Carbon Monoxide

Carbon monoxide is formed by the incomplete oxidation of carbon. It is found in petrol fumes.

Preparation

Lab method

1.        Concentrated sulphuric acid is added to oxalic acid and heated. Dehydration occurs, and a mixture of carbon dioxide and carbon monoxide is formed.
Carbon monoxide is collected by the downward placement of water.
H₂C₂O₄ Δ (Conc. H₂SO₄) → H₂O + CO₂ + CO 
Carbon dioxide is absorbed by potassium hydroxide solution.
KOH + CO₂ → KHCO₃

2.         Concentrated sulphuric acid is added to formic acid and heated. Dehydration occurs, and the carbon monoxide formed is collected over water.
H · COOH Δ (Conc. H₂SO₄) → H₂O + CO

Sodium formate can also be used – first formic acid is liberated, then it is dehydrated

H · COONa + H₂SO₄ → NaHSO₄ + H · COOH
H · COOH Δ (Conc. H₂SO₄) → H₂O + CO

These preparations should be carried out in fume cupboards.

Properties

Physical

1. It is a colorless, odorless and tasteless gas.
2. It is slightly soluble in water.
3. It is highly poisonous.
4. Boiling point -192°C
5. Melting point -207°C

Chemical

1. It is a neutral oxide of carbon.
2. It is a stable compound.
3. It does not support combustion, but is combustible.

               2CO + O₂ → 2CO₂ + 135400 cal.

4. It reduces metal oxides at high temperatures.

               PbO + CO → Pb + CO₂

               CuO  + CO → Cu + CO₂

               Fe₂O₃ + 3CO → 2Fe + 3CO₂

5. It combines with chlorine in sunlight and in the presence of charcoal.

               CO + Cl₂ → COCl₂ carbonylchloride (phosgene)

6. At 200°C and 6-10 atmos. it combines with sodium hydroxide.

               NaOH + CO → H · COONa

7. It forms an addition product with copper (I) chloride in HCl or ammonia solution.

               CuCl + CO + 2H₂O → CuCl · CO · 2H₂O

8.  
1. With hydrogen, at 300°C, and over nickel, it forms methane.

  300°C, Ni

                                 CO + 3H₂ →  CH₄ + H₂O

2. With hydrogen, at 400°C, and zinc and chromium oxides it forms methyl alcohol.

                              CO + 2H₂ →  CH₃OH

Uses

1. As a fuel – producer of water gas
2. To manufacture phosgene, sodium formate, and methyl alcohol

Efflorescent, Deliquescent, and Hygroscopic Substances

1.      In efflorescence, the vapor pressure of the hydrated salt is greater than the vapor pressure of water vapor in the atmosphere. The salt tries to equalize pressure but, in view of the size of the atmosphere, this can never be achieved, and so it passed to a lower hydrate or the anhydrous salt, with a lower vapor pressure.

Na₂CO₃ · 10H₂O → Na₂CO₃ · H₂O + 9H₂O

2.      In deliquescence, the vapor of the salt hydrate (and its saturated solution) is less than the vapor pressure of water vapor in the atmosphere. The salt tries to equalize pressures by absorbing water from the atmosphere, forming eventually an unsaturated solution.

MgCl₂, 6 H₂O, P₂O₅, NaOH

It should be remembered that the water vapor present in the atmosphere is not constant, varying from day to day and especially from summer to winter. Hence, there is a possibility that certain compounds may be either efflorescent or deliquescent depending on the season or the locality.
Ordinary common salt is not deliquescent but because of MgCl₂ which is an impurity, it dissolves and forms a solution in rainy reason and becomes deliquescent.

Calcium chloride is sprinkled on the road to remove dust as it absorbs moisture and forms a saturated solution by dissolving in it. It is used as a dehydrating agent. The term deliquescent is used for solids only.

3.      A hygroscopic substance (e.g. conc. H₂SO₄, CuO) absorbs water from the atmosphere without forming a solution.
Human hair is hygroscopic.
H₂SO₄ is not deliquescent but it is hygroscopic and used as a dehydrating agent.

Drying Apparatus

To Dry	Drying Agent	Apparatus
Gas	·            Conc. H2SO4 ·        P2O5 ·        CaCl2	Woulfe’s bottle
Gas	·        P2O5 ·            CaCl2 ·        CaO	Drying Tower
Gas	·        (Salt and ice) Freezing mixture	U tube
Liquid	·        Conc. H2SO4	Bottle
Solid	·        Silica gel ·        CaO ·        Anhydrous CaCl2	Dessicator
Solid	·        Conc. H2SO4	Bottle

Crystals

A solid bounded by plain surfaces having definite geometrical shapes. In nature, crystals are found as minerals, for example, ruby, diamond, graphite, etc. These crystals have beautiful color due to impurities or traces of water present in them.

Making Crystals

_1.           Dissolving a solid in water or any other solvent and then evaporating the liquid. For example, salt, nitre, alum in water. Sulfur in carbon disulphide or carbon tetrachloride CCl₄, iodine in petrol or benzene or spirit.

_2.           By melting a solid and allowing it to cool properly. For example, prismatic sulfur.

_3.           By sublimation. For example, iodine and ammonium crystals.

_4.           By subjecting a solid to great heat and pressure. For example, diamond and graphite. The cost is prohibitive as artificial diamond is more costly than natural diamond.

Water of Crystallization

Some solids while crystallizing out from solution unite with a definite quantity of H₂O known as water of crystallization/ hydration. This water of crystallization can be driven out by heating the crystal to 100°C, and may be condensed and tested. Such crystals lose their crystalline structure and become anhydrous.

Water of crystallization is the number of molecules of water combined it a loose chemical combination which on heating on exposure to air is partly on fully given off by a hydrated salt.

Hydrated Salts

A hydrated salt is a substance which contains water of crystallization which on exposure to air or heat becomes anhydrous by giving off partly or fully its water of crystallization.

Hydrated Salt	Chemical Formula	Common Name
sodium carbonate	Na2CO3 · 10H2O	washing soda
sodium sulphate	Na2SO4 · 10H2O	Glauber’s salt
copper sulphate	CuSO4 · 5H2O	blue vitriol
ferrous sulphate	FeSO4 · 7H2O	green vitriol
zinc sulphate	ZnSO4 · 7H2O	white vitriol (H2SO4 is called oil of vitriol)
cobalt chloride	CoCl2 · 6H2O
barium chloride	BaCl2 · 2H2O
calcium chloride	CaCl2 · 6H2O
magnesium sulphate	MgSO4 · 7H2O	Epsom salt

Crystals without Water of Crystallization – Anhydrous

Anhydrous Salt	Chemical Formula
sodium chloride (common salt)	NaCl
nitre	KNO3
potassium chromate	K2C5O7
potassium chloride	KCl