Carbon

Question 1

Preparation of Carbon Dioxide

Answer 1

Typically prepared by reacting calcium carbonate with HCl acid. Gas collected by water or air displacement.
Test for carbon dioxide: pass through limewater (calcium hydroxide). If CO2 is present then the limewater will turn cloudy with calcium carbonate (CaCO3). Adding more CO2 will eliminate the cloudiness because the insoluble CaCO3 becomes soluble calcium bicarbonate (Ca(HCO3)2)

Question 2

Important Uses for Carbon Dioxide

Answer 2

Is the acid anhydride of carbonic acid, so CO2+H2O->H2CO3 (soft drinks)
Dry ice used as a refrigerant because it sublimes instead of melting into a liquid. (Absorbs 3x heat per gram as ice)
Fire extinguishers use carbon dioxide because it is heavier than air and does not support combustion
Plants use CO2 in photosynthesis. Chlorophyll (catalyst) and sunlight (energy source) must be present. 6CO2+6H2O->C6H12O6 (cellulose) + 6O2

Question 3

Allotropes of Carbon

Answer 3

Diamond: Close-packed crystal structure give it extreme hardness. Bonded to four other carbons in tetrahedral arrangement. Melts at 3550°C.
Fullerenes: found in soot formed when carbon materials burned with limited oxygen. Near spherical cages of carbon atoms.
Graphite: planes of hexagonal structures weakly bonded to the planes above and below. Slippery and useful as dry lubricant. Conducts electricity.
Amorphous: includes charcoal, coke, bone black, lampblack.