Question

Consider Teflon, the polymer made from tetrafluoroethylene. (a) Draw a portion of the Teflon molecule. (b) Calculate the molar mass of a Teflon molecule that contains \(5.0 \times 10^{4} \mathrm{CF}_{2}\) units. (c) What are the mass percents of \(\mathrm{C}\) and \(\mathrm{F}\) in Teflon?

Short answer

Question: Draw a portion of the Teflon molecule, calculate the molar mass of a Teflon molecule containing \(5.0 \times 10^{4}\) CF\(_2\) units, and find the mass percents of carbon (C) and fluorine (F) in Teflon. Answer: A portion of the Teflon molecule can be represented as: -[-CF\(_2\)-][-CF\(_2\)-][-CF\(_2\)-]... The molar mass of the Teflon molecule containing \(5.0 \times 10^{4}\) CF\(_2\) units is 2,500,500 g/mol. The mass percents of carbon (C) and fluorine (F) in Teflon are 24.02% and 75.98%, respectively.

Step-by-step solution

(a) Drawing a Portion of the Teflon Molecule

Teflon is a polymer made from tetrafluoroethylene, which has the chemical formula C\(_2\)F\(_4\). Its basic unit is a carbon-fluorine (CF\(_2\)) group. In a Teflon molecule, a long chain of CF\(_2\) groups is formed. We can draw a portion of the Teflon molecule as follows: -[-CF\(_2\)-][-CF\(_2\)-][-CF\(_2\)-]... Here, each bracket represents a CF\(_2\) unit, and the dashes indicate the connections between the units.

(b) Calculating the Molar Mass of a Teflon Molecule

To calculate the molar mass of a Teflon molecule with \(5.0 \times 10^{4}\) CF\(_2\) units, we first need to determine the molar mass of a single CF\(_2\) unit. The molar mass of carbon (C) is 12.01 g/mol, and the molar mass of fluorine (F) is 19.00 g/mol. Therefore, the molar mass of a CF\(_2\) unit is: Molar mass of CF\(_2\) = 12.01 g/mol (C) + 2 × 19.00 g/mol (F) = 12.01 + 38.00 = 50.01 g/mol Now we can calculate the molar mass of the entire Teflon molecule with \(5.0 \times 10^{4}\) CF\(_2\) units: Molar mass of Teflon = (50.01 g/mol) × \(5.0 \times 10^{4}\) = 2,500,500 g/mol

(c) Calculating Mass Percents of Carbon and Fluorine in Teflon

To find the mass percents of carbon (C) and fluorine (F) in Teflon, we first need to determine the mass of C and F in one CF\(_2\) unit: Mass of C in CF\(_2\) = 12.01 g/mol Mass of F in CF\(_2\) = 2 × 19.00 g/mol = 38.00 g/mol Now we can calculate the mass percent of each element: Mass percent of C = (Mass of C in CF\(_2\) / Molar mass of CF\(_2\)) × 100 = (12.01 g/mol / 50.01 g/mol) × 100 = 24.02 % Mass percent of F = (Mass of F in CF\(_2\) / Molar mass of CF\(_2\)) × 100 = (38.00 g/mol / 50.01 g/mol) × 100 = 75.98 % Thus, the mass percents of carbon (C) and fluorine (F) in Teflon are 24.02% and 75.98%, respectively.

Key concepts

Molar Mass Calculation

When you encounter the term 'molar mass', it's really just a fancy way of stating the mass of one mole of a substance, measured in grams per mole (g/mol). It's a crucial concept in chemistry because it bridges the gap between the microscopic scale of atoms and molecules and the macroscopic world we live in.

For polymers like Teflon, calculating the molar mass can seem daunting due to the large number of repeating units. The secret is to tackle the problem step by step. First, get the molar mass of the repeating unit, which is the CF₂ group in Teflon's case. Once you have that number, multiply it by the number of such units in the polymer. This will give you the total molar mass of the polymer molecule.

Remember, accuracy is critical. Ensure you check the atomic masses of elements from a reliable periodic table and use the correct number of significant figures to reflect the precision of your calculation.

Polymer Structure

Polymer structure refers to the arrangement of the repeating units that make up the polymer. These structures can get quite complex, but Teflon keeps it relatively simple. It consists of a long chain of carbon atoms, each bonded to two fluorine atoms—denoted as CF₂. This linear structure is what imparts Teflon's unique characteristics, such as its non-stick properties and high heat resistance.

If you're drawing this, imagine it like a long train where each carriage is a CF₂ group. The lines, or bonds, that connect them are like the couplings on a train. A good tip is to always ensure the structure shows clear bonds between the carbon and fluorine atoms, maintaining the order of the chain. Getting familiar with this repetitive structure gives insight into how the physical properties of polymers like Teflon arise from their molecular architecture.

Mass Percent Composition

Mass percent composition is a way to express which parts of a compound's mass come from which elements. In simpler terms, it tells you how much of each element is in a substance, as a percentage of the total mass. This information is incredibly handy when you're trying to figure out if you have the right amount of each element in a compound.

To calculate the mass percent composition, you start by finding the mass contribution of each element in one mole of the compound. Then, divide each of these by the molar mass of the entire compound and multiply by 100 to convert it to a percentage.

• Remember that the sum of the mass percentages of all elements in a compound will always add up to 100%.
• Accuracy in calculations will ensure that you're not left with erroneous percentages that don't add up or reflect the true composition of the substance.

It's an essential technique for understanding the make-up of compounds, especially complex ones like polymers.