Question

A 9.87-mol sample of Zr represents how many atoms?

Answer 1

Solution:
The number of constituent particles (molecules or atoms in case of monoatomic compound) in one mole of substance is known as Avogadro constant and it is equal to 6.02*1023 units/mol.
Zr is monoatomic, so 1 mole of it contains 6.02*1023 atoms.
Then 9.87 moles contain 9.87mol * 6.02*1023atom/mol = 5.94*1024 atoms.

Answer:
5.94*1024 atoms.