250+ TOP MCQs on Refrigerants – Designation System and Answers

Refrigeration Multiple Choice Questions on “Refrigerants – Designation System”.

1. What is the meaning of using two digits after the R letter?
a) The base of refrigerant
b) Number of molecules
c) Number of refrigerants in mixture
d) Number of isotopes
Answer: a
Clarification: When a number follows R, then it shows the base of refrigerant. The base is the main element in the refrigerant. So, for R – 11, R – 12, etc. where two digits are followed, it means these have a base as methane.

2. What is the meaning of using three digits after the R letter?
a) Methane based refrigerants
b) Number of molecules
c) Number of refrigerants in the mixture
d) Ethane based refrigerants
Answer: d
Clarification: When a number follows R, then it shows the base of refrigerant. The base is the main element in the refrigerant. So, for R – 114, R – 113, etc. where three digits are followed, it means these have a base as ethane.

3. What is the meaning of the last digit in three digits after R type of halo-carbon refrigerants?
a) Number of hydrogen atoms
b) Number of fluorine atoms
c) Number of carbon atoms
d) Ethane based refrigerants
Answer: b
Clarification: In the representation of writing a three-digit or ethane-based halo-carbon refrigerant the last digit from left shows the number of fluorine atoms in that refrigerant. Ex. R – 113 is having three fluorine atoms, which is C₂Cl₃F₃.

4. What is the meaning of middle digit in three digits after R type of halo-carbon refrigerants?
a) Number of hydrogen atoms
b) Number of fluorine atoms
c) Number of hydrogen atoms + 1
d) Number of carbon atoms
Answer: c
Clarification: In the representation of writing a three-digit or ethane-based halo-carbon refrigerant the middle digit from left shows one more than the number of hydrogen atoms in that refrigerant. Ex: R – 113 is having 0 hydrogen atoms which is C₂Cl₃F₃.

5. What is the meaning of the first digit in three digits after R type of halo-carbon refrigerants?
a) Number of hydrogen atoms + 2
b) Number of carbon atoms – 1
c) Number of carbon atoms + 1
d) Number of carbon atoms
Answer: b
Clarification: In the representation of writing a three-digit or ethane-based halo-carbon refrigerant the first digit from left shows one less than the number of carbon atoms in that refrigerant. Ex: R – 113 is having two carbon atoms, which is C₂Cl₃F₃.

6. Which letter is assigned to the number of hydrogen atoms in a refrigerant as per designation system?
a) m
b) n
c) p
d) q
Answer: b
Clarification: The general formula is obtained for the number of atoms of each element for methane and ethane-based refrigerants. So, as per the designation system of refrigerants number of a hydrogen atom in a refrigerant is given by letter n. It is denoted as H_n.

7. Which letter is assigned to the number of chlorine atoms in a refrigerant as per designation system?
a) m
b) n
c) p
d) q
Answer: c
Clarification: The general formula is obtained for the number of atoms of each element for methane and ethane-based refrigerants. So, as per the designation system of refrigerants number of the chlorine atom in a refrigerant is given by letter p. It is denoted as Cl_p.

8. Which letter is assigned to the number of carbon atoms in a refrigerant as per designation system?
a) m
b) n
c) p
d) q
Answer: a
Clarification: The general formula is obtained for the number of atoms of each element for methane and ethane-based refrigerants. So, as per the designation system of refrigerants number of carbon atom in a refrigerant is given by letter m. It is denoted as C_m.

9. Which letter is assigned to the number of fluorine atoms in a refrigerant as per designation system?
a) m
b) n
c) p
d) q
Answer: d
Clarification: The general formula is obtained for the number of atoms of each element for methane and ethane-based refrigerants. So, as per the designation system of refrigerants number of the fluorine atom in a refrigerant is given by letter q. It is denoted as F_q.

10. What is the general chemical formula to be fulfilled by the number of atoms present in a refrigerant?
a) n + p + m = 2q + 2
b) n + p + q = 2m + 2
c) n + m + q = 2p + 2
d) m + p + q = 2n + 2
Answer: b
Clarification: The general formula is obtained for the number of atoms of each element for methane and ethane-based refrigerants which is n + p + q = 2m + 2. The summation of the number of atoms of hydrogen, chlorine, and fluorine should be equal to two more than twice the number of carbon atoms in the refrigerant. This general chemical formula is crucial and is very helpful to choose the appropriate refrigerant.

11. Which of the following is the right way to represent a refrigerant number?
a) R (m – 1) (n + 1) (q)
b) R (m + 1) (n + 1) (q)
c) R (m – 1) (n + 1) (p)
d) R (m – 1) (n + 1) (q – 1)
Answer: a
Clarification: When a number follows R, then it shows the base of refrigerant. The base is the main element in the refrigerant. So, for R – 114, R – 113, etc. where three digits are followed, it means these have a base as ethane. Where, the first digit shows one less than the number of carbon atoms i.e., m – 1. The second digit shows one more than the number of hydrogen atoms i.e., n + 1. The third digit shows the number of fluorine atoms i.e., q. So, the correct way of representation is R (m – 1) (n + 1) (q).

12. __________ based refrigerant is represented by two digits, followed by R?
a) Ethane
b) Propane
c) Ammonia
d) Methane
Answer: d
Clarification: When a number follows R, then it shows the base of refrigerant. The base is the main element in the refrigerant. So, for R – 11, R – 12, etc. where two digits are followed, it means these have a base as methane i.e., Methane based refrigerant is represented by two digits followed by R.

13. Dichloro-trifluoro-ethane has a refrigerant number of R-113 as per designation system.
a) False
b) True
Answer: a
Clarification: Refrigerant number of Dichloro-trifluoro-ethane i.e., CHCl₂CF₃ can be found by the formula of designation system,
n = 1, p = 2 and q = 3. Hence, by using n + p + q = 2m + 2, we get m = 2.
So, R (m – 1) (n + 1) (q) = R (2 – 1) (1 + 1) (3) = R123 = R – 123.

14. Dichloro-difluoro-methane has refrigerant number of R-12 as per designation system.
a) False
b) True
Answer: b
Clarification: Refrigerant number of Dichloro-difluoro-methane i.e. CCl₂F₂ can be found by formula of designation system,
n = 0, p = 2 and q = 2. Hence, by using n + p + q = 2m + 2, we get m = 1.
So, R (m – 1) (n + 1) (q) = R (1 – 1) (0 + 1) (2) = R012 = R – 12 as 0 can be omitted.

15. ________ refrigerants follow a formula where the molecular mass of the compound is added.
a) Halocarbon
b) Halo hydrogen
c) Inorganic
d) Azeotrope
Answer: c
Clarification: The general chemical formula for inorganic refrigerants is given by 700 + molecular mass of the compound. Ex: Ammonia is given by R – 717 where 17 is the molecular mass of NH₃ so, 700 + 17 = 717.