Tag: combustion and thermal cracking of hydrocarbons

Questions Related to combustion and thermal cracking of hydrocarbons

Benzene when heated in air burns with ________ and produces $CO _2$ and $H _2O$.

chemistry chemical reactions of organic compounds combustion and thermal cracking of hydrocarbons chemical properties of carbon compounds chemical properties of organic compounds

  1. sooty flame

  2. non-sooty flame

  3. light color flame

  4. none of these

Show answer
Correct Option: A
Explanation:

Benzene when heated in air burns with sooty flame and produces $\displaystyle CO _2 $ and $\displaystyle H _2O$.
$\displaystyle C _6H _6 + \dfrac {15}{2} O _2 \rightarrow 6CO _2 + 3H _2O$
Note: Incomplete combustion of unsaturated hydrocarbons give sooty flame due to presence of black unburnt carbon particles.

LPG releases  ______ of the $CO _2$ per KWh produced by oil.

chemistry chemical reactions of organic compounds combustion and thermal cracking of hydrocarbons chemical properties of carbon compounds chemical properties of organic compounds

  1. 89%

  2. 81%

  3. 79%

  4. 0%

Show answer
Correct Option: B
Explanation:

LPG releases 81% of the $CO _2$ per Kwh produced by oil.
LPG, at atmospheric pressure, has a higher calorific value 94 MJ/m$^3$ which equivalent to 26.1 kWh/m$^3$.

The unit of calorific value is :

chemistry chemical reactions of organic compounds combustion and thermal cracking of hydrocarbons chemical properties of carbon compounds chemical properties of organic compounds

  1. kJ/kg

  2. kg/kJ

  3. kB/kJ

  4. g/kJ

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Correct Option: A
Explanation:

The unit of calorific value is kJ/kg or J/kg.
Calorific value is the heat produced when unit mass of fuel undergoes complete combustion.

Carbon monoxide is produced by :

chemistry chemical reactions of organic compounds combustion and thermal cracking of hydrocarbons chemical properties of carbon compounds chemical properties of organic compounds

  1. incomplete combustion of fuels

  2. complete combustion of fuels

  3. neutralization of fuels

  4. none of these

Show answer
Correct Option: A
Explanation:

Carbon monoxide is produced by incomplete combustion of fuels.
The complete combustion of fuels will give carbon dioxide.
$\displaystyle C + \dfrac {1}{2}O _2 \rightarrow CO$
$\displaystyle C +  O _2 \rightarrow CO _2$

LPG is liquefied petroleum gas which is a compound of butane and propane and used as :

chemistry chemical reactions of organic compounds combustion and thermal cracking of hydrocarbons chemical properties of carbon compounds chemical properties of organic compounds

  1. cooking fuel

  2. motor fuel

  3. refrigeration

  4. All of these

Show answer
Correct Option: D
Explanation:

LPG is liquefied petroleum gas which is a compound of butane and propane. It is used as cooking fuel (in heating appliances, cooking equipment), motor fuel (in vehicles) and refrigeration.


Hence the correct option is D.

 $C _3H _8 + 5O _2\rightarrow  3CO _2 + H _2O$

Name the type of reaction.

chemistry chemical reactions of organic compounds combustion and thermal cracking of hydrocarbons chemical properties of carbon compounds chemical properties of organic compounds

  1. Substitution

  2. Combustion

  3. Hydrogenation

  4. Displacement

Show answer
Correct Option: B
Explanation:

The reaction $\displaystyle C _3H _8 + 5O _2\rightarrow  3CO _2 + H _2O$ is an example of combustion reaction. Propane on complete combustion in  presence of excess oxygen gives carbon dioxide and water.

LPG has a lower energy density than either petrol or fuel-oil, so the equivalent  ______ is higher.

chemistry chemical reactions of organic compounds combustion and thermal cracking of hydrocarbons chemical properties of carbon compounds chemical properties of organic compounds

  1. fuel-consumption

  2. fuel-absorption

  3. fuel density

  4. fuel capacity

Show answer
Correct Option: A
Explanation:

LPG has a lower energy density than either petrol or fuel-oil, so the equivalent fuel-consumption is higher.
Lower energy density means lesser amount of energy is released during combustion of unit mass of fuel. Hence, to obtain certain quantity of fuel more fuel should be combusted.

LPG can be used as a power source for :

chemistry chemical reactions of organic compounds combustion and thermal cracking of hydrocarbons chemical properties of carbon compounds chemical properties of organic compounds

  1. combined heat and power technologies (CHP)

  2. combined heat and energy technologies ( CHP)

  3. combined heat and coal technologies (CHP)

  4. heat and power technologies

Show answer
Correct Option: A
Explanation:

LPG can be used as a power source for combined heat and power technologies (CHP).
Combined  heat and power (CHP) is the simultaneous generation of electricity and useful heating from the combustion of a fuel. It is a thermodynamically efficient use of fuel.

Statement 1 : When a hydrocarbon is combusted in air, carbon monoxide is the major product.
Statement 2 : Air contains much more nitrogen than oxygen.

chemistry chemical reactions of organic compounds combustion and thermal cracking of hydrocarbons chemical properties of carbon compounds chemical properties of organic compounds

  1. Both Statement 1 and Statement 2 are correct and Statement 2 is the correct explanation of Statement 1.

  2. Both Statement 1 and Statement 2 are correct and Statement 2 is not the correct explanation of Statement 1.

  3. Statement 1 is correct but Statement 2 is not correct.

  4. Statement 1 is not correct but Statement 2 is correct.

  5. Both the Statement 1 and Statement 2 are not correct.

Show answer
Correct Option: D
Explanation:

Statement 1 : When a hydrocaron is combusted in air, $CO _2$ is the major product whereas the $CO$ is produced if there is incomplete combustion of some hydrocarbon.
Statement 2: Air contains much more nitrogen than air.
$N _2= 78$%
$O _2 = 21$%