Answer: 3.5 moles
Step-by-step explanation:
Based on Avogadro's law:
1 mole of any substance has 6.02 x 10^23 molecules
So, 1 mole of SiO4 = 6.02 x 10^23 molecules
Zmoles of SiO4 = 2.1 x 10^{24} molecules
To get the value of Z, cross multiply:
(2.1 x 10^{24} molecules x 1mole) = (6.02 x 10^23 molecules x Z moles)
2.1 x 10^{24} molecules = (6.02 x 10^23 x Z)
Z = (2.1 x 10^{24}) ➗ (6.02 x 10^23)
Z = 3.5 moles
Thus, there are 3.5 moles of SiO4.