PREPARATION OF COMMON GASES

LABORATORY PREPARATION OF COMMON GASES

A number of useful gases can be prepared using common chemicals in the laboratory. Some of these gas preparations are listed below. Most can be prepared in quantities sufficient for a variety of uses in a gas preparation apparatus (conical flask, thistle funnel, delivery tube, pneumatic trough and beehive). Toxic gases should be prepared in a fume cupboard. Flammable and explosive gases should be prepared and kept away from flames.

Gas	Reagents	Method	Collect gas	Chemical equation
Oxygen O₂ Method 1	6% Hydrogen peroxide Manganese dioxide (catalyst)	Add hydrogen peroxide to about 5g of MnO2 .	over water	2H₂O₂ Æ 2H₂O + O₂
Oxygen O₂ Method 2	Potassium permanganate	Heat solid KMnO4	over water	2KMnO₄ Æ K₂MnO₄ + MnO₂ + O₂
Hydrogen H₂	Zinc (granulated) 5M Hydrochloric acid	Add 5M hydrochloric acid to 5 - 10g granulated zinc pieces.	over water	2HCl + Zn Æ H₂ + ZnCl₂
Nitrogen N₂	Ammonia Calcium hypochlorite (bleaching poweder)	Shake 20g calcium hypochlorite in 100mL water for several minutes and filter. Add 10mL of conc. ammonia and heat mixture.	displacement of air	2NH₃ + 3CaOCl₂ Æ N₂ + 3H₂O + 3CaCl₂
Chlorine Cl₂	Potassium permanganate Conc. Hyrochloric acid	Add concentrated hydrochloric acid dropwise onto a small amount of potassium permanganate crystals (in flask).	upward displacement of air in a fume cupboard	6HCl + 2KMnO₄ + 2H⁺ Æ 3Cl₂ + 2MnO₂ + 4H₂O + 2K⁺
Carbon dioxide CO₂	Calcium carbonate (marble chips) 5M Hydrochloric acid	Add 5M hydrochloric acid to 5 - 10g marble chips.	upward displacement of air	2HCl + CaCO₃ Æ CO₂+ CaCl₂+ H₂O
Ammonia NH₃	Ammonium chloride Calcium hydroxide	Gently heat a mixture of ammonium chloride and calcium hydroxide in water.	upward displacement of air in a fume cupboard	Ca(OH)₂ + 2NH₄Cl Æ 2NH₃ + CaCl₂ + 2H₂O
Hydrogen chloride HCl	Sodium chloride Conc. Sulfuric acid	Slowly add concentrated sulfuric acid to solid sodium chloride.	displacement of air in a fume cupboard	2NaCl + H₂SO₄Æ Na₂SO₄ + 2HCl
Nitrogen monoxide (Nitric oxide) NO	Copper (turnings) 5M Nitric acid	Add 5M nitric acid to 5-10g copper (turnings preferred).	over water.	3Cu + 8HNO₃ Æ 2NO + 3Cu(NO₃)₂ + 4H₂O
Nitrogen dioxide NO₂	Copper (turnings) 10M Nitric acid	Add concentrated nitric acid to 5-10g copper.	upward displacement of air in a fume cupboard	Cu + 4HNO₃ Æ 2NO₂ + Cu(NO₃)₂ + 2H₂O
di-Nitrogen oxide (Nitrous oxide) N₂O	Sodium nitrate Ammonium sulfate	Powder 10g sodium nitrate and mix well with 9g ammonium sulfate. Heat well.	displacement of air	NH₄NO₃ Æ N₂O + 2H₂O
Sulfur dioxide SO₂	Sodium sulfite (or sodium bisulfite) 2M Hydrochloric acid	Add dilute hydrochloric acid to 5-10g sodium sulfite (or bisulfite).	upward displacement of air in a fume cupboard	Na₂SO₃ + 2HCl Æ SO₂ + H₂O + 2NaCl
Methane CH₄	Sodium acetate (anhydrous) Soda lime	Mix 1 part sodium acetate with 3 parts soda lime. Heat in a dry pyrex test-tube or small flask.	over water	CH₃COONa + NaOH Æ CH₄ + Na₂CO₃

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This page was last updated 24 March 2000.

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