# Environmental Science: Numerical Questions – Conversion CFC to Formula

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## Type I - Number to Formula

1. Chemical formula for CFC-113 is

1. CCl2F2
2. CCl3F3
3. C2 Cl3F3
4. CCl2F3

Explanation:

• Step 1 – Add 90
• Step 2 – Calculate the number of Carbon atoms, Hydrogen atoms and Fluorine atoms
• Step 3 – write the formula using the C, H & F atoms

Step 1: 90 + 113 = 203

Step 2:

• Number of Carbon atoms = 2
• Number of Hydrogen atoms = 0
• Number of Fluorine atoms = 3

Step 3: The CFC formula will be C2F3Cl3

## Type II – Formula to Number

2. What is the CFC number for the halocarbon CCl2F2CF3?

1. 115
2. 132
3. 134
4. 143

Explanation:

To calculate the CFC number:

• Consider the formula in the number of carbon, hydrogen , fluorine (do not include chlorine)
• Subtract the number with 90
• The number obtained thereafter is the formula.

CCl2F2CF3 = C2F5Cl2

Step 1:

• Number of Carbon atoms = 2
• Number of Hydrogen atoms = 0
• Number of Fluorine atoms = 5

So, the number obtained is 205 (as we do not consider Chlorine atoms)

Step 2: 205 - 90 = 115

Step 3: The CFC number will be CFC 115

## Type III – Formula for Halons

3. The halon H − 1211 has the following chemical composition:

1. CF2ClBr
2. CCl2FBr
3. CCl2F2
4. CBr2ClF