Category: Engineering Chemistry Objective Questions

Engineering Chemistry Multiple Choice Questions on “Quantum Efficiency”.

1. To express the relationship between the number of molecules reacting with the number of photons absorbed, the concept of _____ was introduced.
a) quantum efficiency
b) photon analysis
c) quantum mechanism
d) photon degradation
Answer: a
Clarification: The concept of quantum efficiency was introduced to express the relationship between a number of molecules reacting with the number of photons absorbed. It is defined as the number of molecules of the substance undergoing photochemical change per quantum of radiation absorbed.

2. Classification of photochemical reaction on the basis of quantum efficiency can be done into ______ categories.
a) 3
b) 2
c) 4
d) 5
Answer: a
Clarification: Photochemical reactions can be divided into three categories on the basis of quantum efficiency i.e., the reactions in which quantum yield is “a small integer like 1, 2” OR “less than 1” OR “a very high value”.

3. Quantum efficiency is given by _______
a) nNhc/qλ
b) nq/Nhcλ
c) qλ/nNhc
d) ncλ/Nhq
Answer: a
Clarification: Quantum efficiency=Number of molecules reacting in a given time/Number of quanta of light absorbed in the same time. Hence, Quantum efficiency is given by nNhc/qλ.

4. If a reaction obeys Einstein law, quantum yield is _______
a) 1
b) more than 1
c) less than 1
d) 0
Answer: a
Clarification: If a reaction obeys Einstein law, one molecule is decomposed per photon. Quantum efficiency=Number of molecules reacting in a given time/Number of quanta of light absorbed in the same time. So, quantum yield is 1.

5. When two or more molecules are decomposed per photon, the reaction has ______ quantum yield.
a) high
b) low
c) unpredictable
d) variable
Answer: a
Clarification: When two or more molecules are decomposed per photon, the reaction has greater than one quantum yield. So, the reaction has high quantum yield.
Quantum efficiency = Number of molecules reacting in a given time/Number of quanta of light absorbed in the same time.

6. When the number of molecules decomposed is less than one per photon, the reaction has ______ quantum yield.
a) low
b) high
c) unpredictable
d) variable
Answer: a
Clarification: When the number of molecules decomposed is less than one per photon, the reaction has less than one quantum yield. So, the reaction has low quantum yield.
Quantum efficiency=Number of molecules reacting in a given time/Number of quanta of light absorbed in the same time.

7. Decomposition of HI has quantum yield = _______
a) 1
b) 2
c) 0
d) 4
Answer: b
Clarification: HI + hv→ H + I ……………….. Primary reaction H + HI → H₂ + I
I + I → I₂ …………….. Secondary reaction
Overall reaction: 2HI + hv → H₂ + I₂ the overall reaction shows that 2 HI molecules are decomposed by 1 photon. So, quantum yield=2.

8. Which of the following is the condition for high and low quantum yield?
a) The reactivity of the molecules should be temperature dependent
b) All the reactant molecules should be in the different energy state
c) The molecules in the activated state should be largely unstable and decompose to form the products
d) quantum field=1
Answer: c
Clarification: The molecules in the activated state should be largely unstable and decompose to form the products. The reactivity of the molecules should not be independent on temperature. All the reactant molecules should be initially in the same energy state.

Engineering Chemistry Multiple Choice Questions on “Ion-Exchange Resins”.

1. Ion-exchange resin is ____________
a) Linear
b) Low molecular weight
c) Organic polymer with porous structure
d) Soluble
Answer: c
Clarification: Ion-exchange resins are cross-linked, insoluble, high molecular weight, organic polymers with a porous structure.

2. Which of the following ion get released from the cation exchange column?
a) H⁺
b) Na⁺
c) K⁺
d) Ca⁺²
Answer: a
Clarification: Only H⁺ ion get released from the cation exchange column.

3. Which of the following ion get released from the anion exchange column?
a) CO₃^-2
b) OH^–
c) Cl^–
d) SO₄^-2
Answer: b
Clarification: Only OH^– ion get released from the anion exchange column.

4. Ion-free water coming out from the exchanger is known as ____________
a) Potable water
b) Disinfected water
c) Coagulated water
d) Demineralised water
Answer: d
Clarification: Ion-free water coming out from the exchanger is known as demineralised water as it is free from all the mineral impurities.

