Question

What will be the mass of one atom of C - 12 in grams ?

Answer 1

The mass of a carbon - 12 atom was determined by a mass spectrometer and found to be equal to $1.992648\times {10}^{-23}g.$ It is known that 1 mole of C-12 atom weighing 12 g contains $N_A$ number of atoms. Thus,

1 mole of C - 12 atoms = $12g=6.022\times {10}^{23}$ atoms

$\Rightarrow 6.022\times {10}^{23}$ atoms of C - 12 have mass = 12 g

$\therefore$ 1 atom of C - 12 have mass $=\frac{12}{6.022\times {10}^{23}}g$

$=1.992648\times {10}^{-23}g\approx 1.99\times {10}^{-23}g$