Engineering Chemistry Multiple Choice Questions on “Cracking – 1”.
1. Which of the following is a catalytic process?
a) Hydrogenation process
b) Coking
c) Pyrolysis
d) Thermal Cracking
Answer: a
Clarification: The processes in which catalysts are used for the generation of hydrocarbons are called catalytic process. Hydrogenation process is used for hydrofining of various fractions in the presence of elevated temperatures and pressures.
2. Which of the following is called as straight run petrol?
a) Intermediate oils
b) Residue fuel oils
c) Gasoline oils
d) Lubricants
Answer: c
Clarification: Gasoline fuels has the highest demand due to the automobile industries. The quality of straight-run petrol produced is not so good, so it is only used after suitable blending.
3. By which process we can get higher yields of gasoline in cracking?
a) Electrolytic decomposition
b) Thermal decomposition
c) Nuclear energy
d) Destructive distillation
Answer: b
Clarification: The process of cracking involves the thermal or catalytic decomposition of surplus heavier fractions, so as to obtain a higher yield of improved gasoline. It was noticed that cracked gasoline gives better engine performance.
4. Which of the following solid product is formed after thermal cracking of gasoline?
a) Charcoal
b) Sodium chloride
c) Butane
d) Coke
Answer: d
Clarification: The heavier petroleum fractions are decomposed at a temperature of 420 0C to form low molecular weight hydrocarbons. After this process coke, liquid and gaseous products are also formed.
5. In thermal cracking, by which method does the cracked products are separated?
a) Fractional distillation
b) Destructive distillation
c) Oil distillation
d) Steam distillation
Answer: a
Clarification: After the process of thermal decomposition, some of the products undergo polymerisation and the other crack products are separated using fractional distillation method. The yields are from 7-30 %.
6. Liquid-phase cracking can crack any type of oil.
a) True
b) False
Answer: a
Clarification: All types of oils, i.e., residue, fuel oil and gasoline oils can be cracked using liquid-phase cracking. The oils which can be vaporized at low temperatures can be cracked using vapour-phase cracking.
7. In which conditions does hydro-cracking are conducted?
a) In the presence of water
b) In the presence of electricity
c) In the presence of hydrogen
d) In the presence of oxygen
Answer: c
Clarification: The cracking which is brought about in the presence of a catalyst under a hydrogen atmosphere at slightly reduced temperature and high pressure is called hydro-cracking. It is a type of catalytic cracking.
8. Which type of catalyst is used in catalytic cracking?
a) Catalyst containing nitrogen
b) Catalyst containing alumina and silica
c) Catalyst containing noble elements
d) Catalyst with high electronegativity
Answer: b
Clarification: Earlier acid clays were used as a catalyst for catalytic cracking. Now silica and alumina with minor amounts of oxides of Ca, Mg, Na and rare earth are used as a catalyst.
9. Which compounds are formed by cracking of heavy hydrocarbons?
a) Saturated hydrocarbons
b) Unsaturated hydrocarbons
c) Saturated and unsaturated hydrocarbons
d) Inorganic matter
Answer: c
Clarification: In actual practice, during the cracking of heavy hydrocarbons both saturated and unsaturated compound are formed. These compounds are then separated by the process of fractional distillation.
10. Activity of a catalyst determines __________________
a) Yield of end-product
b) Ability to accelerate the reaction
c) Ageing
d) The nature of reactants
Answer: a
Clarification: Activity is a characteristic of alumina-silicate catalyst which determines the yield of the end-product, relative to the starting material used. Selectivity is the measure of the ability of the catalyst to accelerate the desired reaction.