Problem Set One: Episode 701—KEY
How many atoms are in 3.5 grams of silicon?
? atoms Si = 3.5 g Si !
1 mole Si
6.02 ! 10 23 atoms Si
!
= 7.5 ! 10 22 atoms Si
28.1 g Si
1 mole Si
How many formula units are in
32.6 grams of potassium oxide?
? f.u. K 2 O = 32.6 g K 2 O !
1 mole K 2 O
6.02 ! 10 23 f.u. K 2 O
!
= 2.08 ! 10 23 f.u. K 2 O
94.2 g K 2 O
1 mole K 2 O
How many molecules are in
0.25 grams of dinitrogen pentoxide?
? molecules N 2 O5 = 0.25 g N 2 O5 !
1 mole N 2 O5
108.0 g N 2 O5
!
6.02 ! 10 23 molecules N 2 O5
1 mole N 2 O5
= 1.4 ! 1021 molecules N 2 O5
CHEMISTRY: A Study of Matter
© 2004, GPB
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