What is the molar mass constant?

The molar mass constant is M_u = 0.99999999965e-3 kg/mol (uncertainty ±3.0e-13), almost exactly 1 g/mol after the 2019 SI redefinition.

Key facts

Frequently asked questions

What is the molar mass constant?

M_u = 0.99999999965e-3 kg/mol, essentially 1 g/mol, relating atomic mass in u to molar mass in g/mol.

Is the molar mass constant exactly 1 g/mol?

No longer exactly. Since the 2019 SI redefinition it is 1 g/mol within a tiny uncertainty of ±3.0e-13 kg/mol.

What is M_u used for?

It connects relative atomic mass (in u) to molar mass: M = A_r · M_u.

Related pages

• Speed of light
• Planck constant
• Reduced Planck constant
• Avogadro constant
• Boltzmann constant
• Molar gas constant
• Elementary charge
• Gravitational constant

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