18. How many moles of atoms are there in each of

the following? (Hint: See Sample Problems C

and D.)

a. 6.022 x 1023 atoms Ne c. 3.25 x 105 g Pb

b. 3.011 x 1023 atoms Mg d. 4.50 x 10-12 g O

a) 1 mole of Ne

b) i/2 mole of Mg

c) 1570 moles of Pb.

d) 2.18125*10^-13 moles of oxygen.

Explanation:

The number of moles calculated by Avogadro's number in 6.23*10^23 of Neon.

6.23*10^23 = 1 / 6.23*10^23

= 1 mole

The number of moles calculated by Avogadro's number in 3.01*10^23 of Mg

3.2*10^23=1/6.23*10^23

= 1/2 moles of Pb.

Number of moles in 3.25*10^5 gm of lead.

atomic weight of Pb=

n=weight/atomic weight

= 3.25*10^5 / 207

= 1570 moles of Pb.

Number of moles 4.50 x 10-12 g O

number of moles = 4.50*10^-12/16

= 2.18125*10^-13 moles of oxygen.