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The equivalent weight of an element is the mass which combines with or displaces 1.008 gram of hydrogen or 8.0 grams of oxygen or 35.5 grams of chlorine. The equivalent weight of an element is the mass of a mole of the element divided by the element's valence. That is, in grams, the atomic weight of the element divided by the usual valence. [2]
For non-mononuclidic elements that have more than one common isotope, the numerical difference in relative atomic mass (atomic weight) from even the most common relative isotopic mass, can be half a mass unit or more (e.g. see the case of chlorine where atomic weight and standard atomic weight are about 35.45). The atomic mass (relative ...
The gram-atom is a former term for a mole of atoms, and gram-molecule for a mole of molecules. [ 7 ] Molecular weight (M.W.) (for molecular compounds) and formula weight (F.W.) (for non-molecular compounds), are older terms for what is now more correctly called the relative molar mass ( M r ). [ 8 ]
The "hydrogen ion" and the "electron" in these examples are respectively called the "reaction units." By this definition, the number of equivalents of a given ion in a solution is equal to the number of moles of that ion multiplied by its valence. For example, consider a solution of 1 mole of NaCl and 1 mole of CaCl 2.
Theoretical isotope distribution for the molecular ion of caffeine. The molecular mass (abbreviated M r) of a substance, formerly also called molecular weight and abbreviated as MW, is the mass of one molecule of that substance, relative to the unified atomic mass unit u (equal to 1/12 the mass of one atom of 12 C).
The standard atomic weight takes into account the isotopic distribution of the element in a given sample (usually assumed to be "normal"). For example, water has a molar mass of 18.0153(3) g/mol, but individual water molecules have molecular masses which range between 18.010 564 6863(15) Da (1 H 2 16 O) and 22.027 7364(9) Da (2 H 2 18 O).
Identification of the molecular ion can be difficult. Examining organic compounds, the relative intensity of the molecular ion peak diminishes with branching and with increasing mass in a homologous series. In the spectrum for toluene for example, the molecular ion peak is located at 92 m/z corresponding to its molecular mass. Molecular ion ...
Historically, the mole was defined as the amount of substance in 12 grams of the carbon-12 isotope.As a consequence, the mass of one mole of a chemical compound, in grams, is numerically equal (for all practical purposes) to the mass of one molecule or formula unit of the compound, in daltons, and the molar mass of an isotope in grams per mole is approximately equal to the mass number ...