To calculate the number of pennies, we need to multiply the given moles by the Avogadro's number (6.022 x 10^23), which represents the number of atoms, molecules, or ions present in one mole of a substance.

Number of pennies = (3.5 x 10^-16 moles) x (6.022 x 10^23 pennies/mole)

Number of pennies ≈ 2.11 x 10^8 pennies

Therefore, if you had 3.5 x 10^-16 moles of pennies, you would have approximately 211,000,000 pennies.