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At atmospheric pressure, mixtures of ethanol and water form an azeotrope at about 89.4 mol% ethanol (95.6% ethanol by mass, [84] 97% alcohol by volume), with a boiling point of 351.3 K (78.1 °C). [85] At lower pressure, the composition of the ethanol-water azeotrope shifts to more ethanol-rich mixtures. [86]
The interest stems from that accurate measurements of the unit cell volume, atomic weight and mass density of a pure crystalline solid provide a direct determination of the Avogadro constant. [3] The CODATA recommended value for the molar volume of silicon is 1.205 883 199 (60) × 10 −5 m 3 ⋅mol −1, with a relative standard uncertainty of ...
In chemistry, the molar mass (M) (sometimes called molecular weight or formula weight, but see related quantities for usage) of a chemical compound is defined as the ratio between the mass and the amount of substance (measured in moles) of any sample of the compound. [1] The molar mass is a bulk, not molecular, property of a substance.
In biology, the unit "%" is sometimes (incorrectly) used to denote mass concentration, also called mass/volume percentage. A solution with 1 g of solute dissolved in a final volume of 100 mL of solution would be labeled as "1%" or "1% m/v" (mass/volume). This is incorrect because the unit "%" can only be used for dimensionless quantities.
It consists of a methylene bridge (−CH 2 − unit) bonded to a hydroxyl group (−OH). This makes the hydroxymethyl group an alcohol. It has the identical chemical formula with the methoxy group (−O−CH 3) that differs only in the attachment site and orientation to the rest of the molecule. However, their chemical properties are different ...
Mass (m) per unit volume (V) is the density m/V. Mass is conserved on mixing, but the volume of 1 cm 3 of ethanol mixed with 1 cm 3 of water is reduced to less than 2 cm 3 due to the formation of ethanol-water bonds. The plot of volume or density versus molecular fraction of ethanol in water is a quadratic curve.
In meteorology, mixing ratio usually refers to the mass ratio of water , which is defined as the mass of water divided by the mass of dry air in a given air parcel: [3] ζ = m H 2 O m a i r − m H 2 O {\displaystyle \zeta ={\frac {m_{\mathrm {H2O} }}{m_{\mathrm {air} }-m_{\mathrm {H2O} }}}}
The volume of such a mixture is slightly less than the sum of the volumes of the components. Thus, by the above definition, the term "40% alcohol by volume" refers to a mixture of 40 volume units of ethanol with enough water to make a final volume of 100 units, rather than a mixture of 40 units of ethanol with 60 units of water.