What is the mass of 4.91 × 1021 platinum atoms?
Here, we are going to calculate the mass of 4.91 x 1021 platinum atoms.
One mole of any species is that quantity in number having a mass equal to its atomic or molecular mass in grams.
The number of particles (atoms, molecules or ions) present in 1 mole of any substance is fixed, with a value of 6.022 × 1023. This is an experimentally obtained value. This number is called the Avogadro Constant or Avogadro Number.
The number of moles = given number of particles / Avogadro number
Therefore, number of moles of platinum = 4.91 x 1021 / 6.022 × 1023
= 0.815 x 10-2
= 8.15 x 10-3 mol.