Hydrogen

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Boiling point
20K
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Melting point
14K
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Density
0.08g dm-3
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H-H bond length
0.74 angstrums
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Bond energy
436kJ mol-1 (generally unreactive at RT)
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Electronegativity
2.2
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Synthesis of H2
Steam reforming (notes for eqtns) produces most of 40 mill. tonnes p.a.
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Uses of H2
Haber Bosch (produce ammonia). Conversion of syn-gas to methanol. Also hydrogenation of alkenes and reduction of metals
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Group 1 hydrides
React rapidly with H2O. 2MH+H2O -> 2MOH+H2. Laregly ionic, colourless. LiH = largest covalent character
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Group 2 hydrides
Largely ionic, colourless. MgH2 largely covalent character. BeH2 different - covalent polymeric (3c-2e). React with H20 but BeH2 relatively stable.
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Diborane
Made from BF3 and NaH. Gas. Flammable in air -> B(OH)3. 3c-2e bonds. Strong lewis acid
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Group 14 hydrides
Many CnHm. Si, Ge, Sn = gasses + decompose on heating. Combust to EO2 + H2O. Formed from ECl4 + LiAlH4. Act as H+ source with strong base
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Group 15 hydrides
Gas. Free e- pair = lewis bases. Also H+ source for strong bases. Both for ammonia- 2NH3 ->NH4+ + NH2-. Made same way as 14 (except ammonia)
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Group 16 hydrides
toxic gas (except h2o). Lewis bases. Lewis acids in h2o.
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H2O2
Strong oxident. 2 mill. tonnes produced p.a. Bleaching, anti-septics. Thermodynamically unstable.
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Group 17 hydrides
gas. acidic.
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What are guest molecules in the holes of ice called?
Clathrate hydrates
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Card 2

Front

14K

Back

Melting point

Card 3

Front

0.08g dm-3

Back

Preview of the back of card 3

Card 4

Front

0.74 angstrums

Back

Preview of the back of card 4

Card 5

Front

436kJ mol-1 (generally unreactive at RT)

Back

Preview of the back of card 5
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