481. Which one of the following has the highest fuel value?
1. Hydrogen
2. Charcoal
3. Natural gas
4. Gasoline
Option “1” is correct. The heating value of a fuel is the amount of heat that is obtained after one gram (1gm) of fuel is burnt completely in air or oxygen. Hydrogen has the highest heating value among all fuels. Hydrogen is used as a rocket fuel and in burner producing high temperature.
482. The main component of Liquid Petroleum Gas (LPG) are :
1. Methane, Ethane and Hexane
2. Methane, Pentane and Hexane
3. Propane and Butane
4. Methane, Carbon Monoxide and Hydrogen
Option “3” is correct. LPG is the abbreviation or short form Liquefied Petroleum Gas. Like all fossil fuels, it is a non-renewable source of energy. It is extracted from crude oil and natural gas. The normal components of LPG thus are propane and butane
483. Which of the following is mainly used for the production of Aluminium?
1. Hematite
2. Lignite
3. Bauxite
4. Magnetite
Option “3” is correct. Bauxite is an ore of Aluminum, which is found in the form of Hydrated Aluminium Oxides.
484. Solder used in soldering metal pieces consists of any alloy of:
1. Tin and Zinc
2. Tin and Lead
3. Tin, Zinc and Copper
4. Tin, Lead and Zinc
Option “2” is correct. The common composition of solder is 32% Tin, 68% Lead. This combination has a low melting point and is useful for soldering components that are sensitive to heat.
485. Which of the following do not consist carbon?
1. Diamond
2. Graphite
3. Coal
4. None of these
Option “4” is correct. Diamond is an additional form of Carbon. Its relative density is 3.5 Graphite is a slaty-black coloured smooth and brightly organic matter of relative density 2.25, while coal is a solid organic matter used as fuel. All the three are consist of carbon.
486. Which one of the following fuels causes minimum air pollution?
1. Kerosene oil
2. Hydrogen
3. Coal
4. Diesel
Option “2” is correct. Hydrogen is the purest combustion fuel. Water is generated from burning of Hydrogen. While coal, kerosene oil and diesel are known as fossil fuel which generates, Carbon dioxide and many other harmful gases when it burns.
487. Which gas is used in the purification of drinking water?
Option “2” is correct. Chlorine is presently an important chemical for water purification (such as in water treatment plants), disinfectants and in bleach.
488. In a car battery, electrolyte substance used is-
Option “2” is correct. Electrolyte substance used in a car battery is Sulphuric acid . It is a strong acid.
489. The energy, found in dry cell is-
1. Mechanic
2. Electric
3. Chemical
4. Electromagnetic
Option “3” is correct. The best example of changing into electric energy from chemical energy is primary cells or batteries, the dry cell is also made up in this phenomenon.
490. A pungent smell often present near the urinals is due to-
and butane 
. It is a strong acid.