Question

5. What is the mass of 1.63 x 1021 silicon atoms? (A) 2.71 x 10 g (B) 4.58 x 1022g (C) 28.08 g (D) 1.04 x 10 g (E) 7.58 x 102 g

Answer 1

ANSWER:-  

we know that atomic mass of Si atom is 28.08 from periodic table and one mole of Si atom is 6.023 * 10²³ (Avagadro's number) atoms of Si that is,

mass of 1 atom / 1 atom = mass of a mole of atoms / 6.022 x 10²³ atoms

Plug in the atomic mass of silicon to solve for the mass of 1 atom:

mass of 1 atom = mass of a mole of atoms / 6.022 x 10²³

mass of 1 Si atom = 28.08 g / 6.022 x 10²³ Si atoms
mass of 1 Si atom = 4.6629 x 10^-23 g

so mass of 1.63*10²¹ Si atom is = 4.6629 * 10^-23

=4.6629 * 10^-23 * 1.63*10²¹

  =7.60 *10^-2 g

so the correct option is E