Molar Volume of a Gas at STP Name
To determine the molar volume of H
2 gas at STP. Purpose
Theory
Bl
The molar volume of a gas is the volume in litres per 1 mole of gas. STP is standard temperature and pressure, which is, 0 o
C and 101 Kpa. To calculate the molar mass, divide the number of litres by the number of moles.
Procedure
1.
Weigh a 2.6 cm piece of magnesium strip.
2.
Add about 10 mL of concentrated HCl to a gas collecting tube. Caution: HCl is very corrosive! Carefully pour water over the HCl to fill the gas collecting tube.
3.
Fill a 500 mL beaker to 400 mL with water.
4.
Roll the magnesium into a coil that is small to fit into the gas collecting tube.
Place it into the tube and allow it to sink down to the acid. When it reaches the acid it will begin to bubble and rise. As soon as it begins to rise, place your thumb on the top of the tube to completely seal the opening, invert the tube and place under the water in the 500 ml beaker. Remove your thumb as soon as the tube is under the surface of the water. Clamp the tube to a ring stand to secure it.
5.
After the reaction is over allow five minutes for the hydrogen gas to reach room temperature. Record the volume of the hydrogen gas.
6.
Clean and put away all of your equipment. Wash your lab bench.
Data
Mass of Mg
Volume of H
Calculations
2
0.046 g
46.4 mL = 0.0464 L
1. Write a balanced single replacement equation for the reaction between HCl and Mg.
Mg
(s)
+ 2HCl
(aq)
H
2(g)
+ MgCl
2(aq)
0.046 g ? moles
2. Covert grams Mg into moles H
2
at room pressure and temperature.
3. Convert the volume of H
2
in litres to STP conditions by multiplying by the conversion factor 0.90183. This lowers the volume to what it would be at 0
0
C and 101 Kpa.

4. Calculate the molar volume by dividing the volume of H
2
in litres by the number of mole H
2
.
5. Determine an accepted value from your textbook for the molar volume of a gas at STP.
6. Calculate the percentage difference between the accepted value and the experimental value of the molar volume. Take the difference and divide it by the accepted value and then multiple by 100%.
STP Calculations
1. Calculate the volume of F
2
gas at STP produced by the electrolysis of 8.2 g of KF.
2KF → 2K + F
2
2. Calculate the mass of KF required to produce 100L of F
2
gas at STP.
2KF → 2K + F
2
3. 5.31 g of a common gas at STP occupies 4.25 L. Calculate the molar mass of the gas. Determine the gas.

4. 2.00 g of a common gas at STP occupies 1.018 L. Calculate the molar mass of the gas. Determine the gas.
5. Calculate the volume of 10 lb of CO
2
gas at STP (2.21 lb = 1.00Kg).
6. Calculate the volume of H
2
gas at STP produced by the complete reaction of
10.0 g Na with water. The percentage yield for this reaction is 96% (You need to write an equation for this reaction).
7. How many litres of 0
2
, measured at STP, will be released on the decomposition of
8.56 g of mercury (II) oxide: 2HgO → 2Hg + O
2
8. Calculate the mass of Fe produced by the reaction of 3.25 g of Fe
2
O
3
if the percentage yield is 75.0 %.
2Fe
2
O
3
+ 3C
→ 4 Fe + 3CO
2

9. Calculate the amount of energy required to refine 100g of Fe
2
O
3
.
2Fe
2
O
3
+ 3C + 800 KJ → 4 Fe + 3CO
2
10. Calculate the energy produced by the complete reaction of 20.0 g H
2
.
2H
2
+ O
2
→ 2H
2
O + 250 KJ
11. Calculate the number of molecules in 10.0 lb of CO
2
gas at STP
(2.21 lb = 1.00Kg).
12. Calculate the molar mass of Co(NH
3
)
6
Cl
3
.
13. Calculate the number of Cl atoms in 50.0 g Co(NH
3
)
6
Cl
3
.
14. Covert 2.0 x 10 26 FU of MgCl
2
to Kg.