Answer : The mass of carbon-12 atoms is, 3 amu
Solution : Given,
Moles of carbon-12 atoms = 0.25 moles
The molar mass of carbon-12 atoms = 12 g/mole = 12 amu
(1 amu = 1 gram/mole)
Now we have to calculate the mass of carbon-12 atoms.

Now put all the given values in this formula, we get the mass of carbon-12 atoms.

Therefore, the mass of carbon-12 atoms is, 3 amu