Refining of petroleum is carried out using which one of the following techniques?
- A.Evaporation
- B.Fractional distillation
- C.Separating funnel
- D.Sublimation
Correct answer
Explanation
The correct answer is B, Fractional distillation. Crude petroleum is a mixture of hydrocarbons with different boiling points, and fractional distillation separates them.
In a refinery, crude oil is heated to about 400 °C and its vapour enters a tall fractionating column that is hot at the bottom and cooler towards the top. Each fraction condenses at the height where the temperature matches its boiling range: petroleum gas and petrol near the top, then kerosene and diesel, with lubricating oil, paraffin wax and bitumen near the bottom. The same method separates the gases of liquefied air.
A is wrong: evaporation removes a liquid to leave a dissolved solid behind, as in getting salt from sea water.
C is wrong: a separating funnel separates two liquids that do not mix, such as oil and water.
D is wrong: sublimation separates a solid that turns directly into vapour, such as camphor or ammonium chloride.
Exam tip: crude oil and liquids with close boiling points = fractional distillation; oil and water = separating funnel.
Practice Questions
View allSyngamy results in formation of
- A.haploid zygote
- B.diploid zygote
- C.non-motile male gametes
- D.motile male gametes
Show answer
Syngamy is the fusion of a male and a female gamete, and since each gamete is haploid, their union gives a diploid zygote.
Read the full explanation →Human insulin molecule is composed of one α-chain having 21 amino acids and one β-chain having 30 amino acids. How many functional insulin genes occur in adult humans?
- A.One
- B.Two
- C.Three
- D.Four
Show answer
Humans have a single functional insulin gene, INS, on the short arm of chromosome 11, and both chains of insulin come from it.
Read the full explanation →Which one of the following is the value of one nanometer?
- A.10⁻⁷ cm
- B.10⁻⁶ cm
- C.10⁻⁴ cm
- D.10⁻³ cm
Show answer
One nanometre is 10⁻⁹ metre, and since one metre is 100 (10²) centimetres, it equals 10⁻⁷ centimetre. The prefix nano means one billionth.
Read the full explanation →Which of the following is the general formula for saturated hydrocarbons?
- A.CₙH₂ₙ₊₂
- B.CₙH₂ₙ₋₂
- C.CₙH₂ₙ₊₁
- D.CₙH₂ₙ₋₁
Show answer
Saturated open-chain hydrocarbons are the alkanes, and every alkane fits the formula CₙH₂ₙ₊₂. In a saturated hydrocarbon every carbon atom is joined to others only by single bonds, so each carbon holds the largest possible number of hydrogen atoms.
Read the full explanation →Which one of the following is not an epidemic disease?
- A.Cholera
- B.Malaria
- C.Smallpox
- D.Elephantiasis
Show answer
Elephantiasis, or lymphatic filariasis, is an endemic disease: it stays steadily present in certain regions and develops slowly over years, rather than breaking out suddenly in a large number of people.
Read the full explanation →