*A) What is the mass of 0.25 mol aspirin (C _{9}H_{8}O_{4})?*

The formula mass of aspirin is 180 g/mol.

Thus, 0.25

* How many aspirin molecules are in 500 mg aspirin?*

There are 6.02
´ 10^{23} molecules
in 1 mol.

500 mg aspirin is 2.78
´ 10^{–3} mol, and thus
has 6.02 ´ 10^{23}
molecule/~~mol~~ ´ 2.78
´ 10^{–3} ~~mol~~
= 1.67 ´ 10^{21}
molecules.

*B) What is the mass of 2.30 mol acetominophen (Tylenol) (C _{8}H_{9}NO_{2})?*

The formula mass of acetominophen is 151 g/mol.

Thus, 2.30

* How many molecules are in 500 mg acetominophen?
How many moles are there?*

500 mg acetominophen is
3.31 ´ 10^{–3}
mol, and thus has 6.02 ´
10^{23} molecule/~~mol~~ ´
3.31 ´ 10^{–3}
~~mol~~ = 1.99 ´
10^{21} molecules

0.5 ~~g~~ ¸
151 ~~g~~/mol (or ´
D mol/~~g~~) = 3.31 ´
10^{–3} mol

*C) How many Pb molecules are in 1.000 g Pb mass?*

1.000
~~g~~ ¸ 207.19 ~~g~~/mol
= 4.826 ´ 10^{–3} mol, which has
6.02 ´ 10^{23} molecule/~~mol~~
´ 4.826 ´
10^{–3} ~~mol~~ = 2.91 ´
10^{21} molecules.

*D) 1 mol oxygen gas is 22.4 L at 1 atm and 0 ºC. How many L
does 32 g oxygen gas occupy at 1 atm and 0 ºC? How about 32 g ozone
gas? (Hint: How many moles are there in 32 oxygen
gas and ozone gas?)*

32
g oxygen gas is 1.0 mol, which is thus 22.4 L.

32
g ozone gas (O_{3}) is 0.67 mol, which is 0.67 ~~mol~~
´ 151 L/~~mol~~ = 15 L