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Carbon monoxide and carbon dioxide MCQ - Practice Questions with Answers

Edited By admin | Updated on Sep 25, 2023 25:24 PM | #NEET

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Compounds of Carbon(CO)

Direct oxidation of C in limited supply of oxygen or air yields carbon monoxide.

$2 \mathrm{C}(\mathrm{s})+\mathrm{O}_{2}(\mathrm{g}) \stackrel{\Delta}{\longrightarrow} 2 \mathrm{CO}(\mathrm{g})$

On small scale pure CO is prepared by dehydration of formic acid with concentrated H₂SO₄ at 373 K.

$\mathrm{HCOOH}\: \xrightarrow[\mathrm{conc.}\: \mathrm{H_{2}SO_{4}}]{373\: \mathrm{K}}\mathrm{H}_{2} \mathrm{O}+\mathrm{CO}$

On commercial scale, it is prepared by the passage of steam over hot coke. The mixture of CO and H₂ thus produced is known as water gas or synthesis gas.

$\mathrm{C}(\mathrm{s})+\mathrm{H}_{2} \mathrm{O}(\mathrm{g}) \overset{473-1273 \mathrm{K}}{\longrightarrow}\mathrm{CO}(\mathrm{g})+\mathrm{H}_{2}(\mathrm{g})$

When air is used instead of steam, a mixture of CO and N₂ is produced, which is called producer gas.

$2 \mathrm{C}(\mathrm{s})+\mathrm{O}_{2}(\mathrm{g})+4 \mathrm{N}_{2}(\mathrm{g}) \stackrel{1273 \mathrm{K}}{\longrightarrow} 2 \mathrm{CO}(\mathrm{g})\: +\: \mathrm{4N_{2}(g)}$

Water-gas and producer gas are very important industrial fuels. Carbon monoxide in water gas or producer gas can undergo further combustion forming carbon dioxide with the liberation of heat. Carbon monoxide is a colourless, odourless and almost water insoluble gas. It is a powerful reducing agent and reduces almost all metal oxides other than those of the alkali and alkaline earth metals, aluminium and a few transition metals. This property of CO is used in the extraction of many metals from their oxides ores.

$\begin{array}{l}{\mathrm{Fe}_{2} \mathrm{O}_{3}(\mathrm{s})+3 \mathrm{CO}(\mathrm{g}) \stackrel{\Delta}{\longrightarrow} 2 \mathrm{Fe}(\mathrm{s})+3 \mathrm{CO}_{2}(\mathrm{g})} \\ {\mathrm{ZnO}(\mathrm{s})+\mathrm{CO}(\mathrm{g}) \stackrel{\Delta}{\longrightarrow} \mathrm{Zn}(\mathrm{s})+\mathrm{CO}_{2}(\mathrm{g})}\end{array}$

In CO molecule, there are one sigma and two π bonds between carbon and oxygen, :C ≡ O:. Because of the presence of a lone pair on carbon, CO molecule acts as a donor and reacts with certain metals when heated to form metal carbonyls. The highly poisonous nature of CO arises because of its ability to form a complex with haemoglobin, which is about 300 times more stable than the oxygen-haemoglobin complex. This prevents haemoglobin in the red blood corpuscles from carrying oxygen round the body and ultimately resulting in death.

Compounds of Carbon(CO2)

It is prepared by the complete combustion of carbon and carbon-containing fuels in excess of air.

$\begin{array}{l}{\mathrm{C}(\mathrm{s})+\mathrm{O}_{2}(\mathrm{g}) \stackrel{\Delta}{\longrightarrow} \mathrm{CO}_{2}(\mathrm{g})} \\ {\mathrm{CH}_{4}(\mathrm{g})+2 \mathrm{O}_{2}(\mathrm{g}) \overset{\Delta}{\longrightarrow} \mathrm{CO}_{2}(\mathrm{g})+2 \mathrm{H}_{2} \mathrm{O}(\mathrm{g})}\end{array}$

In the laboratory, it is conveniently prepared by the action of dilute HCl on calcium carbonate.

$\mathrm{CaCO}_{3}(\mathrm{s})+2 \mathrm{HCl}(\mathrm{aq}) \rightarrow \mathrm{CaCl}_{2}(\mathrm{aq})+\mathrm{CO}_{2}(\mathrm{g})\: +\:\mathrm{H_{2}O(l)}$

On commercial scale, it is obtained by heating limestone.
It is a colourless and odourless gas. Its low solubility in water makes it of immense bio-chemical and geo-chemical importance. With water, it forms carbonic acid, H₂CO₃ which is a weak dibasic acid and dissociates in two steps:

$\begin{array}{l}{\mathrm{H}_{2} \mathrm{CO}_{3}(\mathrm{aq})+\mathrm{H}_{2} \mathrm{O(l)} \rightleftharpoons \mathrm{HCO}_{3}^{-}(\mathrm{aq})+\mathrm{H}_{3} \mathrm{O}^{+}(\mathrm{aq})} \\ {\mathrm{HCO}_{3}^{-}(\mathrm{aq})+\mathrm{H}_{2} \mathrm{O(l)} \rightleftharpoons \mathrm{CO}_{3}^{2-}(\mathrm{aq})+\mathrm{H}_{3} \mathrm{O}^{+}(\mathrm{aq})}\end{array}$
H₂CO₃/HCO₃^– buffer system helps to maintain pH of blood between 7.26 to 7.42. Being acidic in nature, it combines with alkalies to form metal carbonates.
Carbon dioxide, which is normally present to the extent of ~ 0.03 % by volume in the atmosphere, is removed from it by the process known as photosynthesis. It is the process by which green plants convert atmospheric CO₂ into carbohydrates such as glucose. By this process, plants make food for themselves as well as for animals and human beings. Unlike CO, it is not poisonous. But the increase in combustion of fossil fuels and decomposition of limestone for cement manufacture in recent years seem to increase the CO₂content of the atmosphere. This may lead to an increase in greenhouse effect and thus, raise the temperature of the atmosphere which might have serious consequences.
Carbon dioxide can be obtained as a solid in the form of dry ice by allowing the liquified CO₂to expand rapidly. Dry ice is used as a refrigerant for ice-cream and frozen food. Gaseous CO₂ is extensively used to carbonate soft drinks. Being heavy and non-supporter of combustion it is used as fire extinguisher. A substantial amount of CO₂ is used to manufacture urea.