Question

An element of group 14 forms two oxides one of which is highly poisonous and neutral. Other oxide can be easily liquefied and compressed to give a solid which is used as a refrigerant under the name of drikold. The element and the oxides are (a) \(\mathrm{Si}, \mathrm{SiO}, \mathrm{SiO}_{2}\) (b) \(\mathrm{Pb}, \mathrm{PbO}, \mathrm{PbO}_{2}\) (c) \(\mathrm{C}, \mathrm{CO}, \mathrm{CO}_{2}\) (d) \(\mathrm{Sn}, \mathrm{SnO}, \mathrm{SnO}_{2}\)

Short answer

The element is Carbon (C) with the two oxides being Carbon Monoxide (CO) and Carbon Dioxide (CO2), corresponding to option (c).

Step-by-step solution

Identify the Poisonous Oxide

The highly poisonous and neutral oxide is carbon monoxide (CO). It is well-known for its toxicity. This helps in identifying the element as Carbon (C), which is a member of group 14.

Identify the Oxide Used as a Refrigerant

The oxide that can be liquefied and compressed into a solid refrigerant known as 'drikold' is carbon dioxide (CO2). When CO2 is compressed, it can be transformed into a solid state known as 'dry ice,' which is used as a refrigerant.

Confirm the Element and its Oxides

With both oxides identified as CO and CO2, the element that forms these oxides is Carbon (C). This confirms that the correct answer is option (c): C, CO, CO2.

Key concepts

Carbon Monoxide

Carbon monoxide (CO) is a colorless, odorless, and tasteless gas that is highly toxic to humans and animals when encountered in higher concentrations. It is formed by the incomplete combustion of carbon-containing materials when there is insufficient oxygen to produce carbon dioxide (CO₂).

CO binds with hemoglobin in the blood, reducing its oxygen-carrying capacity and leading to oxygen deprivation of the body's organs and tissues. This condition, known as carbon monoxide poisoning, can be fatal if not immediately addressed. Students should take great care to understand the properties of CO, its implications for health and safety, and the reaction conditions under which it is formed.

One helpful way to remember CO is to associate it with its sources, such as car exhausts, and its silent, but deadly nature due to its lack of color and scent, which reinforces the importance of carbon monoxide detectors in homes.

Carbon Dioxide

Carbon dioxide (CO₂) is a naturally occurring gas and a vital component of the Earth's atmosphere. It is colorless, has a slightly sharp odor, and is about 1.5 times heavier than air. Plants utilize CO₂ for photosynthesis, making it essential for life on Earth. However, its concentration in the atmosphere plays a significant role in the greenhouse effect and global climate change.

In pure form, carbon dioxide can be compressed and cooled to produce 'dry ice,' solid CO₂, used as a refrigerant due to its cooling properties and because it sublimates—transitioning directly from a solid to a gas without a liquid phase—thus leaving no liquid residue behind. This characteristic makes it ideal for transporting perishables and for use in processes where moisture can pose a problem. When studying CO₂, students should also explore its role in carbonation of beverages, as a fire extinguisher, and understand its implication in climate-related discussions.

Refrigerant Properties

A refrigerant is a substance used in heat pumps and refrigeration cycles to absorb and release heat in order to cool an area or substance. Refrigerants are chosen for their favorable thermodynamic properties, non-corrosiveness, and lack of toxicity or flammability. They can exist as liquids or gases, depending on pressure and temperature.

Carbon dioxide, as mentioned, when in its solid form as dry ice, has refrigerant properties. It is advantageous as a refrigerant because it is non-toxic, non-flammable, and environmentally friendly since it does not deplete the ozone layer and has a low Global Warming Potential (GWP) compared to other synthetic refrigerants.

In the context of the properties important in refrigerants, students should note that the transition from a gas to a solid or vice versa involves latent heat, which is harnessed in various cooling applications. It's also worth mentioning that new refrigerants continue to be researched and developed to minimize environmental impact while maximizing efficiency.