Lab 5: Molar Volume of an Ideal Gas
Fall 2022
Remember to report data and calculated results to the correct number of significant figures.
1. Write the balanced equation for the reaction between solid zinc and aqueous hydrochloric
acid. Be sure to include physical states.
2. Record the initial temperature (in °C) and pressure (in atm) to reference later. These are the
conditions that the molar volume value is valid.
Under what conditions of temperature pressure and did you
measure volume? Include units.
T = 21.5 Degrees C
P = 1.000atm
Determining the Experimental Average Molar Volume
In this part of the assignment you will calculate values for molar volume from experimental data for
each of your trials and then determine the average experimental molar volume.
3. Record and calculate the following for all three required trials.
Trial 1 Trial 2 Trial 3
aVolume of 6.0 HCl used (mL)M 100mL 100mL 100mL
bMoles of HCl reactant calculated using and Molarity Volume 0.60mol 0.60mol 0.60mol
cMass of zinc used (g) [Report all three sig figs] 0.100g 0.150g 0.200g
dMolar mass of zinc (g/mol)
[General Rule: Use least 4 significant figures from periodic
table for determining molar mass]
65.39(g/mol) 65.39(g/mol) 65.39(g/mol
)
eMoles of zinc reactant calculated using the molar mass 0.0015mol 0.0023mol 0.0031mol
fIdentity of Limiting Reactant Zn Zn Zn
gVolume of gas produced, measured at initial room
temperature (mL)
36.80mL 55.21mL 73.61mL
h
Moles of H gas produced
2 using stoichiometry from limiting
reactant (mol)
0.0015mol 0.0023mol 0.0031mol
Show your work and answer for Trial 1 only:
Number of moles of Zn = 0.100g/65.39g = 0.0015mol; Number of moles of H =
2
Zn(s) + 2 HCl(aq) = ZnCl (aq) + H
2 2(g)
Trial 1 Trial 2 Trial 3
0.0015mol
4. Calculate an experimental value for molar volume from your data above by dividing the
volume of gas produced by the moles of gas produced:
Molar volume = (volume of gas)/(moles of gas) = V/n
Trial 1 Trial 2 Trial 3
Calculated Molar Volume of the hydrogen gas at room
temperature (Volume/moles), expressed in units of L/mol,
calculated from your experimental data. [Report with 4
significant figures (one extra)]
24.53(L/mol) 24.00(L/mol) 23.75(L/mol
)
Show your work and answer for Trial 1 only:
36.80mL/0.0015mol = 24,533mL = 24.53L at 21.5C and 1atm pressure
5. Calculate the Experimental Average Molar Volume at 21.5 °C from Trials 1, 2 and 3 with
units of L/mol. This is your . [Report with 3 significant figures]experimental value
24.1(L/mol)
6. Compare the experimental molar volumes obtained in all three trials. Do you expect the molar
volume values to be similar? Explain your reasoning.
Determining the Theoretical Molar Volume
In this part of the assignment you will be using the ideal gas law equation:
PV=nRT where = 0.08206 L·atm/(K·mol)R
7. Calculate the theoretical value of the molar volume of an ideal gas under the same
conditions of temperature and pressure used in your experiment (refer to Question 2). To solve
for molar volume, rearrange the ideal gas law equation so you are solving for V/n with an
answer with l. units of L/mo
The molar volumes are almost identical. When the zinc in each trial was increased the number
of moles also increased. With the increase in moles the volume of H2 gas increased. Each trial
used the same temperature and pressure hence the molar volumes being similar.
8. Compare the average value for the molar volume at 21.5 °C (from Question 5) experimental
with the theoretical “ideal” value at the same temperature (from Question 7).
(a) Experimental Average Molar Volume from Trials 1, 2
and 3 (L/mol). This is your . [Report with experimental value
3 significant figures]
24.1(L/mol)
(b) Ideal Molar volume from #4 (L/mol). This is your
theoretical value.24.2L/mol
(c) Explain any differences between these two values for
molar volume. If there is no difference, explain why you
should expect a difference.
There is no difference because we
calculated the moles of Zn as the
limiting reagent with no
consideration to yield. So, our
Average molar volume and Ideal
molar volume are almost exact.
9. Use your from the first row in the above table to predict the experimental molar volume value
number of moles of hydrogen gas in a volume of 155 mL (0.155 L) under the same conditions of
temperature and pressure as your experiment. Show calculation with answer that includes units and
correct significant figures.
Show calculation with answer that includes and correct units significant figures:
PV= nRT = (0.08206 X 294.65)/1
P= 1.0atm = 24.2L/mol
R= 0.08206L-atm/(K-mol)
T= 21.5C
= 273.15 + 21.5
= 294.65
V/n= RT/P
Show calculation with answer that includes and correct units significant figures:
24.2L/mol/(0.155L) = 156mol
