Preparation and Properties of Gases

 

This week, we will be preparing four different gases and examining some of their properties.  We will observe whether those gases support combustion or are combustible and we will determine whether the gases chemically react with a mixture known as limewater.  The four gases we will be preparing are:  hydrogen, carbon dioxide, nitrogen, and oxygen.  We will prepare these gases in a large syringe; some of the gas will be bubbled through limewater in a test tube, and some of the gas will be transferred to a test tube in order to test its combustion properties.  Your lab instructor will show you the techniques for running these reactions.  You will use the amounts of the reagents shown on the Table below.  Your lab report should include a purpose, brief procedure, data/observations, and conclusion.  Please combine your observations and conclusions onto one neatly organized table.  Your conclusion should include a balanced equation representing the reaction used to prepare each of the gases.  Also, name the type of reaction that each belongs to.  (Some of these may not fit perfectly into our classification scheme, but using the reactants, try to classify these reactions as best you can.)  One hint, catalysts are not consumed during a chemical reaction, so you may considercatalysts not to be present in the chemical equation. Pay particular attention, and take good notes – these observations may be helpful in future lab experiences. 

 

Table

Reagents for Preparing Gases

 

Gas Prepared	Solid Reagent	Liquid Reagent
Carbon dioxide	0.22 grams NaHCO3	5 mL 1 M HCl
Oxygen	0.10 grams KI	5 mL 6% H2O2
Nitrogen	0.20 grams HSO3NH2	5 mL 0.50 M NaNO2
Hydrogen	0.07 grams Mg	5 mL 1 M HCl

 

After preparing your gas in a syringe, place a latex tube onto the syringe, and transfer the gas into a test tube as shown by your instructor.  Light a wood splint and put the lit splint into the test tube of your gas sample.  Observe. 

 

Prepare a second sample of gas in the syringe. Then, attach a latex tube to the syringe and bubble the gas through about 10 mL of limewater in a test tube.  Observe. 

 

Some of the chemicals used for producing different gases will react with each other.  For example, HCl (used to produce hydrogen and carbon dioxide) will react with H₂O₂ (used to produce oxygen).  We don’t want the chemicals from different runs reacting.  Make sure your equipment is well cleaned and rinsed between each run.  Also, iodine is formed when KI and H₂O₂ are reacted together (to make oxygen).  Iodine can stain your skin.  Gloves will be provided in lab to avoid skin contact.  Work very carefully with all these chemicals, and follow your lab instructor’s direction.  If you have any questions about using these substances, ask your lab instructor.  Be sure to wear your goggles at all times. 

 

The equations for the four reactions are given below (they may or may not be balanced). 

 

                NaHCO₃(s)   +    HCl (aq)    à     CO₂ (g)   +   NaCl (aq)    +    H₂O

 

                H₂O₂ (aq)    +  KI (catalyst)   à    H₂O   +   O₂   +   KI (catalyst)

 

                NaNO₂ (aq)   +   HSO₃NH₂ (s)   à    NaHSO₄ (aq)   +   H₂O   +   N₂ (g)

 

                Mg (s)   +    HCl (aq)    à     MgCl₂ (aq)    +    H₂ (g)  

 

Question - A colorless gas is tested.  It is not combustible nor does it support combustion.  It chemically reacts with limewater forming a cloudy white precipitate.  What could this gas be?  Put your answer in your conclusion.