Mole Practice KEY
Name: ____________________________________________
Date: ______________
Avogadro’s Number (6.02 x 1023) was not discovered by him, but named
in honor of him. It was Dr. Avogadro’s original hypothesis about the
volume of gas molecules that led to the development of the mole concept
many years later.
Use your newfound molar repertoire to complete the following
problems:
The only known picture of
Amedeo Avogadro
1) What is the mass of 5.7 L of NH3 (g) at STP?
5.7L NH 3 x
1 mol 17.04g
x
= 4.3g NH 3
22.4 L 1 mol
2) How many molecules are in 75.0 g of diphosphorus pentoxide?
5.0g P2O5 x
1 mol 6.02 x 10 23 molec
x
= 3.18x10 23 molec
141.94g
1 mol
3) What is the mass of 2.5 moles of chlorine gas at STP?
2.4 mol Cl2 x
70.90g
= 170. g Cl2
1 mol
4) What volume is occupied by 55 g of methane at STP?
55 g x
1 mol 22.4 L
x
= 77 L
16.05g 1 mol
5) How many atoms of neon gas would a container with a volume of 67.2 L hold at STP?
1 mol 6.02 x 10 23 atoms
67.2 L Ne x
x
= 1.54 x10 23 Atoms Ne
22.4 L
1 mol
Q: What did Avogadro teach his students in math class?
A: Moletiplication!
Q: What do you get when you have a bunch of moles acting like idiots?
A: A lot of Moleasses!
10) One drop of water weighs 0.040 g. How many molecules are there in one drop?
0.040g H 2O x
1 mol 6.02 x 10 23 molec
x
= 1.3x10 21 molec H 2O
18.02g
1 mol
11) Isopentyl acetate, C7H14O2, the compound responsible for the scent of bananas, can be
produced commercially. Interestingly, some bees release about 1.0 ug of this compound
when they sting. It is believed the resulting scent attracts other bees to join the attack. How
many molecules of isopentyl acetate are released in a typical bee sting?
1.0 m g H 2O x
1g
1 mol 6.02 x 10 23 molec
x
x
= 4.6x1016 molec C7 H14O2
1000000 m g 130.21g
1 mol
12) How many atoms are there in 303 g of potassium nitrate?
303g KNO3 x
1 mol 6.02 x 10 23 molec 5 atoms
x
x
= 9.02x10 24 atoms
101.11g
1 mol
1 molec
13) A silicon chip used in an integrated circuit of a microcomputer has a mass of 0.0060 g. How
many silicon atoms are present in the chip?
1 mol 6.02 x 10 23 atoms
0.0060g Si3 x
x
= 1.3x10 20 atoms Si
28.09g
1 mol
Amedeo Avogadro Fun Facts!
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

He was born in 1776; one month after the Declaration of Independence was signed.
He received a degree in law at the age of 16.
He had 6 children. (Yes, he was married, although his picture would make you think
otherwise.)
He was a chemistry professor at the University of Turin, which still exists in the city
where the Winter Olympics were recently held.