Express 1 amu in kilogram.

Explanation

To express 1 atomic mass unit (amu) in kilograms, we can follow these steps:

### Step 1: Understand the Definition of 1 amu
1 amu is defined as one twelfth (1/12) of the mass of an unexcited carbon-12 (C-12) atom.

### Step 2: Find the Mass of a Carbon-12 Atom
The mass of 6.023 x 10^23 atoms of carbon-12 is equal to 12 grams (this is based on Avogadro's number).

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