- No.7. What happens when ammonical brine is carbonated?
Answer. Ammonical brine is fed into carbonating tower and carbon dioxide is passed through it. Following reactions take place in the carbonating tower.
CO2(g) + NH3(g) + H2O NH4HCO3(1)
NH4HCO3(1) + NaCl (brine) NaHCO3(1) + NH4Cl(s)
The temperature of the mixture is lowered to 15°G and precipitates of NaHCO3 are obtained.
- No.8. How NaHCO3 is converted to Na2CO3?
Answer. The precipitates of sodium bicarbonate are filtered, washed with cold water and heated to form sodium carbonate.
2NaHCO3 ———> Na2CO3 + CO2 + H2O
- No.9. How ammonia is recovered in the Solvay’s process?
Answer. Ammonia is recovered from ammonium chloride solution produced in the carbonated tower and calcium hydroxide formed in lime kiln. Both of these are pumped to the top of the ammonia recovery tower. Steam is introduced from the base of the tower for heating purposes. Ammonia is recovered from NH4C1 as:
2NH4C1 + Ca(OH)2 ———> 2NH3 + CaCl2 + 2H2O
- No.10. How ammonia is prepared for the synthesis of urea?
Answer. It is prepared by the Harber’s process. One volume of nitrogen (from air) and three volumes of hydrogen (obtained by passing methane and steam over nickel catalyst) are passed over iron catalyst at 450 °C and 200 atm pressure
N2(g)+ 3H2(g) ———> 2NH3(g)
Q.No.11. Describe the formation of petroleum.
Answer. Petroleum was formed by the decomposition of dead plants and animals buried under Earth’s crust millions of years ago. It is believed that millions of years ago living plants and animals in the seas died. Their bodies sank and buried under mud and sand. 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.
- No.12.What is refining of petroleum and how it is carried out?
Answer. Refining process is the separation of crude oil mixture into various useful products (fractions). It is carried out by a process called fractional distillation in a fractionating tower. The crude oil is heated in a furnace up to a temperature of 400°C under high pressure. Then vapours are passed through a fractionating column from near its bottom, hot vapours rise up in the column and gradually cool down and condense. Such that vapours of higher boiling point fraction (350— 400°C) condense first in the lower part of the tower, while vapours of medium and lower boiling point fractions rise upwards in the tower and condense gradually with respect their boiling points at different levels. In this way crude oil is separated into six hydrocarbon fractions as discussed below. Each fraction has its specific boiling range, composition and uses.
- No.13. Give a use of kerosene oil.
Answer. Kerosene oil is used as domestic fuel a special grade of it is used as an aeroplane fuel.
- No.14. Describe the difference between diesel oil and fuel oil.
Answer. Diesel oil consists of C13 to C15 carbon atom while fuel oil consists of C15 to C18. The boiling range of diesel oil varies from 250°C to 350°C. While, boiling range of fuel oil varies from 350°C to 400°C. Diesel oil is used as a fuel in buses, trucks, railway engines, tube well engines and other heavy transport vehicles. While, fuel oil is used in ships and industries to heat up boilers and furnaces
- No.15. Write down the names of four fractions obtained by the fractional distillation of residual oil.
Answer. Four fractions obtained from the fractional distillation of residual oil are:
- Lubricants b. Paraffin wax
- Asphalt d. Petroleum coke