Foundations

Scientific relationships · 6 / 6

The relationship type describes the connection. Its linked statements, sources and conditions define the scope.

1. Intensive, extensive, specific and molar properties → Molar mass and mass–amount conversion
   Related to
   Relationship sources · 2

   • §1.4 Muddiest points: specific, extensive and intensive properties ↗
   • Chemistry 2e (2019), §1.3 Physical and chemical properties ↗

   Linked statements

   • In the ordinary bulk thermodynamic model, extensive properties such as mass and volume scale with system amount at fixed state and composition. Intensive properties such as temperature and pressure do not scale that way. A specific property is expressed per mass; a molar property per amount of substance. Density can be intensive for a homogeneous material without being independent of temperature, pressure or composition.

   Molar mass is one explicitly amount-normalized property, not an extensive total sample mass.

2. Relative atomic mass and isotope composition → Molar mass and mass–amount conversion
   Related to
   Relationship sources · 2

   • SI Brochure, ninth edition, version 4.01: mole, mass constants and accepted non-SI units ↗
   • Natural variations in atomic weights ↗

   Linked statements

   • The atomic mass constant mu is one twelfth of the mass of a free carbon-12 atom at rest in its ground state. A sample's relative atomic mass is its mean atomic mass divided by mu. Isotope fractions determine the mean; this is distinct from an isotope's integer mass number. Standard atomic weights describe specified normal terrestrial materials and may have intervals because isotope abundances vary.

   Relative mass becomes a molar mass through the measured molar mass constant, rather than an exact post-2019 g/mol identity.

3. Molar mass and mass–amount conversion → Mole and amount of substance
   Uses definition
   Relationship sources · 2

   • SI Brochure, ninth edition, version 4.01: mole, mass constants and accepted non-SI units ↗
   • Chemistry 2e (2019), §3.1 Formula mass and the mole concept ↗

   Linked statements

   • Molar mass M is mass divided by amount of substance for specified entities and composition, so n = m/M. For entities with mean mass m_entity, M = NA m_entity. Since the 2019 SI revision, NA is exact but the atomic mass constant in kilograms is measured: the molar mass constant Mu = NA mu is close to, and no longer exactly, 0.001 kg/mol.

   Mass–amount conversion requires a mole of specified entities and a stated composition.

4. Molar mass and mass–amount conversion → Avogadro constant
   Uses definition
   Relationship sources · 2

   • SI Brochure, ninth edition, version 4.01: mole, mass constants and accepted non-SI units ↗
   • Chemistry 2e (2019), §3.1 Formula mass and the mole concept ↗

   Linked statements

   • Molar mass M is mass divided by amount of substance for specified entities and composition, so n = m/M. For entities with mean mass m_entity, M = NA m_entity. Since the 2019 SI revision, NA is exact but the atomic mass constant in kilograms is measured: the molar mass constant Mu = NA mu is close to, and no longer exactly, 0.001 kg/mol.

   M = NA m_entity uses the exact Avogadro constant with a specified mean entity mass.

5. Limiting reagent, theoretical yield and percent yield → Molar mass and mass–amount conversion
   Uses definition
   Relationship sources · 1

   • Chemistry 2e (2019), §4.4 Reaction yields ↗

   Linked statements

   • For a single fixed net reaction taken to complete conversion, the limiting initial reactant gives the smallest available amount divided by its positive stoichiometric coefficient. Multiplying that minimum by a product coefficient gives theoretical product amount. Percent yield compares actual recovered and theoretical product on the same basis; side reactions, equilibrium, transfer losses or impurities can alter the observed result.

   Mass-based initial amounts and product yields must use the specified molar masses and consistent purity basis.

6. Inferring empirical and molecular formulas from composition → Molar mass and mass–amount conversion
   Uses definition
   Relationship sources · 1

   • Chemistry 2e (2019), §3.2 Determining empirical and molecular formulas ↗

   Linked statements

   • For a pure compound of fixed composition, convert each constituent element's measured mass to amount using its appropriate molar mass. Divide those amounts by a common reference amount and identify a smallest whole-number atom ratio consistent with the measurements. This gives an empirical formula, not atom connectivity. For a molecular compound with independently known molar mass, the ratio to the empirical formula-unit molar mass gives the positive integer multiplier for molecular subscripts, within measurement uncertainty.

   Constituent masses are converted to amounts using the stated entity molar masses.