5. Which of the following statement is incorrect about the demineralised water?
a) It is as pure as distilled water
b) It is very good for use in high pressure boilers
c) It is fit for domestic use
d) It can be made either by distillation or by using cation and anion exchangers
Answer: c
Clarification: Demineralised water is not recommended for domestic use such as drinking purposes. All the other options are correct.

6. The exhausted cation exchange column is regenerated by passing a solution of ____________
a) Dil. HCl
b) Dil. NaCl
c) Conc. HCl
d) Conc. NaCl
Answer: a
Clarification: The exhausted cation exchange column is regenerated by passing a solution of dil. HCl. Dil HCl is also known as brine solution.

7. The exhausted anion exchange column is regenerated by passing a solution of ____________
a) Dil. KOH
b) Conc. KOH
c) Conc. NaOH
d) Dil. NaOH
Answer: d
Clarification: By passing a solution of dil. NaOH, the exhausted anion exchange column is regenerated.

8. The raw water used for ion-exchange process should be turbid.
a) True
b) False
Answer: b
Clarification: The raw water used for ion-exchange process should be non-turbid and free from impurities.

9. In ion-exchange process, the capital cost is _________ and the operational expenses are ______________
a) Low, high
b) High, low
c) High, high
d) Low, low
Answer: c
Clarification: In ion-exchange process, the capital cost is very high and the operational expenses are also high.

10. The residual hardness in ion-exchange process is ____________
a) 0-2 ppm
b) 5-10 ppm
c) 10-15 ppm
d) 20-30 ppm
Answer: a
Clarification: The residual hardness in the ion-exchange process is 0-2 ppm. In waters containing more hardness than alkalinity, some hardness remains after treatment.

Engineering Chemistry Multiple Choice Questions on “Coal – 2”.

1. At what temperature does the ash is determined by heating to complete its combustion?
a) 400^o C
b) 600^o C
c) 850^o C
d) 750^o C
Answer: d
Clarification: Precisely the determination of ash is done by heating it at 400^o C, until most of its carbonaceous matter is burnt off. Then is it heated at 750^o C for one hour so as to complete its combustion.

2. In ultimate analysis, how does the percentage of carbon and hydrogen are determined?
a) By using pure oxygen
b) By using pure nitrogen
c) By using pure sulphur
d) By using pure silicon
Answer: a
Clarification: The weight of sample carrying carbon and hydrogen is placed in steam of pure oxygen in a combustion reaction similar to that for the analysis of organic compounds. Carbon and hydrogen are respectively converted into CO₂ and H₂O which are then absorbed settled down into different chambers.

3. What is the product obtained in the determination of the percentage of nitrogen by ultimate analysis?
a) Nitrogen di-oxide
b) Nitrogen oxide
c) Ammonia
d) Ammonium ion
Answer: c
Clarification: The sample containing nitrogen is added to Kjeldahl flask, in which the nitrogen present is converted into the ammonium salts. The sample is then made alkaline with the help of alcoholic NaOH. Ammonia is liberated and is distilled into a measured amount of standard acid.

4. Carbon, hydrogen and oxygen directly contribute towards the calorific value of the coal.
a) True
b) False
Answer: b
Clarification: Carbon and oxygen contributes to the calorific value of the coal, whereas oxygen content of is generally associated with the moisture. The higher the percentages of carbon and oxygen in coal, the better is the quality of coal. The lower the oxygen content of the coal, greater is its calorific value.

5. Which of the following substance contributes towards its heating value?
a) Nitrogen
b) Hydrogen
c) Sulphur
d) Oxygen
Answer: c
Clarification: Pure sulphur contributes towards the heating effect of coal, whereas the combustion products of sulphur such as SO2 and SO3 have corrosion effects on the equipment. Nitrogen present in the coal is of negligible amount due to which it does not have effect on properties of coal.

6. Which of the following is the expression for determination of calorific value of coal using Davies formulae? (where CV is calorific value, %H is percentage of hydrogen, %C is percentage of carbon, %O is percentage of oxygen and %S is percentage of sulphur.)
a) CV = (6.543×%H + 403)[%C/3 + %H – (%O – %S)/8]
b) CV = (6.543×%H + 403)[%C/3 + %H + (%O – %S)/8]
c) CV = (6.543×%H – 403)[%C/3 + %H – (%O – %S)/8]
d) CV = (6.543×%H – 403)[%C/3 + %H + (%O – %S)/8]
Answer: a
Clarification: This formulae is based on ultimate analysis of fuel. The calorific value calculated here is expressed in B.Th.U./lb. Here we have only one calorific value not such as the Dulong’s formulae where we have GCV and NCV.

