CARBON DIOXIDE

Carbon dioxide is a colourless, odourless gas with a weakly acid taste, due to the formation of some carbonic acid when it is dissolved in water. It appears to be about 50% heavier than air. It is easily soluble in water, one liter of water at 0°C dissolving 1,713 ml of gas under 1 atm pressure.

When crystalline carbon dioxide is heated from a very low temperature its vapour pressure reaches 1 atm at 79° at which temperature it vaporizes without melting. If pressure were in­creased to 2,5 atm the crystalline substance could be changed directly to a gas.

Carbon dioxide is known to combine with water to form carbo­nic acid H2CO3, it being a weak acid.

If you studied all the properties more thoroughly you would see that carbon dioxide is used for the manufacture of sodium carbonate, sodium hydrogen carbonate, and carbonated water and for many other uses.

From this short review it’s clear that chemistry of carbon and its compounds is a very important field of chemistry and should be studied carefully.

Words to be remembered:

colourless to vaporize

odourless to increase

acid to combine

taste weak

due to sodium

to dissolve review

soluable carefully

№18

FUEL

Carbon and hydrogen are the principal constituents of the solid fuels coal and wood. Coal has been formed in nature by the slow decomposition of vegetable matter, in the presence of water and absence of air. Most of it was formed during the Carboniferous Period of geologic time, about 250 million years ago. Coal consists of free carbon mixed with various carbon compounds and some mineral matter. Anthracite coal (hard coal) contains much volatile matter, and burns with a smoky flame.

Bituminous coal can be converted into coke by heating without access of air. When the heating is carried out in a by-product coke oven, many substances distill out, including gas for fuel, ammonia and a complex mixture of liquid and solid organic com­pounds. The solid material remaining in the ovens, consisting mainly of carbon, is called coke. It burns with a nearly colorless flame, and is used in great amounts in metallurgical processes.

Petroleum is a very important liquid fuel. It is a complex mixture of compounds of carbon and hydrogen.

The gas obtained from a coke furnace (coal gas) consists of hydrogen (about 50%), methane CH4 (30%), carbon monoxide (10%) and minor components. This coal gas was the original illuminat­ing gas.

Natural gas, from gas wells and all wells, consists largely of methane.

Words to be remembered:

hydrogen mixture

principal petroleum

decomposition furnace

vegetable to consist

presence to remain

absence gas well

volatile oil well

access compound

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Date: 2015-01-12; view: 2652