Moles in Concentration Specifications

The molar volume 

The molar volume of a substance is a substance-specific property that indicates the volume filled by one mole of a substance. For an ideal gas, one mole occupies a volume of 22.414 liters under normal conditions (273.15 K, 101325 Pa). For real gases, solids and liquids, however, the molar volume depends on the substance.
 

Molar mass

Molar mass M  is the quotient of the mass and the amount of a substance. In the unit g/mol it has the same numerical value as the atomic or molecular mass of the substance in the unit u  (atomic mass unit). Its meaning is equivalent to the earlier “atomic weight” in chemistry. 
 
 

Calculation of substance quantities 

Formula: n = m / M

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

The atomic mass given in tables for each chemical element refers to the natural isotope mixture. For example, the atomic mass for carbon is given as 12.0107 u. This value  cannot be used, for example, for material enriched in 13 C. While for stable elements the deviations from isotope mixtures as they occur in nature are relatively small, particularly for radioactive elements the isotope mixture can depend heavily on the origin and age of the material.

 

Use of the mole unit for concentration information

Concentrations (salinity of solutions, acidity of solutions, etc.). One of the most common uses is the  x-molar solution  (the x stands for any rational positive number).
 
 
Examples
A  2.5 molar A solution  contains 2.5 moles of solute A in 1 liter of the solution.
Helium has a mass of approximately 4 u (u is the atomic mass unit; a helium atom has 2 protons and 2 neutrons). Helium gas is monatomic, so in the following example the mole refers to He atoms without the need for specific mention.
  • 1 mol of helium has a mass of about 4 g and contains about 6,022 e 23 helium  atoms.

 

Mass of 1 mol of water

  • A water molecule usually contains 18 nucleons.
  • The mass of a nuclear particle is approximately 1 .6605 e -24  g.
  • 1 water molecule usually has the mass 18  ·  1 .6605 e -24  g.
  • The mass of 1 mol of water is 6 .022 e 23 times the mass of a water molecule.
  • The mass of 1 mol of water is therefore 6 .022 e 23  ·  18  ·  1 .6605 e -24  g = 18 g (the numerical value is equal to the molecular mass in u).

If you take the more precise atomic masses instead of the number of nucleons, the result is a slightly higher value of 18.015 g.

 

Production of lithium hydroxide from lithium and water

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).

For example, 6.94 g of lithium twice and 18 g of water twice react to form 2 g of hydrogen and 47.88 g of lithium hydroxide.

See also: mole  concentration , moles in grams , grams in moles

 
Source among others:  https://de.wikipedia.org/wiki/Mol
 
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