7. How can we calculate the calorific value of coal using proximate analysis?
a) By using Seyler’s formulae
b) By using Dulong’s formula
c) By using Davies formulae
d) By using Nakamura’s formulae
Answer: d
Clarification: The proximate analysis of the coal depends on moisture, ash content, volatile matter and fixed carbon. The Nakamura’s formulae is as follows-
CV = a [V – (%Ash/10)] + 140.4 C
Here a depends on the percentile of volatile matter.

8. Which region of Gondwana coals have prime coking coals deposits?
a) Bilaspur
b) Raniganj
c) Jharia
d) Chhindwara
Answer: c
Clarification: The Gondwana region covers the areas of Chhattisgarh, West Bengal and Madhya Pradesh. The volatile matter present in these deposits of coal is about 28-32 %. It is also found in Giridh and East Bokaro.

9. Which type of coal is found in the Cutch and Lameta ghat of Narbada valley?
a) Gondwana
b) Jurassic
c) Tertiary
d) Cretaceous
Answer: b
Clarification: These coals belong form the Jurassic period. The tertiary coal are found in the Assam, Kashmir and Rajasthan. The cretaceous coal are found in Garo hills.

10. On what basis does the grading of coals is done in India for coals containing high moisture?
a) On the basis of its calorific value
b) On the basis of its volatile matter
c) On the basis of its ignition temperature
d) On the basis of its ash content and moisture
Answer: d
Clarification: For coals containing low moisture content, the grading is done by the calculation of percentile of moisture whereas for high moisture content, both ash and moisture content are taken into consideration. It is not done on the basis of its calorific value.

Engineering Chemistry Multiple Choice Questions on “Knocking”.

1. Which compound of fuel is oxidised in the process of knocking?
a) Coke
b) Gasoline
c) Hydrocarbon
d) Compounds containing sulphur
Answer: c
Clarification: In an internal combustion engine, a mixture of air and petrol vapour is compressed and ignited by an electric spark and the essential chemical reaction is the oxidation of the hydrocarbon molecules.

2. On what factor does the rate of oxidation of a hydrocarbon molecule depend?
a) On the calorific value of the compound
b) On the number of carbon atoms
c) On the rate of combustion
d) On its moisture content
Answer: b
Clarification: The rate of oxidation of a hydrocarbon molecule depends on the number of carbon atoms in the molecule, on the structure and on the temperature. The rate of oxidation should be moderate.

3. How will be the knocking sound produce in an engine?
a) Due to an increase in the rate of oxidation of hydrocarbon
b) Due to a decrease in the rate of oxidation of hydrocarbon
c) Due to the impurities present in fuel
d) Due to an increase in the percentile of ethanol molecule
Answer: a
Clarification: In the mixture of air and petrol vapour, there occurs a condition when the rate of oxidation increases to such a value that it starts producing sound in the engine which are called a knock. This decreases the octane rating of gasoline.

4. On what factor does the temperature of the engine depend?
a) Rate of oxidation
b) Size of the engine
c) Compression ratio of the engine
d) Fuel used in the engine
Answer: c
Clarification: Compression ratio is the ratio of the cylinder volume at the end of the suction stroke to the volume at the end of the compression stroke of the piston. Rate of oxidation is depended on the temperature.

5. The power output of engine increases continuously with an increase in the compression ratio.
a) True
b) False
Answer: b
Clarification: With the help of a variable compression engine, in actual practice, the power increases to a maximum value and then falls rapidly with a further increase in the compression ratio.

6. At what value of compression ratio, a knock can be heard?
a) At the minimum value
b) At the maximum value for power output
c) At the maximum value above the power output
d) In between of lowest and highest value
Answer: c
Clarification: The compression rate, corresponding to the maximum power output is known as a useful compression ratio at which a slight metallic knock can be heard. This knock becomes louder when the compression ratio goes on increasing.

7. Which of the following compound produces the least knocking?
a) Benzyl
b) Paraffin
c) Olefin
d) Diesel
Answer: a
Clarification: Aromatic compounds produces least knocking due to their cyclic structures. Straight chain hydrocarbons produces more knocking due to this effect.

