Question
The gases produced by a burning fuel are passed through solution Z using the apparatus shown. The fuel contains compounds of sulfur.
Which row identifies solution Z and the result obtained when the fuel contains compounds of sulfur?
▶️Answer/Explanation
Ans:
A
The purpose of passing the gases through the acidified potassium manganate solution is to test for the presence of sulfur-containing compounds in the fuel. Sulfur compounds, such as sulfur dioxide (SO2), can react with the potassium manganate, causing it to change color from purple to colorless or brown. This is a common chemical test for the presence of sulfur-containing compounds in a gas mixture. If sulfur-containing compounds are present in the gases produced during combustion, the purple color of the potassium manganate solution will fade or change, indicating the presence of sulfur compounds in the fuel. The intensity of the color change can also give an idea of the amount of sulfur present.
Question
The fractional distillation of petroleum produces a series of fractions with different uses. Which row identifies a use for a fraction?
▶️Answer/Explanation
Ans:
D
Fractional distillation is the primary process used to separate crude oil (petroleum) into various fractions based on their boiling points. Each fraction obtained during the distillation process has different properties and uses. One of the fractions produced is called “naphtha.”
Naphtha is a light, volatile hydrocarbon mixture that typically consists of hydrocarbons with 5 to 12 carbon atoms. Its boiling point range falls between those of gasoline and kerosene. Naphtha can be further classified into different subtypes based on its boiling point range, such as light naphtha, heavy naphtha, and reformate.
Naphtha is an essential feedstock in the petrochemical industry. It is used as a raw material to produce various petrochemicals, such as ethylene, propylene, butadiene, benzene, toluene, and xylenes. These chemicals serve as building blocks for the manufacturing of plastics, synthetic rubbers, resins, solvents, and other chemical products.
Question
Which statement about fuels is correct?
A. Heat energy is only produced by burning fuels.
B. Hydrogen is used as a fuel although it is difficult to store.
C. Methane is a good fuel because it produces only water when burned.
D. Uranium is burned in air to produce energy.
▶️Answer/Explanation
Ans:
B
Hydrogen is considered a promising fuel due to its high energy content and the fact that it produces only water vapor when burned, making it a clean energy source. However, there are challenges associated with its storage, which have been a significant hurdle in its widespread adoption as a mainstream fuel. Hydrogen has a very low density, which means that it requires a large volume to store a sufficient amount of energy. This makes it challenging to store enough hydrogen to achieve a reasonable driving range for vehicles or maintain a suitable energy supply for various applications.
Question
Which list shows the fractions obtained from distilling petroleum, in order of increasing boiling point?
A bitumen $\rightarrow$ diesel oil $\rightarrow$ fuel oil $\rightarrow$ lubricating oil
B diesel oil $\rightarrow$ gasoline $\rightarrow$ naphtha $\rightarrow$ kerosene
C gasoline $\rightarrow$ naphtha $\rightarrow$ kerosene $\rightarrow$ diesel oil
D kerosene $\rightarrow$ lubricating oil $\rightarrow$ naphtha $\rightarrow$ refinery gas
▶️Answer/Explanation
Ans:C
Fractional distillation is a refining process used in the petroleum industry to separate crude oil into its various components based on their boiling points.
The process involves heating the crude oil in a tall fractionating column, where the temperature gradually decreases from the bottom to the top. As the heated crude oil rises through the column, it condenses into different fractions at various heights, each corresponding to a specific boiling point range. These fractions are then collected and further processed to obtain various petroleum products.
Gasoline: Gasoline is the lightest and most volatile fraction obtained from crude oil during fractional distillation. It has a relatively low boiling point and consists of hydrocarbons with 5 to 12 carbon atoms. Gasoline is a primary fuel used in internal combustion engines for automobiles.
Naphtha: Naphtha is the next fraction obtained with a slightly higher boiling point than gasoline. It contains hydrocarbons with 5 to 12 carbon atoms and is used as a feedstock in the petrochemical industry for producing various chemicals and as a solvent.
Kerosene: Kerosene is a middle distillate fraction with a higher boiling point than naphtha. It contains hydrocarbons with 10 to 16 carbon atoms. Kerosene is commonly used as jet fuel for aviation, as well as for heating, lighting, and in some parts of the world, as a cooking fuel.
Diesel Oil: Diesel oil is a heavier fraction with a higher boiling point than kerosene. It consists of hydrocarbons with 12 to 20 carbon atoms. Diesel fuel is commonly used in diesel engines for various transportation vehicles, industrial machinery, and power generation.
This process of fractional distillation allows for the separation of crude oil into different fractions, each of which can be further refined and processed to obtain various valuable products that serve different purposes in our daily lives.
Question
Which substance does not require oxygen in order to produce energy?
A coal
B hydrogen
C natural gas
D ${ }^{235} \mathrm{U}$
▶️Answer/Explanation
Ans:D
Uranium-235 (U-235) is a naturally occurring fissile isotope of uranium, which means it can undergo nuclear fission and release a tremendous amount of energy when struck by a neutron. The energy released in the fission process is not dependent on oxygen or any other external element. Instead, the energy is produced by splitting the U-235 nucleus into two smaller nuclei along with the release of neutrons and gamma radiation.