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• Convert 1 Amu To Kg

Convert 1 amu to MeV

Solution:

1) Determine mass of 1 amu (in kg):

How to Convert Dalton to Kilogram. 1 dalton = 1.013E-27 kg. 1 kg = 6.5E+26 dalton. Example: convert 15 dalton to kg: 15 dalton = 15 × 1.013E-27 kg = 2.02E-26 kg. By definition: 1 amu = mass of 1/12 of a C12 atom. Now we know that 1 mol C12 atoms has mass = 12.000g So 1 mol of amu must have mass 1/12.12 = 1.000g But 1 mol amu = 6.022.10^23 amu. 1.9926468 x 10¯ 26 kg/atom / 12 amu/atom = 1.660539 x 10¯ 27 kg/amu (this is the mass of 1 amu) 2) Use Einstein's mass-energy equation to determine Joules in one amu: E = mc 2.

By definition, the mass of 1 atom of C-12 is 12 amu.

Therefore, the mass of one mole of C-12 atoms is, by definition, 12 g

Avogadro's Number is 6.0221409 x 10²³ mol¯¹

12 g/mol / 6.0221409 x 10²³ mol¯¹ = 1.9926468 x 10¯²³ g (mass of one atom of C-12 in g)

(1.9926468 x 10¯²³ g) (1 kg / 1000 g) = 1.9926468 x 10¯²⁶ kg (mass of one atom of C-12 in kg)

1.9926468 x 10¯²⁶ kg/atom / 12 amu/atom = 1.660539 x 10¯²⁷ kg/amu (this is the mass of 1 amu)

2) Use Einstein's mass-energy equation to determine Joules in one amu:

E = mc²

E = (1.660539 x 10¯²⁷ kg) (2.99792458 x 10⁸ m/s)²

E = 1.49242 x 10¯¹⁰ kg-m²/s² (this is Joules)

3) Convert J to eV, then MeV

1 eV = 1.60217733 x 10¯¹⁹ J

1.49242 x 10¯¹⁰ J / 1.60217733 x 10¯¹⁹ J/eV = 931494893 eV

(931494893 eV) (1 MeV / 10⁶ eV) = 931.494893 MeV

Often, 931.5 MeV is the value used in problem solving.

4) 931.5 MeV is the energy in one amu. Is it possible to express the mass of one amu using MeV in some way? I'm glad you asked:

E = mc²

931.5 MeV = mc²

m = 931.5 MeV/c²

The use of 931.5 MeV/c² for the mass of 1 u is wide-spread. So much so that the c² is often not written and you must infer its presence by context.

1 Amu To Kg

5) To sum up:

1 u = 931.5 MeV (expressed as energy)

1 u = 931.5 MeV/c² (expressed as mass)

In solving problems, you may see this unit:

931.5 MeV/u-c

Weight To Kg Chart

²

read it as 931.5 MeV/c² per 1 u

By the way, if you look around the Internet, you will find values different than the 931.494893 value I calculated. This is because different authors will use values that they have rounded off differently than the ones I used.

G Cm3 To Lb Ft3

For example, I used 1.660539 x 10¯²⁷ kg for the mass of 1 amu. Often, you will see it as 1.66 x 10¯²⁷ kg.

Convert 1 Amu To Kg

The cumulative effect of these rounding off decisions will be seen in slightly different answers from different authors.