The refrigerant R-12, also known as dichlorodifluoromethane (CCl2F2), is a chlorofluorocarbon (CFC) that was commonly used in air conditioning and refrigeration systems. It is a colorless gas that is highly stable and has a low boiling point, making it suitable for use as a refrigerant.

To determine the number of hydrogen atoms in R-12, we need to examine its molecular structure. R-12 consists of two chlorine atoms (Cl), one carbon atom (C), and two fluorine atoms (F) bonded together. The molecular formula for R-12 is CCl2F2.

- Molecular Structure of R-12:

C
/ \
Cl Cl
\ /
F
|
F

- Chlorine atoms (Cl): R-12 has two chlorine atoms, which are represented by the symbol Cl. Each chlorine atom has 7 valence electrons. In R-12, both chlorine atoms are bonded to the central carbon atom.

- Carbon atom (C): R-12 has one carbon atom, represented by the symbol C. Carbon has 4 valence electrons. In R-12, the carbon atom is bonded to both chlorine atoms and two fluorine atoms.

- Fluorine atoms (F): R-12 has two fluorine atoms, represented by the symbol F. Each fluorine atom has 7 valence electrons. In R-12, both fluorine atoms are bonded to the central carbon atom.

- Calculation:

To determine the number of hydrogen atoms in R-12, we need to look at the molecular formula and structure. In this case, there are no hydrogen atoms present in the molecular formula CCl2F2. Therefore, the correct answer is option 'D' - 0 hydrogen atoms.

In summary, the refrigerant R-12 (CCl2F2) does not contain any hydrogen atoms. It consists of two chlorine atoms, one carbon atom, and two fluorine atoms. This lack of hydrogen atoms contributes to its stability and low reactivity, which made it a popular choice for refrigeration applications in the past. However, R-12 has been phased out due to its detrimental effects on the ozone layer.