File_39 - Appendix 3 Laboratory Preparations To study the properties of elements and compounds it is necessary when possible to prepare and collect

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Unformatted text preview: Appendix 3 Laboratory Preparations To study the properties of elements and compounds, it is necessary, when possible, to prepare and collect small samples of the substances. A sample is prepared by use of a reaction in which the element or compound is formed. To insure that a sample of sufficient quantity will be obtained, the reaction should be one that goes to completion. The reaction takes place in a vessel, such as a test tube or a flask, which is called the generator. The method by which the sample is collected depends on the physical properties of the substance. If the sample is a gas, it can be collected in one of two ways, depending on the solubility and density of the gas. Gases that have limited solubility in water are collected by water displacement. This method is used to collect oxygen and hydrogen, for example. Gases that are soluble in water are collected by air displacement. Ammonia is one of the gases collected by this method. A third method, condensation, is used in some special cases for gases, such as bromine, that can be condensed easily. Caution: Special methods of preparation and collection are important for certain substances because they are dangerous to handle. Students should not perform any of the following preparations without the approval and supervision of their teacher. 583 Preparation and Collection of Gases Diagrams for the preparation and collection of the following gases are included: Oxygen, hydrogen, chlorine, carbon dioxide, sulfur dioxide, ammonia, and hydrogen chloride. (Following the section on the collection of gases you will find diagrams for the Preparation and Collection of Volatile Liquids and Solids.) Oxygen 2 H2O2 (l ) h 2 H2O Ringstand O2 ( g) Delivery tube Collecting bottle H2O2 O2 Pan of water Bunsen burner To sink Hydrogen (1) Zn (s) (2) Mg (s) H2SO4 (aq) h ZnSO4 (aq) 2 HCl (aq) h MgCl2 (aq) Dilute H2SO4 Thistle tube H2 ( g) H2 ( g) Delivery tube Collecting tube H2 Zn Pan of water To sink 584 | Appendix 3: Laboratory Preparations Chlorine (1) MnO2 (s) 4 HCl (aq) h MnCl2 (aq) 2 H2O (2) 2 KMnO4 (s) 16 HCl (aq) h 2KCl (aq) 2 MnCl2 (aq) 8 H2O 5 Cl2 ( g) (3) 2 NaCl (s) 2 H2SO4 (aq) MnO2 (s) h Na2SO4 (aq) MnSO4 (aq) 2 H2O Cl2 ( g) HCl Cl2 ( g) MnO2 Na2S2O3(aq) to trap excess chlorine Cl2 Carbon Dioxide (1) CaCO3 (s) 2 HCl (aq) h CaCl2 (aq) (2) NaHCO3 (s) HCl (aq) h NaCl (aq) HCI H2O H2O CO2 ( g) CO2 ( g) CO2 CaCO3 Preparation and Collection of Gases | 585 Sulfur Dioxide (1) Na2SO3 (s) (2) NaHSO3 (s) 2 HCl (aq) h 2 NaCl (aq) H2O SO2 ( g) HCl (aq) h NaCl (aq) H2O SO2 ( g) HCI Na2SO3 SO2 Ammonia 2 NH4Cl (s) Ca(OH)2 (s) h CaCl2 (s) 2 H2O 2 NH3 ( g) NH3 NH4Cl + Ca(OH)2 586 | Appendix 3: Laboratory Preparations Hydrogen Chloride 2 NaCl (s) H2SO4 (aq) h Na2SO4 (aq) 2 HCl (g) H2SO4 NaCl HCl Preparation and Collection of Gases | 587 Preparation and Collection of Volatile Liquids Bromine H2SO4 2 KBr (s) 2 H2SO4 (aq) MnO2 (s) h K2SO4 (aq) MnSO4 (aq) 2 H2O Br2 (l ) MnO2 + KBr Water Liquid Br2 Nitric Acid 2 NaNO3 (s) H2SO4 (l ) h Na2SO4 (s) 2 HNO3 (l ) NaNO3 + H2SO4 Glass retort HNO3 Cold water 588 | Appendix 3: Laboratory Preparations Preparation and Collection of a Volatile Solid Iodine 2 KI (s) 2 H2SO4 (aq) MnO2 (s) h K2SO4 (aq) MnSO4 (aq) 2 H2O I2 (s) Cold water Watch glass I2 crystals I2 vapor Kl + MnO2 + H2SO4 Preparation and Collection of a Volatile Solid | 589 ...
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This note was uploaded on 02/28/2010 for the course CHEM 111 taught by Professor Yensen during the Spring '09 term at Northern Virginia.

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