Several ways to represent the content of standard gases

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I. Methods of expressing the content of standard gases Common methods for expressing the content of standard gases include: mole fraction x； Mass molar concentration m ； Mass fraction w ； Mass concentration p ； Volume fraction φ ； Molar concentration c. 1. The molar fraction of a gas (xB) is the ratio of the amount of substance of component gas B to the sum of the amounts of substance of all components in the standard gas. 740") this.width=740" border=undefined> Where nB represents the amount of substance of component gas B in the standard gas ； ni——the sum of the amounts of substance of various components in the standard gas. The dimension of this quantity is 1, and it is usually expressed as 10-2 (%), or 10-6. 2. The mass molar concentration (mB) of a gas is the amount of substance of component gas B in the standard gas divided by the total mass of the standard gas. 740”) this.width=740” border=undefined> Where nB is the amount of substance of component gas B in the standard gas ； mA — total mass of the standard gas. It is commonly expressed in mol/kg, mol/g, and mmol/g. 3. The mass fraction (wB) of the standard gas is the ratio of the mass of component gas B to the total mass of all components in the standard gas. 740”) this.width=740” border=undefined> The dimension of this quantity is 1; it is usually expressed as 10-2 (%), or 10-6. 4. Mass concentration of the standard gas (pB): The mass (m) of component gas B divided by the volume (V) of the standard mixture gives the mass concentration of the standard gas. 740”) this.width=740” border=undefined> It is commonly expressed in units of kg/m3, g/L, mg/L, and ug/L. 5. Volume fraction of the standard gas (φB): The volume fraction of component gas B is the ratio of the volume of component B to the total volume of all components in the standard gas. 740”) this.width=740” border=undefined> The dimension of this quantity is 1; it is usually expressed as 10-2 (%), or 10-6. 6. The molar concentration (cB) of the standard gas: The molar concentration of the standard gas is the ratio of the amount of component gas B to the volume of the standard gas. 740”) this.width=740” border=undefined> It is commonly expressed in mol/m3 or mol/L. II. General conversions between gas concentrations 1. Conversion between mole fraction (xB) and mass concentration (pB) 740)” width=740” border=undefined> 2. Conversion between mass fraction (wB) and mass concentration (pB): Since wB = mB/m and m = ρ•V (where ρ is the density of the component), and also pB = mB/V and mB = pB•V, it follows that wB = pB•V/ρ•V = pB/ρ; therefore, pB = ρ•wB. 3. Conversion between mass concentration (pB) and molar concentration (cB): From their respective definitions, we have pB = mB/V and cB = nB/V; the denominator in both cases is the volume of the standard mixture gas. Then: pB = cB • mB / nB