Stoichiometry – mass –volume relationships Name ______Partner ______
Date ______
Background: The objective of this lab is to measure a quantity of magnesium metal and to use
stoichiometric principles to predict the volume of hydrogen gas you would expect to make from this amount of metal. After comparing the predicted volume of gas produced with the actual volume of gas produced, the percent error of your results will be determined.
Theory/procedure: Magnesium metal reacts with hydrochloric acid (HCl) by single displacement to
produce hydrogen gas. The magnesium metal has already been cut to the predetermined length. Before you do any part of the lab, write the balanced equation for this reaction:
Balanced equation:
After writing a balanced equation, follow the basic steps below to collect your data.
1. Obtain a manometer with a stopper and a pre-cut piece of magnesium . Record the mass of the magnesium.
2. Make certain the sink is ¾ full of water.
3. Fill the manometer with 1M HCl solution.
4. Using a piece of copper ribbon, tie the magnesium metal to the inside of the one-holed stopper. (As demonstrated in class.)
5. Quickly add the stopper with the magnesium metal to the gas collecting tube and invert the gas collecting tube and place into the water in the sink.
6. Measure the temperature of the water in the sink. Record.
7. Record the air pressure.
8. After the magnesium has completely reacted, record the volume of hydrogen gas inside the gas collecting tube (produced in this reaction.)
9. Clean up your mess and return the gas collecting tube with stoppers to their correct location.
Data/Result/calculations table: Complete the following table. For calculations, make certain to show all work including the equation, substitution, and solution.
Mass of magnesium metal ______g
Temperature of water in the sink ______oC ______K
(this is the temperature of the hydrogen gas)
Atmospheric pressure (Given to you) ______inHg
Atmospheric Pressure (converted to mmHg – show work below) ______mmHg
Pressure of the dry hydrogen gas (use Dalton’s Law) ______mmHg
(show work below:)
Balanced equation for the reaction between magnesium metal and hydrochloric acid
Using stoichiometry, how many moles of hydrogen gas would you expect to make? ______moles
Using the Ideal Gas Law and the moles of a gas calculated above with the known temperature and pressure of the gas, what volume of gas would you expect to make? ______ml = ______liters
(Show work below)
Actual volume of Hydrogen gas produced ______ml = ______liters
% error (in volume)(show work below) ______%
Questions: Answer the following questions using Complete Sentences!
1. What was the limiting reactant of this reaction? How do you know this?
2. What is the density of hydrogen gas @STP? (Show work)
3. Was the hydrogen gas collected at STP conditions? How do you know this?
4. What is the density of hydrogen at the conditions for which the experiment was run? (show work below)