Question Discussion & Solution

The correct answer is Butane.

Key Points 

• Liquefied Petroleum Gas (LPG) is a blend of light hydrocarbon compounds.
  • It mainly consists of butane or propane or a mixture of both.
  • At room temperature, both gases are colourless and odourless.
  • It is a mixture of 48% propane, 50% butane, and 2% pentane.

Additional Information

• Water Gas:
  • Water-gas is a mixture of CO and H₂.
  • However, by-products such as char, tar, soot, ash, and condensates are also produced. 
• Natural gas is a naturally occurring hydrocarbon gas mixture consisting primarily of methane, but commonly including varying amounts of other higher alkanes, and sometimes a small percentage of carbon dioxide, nitrogen, hydrogen sulfide, or helium.
• Compressed natural gas is a fuel that can be used in place of petrol (gasoline), diesel fuel, and liquefied petroleum gas (LPG).
  • CNG combustion produces fewer undesirable gases than the aforementioned fuels.
  • In comparison to other fuels, natural gas poses less of a threat in the event of a spill, because it is lighter than air and disperses quickly when released.

The correct answer is Methane.

Key Points

• Methane (CH4)
  • It is the simplest hydrocarbon consisting of one carbon atom and four hydrogen atoms and the simplest hydrocarbon, is the most abundant hydrocarbon pollutant.
  • It is a powerful greenhouse gas.
  • Major natural sources of methane include emissions from wetlands, and oceans and from the digestive processes of termites.
  • Methane is more than 25 times as potent as carbon dioxide at trapping heat in the atmosphere.

Additional Information

• Butane is a gaseous component (at room temperature and atmospheric pressure) of the Alkane group having the chemical formula is C4H10.
• It is a colourless, highly flammable, and easily liquefied gas.
• In the abundance of oxygen, it forms Carbon dioxide, but if limited oxygen is available, then it forms Carbon Monoxide.

2C4H10 + 13O2 → 8CO2 + 10H2O                   (oxygen in plenty)

2C4H10 + 9O2 → 8CO + 10H2O                      (oxygen is limited)

• Uses –
  • Gasoline blending
  • Fuel gas
  • Fragrance extraction solvent
  • Feedstock for the manufacture of ethylene and butadiene
  • Ingredient for synthetic rubber
  • Isobutane to enhance the Octane number of gasoline in refineries.
• A propane molecule has three carbon atoms and eight hydrogen bonds and has the formula C3H8. 
• Propane is a colourless, easily liquefied, gaseous hydrocarbon (compound of carbon and hydrogen) and the third member of the paraffin series following methane and ethane.
• Propane is produced as a by-product of two other processes, natural gas processing and petroleum refining.
• It is separated in large quantities from natural gas, light crude oil, and oil-refinery gases and is commercially available as liquefied propane or as a major constituent of liquefied petroleum gas (LPG).
• Uses: 
  • It is used in LPG, also used as biofuel in buses and taxis and it is also the main gas in blowtorches and for hot air balloons.
  • Propane gas has become a popular choice for barbecues and portable stoves because its low boiling point makes it vaporize as soon as it is released from its pressurized container.
• The chemical formula of Ethane is C2H6.
• It is a colourless, odourless gas at normal temperature and pressure.
• It is extracted from natural gas on an industrial scale and is a petrochemical by-product of petroleum refining.
• Michael Faraday first synthesized it in 1834, using the electrolysis of a solution of potassium acetate.

The correct answer is Lactometer.

• Some other important measuring instruments are:

CONCEPT:

• Plane mirror: This mirror is straight without any inward or outward curve.
  • It forms a virtual image and upright image which is of size as same as the object.
  • The bathroom mirrors are an example.
• Concave mirror: The mirrors curved inside on the reflecting side are called concave mirrors.
  • These mirrors produce a real, inverted, and magnified image of the object.
  • These are used in reflecting telescopes, shaving mirrors, and ophthalmoscope.

• Convex mirror: It is an outward curved mirror that produces a diminished image.
  • Convex mirrors either diverge a parallel beam of light into all directions or gather light from all directions and produce a parallel beam out of it.

EXPLANATION:

• Following are the reasons as to why a convex mirror is used as a rearview mirror in the vehicle

• The image formed by the convex mirror is virtual and erect in contrast to that of the real but inverted image of the concave mirror.
• It gathers light from all directions and aligns it as a parallel beam so that it provides a wider view to the viewer. That's why the convex mirror is used as a rear-view mirror in vehicles. So option 2 is correct.

The correct answer is option 2 i.e C₄H_10.

Concept:

Hydrocarbons

• Compounds made of carbon and hydrogen atoms only are called hydrocarbons.
• Saturated hydrocarbons:
  • The hydrocarbons in which carbon atoms are singly bonded are called saturated hydrocarbons.
  • Saturated hydrocarbons are also called alkanes or paraffin.
    • The general formula of alkane– CnH2n+2.
• Unsaturated hydrocarbons:
  • The hydrocarbons in which carbon atoms are either doubly or triply bonded are called unsaturated hydrocarbons.
  • Doubly bonded (carbon atoms) hydrocarbons are called alkenes.
  • The general formula of alkene is CnH2n.

• The formula for alkane should be mentioned C_nH_2n+2

Explanation: