Examples of molar mass in the following topics:

 Apply knowledge of molar mass to the Ideal Gas Law
We can derive a form of the Ideal Gas Equation, PV=nRT, that incorporates the molar mass of the gas (M, $g*mol^{1}$ ).
 The molecular weight (molar mass) of any gas is the mass of one particle of that gas multiplied by Avogadro's number (6.02 x 10^{23}).
 Molar mass (M) is equal to the mass of one mole of a particular element or compound; as such, molar masses are expressed in units of grams per mole (g mol^{–1}) and are often referred to as molecular weights.
 For a mixture of gases, the molar mass depends on the molar masses of each of its components and on the fractional abundance of each kind of gas in the mixture.
 What is the molar mass of the gas?
 molar mass (noun) the mass of one mole of an element or compound

 Identify the properties of a mole
Calculate the molar mass of an element or compound
The molar mass of a particular substance is the mass of one mole of that substance.
 Molar mass is the mass of a given substance divided by the amount of that substance, measured in g/mol.
 The characteristic molar mass of an element is simply the atomic mass in g/mol.
 However, molar mass can also be calculated by multiplying the atomic mass in amu by the molar mass constant (1 g/mol).
 The molar mass of NaCl is 58.44 g/mol.
 molar mass (noun) The mass of a given substance (chemical element or chemical compound in g) divided by its amount of substance (mol).

 Convert from grams to moles using a compound's molar mass.
 A substance's molar mass is calculated by multiplying its relative atomic mass by the molar mass constant (1 g/mol).
 The molar mass constant can be used to convert mass to moles.
 For a single element, the molar mass is equivalent to its atomic weight multiplied by the molar mass constant (1 g/mol).
 The molar mass of water is 18 g/mol.
 molar mass (noun) The mass of a given substance (chemical element or chemical compound) divided by its amount (mol) of substance.

 To convert between mass and number of moles, you can use the molar mass of the substance.
 For example, if the atomic mass of sulfer (S) is 32.066 amu, then its molar mass is 32.066 g/mol.
 In a compound of NaOH, the molar mass of Na alone is 23 g/mol, the molar mass of O is 16 g/mol, and H is 1 g/mol.
 What is the molar mass of NaOH?
 Since the molar mass of NaOH is 40 g/mol, we can divide the 90 g of NaOH by the molar mass (40 g/mol) to find the moles of NaOH.
 dimensional analysis (noun) The analysis of the relationships between different physical quantities by identifying their fundamental dimensions (such as length, mass, time, and electric charge) and units of measure (such as miles vs.
kilometers, or pounds vs.
kilograms vs.
grams) and tracking these dimensions as calculations or comparisons are performed.
 molar mass (noun) The mass of a given substance (chemical element or chemical compound) divided by its amount of substance (mol), in g/mol.

 We also know that:
$n=\text{# moles of gas}=\frac{\text{mass of gas (m)}}{\text{molecular weight (M)}}=\frac{m}{M}$
If we substitute $\frac{m}{M}$ for n:
$PV= \frac{m}{M}RT$
Rearranging the above equation, we get:
$\frac{P}{RT}=\frac{m}{MV}$
Now, recall that density is equal to mass divided by volume:
$D=\frac{m}{V}$
The term $\frac{m}{V}$ appears on the righthand side of the above rearranged Ideal Gas Law.
 We can substitute in density, D, and get the following:
$\frac{P}{RT}=\frac{D}{M}$
Rearranging in terms of D, we have:
$D=\frac{MP}{RT}$
This derivation of the Ideal Gas Equation allows us to characterize the relationship between the pressure, density, and temperature of the gas sample independent of the volume the gas occupies; it also allows us to determine the density of a gas sample given its pressure and temperature, or determine the molar mass of a gas sample given its density.
 Instead of using the regular ideal gas equation, PV=nRT, we use a transformed version (D=PM/RT) to solve a problem with density and molar mass.

 Translate between a molecular formula of a compound and its percent composition by mass
The percent composition (by mass) of a compound can be calculated by dividing the mass of each element by the total mass of the compound.
 The percent composition of a compound is calculated with the molecular formula: divide the mass of each element found in one mole of the compound by the total molar mass of the compound.
 Another convenient way to describe atomic composition is to examine the percent composition of a compound by mass.
 Percent composition is calculated from a molecular formula by dividing the mass of a single element in one mole of a compound by the mass of one mole of the entire compound.
 Butane's percent composition can be calculated as follows:
Mass of H per mol butane: $10\:mol\:H \cdot \frac{1.00794\:g}{1\:mol\: H} = 10.079\:g\:H$
Mass of C per mol butane: $4\:mol\:C\cdot\frac{12.011\:g\:C}{1\:mol\:C}=48.044\:g\:C$
Mass percent H in butane: $\frac{10.079\:g\:H}{58.123\:g\:butane} \cdot 100$ = 17.3% H
Mass percent C in butane: $\frac {48.044\:g \:C}{ 58.123 \:g \:butane} \cdot 100$ = 82.7% C
Therefore, the atomic composition of butane can also be described as 17.3% hydrogen and 82.7% carbon, and, as expected, these values sum to 100%.
 percent by mass (noun) The fraction, by weight, of one element of a compound.

 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.
 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.
 What mass of copper will be deposited if a current of 0.22 amp flows through the cell for 1.5 hours?

 If the amount of solute is given in grams, we must first calculate the number of moles of solute using the solute's molar mass, then calculate the molarity using the number of moles and total volume.
 First, we must convert the mass of NaCl in grams into moles.
 We can also calculate the volume required to meet a specific mass in grams given the molarity of the solution.
 This is useful with particular solutes that cannot be easily massed with a balance.
 First we must convert grams of BH_{3} to moles by dividing the mass by the molecular weight.
 molarity (noun) The concentration of a substance in solution, expressed as the number moles of solute per liter of solution.

 Graham's Law states that the effusion rate of a gas is inversely proportional to the square root of the mass of its particles.
 The rate of this movement is a function of temperature, viscosity of the medium, and the size (mass) of the particles.
 Scottish chemist Thomas Graham experimentally determined that the ratio of the rates of effusion for two gases is equal to the square root of inverse ratio of the gases' molar masses.
 This is written as follows:
$\frac{\text{rate of effusion gas 1}}{\text{rate of effusion gas 2}}=\sqrt{\frac{M_2}{M_1}}$
where M represents the molar mass of the gases.

 The Ideal Gas Law, along with a balanced chemical equation, can be used to solve for the amount, either in volume or mass, of gas consumed or produced in a chemical reaction.
 Stoichiometry is based on the law of conservation of mass, meaning that the mass of the reactants must be equal to the mass of the products.
 Stoichiometric calculations involving gases allow us to convert between mass, number of moles, and most importantly, volume of gases.
 From the periodic table, we can determine that the molar mass of ammonia, NH_{3}(g), is 17 g/mol, and perform the following stoichiometric calculation:
$\left(\frac{\text{100 g }NH_3}{ }\right)\times\left(\frac{\text{1 mol }NH_3}{\text{17 }g}\right)\times \left(\frac{\text{4 mol }NO_2}{\text{4 mol }NH_3}\right)\times \left(\frac{\text{22.4 }L}{\text{1 mol }NO_2}\right)=\text{132 L }NO_2(g)$
Note the final conversion factor.