8. How is the knocking tendency increased?
a) Due to the compression ratio of the engine
b) Due to size of the engine
c) Due to the decrease in the engine speed
d) Due to a defect in an engine
Answer: c
Clarification: The knocking tendency is increased by reducing the engine speed and by advancing the ignition of the engine. The engine should work in its original way.

9. Which of the following compound has the least knocking properties?
a) n-heptane
b) n-hexane
c) n-pentane
d) n-butane
Answer: d
Clarification: The anti-knock properties decreases with an increase in the length of the hydrocarbon chain. The octane number of n-butane, n-pentane, n-hexane and n-heptane are 90, 60, 29 and 0 respectively.

10. Olefins have higher anti-knocking properties than the corresponding ______________
a) Paraffin
b) Benzene
c) Toluene
d) Nitrobenzene
Answer: a
Clarification: The anti-knocking tendency increases as the position of a double bond approaches the centre of the chain. Paraffin consists of a single bond and are straight chained due to which they are less anti-knocking then olefins.

Engineering Chemistry Multiple Choice Questions on “Desalination of Brackish Water”.

1. The example of brackish water is ___________
a) Ground water
b) Rain water
c) Sea water
d) Underground water
Answer: c
Clarification: The example of brackish water is sea water. Ground water, underground water and rain water are not brackish water. Sea water is also saline in nature and not fit for domestic purpose.

2. Which of the following technique is not used for the desalination of brackish water?
a) Electrolysis
b) Electrodialysis
c) Reverse osmosis
d) Distillation
Answer: a
Clarification: Electrolysis technique is not used for the desalination of brackish water. Electrodialysis, reverse osmosis and distillation are the few techniques used for desalination of brackish water.

3. Salt cannot be separated from brackish water by freezing.
a) True
b) False
Answer: b
Clarification: Salt can be separated from brackish water by freezing.

4. Electrodialysis is based on the fact that the ions present in saline water migrate towards their respective electrodes under the influence of applied ___________
a) Current
b) Resistance
c) Conductance
d) EMF
Answer: d
Clarification: Electrodialysis is based on the fact that the ions present in saline water migrate towards their respective electrodes under the influence of applied emf. The potential difference generated between the elctrodes is the main cause of flow of electrons.

5. The cation selective membrane is embedded with functional groups of ___________
a) Positive charge
b) Negative charge
c) Both positive as well as negative charge
d) Neutral
Answer: b
Clarification: The cation selective membrane is embedded with functional groups of negative charge as it attracts only positive charges towards them.

6. In electrodialysis cell, the pressure is about ___________
a) 2 kg/m²
b) 3 kg/m²
c) 5-6 kg/m²
d) 10 kg/m²
Answer: c
Clarification: Electrodialysis is an electrically driven separation conducted at very low pressure-driven of about 5-6 kg/m².

7. Electrodialysis is an electrically driven separation conducted at a very low pressure-driven, size-exclusion filtering process.
a) True
b) False
Answer: a
Clarification: Electrodialysis is an electrically driven separation conducted at a very low pressure-driven, size-exclusion filtering process. Electrodialysis is used to transport salt ions from one solution through ion-exchange membranes to another solution under the influence of an applied electric potential difference.

8. The ion-exchange membrane are electrically conductive and are not permeable to ___________ flow, even under pressure.
a) Electron
b) Oil
c) Fluorine
d) Water
Answer: d
Clarification: The ion-exchange membrane are electrically conductive and impermeable to water flow, even under pressure. Electrons can easily flow through these membranes.

9. Select the incorrect statement from the following option.
a) Electrodialysis reversal (EDR) was introduced in the commercial sector to improve electrodialysis process
b) The EDR process and conventional ED unit operates on the same principle, except at intervals of several times an hour
c) The reversal feature is useful in breaking up films, scales and other deposits
d) Electrodialysis process is not economical as per capital cost
Answer: d
Clarification: Electrodialysis process is economical as per capital cost and operational expenses are concerned. All the other options are correct.

10. Which one of the following is not a cation exchanger?
a) Amberlite
b) Triolite
c) Dowex
d) Duolite
Answer: b
Clarification: Triolite is not a cation exchanger. Amberlite, dowex and duolite are some of the examples of the cation exchanger.