Hydrogen

• Hydrogen is prepared by the reaction between a metal ( magnesium or zinc) with dilute acid. Hydrogen gas can be collected over water and in upward delivery


  mg (s) + 2HCL (aq) --> MGCL (aq) + H2 (g)

  2n (s) + h2SO4 (aq) --ZNSO4 (aq) + H2 (g)
• Hydrogen can be prepared in industry by the electrolysis of brine. brine is a concentrated solution of sodium chloride (nacl). On preforming electrolysis on brine, hydrogen is evolved around the cathode (the negative electrode) 


  2H+ + 2E- --> H2 H+ is the ion of hydrogen
• Hydrogen can be prepared in industry by hydrocarbons steam reforming process. Methane (ch4) is reacted with steam at 800 degrees and 30 atmospheric pressure using nickle as a catylist. 


  CH4 (g) + H2O (l) ---> CO (g) 4H2 (g)
• To remove carbon monoxide pass both gasses with more steam at 450 degrees using iron (III) oxide as a catylist


  CO (g) + H2 (g) + H2O (g) -->.4H2 (g) + CO2 (g)
• lastly, pass both gasses through lime water to remove carbon dioxide gas
• Hydrogen can be identified by placing a lighted wooden splint into a gas jar of hydrogen and it will burn with a pop
• Hydrogen can be used in the manufacture of ammonia. Harber process. Ammonia will be used to produce explosives and fertilizers

  N2 (g) + 3H2 (g) <--> 2NH3 (g) 


  Hydrogen can be used in the hardening of oils to make margarine, hydrogen is added to unsaturated fats (oils) to solidify them. This process is called hydrogention
• Hydrogen can be used to produce hydrochloric acid

  H2 (g) + CL2 (g) --> 2HCL (aq) 


  Hydrogen can be used to fill up balloons
• Pure water contains only free molecules. That is, it does not contain amy dissolved solutes example


  distilled water
• When solutes are added to water, water molecules are no longer free. the water molecules surround the solute
• To form temporary hardness carbon dioxide reacts with water to produce carbon acid 


  CO2 (g) + H2O (l) <--> H2CO3 (aq)
• The PH of rain water is 6. When rain water touches the ground (limestone) temporary hardness is produced. Limestone contains Calcium carbonate (caco3) and magnesium carbonate (mgco3)


  H2CO3 (aq) + CACO3 (s) --> CA(HCO3)2 (aq)

  H2CO3 (aq) + MGCO3 (s) --> MH(HCO3)2 (aq)
• To form permanent hardness the rain water passes through the different rock strata dissolving solutes. The solutes present are magnesium sulfate and calcium sulfate (mgso4) (caso4)


  Hardness of water is a problem when washing with soap because soap does not lather easily with hard water
• Soap is produced by mixing animal fat of a blunt oil with sodium hydroxide 


  fat/oil + NaOH --> soap + glycerol
• soap is made up from two types of molecules : Hydrophobic part (hates water loves dirt) and Hydrophilic part (loves water hates dirt) 


  Example: Sodium stearate

  C17H35COO-NA+ zig zag -> Hydrophobic circle -> Hydrophilic
• when cleaning with soap, soap is rubbed on the dirt molecule. The hydrophobic part of the soap molecule will enter the dirt molecule. On agitation, the dirt molecule is broken down into smaller pieces.

  On rinsing the hydrophilic part of the soap molecule will move with water dragging with it the dirt molecule. therefore the cloth is cleaned.

  NOTE: the above occurs when washing with soft water
• Temporary hardness:

  Both calcium hydrogen carbonate and magnesium hydrogen carbonate react with soap to produce scum 


  CA(hco3)2 (aq) + 2NAST (aq) --> CAST2 (s) + 2NAHCO3 (aq)

  calcium hydrogen carbonate scum (calcium stearate)

  MG(HCO3)2 (aq) + 2NAST (aq) --> MGST2 (s) +2NAHCO3 (aq)

  Magnesium hydrogen carbonate magnesium stearate
• Permanent hardness

  Both calcium sulfate and magnesium sulfate react with soap to produce scum.


  CASO4 (aq) + 2NAST (aq) --> CAST2 (s) + NA2SO4 (aq)

  calcium sulfate + soap calcium stearate

  MGSO4 (aq) + 2NAST (aq) --> MGST2 (s) + NA2SO4 (aq)

  mg sulfate soap mg stearate
• Water hardness can be removed by distillation. Distillation removes all types of water hardness. It is not practical because in order to preform distillation a lot of energy is required
• Water hardness can be removed by boiling. Boiling only removes half of water hardness. Only temporary hardness is removes. Permanent hardness remains. Both calcium hydrogen carbonate and magnesium hydrogen carbonate decompose to produce limescale or kettle fur 


  CA(HCO3)2 (aq) --> CACO3 (s) + H2O (l) +CO2 (g)

  MG(HCO3)2 (aq) --> MGCO3 (s) +H2O (l) +CO2 (g)
• Disadvantages of boiling water are that it can block hot water pipes and inefficient heat exchange
• Water hardness can be removed by adding washing soda. Washing soda (sodium carbonate) removes all types of hardness
• Water hardness can be removed by washing soda. For temporary hardness: 


  CA(HCO3)2 (aq) +NA2CO3 (aq) --> CACO3 (s) + 2NAHCO3 (aq)

  MG(HCO3)2 (aq) + NA2CO3 (aq) --> MGCO3 (s) + 2NAHCO3 (aq)
• Water hardness can be removed by washing soda. For permanent hardness:

  CASO4 (aq) +NA2CO3 (aq) --> CACO3 (s) + NA2SO4 (aq)

  MGSO4 (aq) + NA2CO3 (aq) --> MGCO3 (s) +NA2SO4 (aq)
• NOTE: sodium carbonate dehydrate (Na2Co3 . 10H2O) On its own losses water of crystallisation to form anhydrous sodium carbonate (Na2Co3) This process is called efflorescne 


  Na2Co3 . 10H2O --> Na2Co3 + 10H2O
• An efflorescent substance is a substance that looses water of crystallisation
• An advantage of hardness of water is that it is a good source calcium for bones and teeth
• Detergents are a family of components which are similar in chemical structure to soap. Detergents are made up from petromin (product of crude oil). Detergents have a longer hydrophobic tail then soap.


  The hydrophilic head is made up from a sulfonyl group (-So3H). Detergents are not affected by any hardness of water
• After the detergent is used, it is flushed into the sewage systems when detergents are present in the environment they do not decompose. As a result, it causes environmental harm
• Osmosis is the movement of free water molecules from a region of high concentration to a region of low concentration across a semi-permable membrane
• Reverse osmosis is the exact opposite of osmosis , that is free will move from a low to high concentration across a semi-permable membrane with the application of high pressure (132KP)
• Malta obtains its water by its 4 reverse osmosis plants which are found in Ghar Lapsi L.O SIggiewi, Pembroke, Cirkewwa and Hondoq