National Science Olympiad Model Paper 2 Questions and Answers Part 17

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19. Identify A, B, C and D respectively in the process of involve in distillation process of crude oil.

Process of Crude Oil

A) Fractionating column, Thermometer, Water, Crude oil

B) Thermometer, fractionating column, Crude oil, Water

C) Thermometer, fractionating column, Water, Crude oil

D) Crude oil, fractionating column, Thermometer, Water

Answer: B

Explanation:

The crude oil vapour ascends the fractionating column to the highest boiling liquid hydrocarbons condense out and the lowest boiling hydrocarbon liquid՚s vapour exits the top of the fractionating column and enters the condenser and runs into the collection tube.

In that way it can distil over continuously higher boiling fractions, which are themselves narrow boiling point ranges of different hydrocarbons of similar carbon chain length.

Process of Crude Oil

Q. 20 to 22 represents the phase diagram answer the following question.

Represented Diagram

Q. 21. The melting point of substance is represented by

A) A to B

B) C to D

C) B to C

D) D to E

Answer: B to C

Q. 22. Heat is added between points D and E. The substance is

A) Sublimating

B) Freezing

C) Melting

D) Boiling

Answer: D

Q. 23. If heat is removed from point E and the temperature is not changed, the substance will

A) Condense

B) Melt

C) Boil

D) Evaporate

Answer: A

Explanation 21 - 23

Solid Ice is Heated

Solid ice is heated and therefore the temperature increases until the traditional freezing/melting point of zero degrees Celsius is reached. The quantity of heat is added

The first phase transition is melting; (B-C) as a substance melts, the temperature stays an equivalent.

For water, this happens at 0o C.

After all of the solid substance has melted into liquid, the temperature of the liquid begins to extend as heat is absorbed.

The liquid will begin to boil when enough heat has been absorbed by the result that the temperature reaches the boiling point (Boiling) , where again, the temperature remains constant until all of the liquid has become gaseous water. At the air pressure of 1 atm, this phase change occurs at 100o C (the normal boiling point of water) . Liquid water becomes water vapour or steam when it enters the gaseous phase. (E-F)

After all of the liquid has been converted to gas, the temperature will still increase as heat as added. Again, the heat is added that leads to a particular change temperature

Water features a high boiling point due to the presence of in-depth chemical bonding interactions between the water molecules within the liquid phase (water is both a robust hydrogen bond donor and acceptor) .

When heat is first applied to water, it must break the intermolecular hydrogen bonds within the sample.

After breaking the bonds, heat is then absorbed and converted to increase K. E. of the molecules so as to vaporize them.

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