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The molar volume, symbol ''V''m, is the volume occupied by one mole of a substance (chemical element or chemical compound) at a given temperature and pressure. It is equal to the molar mass (''M'') divided by the mass density (ρ). It has the SI unit cubic metres per mole (m3/mol),〔 although it is more practical to use the units cubic decimetres per mole (dm3/mol) for gases and cubic centimetres per mole (cm3/mol) for liquids and solids. The molar volume of a substance can be found by measuring its molar mass and density then applying the relation ::. If the sample is a mixture containing ''N'' components, the molar volume is calculated using: ::. For ideal gases, the molar volume is given by the ideal gas equation: this is a good approximation for many common gases at standard temperature and pressure. For crystalline solids, the molar volume can be measured by X-ray crystallography. == Ideal gases == The ideal gas equation can be rearranged to give an expression for the molar volume of an ideal gas: ::. Hence, for a given temperature and pressure, the molar volume is the same for all ideal gases and is known to the same precision as the gas constant: ''R'' = 0.08206 L atm K−1 mol−1 , that is a relative standard uncertainty of 9.1×10−7, according to the 2010 CODATA recommended value.〔(【引用サイトリンク】 url = http://physics.nist.gov/cgi-bin/cuu/Value?r )〕 The molar volume of an ideal gas at 100 kPa (1 bar) is :22.710 980(38) (dm)3/mol at 0 °C :24.789 598(42) (dm)3/mol at 25 °C The molar volume of an ideal gas at 1 atmosphere of pressure is :22.414 (dm)3/mol at 0 °C :24.465 (dm)3/mol at 25 °C 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Molar volume」の詳細全文を読む スポンサード リンク
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