molar mass
(noun)Definition of molar mass
the mass of a given substance (chemical element or chemical compound) divided by its amount of substance
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Examples of molar mass in the following topics:

MasstoMole Conversions
 From the relative atomic mass of each element, we can determine each element's molar mass by multiplying the molar mass constant (1 g/mol) by the atomic weight of that particular element.
 The molar mass value can be used as a conversion factor to facilitate masstomole and moletomass conversions.
 To convert from grams to moles, we need the compound's molar mass.
 For a single element, the molar mass is equivalent to its atomic weight multiplied by the molar mass constant.
 For a compound, the molar mass is the sum of the atomic weights of each element in the compound multiplied by the molar mass constant.
 Masstomole conversions can be facilitated by employing the molar mass as a conversion ratio.

Molar Mass of Compounds
 Each ion, or atom, has a particular mass; similarly, each mole of a given pure substance also has a definite mass.
 We call "molar mass" the mass of a given substance divided by the amount of that substance, and we measure it in grams/mole.
 The characteristic molar mass of an element is calculated by multiplying the atomic weight of the element by the molar mass constant (1 g/mol).
 To calculate the molar mass of a compound, you need to first sum all the atomic weights of the constituent atoms.
 For example, the molar mass of NaCl is determined as follows (22.99 is the atomic mass of sodium, which 35.45 is the atomic mass of chlorine): (22.99 + 35.45) x 1 g/mol = 58.443 g/mol
 The molar mass of a particular substance is the mass, or weight, of one mole (a certain number of atoms) of that substance.

Converting Between Mass and Number of Moles
 It is possible, however, to calculate the number of atoms or molecules in a pure sample so long as the sample's identity and mass are known.
 Knowing the relationship between the atomic weight, molar mass, and moles, we can convert between mass, number of moles and number of atoms very easily.
 A compound's or element's molar mass is equal to the atomic weight of the substance multiplied by the molar constant (1g/mol).
 The atomic weight of nickel is 58.69 amu, which means that the molar mass of nickel is 58.69g/mol.
 If a sample's mass and the number of moles thereof are known, its atomic (or molecular, in the case of a nonelemental substance) mass can be confirmed by dividing the mass by the number of moles.
 Converting between the mass and number of moles of a substance can be easily done using a substance's molar mass.

Molar Mass of Gas
 Molar mass (M) is a physical property of chemical elements and compounds.
 The molar mass of an element or compound is defined as the mass of one mole of said element or compound.
 The molar mass of an element is relative to its atomic mass.
 The molecular weight (molar mass) of any gas is the mass, expressed in grams, of Avogadro's number (6.02 x 1023 ) of its molecules.
 The term "average molecular weight" is often used to describe the molar mass of a gas mixture.
 We can derive a form of the ideal gas equation, PV=nRT, which makes use of the molar mass of gas (n, grams per mole).

Distribution of Molecular Speeds and Collision Frequency
 By relating the RMS velocity to temperature and molar mass, we can rearrange the formula: $\bar{v}=v_{rms}=\sqrt{\frac{3RT}{m}}$ where R is the gas constant, T is temperature, and m is molar mass in kg/mol.
 The peak of the curve represents the most probable velocity Velocity distributions are directly dependent on temperature and mass.

Molality
 Usage Considerations Compared to molar concentration or mass concentration, the preparation of a solution of a given molality requires only a good scale: both solvent and solute need to be weighed, as opposed to measured volumetrically.
 This is because chemical reactions occur in proportions of mass, not volume.
 The massbased nature of molality implies that it can be readily converted into a mass ratio (or mass fraction, "w," ratio): $bM_{solute}=\frac{m_{solute}}{m_{solvent}}=\frac{w_{solute}}{w_{solvent}}$ where the symbol M stands for molar mass.
 This works because the units of molality are mol solute/kg solvent, and if we multiply the moles of solute by its molar mass (in grams per mole), we obtain grams of solute.
 The equation thus ultimately yields grams solute per kg of solvent, a mass ratio.

Density Calculations
 For the purposes of studying gases with volumes that are difficult to quantify, we can make use of calculations employing the physical property of density, defined as the mass of the gas per unit volume, to derive a form of the ideal gas equation that has broader applications. n = # moles of gas = mass of gas (m)/molecular weight (M) We know the ideal gas equation in the form $PV=nRT$.
 It allows us to determine the density of a gas sample given its pressure and temperature or to determine the molar mass of a gas sample given its density.

RootMeanSquare Speed
 It is represented by the equation: $v_{rms}=\sqrt{\frac{3RT}{M}}$, where vrms is the root mean square of the velocity, Mm is the molar mass of the gas in kilograms per mole, R is the molar gas constant, and T is the temperature in Kelvin.

Electrolysis Stoichiometry
 The equivalent weight of a substance is defined as the molar mass divided by the number of electrons required to oxidize or reduce each unit of the substance.

Avogadro's Law: Volume and Amount
 Thus, the number of molecules or atoms in a specific volume of ideal gas is independent of their size or the molar mass of the gas.