# Environmental Science: Numerical Questions – Conversion CFC to Formula

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## Type I - Number to Formula

1. Chemical formula for CFC-113 is

CC

*l*2F2CC

*l*3F3C2 C

*l*3F3CC

*l*2F3

Answer: (C) C2 C*l*3F3

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 CCl_{2}F_{2}CF_{3} ?

115

132

134

143

Answer: (A) 115

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.

CCl_{2}F_{2}CF_{3} = C_{2}F_{5}Cl_{2}

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:

CF

_{2}ClBrCCl

_{2}FBrCCl

_{2}F_{2}CBr

_{2}ClF

Answer: CF_{2}ClBr

Each halon has a number system of abcd where.

a - Is the number of carbon atoms

b - The number of fluorine atoms

c - The number of chlorine atoms

d - The number of bromine atoms

-Mayank