Question Discussion & Solution

CONCEPT:

• Electric Power: The rate at which electrical energy is dissipated into other forms of energy is called electrical power i.e.,

\(P = \frac{W}{t} = VI = {I^2}R = \frac{{{V^2}}}{R}\)

Where V = Potential difference, R = Resistance and I = current.

EXPLANATION:

• Mathematically power can be written as,

\(\Rightarrow P = \frac{W}{t} = VI \)

If, W = 1 J and t = 1 sec, then P = 1 watt

• Thus the power of an electric circuit is said to be one watt or 1 ampere - volt if one joule of energy is consumed in one second. Therefore option 1 is correct.

CONCEPT:

• It is the property of liquid by virtue of which the free surface of the liquid at rest acting like a stretched membrane trying to contract to reduce its surface area.
• Surface tension is a force per unit length (or surface energy per unit area) acting in the plane of interface between the liquid and the bounding surface.
• It is the extra energy that the molecules at the interface have as compared to the interior.
• The surface tension is the force acting perpendicular on a unit length of an imaginary line drawn on the surface of the liquid and it can be expressed as

\(\Rightarrow T = \frac{F}{l}\)

• Because of this surface tension, few insects can easily float on liquid surface similarly a needle can be made to float on the surface of liquid using this principle

Here,

T = surface tension,

F = force acting on the surface (Cohesive force)

l = unit length

EXPLANATION:

• As explained above, the surface tension acting on a fluid surface can be expressed as

Surface tension, \(T = \frac{{{\rm{The\;cohesive\;force\;between\;molecule}}}}{{unit\;length}}\) 

• Also, we know that cohesive force or the attractive force between the liquid molecules is inversely proportional to its temperature.
• Since as we increase the temperature of fluid its interatomic distance will keep on increasing hence it will cause a decrease in the surface tension of the fluid.

i.e., \(surface\;tension,\;T \propto \frac{1}{{temperature}}\)

So, only option 3^rd is correct.

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 pattern is,

So, we get:

E = 1,

R = 8,

A = 7,

D = 3

Hence, 3781 is the correct answer.

The Correct Answer is Ctrl + A.

 Key Points

• Ctrl + A Select all contents of the page in Microsoft Word.

 Additional Information

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