Question

A polymeric substance, tetrafluoroethylene, can be represented by the formula
${{\text{(}}{{\text{C}}_{\text{2}}}{{\text{F}}_{\text{4}}}{\text{)}}_{\text{x}}}{\text{\;}}$where x is a large number. The material was prepared by polymerizing ${{\text{C}}_{\text{2}}}{{\text{F}}_{\text{4}}}$ ​ in the presence of a sulphur-bearing catalyst that serves as a nucleus upon which the polymer grew. The final product was found to contain $0.012\% \;{\text{ S}}$. What is that value of x, if each polymeric molecule contains one sulphur atom? Assume that the catalyst contributes a negligible amount to the total mass of the polymer. ($F = 19,\;S = 32$)

Answer 1

To answer this question, you should know how to calculate the presence of one mole of sulphur in how much amount of polymer. Use this value to find the value of x as you know the mass of the single monomer of the polymer.

Complete Step by step solution:
We know that a monomer is a molecule that forms the basic unit for polymers. One monomer binds to other monomers to generate repeating chain molecules through a process known as polymerization.
Since 1 molecule of the polymer contains 1 atom of ${\text{S}}$ .
1-gram mole of this polymer should contain 1 gram mole of S or $1 \times 32$g of Sulphur.
Now we are given that, $0.012\% \;{\text{ S}}$ is present in this compound. That means $0.012$g S is present in 100g of the polymer. So, ${\text{1g of S}}$ will be present in $\frac{{100}}{{0.012}}$ g of polymer.
Now, ${\text{32 g of S}}$will be present in $\frac{{100}}{{0.012}} \times 32$g of polymer. Solving this relation, we get $2.7 \times {10^5}$g of polymer.
It is mentioned in the question that molecular formula of the polymer is ${{\text{(}}{{\text{C}}_{\text{2}}}{{\text{F}}_{\text{4}}}{\text{)}}_{\text{x}}}{\text{\;}}$ .
Now, Molar mass = 100 x
But we already have calculated the mass of the polymer. Hence, 100x=$2.7 \times {10^5}$g
$\therefore {\text{x}} = 2.7 \times {10^3}$ formula unit/ mass

Note: Tetrafluoroethylene is used to synthesize Teflon. It is stable at low temperature and has a very high melting point. It has electric insulator and hydrophobic properties. It is used in laboratory equipment so that equipment can resist corrosive chemicals. It is used in the coating of cookware and utensils. Teflon is used to impart strain-resistance to fabric, carpets and wall cover. The following equation shows the chemical formula of Teflon:
${\text{n}}{{\text{F}}_{\text{2}}}{\text{C = C}}{{\text{F}}_{\text{2}}} \to {({\text{ - }}{{\text{F}}_{\text{2}}}{\text{C - C}}{{\text{F}}_{\text{2}}} - )_n}$