Chemical calculations theory. Matter and its transformations.

Chemical calculations

Mole concept: Mol is the amount of substance of a system which contains as many elementary entities as there are atoms in 0.012 kg of carbon 12.

Relationship between mole and atomic or molecular mass: The mass of 1 mole of any substance (simple or compound), expressed in grams, coincides with the numerical value of its atomic or molecular mass.

Avogadro’s Number: The number of elementary entities in one mole of any substance: N_o = 6.022 · 10²³ mol -1.

Molar volume of a gas normally, Vmn: is the volume occupied by 1 mole of any gas, measured at normal conditions (0ºC and 1 atm), Vmn = 22.4 L / mol.

Equivalent weight of an element or compound, also called chemical equivalent, Peq: is the amount that is combined or replaced (chemically equivalent) to 1.008 parts of hydrogen.

FORMULA SUMMARY

Percentage composition of a substance:

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Deduction of formulas from the percentage composition:

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(A = atomic mass of the element; M = molecular mass of the compound)

Relationship between the number of moles and the mass in grams of a substance:

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(a = mass, in grams, of the substance, M = molecular mass of the substance)

Electric charge of 1 mole of electrons:

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(F = faraday electricity = 96500 C; N_o = Avogadro’s number, e = electron charge = 1.6 ·10^-19C)

Equivalent weight:

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(A = atomic mass of the element; M = molecular mass of the compound; val = valence)

Dulong-Petit law:

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(A = atomic mass of the solid element; C_e = specific heat of solid element)

You can download the App BioProfe READER to practice this theory with self-corrected exercises.