This set of Applied Chemistry Multiple Choice Questions & Answers (MCQs) focuses on “Cracking and Knocking of Petroleum”.
1. Octane number is a rating of ___________
a) petrol knocking
b) diesel knocking
c) petrol cracking
d) diesel cracking
View Answer
Explanation: Octane number is the rating for petrol knocking and cetane number is the rating for diesel knocking.
2. Which of the following element has 100% anti knocking?
a) 2-methyl naphthalene
b) heptadecane
c) CH3-(-CH2-)14-CH3
d) 3-methyl naphthalene
View Answer
Explanation: CH3-(-CH2-)14-CH3 has the 100% anti knocking value. It is also called as n-hexa decane. The lowest anti knocking value that is 0 is for the element 2-methyl naphthalene.
3. To improve anti knock of diesel ___________ are added.
a) TEL
b) Pre-ignition dopes
c) Di ethyl telluride
d) N-hexa decane
View Answer
Explanation: To improve the anti-knock of diesel the pre-ignition dopes are added. Generally ethyl nitrate, isoamyl nitrate and acetane peroxide are added as pre-ignition dopes.
4. What are the best anti knocking reagents of petrol?
a) straight chain alkanes
b) straight chain alkenes
c) alkynes
d) aromatics
View Answer
Explanation: The straight chain compounds cause maximum petrol knock and aromatics are called the best anti knock agents of petrol.
5. Pre-ignition of the fuel is seen in _________
a) petrol knocking
b) petrol cracking
c) diesel cracking
d) diesel knocking
View Answer
Explanation: Petrol knocking is due to the pre-ignition of the fuel and in diesel knocking is because of ignition-lag of the fuel.
6. In liquid phase thermal cracking, the yield of petrol is ________
a) 50%-60%
b) 60%-70%
c) 70%-80%
d) 80%-90%
View Answer
Explanation: In liquid phase catalytic cracking, the yield of petrol is 50-60% with good octane rating of 65-70. Here, the cracked products are sent through fractionating where the products are separated.
7. Knocking is also called as __________
a) cracking
b) pinging
c) doping
d) crushing
View Answer
Explanation: Pinging is the other name of knocking. Cracking means the process of breaking the higher hydrocarbons into simple atoms. Doping means adding impurity to a pure metal to improve its conductivity. Crushing means divided into small pieces.
8. In the catalytic cracking, what Is the catalyst used?
a) Nacl
b) Kcl
c) ZnSO4
d) Al2O3
View Answer
Explanation: Al2O3 and also Al2(SiO3)3 acts as catalysts in catalytic cracking. Usage of these catalysts, the quality of petrol is high without any heating.
9. Which of the following order of petrol knocking is true?
a) aromatics > branched paraffins > olefins > cyclo paraffins > aromatics
b) straight chain paraffins > olefins > branched paraffins > cyclo paraffins > straight chain paraffins
c) straight chain paraffins > branched paraffins > olefins > cyclo paraffins > aromatics
d) straight chain paraffins > branched paraffins > olefins > aromatics > cyclo paraffins
View Answer
Explanation: The order of petrol knocking is given by straight chain paraffins > branched paraffins > olefins>cyclo paraffins > aromatics. As we know that aromatics are the best anti knock agents so, the petrol knock for them is very low.
10. In fixed bed catalytic cracking, the catalyst is reactivated after every __________
a) 8-10hrs
b) 20-24hrs
c) 5-7hrs
d) 12-15hrs
View Answer
Explanation: In fixed-bed catalytic cracking, the catalyst is reactivated after every 8-10hrs and continuous by burning the deposited carbon.
11. In vapour phase thermal cracking, the temperature achieved is ___________
a) 200-400oC
b) 600-650oC
c) 500-820oC
d) 700-800oC
View Answer
Explanation: In vapour phase thermal cracking, the temperature achieved is 600-650oC and in fixed-bed catalytic cracking, the temperature is about 425-250oC.
12. In moving bed catalytic cracking, the catalyst is in the form of ____________
a) fine powder
b) pallets
c) liquid form
d) gaseous form
View Answer
Explanation: In moving bed catalytic cracking, the catalyst is made into a fine powder and charged into the catalyst chamber. So, they move freely like fluids.
13. The gasoline vapours are purified by __________
a) thermal cracking
b) catalytic cracking
c) stabilization
d) knocking
View Answer
Explanation: The stabilization is the process in which the gasoline vapours are purified. Thermal cracking and catalytic cracking are the processes to purify the petrol.
14. The pressure applied in vapour phase cracking is __________
a) 10-20kg/cm2
b) 100kg/cm2
c) 50kg/cm2
d) 80kg/cm2
View Answer
Explanation: The pressure applied in the vapour phase cracking is very small about 10-20kg/cm2.The oils will be very easily vaporized.
15. The pressure applied in fixed-bed catalytic cracking is __________
a) 10kg/cm2
b) 50kg/cm2
c) 100kg/cm2
d) 1.5kg/cm2
View Answer
Explanation: The pressure of 1.5kg/cm2 applied in the fixed bed catalytic cracking and during this process 40% of charge is converted into gasoline.
Sanfoundry Global Education & Learning Series – Applied Chemistry.
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