Molar Mass = M

@wikipedia

Synonym: Molar Mass = Molecular Weight

Material property defined as the mass of a given substance (chemical element or chemical compound) contained within one mole of the substance.

Symbol	Dimension	SI units	Oil metric units	Oil field units	Additional
$\begin{array}{l}M\end{array}$	M N^-1	kg/mol	kg/mol	lb_m / mol = 0.45359237 kg/mol	g/mol = 0.001 kg/mol

It measures as ratio of substance mass $\begin{array}{l}m\end{array}$ to amount of substance $\begin{array}{l}\nu\end{array}$ :

$\begin{array}{l}\displaystyle M = \frac{m}{\nu}\end{array}$

It relates to molecular mass $\begin{array}{l}m_u\end{array}$ and Avogadro constant $\begin{array}{l}N_A\end{array}$ as:

$\begin{array}{l}\displaystyle M = m_u \cdot N_A\end{array}$

Derivation

$\begin{array}{l}\displaystyle M = \frac{m}{\nu} = m \cdot \frac{N_A}{N} = m_u \cdot N_A\end{array}$

where

$\begin{array}{l}N\end{array}$

number of molecules in a substance of amount $\begin{array}{l}\nu\end{array}$

The molar mass of a mixture is:

$\begin{array}{l}\displaystyle M = \sum_k M_k \cdot x_k\end{array}$

where

$\begin{array}{l}M_k\end{array}$	molar mass of the k-th mixture component
$\begin{array}{l}x_k\end{array}$	mole fraction of the k-th mixture component

Derivation

$\begin{array}{l}\displaystyle M = \frac{m}{\nu} = \frac{N_A}{N} \cdot m = \frac{N_A}{N} \cdot \sum_k m_{u,k} \cdot N_k = \frac{N_A}{N} \cdot \sum_k \frac{M_k}{N_A} \cdot N \cdot x_k =\sum_k M_k \cdot x_k\end{array}$

where

$\begin{array}{l}N_k\end{array}$	number of particles in the k-th mixture component
$\begin{array}{l}N = \sum_k N_k\end{array}$	total number of particles in mixture
$\begin{array}{l}m_{u,k}\end{array}$	molecular mass of the particles in the k-th mixture component

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Molar Mass = M