Carbon Dioxide

• Van Helmont in 1630 discovered that when charcoal was burnt in air it formed carbon dioxide

  Joseph Black in 1775 prepared carbon dioxide by heating calcium carbonate

  Lavoisier in 1783 formulated its basic structure and found it to be an oxide of carbon
• Carbon dioxide is added to the atmosphere by natural water since it is fairly soluble and dissolved in water
• In combined state carbon dioxide exists as metallic carbonates and bicarbonates in the earth's crust
• Magnesite -MgCO3

  Dolomite - MgCO3.CaCO3
• Carbon dioxide consists of 0.03% of the atmosphere
• Carbon dioxide can be prepared by the action of dilute mineral acids on carbonates and bicarbonates
• Calcium hydrogen carbonate (calcite) Ca(HCO3)2
• CARBONATE / BICARBONATE + ACID (DIL) => SALT + CARBON DIOXIDE + WATER
• A flat bottom flask is taken for the laboratory preparation of carbon dioxide
• Reactants for the laboratory preparation of hydrogen are

  1. Marble chips - CaCO3
  2. Dilute HCl
• pure dry carbon dioxide is collected by the upward displacement of air
• To purify the evolved carbon dioxide, it should be passed through

  1. KHCO3 solution to absorb the residual HCl acid vapors
  2. Conc. H2SO4 to absorb moisture
• Why is carbon dioxide collected by the upward displacement of air?

  It is collected by the upward displacement of air because carbon dioxide is about 1.5 times heavier than air and it is not collected over water since it is slightly soluble in water
• Dilute sulphuric acid is not used instead of dilute hydrochloric acid because it reacts with calcium carbonate forming a coating of insoluble calcium sulphate on the marble chips because of which the reaction slowly comes to a stop
• Vapour density of air is 14.4
• Vapour density of carbon dioxide is 22
• Carbon dioxide is about 1.5 times heavier than air
• Carbon dioxide can be easily liquified at 70 atmospheric pressure
• Carbon dioxide solidifies on cooling at -78*C to form a white solid commonly called dry ice
• Carbon Dioxide can be prepared by taking carbon dioxide at high atmospheric pressure and then allowing it to expand through a small nozzle. Carbon Dioxide solidifies forming dry ice
• Carbon dioxide is slightly acidic in nature as it turns blue litmus paper into pink
• Carbon dioxide has a slightly sour taste
• carbonic acid - weak acid
• urea - important nitrogenous fertilizer
• highly poisonous gas - carbon
• CaSO4 is insoluble
• Carbon dioxide reacts with

  1. Water
  2. Magnesium - metal
  3. Ammonia
  4. Basic oxides
  5. Lime water
  6. Carbon - non metal
• Calcium bicarbonate is insoluble in water
• Calcium bicarbonate - Ca(HCO3)2
• Limewater is the solution of calcium hydroxide
• Baking soda is sodium bicarbonate
• Carbon dioxide reacts with ammonia gas at elevated temperatures to form urea
• Carbon dioxide when passed through over heated coke gets reduced to carbon monoxide
• Burning magnesium burns in carbon dioxide producing magnesium oxide and carbon Magnesium oxide and carbon
• When carbon dioxide is bubbled through lime water, it turns milky white due to formation of insoluble calcium carbonate.
• Why do soft drinks produce a fizz when opened?

  Carbon dioxide gives a fizz to the effervescent drink, since on opening the bottle it escapes out due to fall in pressure
• Liquid carbon dioxide on sudden evaporation freezes and forms solid carbon dioxide
• Dry ice freezes faster and lasts longer than ordinary ice
• Baking powder contains:-

  1. Baking soda(NaHCO3)
  2. Potassium hydrogen tartrate
  3. Starch
• Food is manufactured by plants in the form of carbohydrates i.e glucose