Chemistry - Study Mode

[#336] The most pure form of Carbon among the options is
Correct Answer

(A) Anthracite

Explanation

Solution: There are three forms of pure carbon: graphite, coal and diamond. Among coal, Anthracite has the highest carbon content, the fewest impurities, and the highest calorific content of all types of coal except for graphite. Anthracite is the most metamorphosed type of coal in which the carbon content is between 92.1% and 98%.

[#337] Carbon footprint can be reduced by
Correct Answer

(A) All of these

Explanation

Solution: Carbon footprint can be reduced by recycling waste materials, using energy efficient appliances and commuting by public transport.

[#338] Which of the following gases is most toxic ?
Correct Answer

(B) Carbon monoxide

Explanation

Solution: Carbon monoxide (CO) is a colourless, odorless, and tasteless gas that is slightly lighter than air. It is toxic to humans and animals when encountered in higher concentrations, although it is also produced in normal animal metabolism in low quantities, and is thought to have some normal biological functions. In the atmosphere it is spatially variable, short lived, having a role in the formation of ground-level ozone. Carbon monoxide is colourless, odorless, and tasteless, but highly toxic. It combines with hemoglobin to produce carboxyhemoglobin, which is ineffective for delivering oxygen to bodily tissues. Concentrations as low as 667 ppm may cause up to 50% of the body’s hemoglobin to convert to carboxyhemoglobin. A level of 50% carboxyhemoglobin may result in seizure, coma, and fatality.

[#339] Why is water not suitable for putting out a petrol fire ?
Correct Answer

(D) Water, being heavy, slips below petrol which thus remains in contact with air and burns

Explanation

Solution: Water being heavier than petrol slips down permitting the petrol to rise to the surface and continue to burn. Also, the existing temperature is so high that most of the water poured on the fire evaporates even before it can extinguish the fire.

[#340] Which of the following is used as a lubricant in heavy machines?
Correct Answer

(D) Graphite

Explanation

Solution: Graphite is used as a lubricant in heavy machines. it is made of carbon atoms arranged in sheets of hexagonal units - looks a lot like chicken-wire. Another sheet forms on top of this and so on. There is no proper connection (in ideal graphite) between the sheets, so they are able to slide freely over each other without breaking any bonds.