Ncert Exercises & Solutions

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

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 = 12 g = 6.022 \times 10^{23} atoms

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

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

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