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24sec4

  1. 1. 24.4 Hydrogen and Noble Gases
  2. 2. Hydrogen <ul><li>Isotopes </li></ul><ul><li>Three isotopes of hydrogen are known: </li></ul><ul><li> Percent Alternate </li></ul><ul><li>Form Abundance Name Symbol </li></ul><ul><li>1 H 99.985 Protium </li></ul><ul><li>2 H 0.015 Deuterium 3 H trace Tritium </li></ul><ul><li>Note: Tritium is radioactive with a half-life of 12.3 years. It emits  - . </li></ul>
  3. 3. Hydrogen <ul><li>Most abundant element in universe, but on Earth it is generally just found in compounds </li></ul><ul><li>Found in living things, coal, natural gas, petroleum and petroleum products </li></ul><ul><li>Found in Group 1A, but is not a metal, it is not a good conductor; it does react w/ halogens though and can have a 1+ charge </li></ul><ul><li>Also can act like a halogen and react w/alkali metals to for m hydrides ( H - ) </li></ul>
  4. 4. Physical properties of H 2 <ul><li>Hydrogen is a colorless gas with an extremely low melting and boiling point. </li></ul><ul><li>This indicates that the London forces are very weak. </li></ul><ul><li>H 2 molecules actually repel each other under ordinary conditions. </li></ul><ul><li>At 25 o C and 1 atm pressure, the density of H 2 is 0.0824 g/L - the lowest density of any substance under these conditions. </li></ul>
  5. 5. Preparation of H 2 <ul><li>Industrially, most hydrogen is produced from hydrocarbons and steam - water-gas shift reaction . </li></ul><ul><li>(1) CH 4 (g) + H 2 O (g) 3H 2 (g) + CO (g) </li></ul><ul><li>(2) CO (g) + H 2 O (g) H 2 (g) + CO 2 (g) </li></ul><ul><li>Another way to produce Hydrogen is the Bosch process: steam is passed over red-hot iron </li></ul><ul><li>3Fe (s) + 4H 2 O (g) --------Fe 3 O 4(s) + 4H 2(g) </li></ul>Catalyst, 900 o C Catalyst 200-400 o C
  6. 6. Uses of H 2 <ul><li>More hydrogen is used to make ammonia by the Haber process than for any other purpose. </li></ul><ul><li>Another use is hydrogenation of vegetable oils to make margarine and vegetable shortening. </li></ul>Vegetable oil + H 2 Margarine Ni Heat
  7. 7. Water <ul><li>Most of the hydrogen on Earth is in the form of water. </li></ul><ul><li>Water is the only liquid that is common on Earth. </li></ul><ul><li>Hydrogen bonding by water accounts for many of its unique properties. </li></ul><ul><ul><li>High melting and boiling point </li></ul></ul><ul><ul><li>Large temperature range for the liquid form. </li></ul></ul><ul><ul><li>High specific heat. </li></ul></ul>
  8. 8. Noble Gases <ul><li>Group O elements </li></ul><ul><li>Are very unreactive (inert gases) </li></ul><ul><li>Flourine will react w/ Xe to form XeF 4, and Kr and Rn have been found to form a compund </li></ul><ul><li>Occur in atmosphere in rare amounts (rare gases) </li></ul><ul><li>He is used to fill balloons; Ne and He are mixed w/ oxygen to fo rm an artificial atmosphere ( deep sea divers) </li></ul><ul><li>Used in neon signs </li></ul><ul><li>Ar,Kr,Xe used in flashbulbs </li></ul>

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