {mol} ^ {- 1} $

One mole of a substance contains about 602 trillion particles of this substance.

Historical

The term “mol” was coined by Wilhelm Ostwald in 1893 and is probably derived from “molecule”. In 1971 the mole was introduced as a basic unit in the SI. This extended the scope of the SI to include chemistry. Before the establishment of the SI, the mole was predominantly viewed as a unit of mass. Older names are Gram atom (only for elements) and Gram molecule (only for connections). So it says in DIN 1310 “Content of solutions” from April 1927: “The mass units are [...] the mole, i. H. as many grams of the substance as its molecular weight indicates [...] ”. However, by using the molecular “weight”, a mass of substance - not an amount from today's point of view - was described and referred to as the “amount of substance”. In the current mole definition of the SI, on the other hand, the amount of substance is formally clearly distinguished from particle number and mass.

Decimal units

Common decimal parts and multiples of the mole are:

description unit factor Multiples annotation
Kilomole kmol 103-0 1,000 moles Equivalent to 1000 moles.
Millimoles mmol 10−3 0.001 mol Corresponds to a thousandth of a mole.
Micromoles µmol 10−60 0.001 mmol Corresponds to a millionth of a mole (one thousandth of a millimole)
Nanomoles nmol 10−90 0.001 µmol Equivalent to a billionth of a mole (one millionth of a millimole).

Molar volume

The molar volume of a substance is a substance-specific property that indicates the volume of one mole of a substance. For an ideal gas, one mole takes up a volume of 22.414 liters under normal conditions (273.15 K, 101325 Pa). For real gases, solids and liquids, on the other hand, the molar volume is dependent on the substance.

Molar mass

The molar massM. is the quotient of mass and amount of substance of a substance. In the unit g / mol it has the same numerical value as the atomic mass, i.e. the mass of an atom in u (atomic mass unit). Their meaning is equivalent to the earlier “atomic weight” in chemistry.

Calculation of substance quantities

The following formula is used for the calculation: $ n = \ frac {m} {M} $

$ N $ denotes the amount of substance, $ m $ the mass and $ M $ the molar mass. $ M $ can be taken from tables for chemical elements and calculated from such values ​​for chemical compounds of known composition.

The atomic mass, which is given in tables for each chemical element, relates to the natural isotope mixture. For example, the atomic mass for carbon is 12.0107 u. For example, this value is for in 13C-enriched material not to be used. While with stable elements the deviations from isotope mixtures as they occur in nature are relatively small, especially with radioactive elements the isotope mixture can strongly depend on the origin and the age of the material.

Use of the unit mol when specifying concentrations

The unit Mole Often used in compound units to indicate concentrations (solutions, acidity of solutions, etc.). One of the most common uses is that x-molar solution (the x stands for any rational positive number). The meaning is

Example:
A 2.5 molar A solution contains 2.5 mol of the solute A in 1 liter of the solution.
See also:Amount of substance concentration

Examples

Mass of 1 mole of helium

  • 1 atom of helium has a mass of about 4 u (a helium atom has 2 protons and 2 neutrons, the electrons are neglected in this example because of their comparatively very low mass, as is the mass defect due to the binding energy released during nucleus formation. Gas is monatomic, so in the following example the mole refers to He atoms without needing to be specifically mentioned.)
  • So 1 mol of helium has a mass of about 4 g and contains about 6.022 x 10 623 Helium atoms.

Mass of 1 mole of water

  • 1 mol of a substance contains approximately 6.022 x 10 623 Particle.
  • 1 water molecule H2O consists of 1 oxygen atom and 2 hydrogen atoms.
  • The oxygen atom has 16 nucleons (core particles, i.e. neutrons and protons), a hydrogen atom has 1 core particle (one proton).
  • A water molecule therefore contains 18 nucleons.
  • The mass of a core particle is approximately 1.6605 x 10 6-24 G.
  • 1 water molecule thus has the mass 18 · 1.6605 · 10-24 G.
  • The mass of 1 mole of water is that 6.022 x 1023times the mass of a water molecule.
  • The mass of 1 mol of water is thus 6.022 · 1023 · 18 · 1,6605·10-24 g = 18.016 g (the numerical value is equal to the molecular mass in u).

Production of lithium hydroxide from lithium and water

$ \ mathrm {2 \, Li + 2 \, H_2O \ rightarrow 1 \, H_2 + 2 \, LiOH} $

When LiOH is formed, two water molecules are split by two lithium atoms into one H and one OH part. Because there are the same number of particles in every mole of every substance (see above), you need, for example, 2 moles of lithium and 2 moles of water (or any other amount of substance in a 2: 2 ratio).

2 times 6.94 g lithium and 2 times 18 g water react, for example, to form 2 g hydrogen and 47.88 g lithium hydroxide.

Individual evidence

  1. ↑ Translated from http://www.bipm.org/utils/common/pdf/si_brochure_8_en.pdf
  2. CODATA Recommended Values. National Institute of Standards and Technology, accessed June 16, 2011. Value for Avogadro's constant

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