Engineering Chemistry Multiple Choice Questions on “Determination of Calorific Value of Solid and Non-Volatile Liquid Fuels – 1”.
1. What is the use of a bomb calorimeter?
a) To calculate the calorific value of a volatile liquid
b) To calculate the calorific value of a gas
c) To calculate the calorific value of a non-volatile liquid
d) To calculate the calorific value of sparingly soluble salt
Answer: c
Clarification: It can also be used for calculating the calorific value of solids. If the compound in a volatile liquid or gas, the flame calorimeter offers itself as an instrument due to which further processes cannot take place.
2. Why does bomb calorimeter require high pressure oxygen?
a) To increase the rate of reaction
b) To ensure that the given sample in the crucible burns completely
c) To increase the ignition temperature
d) To increase the kinetic energy
Answer: b
Clarification: A pressure of 30 bar should be used to carry out this whole process. The oxygen assists in the burning of coal sample.
3. Which material is used in the making of the cylindrical bomb?
a) Carbon steels
b) Alloy steels
c) Ferritic stainless steels
d) Austenitic stainless steels
Answer: d
Clarification: These steels are used to prevent the bomb from corrosion. These steels are also capable of withstanding a pressure of at least 50 atm.
4. What is the role of the small ring attached to the electrode in a bomb?
a) It acts as a support to the crucible
b) It is used to connect the electrode and the crucible
c) It is used as an intermediate for magnesium wire
d) It helps to collect the fuel at a point in the crucible
Answer: a
Clarification: Since the electrode connected is of tubular form, the ring attached to it makes good support between them. This electrode also acts as an oxygen inlet.
5. Why does the copper calorimeter surrounded by an air jacket and water jacket respectively in a bomb?
a) To resist the calorimeter with moisture particles
b) To carry out the process of combustion
c) To prevent the loss of heat due to radiation
d) To provide stability to the crucible inside the bomb
Answer: c
Clarification: When there is a change in temperature inside the bomb, there is a loss of heat due to radiation which is then absorbed by the air jacket and water jacket present in it.
6. Why only Beckmann or fixed zero thermometer are used to note down the temperature reading?
a) Since they can read temperature difference upto 1/100th of a degree
b) Since they have a high mercury level
c) Since they give a precise value of the temperature
d) Since they give accurate readings when dissolved in water
Answer: a
Clarification: When the current is supplied from a 6 volt battery, then there is a rise in temperature, due to which some temperature change occurs which is very small, so to calculate a perfect value for this temperature change Beckmann thermometer is used.
7. What is the use of gas releasing pin in the bomb?
a) To remove the oxygen gas from the bomb
b) To release the pressure from the bomb
c) To release the water vapour
d) To remove the carbon containing gases (such as CH4, CO2 etc)
Answer: b
Clarification: The pressure required in the bomb should be constant, so as to measure the change in enthalpy of the solution. Sometimes when the value of pressure is increased above to the suitability of the bomb, then to keep the pressure constant gas releasing pin is used.
8. Which material is used for making the wires, which are connected to the crucible containing fuel sample?
a) Arsenic
b) Phosphorous
c) Sulphur
d) Magnesium
Answer: d
Clarification: Since these wires are connected to the electrode from the crucible, they should be good conductors. Platinum is also used for this process.
9. What is the basic formulae for calculating gross calorific value in bomb calorimeter?
a) θ = [(W+w)(t2+t1)]/m
b) θ = [(W-w)(t2-t1)]/m
c) θ = [(W+w)(t2-t1)]/m
d) θ = [(W+w)(t2+t1)]/m
Answer: c
Clarification: Its unit is cal/gm. Here t2-t1 is the temperature difference and W+w is the total weight.
θ = [(W+w)(t2-t1)]/m
where θ is gross calorific value, W is the weight of the water sample taken in calorimeter, w is the weight of water equivalent, t1 is the initial temperature, t2 is the final temperature and m is the weight of the fuel sample taken respectively.