Laboratory preparation, properties and uses of carbon monoxides

Carbon monoxide was first prepared in the laboratory in 1776 by J.M.F. de Lassone, a French chemist. As carbon monoxide is extremely poisonous, its preparation should be carried out only in a fume chamber. Under no circumstances must the gas be inhaled or smelled.

Preparation of carbon monoxide by dehydrating oxalic acid with hot concentrated sulphuric acid

Experiment 1

Carbon monoxide is prepared with the help of oxalic acid and concentrated sulphuric acid as shown in figure 11.2.

Oxalic acid has the formula . Sulphuric acid reacts with oxalic acid and removes from it one molecule of water (both the hydrogen atoms, along with an oxygen atom). The product left behind due to this reaction, is a molecule of carbon dioxide and a molecule of carbon monoxide. The carbon dioxide can be removed by passing it through a concentrated solution of potassium hydroxide.

Preparation of carbon monoxide by dehydrating formic acid

Experiment 2

Formic acid has the formula HCOOH. Formic acid can also be dehydrated in a similar way by hot concentrated sulphuric acid. Sulphuric acid removes two atoms of hydrogen and one atom of oxygen as a molecule of water from it, and leaves behind one molecule of carbon monoxide (Fig.11.3).

Physical properties of carbon monoxide

a) Nature

Carbon monoxide is colorless, almost odorless and tasteless gas.

b) Density

It is very slightly lighter than air.

Vapor Density=14 [Vapor density of air =14.4].

c) Solubility

Carbon monoxide is only very slightly soluble in water.100 volumes of water can dissolve only 3.5 volumes of the gas at S.T.P

d) Poisonous nature

This is a highly poisonous gas. Air containing even less than 1% of carbon monoxide, can be fatal, if breathed in for about 10 to 15 minutes.

Chemical properties of carbon monoxide

a) Nature

Carbon monoxide is a neutral oxide. It is neither acidic nor basic.

b) Stability

It is very stable and cannot be decomposed by heat.

c) Combustibility

It is a combustible gas. It burns well in air or oxygen to form carbon dioxide. The formation of carbon dioxide is tested by passing it through a solution of lime water. (Fig.11.4).

This is a highly exothermic reaction. Hence it is a very good fuel.

However, it is not a supporter of combustion,

d)

Combination with chlorine

Carbon monoxide combines with chlorine in presence of sunlight and charcoal as catalyst, to form carbonyl chloride, commonly called as phosgene.

e) Combination with sodium hydroxide

Carbon monoxide when heated under a pressure of six atmosphere, combines with sodium hydroxide and flakes to form sodium formate.

f) Reducing property

Carbon monoxide is a powerful reducing agent.

Experiment 3

When CO is passed over heated metallic oxides, it takes away the oxygen to form carbon dioxide and reduces the oxides to their respective metals (Fig.11.5).

g) As a synthetic reagent

Carbon monoxide acts as the staring material for the synthesis of many important organic substances. For e.g., the synthesis of methyl alcohol, or methanol, (CH₃OH) takes place by the reaction of carbon monoxide and hydrogen.

h) Combination with metals

When carbon monoxide is passed over heated metals under pressure, metal carbonyls are formed.

i) Combination with cuprous chloride

Carbon monoxide is absorbed by ammonical cuprous chloride to form an addition compound.

Uses of carbonmonoxide

1. Carbon monoxide is used as a fuel by itself, or in the form of producer gas (mixture of carbon monoxide and nitrogen), or water gas (mixture of carbon monoxide and hydrogen). It is also present in fuel gases like coal gas.

2. It is used as a reducing agent in the extraction of metals. Carbon monoxide reduces the metal oxides to metals. Usually coke is used to generate this gas. In this process coke combines with oxygen to form carbon dioxide, which gets reduced to carbon monoxide due to the lack of oxygen.

3. Carbon monoxide is used in the manufacture of methyl alcohol, sodium formate, phosgene, etc.