Question

What net charge would you place on a 527 g piece of sulfur if you put an extra electron on 1 in 10¹² of its atoms? (Sulfur has an atomic mass of 32.1.)

___ C

Answer 1

mass, M = 527g

atomic mass of sulfur = 32.1 u

molar mass of sulfur, m = 32.1g

no. of moles, n = M/m

n = 527/32.1

n = 16.42

no. atoms in 1 mole = 6.022 x 10²³ atoms (Avogadro number)

no. atoms in 16.42 mole = 6.022 x 10²³ x 16.42

                                    = 9.89 x 10²⁴ atoms

no. of electrons in 10¹² atoms = 1

no. of electrons in 1 atoms = 10^-12

no. of electrons in 9.89 x 10²⁴ atoms, N = 9.89 x 10¹² electrons

Charge, Q = 9.89 x 10¹²/6.24 x 10¹⁸     (1 C = 6.24 x 10¹⁸ electrons)

Q = 1.58 x 10^-6 C

Answer: 1.58 x 10^-6 C