Community College of Philadelphia
Department of Chemistry
CHEM 101 Distance Course
Laboratory Report Sheet
Name:
Date:
Email:
Laboratory Instructor:
Course Nbr.: CHEM 101 Distance
Section:
Experiment Nbr.: C Home-based Lab
Experiment Title: Molar Mass of Mg using Gas Laws
Purpose:
Concepts related to the textbook:
Conclusion:
CHEM 101 Online Lab Instructions for Exp. C
Ideal Gas Law: Estimation of Molar Mass of Magnesium
(adapted from CHEM 110 Experiment 8 on 7/01/2020)
1. Read Chapter 7 sections on Gases and the Ideal Gas Law
2. Watch the following videos in substitution for the procedure that would be done in an actual lab:
Mg (s) + 2 HCl (aq) MgCl2 (aq) + H2 (g)
It is important to note that for every one mol of Mg reacted, one mol of H2 gas forms (1:1 mol ratio from the balanced equation) in this single replacement reaction.
*Please note the experiments in the videos may have a different set up, but it involves the same reaction: magnesium metal reacts with an acid to produce hydrogen gas. The hydrogen gas is captured over water in an overturned graduated cylinder or eudiometer.
3. Complete the following charts below. The data in blue is being provided as acceptable data from previous experiments. Refer to the videos above and the left hand columns for math calculation tips. The ideal gas law (PV=nRT) is applied to initially solve for moles (n) of hydrogen gas, which is the same as the moles of Mg reacted. From that result, molar mass is calculated which is the mass of a substance per 1 mol of that substance.
Hypothetical Data and Molar Mass Determination
In this section, data similar to what you would have collected in the experiment is presented. Use this data to calculate the molar mass of Mg. Make sure to show your work for any calculations in the space provided!
Trial 1
Trial 2
Trial 3
A Mass of Magnesium (g)
0.047 g
0.048 g
0.041 g
B Volume of Hydrogen Gas (mL)
50.7 mL
50.8 mL
43.0 mL
C Volume of Hydrogen Gas (L)
Sample Calculation for C
D Temperature of Gas (Celsius)
20.0 ?
21.0?
23.0 ?
E Temperature of Gas (Kelvin)
Sample Calculation for E
F Atmospheric Pressure (mmHg)
761.9 mm Hg
761.0 mm Hg
762.8 mm Hg
G Vapor Pressure of Water According to Temperature (mmHg)
17.5 mm Hg
18.6 mm Hg
21.1 mm Hg
H Height of Water Column (mm)
* obtained from difference in water levels
** note the units are millimeters!
114.0 mm
111.0 mm
89.9 mm
I Mercury Equivalent Height (mm Hg)
* obtained by dividing H by 13.6
Sample Calculation for I
J Pressure of Hydrogen (mm Hg)
* to calculate…
F-G-I= J
Sample calculation for J
K Pressure of Hydrogen (atm)
* convert mm Hg to atm by dividing J
by 760 mm Hg
Sample calculation for K
L Moles of Hydrogen Gas (moles)
* calculate using the equation n = PV/RT
P = K V = C T = E
R = 0.0821 (L?atm)/(mol?K)
Sample Calculation for L
M Moles of Magnesium (moles
* use stoichiometry to convert L to M
(1 mole Mg produces 1 mole H2)
Sample Calculation for M
N Calculated Molar Mass of Magnesium (g/mol)
* calculate by dividing mass of sample by moles
A ÷ M = N
Sample Calculation for N
O Average Molar Mass
* find by averaging N for all three trials
Calculation for O
P % Error
* compare average molar mass to actual molar
mass of Magnesium (24.31 g/mol)
Calculation for P
M. OConnor/M. Rathmill/L. Gerz Summer 2020
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