Matric Notes Chemistry 10th Chapter 16 Chemical Industries Exercise Short Questions

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Exercise Short Questions:

Q1. What role is played by pine oil in the froth flotation process?

Ans. Pine oil plays an important role in froth flotation process because Pine oil coated ore particles being lighter come to the surface in the form of froth that can be skimmed easily.

Q2. Name the various metallurgical operations.

Ans. The processes involved in metallurgy for extraction of a metal in the pure state from its ore are.

• Concentration of the ores
• Extraction of the metal
• Refining of the metal

Q3. How is roasting carried out?

Ans. Roasting is process of heating the concentrated ore at high temperature in excess of air. This process is carried out in a special furnace which is called Reverberatory furnace.

2CuFeS₂ + O₂ ---> Cu₂S + 2FeS + SO₂

Q4. Explain the process of electro-refining.

Ans. Electrolytic refining of copper is carried out in an electrolytic tank having copper sulphate solution in it. Two electrodes; one of impure copper metal that acts as anode and the other of pure copper metal that acts as cathode are suspended in the electrolytic solution.

At anode: Cu^(o) Cu⁽²⁺⁾2e^(2-)

At cathode: Cu⁽²⁺⁾2e^-> --->  Cu^(o)

On passing the electric current through the solution, anode (impure copper) dissolves to provide Cu⁽²⁺⁾ ions to the solution. These Cu⁽²⁺⁾ ions are discharged by gaining of electrons from the cathode. Thereby copper atoms deposit on the cathode, making it thick block of pure copper metal. The impurities like gold and silver settle down as anode mud.

Q5. What are the advantages of Solvay's process?

Ans. i. It is a cheap process as raw materials are available at very low prices.

ii. Carbon dioxide and ammonia are recovered and reused.

iii. Process is pollution free, because the only waste is calcium chloride solution.

iv. Sodium carbonate of very high purity is obtained.

v. Consumption of fuel is very less since no solution is to be evaporated.

Q6. What is the principle of Solvay's process?

Ans. Principle of Solvay's process lies in the low solubility of sodium bicarbonate at low temperature i.e. at 15 ^(o) C. When CO₂  is passed through an ammonical solution of NaCl called ammonical brine only NaHCO₃  precipitates.

Na⁺ + HCO^-₃---> NaHCO₃

Q7. What happens when ammonical brine is carbonated?

Ans. Ammonical brine is fed into carbonating tower and carbon dioxide is passed through it. Following reaction take place in carbonating tower.

CO₂ + NH₃ + H₂O --- > NH₄HCO₃

NH₄HCO₃ + NaCl (brine) ---->  NaHCO₃ + NH₄Cl

The temperature of the mixture is lowered to 15 ^(o) C and precipitates of NaHCO₃ are obtained.

Q8.How is NaHCO₃ converted to Na₂CO₃?

Ans. Sodium hydrogen carbonate is heated to get sodium carbonate.

2NaHCO₃ ---> Na₂CO₂ + CO₂ + H₂O

CO₂ is again used in tower. It is about half of H₂O needed in the process.

Q9. How is ammonia recovered in Solvay's process?

Ans. Ammonia is recovered in ammonia recovery tower from ammonia chloride solution produced in the carbonated tower and calcium hydroxide formed in lime kiln.

2NH₄Cl + Ca(OH)₂ ---> 2NH₃ + CaCl₂ + 2H₂O

In fact all ammonia is recovered in this tower and is reused in the process.

Q10. How is ammonia prepared for the synthesis of Urea? OR How is ammonia prepared by Haber's process?

Ans. Ammonia is prepared by the "Haber's process". One Volume of nitrogen (from air) and three volumes of hydrogen (obtained by passing methane and steam over heated nickel catalyst) is passed over iron catalyst at. 450 ^(o) C and 200 atm pressure.

N₂ + 3H₂ == 2NH₃

Q11. Describe the formation of petroleum.

Ans. Petroleum was formed by the decomposition of dead plants and animals buried under Earth's crust millions of years ago. Then decomposition process took place in the absence of air because of high pressure, temperature and bacterial effects. This process took millions of years for completion. Thus, remains of dead plants and animals were converted into a dark brownish viscous crude oil. It was trapped between two layers of impervious rocks.

Q12. What is refining of petroleum and how it is carried out?

Ans. Refining process is the separation of crude oil mixture into various useful products (fractions). It is carried out by a process called fractional distillation.

Q13. Give uses of kerosene oil.

Ans. It is used as domestic fuel. a special grade of it is used as jet fuel.

Q14. Describe the difference between diesel oil and fuel oil.

Ans. Diesel Oil:

• It contains 13 to 15 carbon atoms.
• It is used as fuel for buses, trucks, railway engines, tube-well engines and other heavy vehicles.

Fuel Oil:

• It contains 5 to 18 carbon atoms.
• It is used in ships and industries to heat boilers and furnaces.

Q15. Write down the names of four fraction obtained by the fractional distillation of residual oil. (Enlist the names of fractions of residual oil.)

Ans. The four fractions of residual oil are:

• Lubricants
• Paraffin wax
• Asphalt
• Petroleum coke

Q16. What is the difference between crude oil and residual oil?

Ans. Crude oil:

It is dark brownish viscous liquid which is formed by decomposition of dead plants and animals in absence of air.

Residual oil:

After the fractional distillation of petroleum, the oil left behind is called residual oil.

Q17. Which petroleum fraction is used in dry cleaning?

Ans. Gasoline or petrol is used in dry cleaning.