Question

An organic compound is found to have the formula \(\mathrm{C}_{5} \mathrm{H}_{10} \mathrm{ONCl}\). The percentage of nitrogen present in it is: (a) \(23.36 \%\) (b) \(10.3 \%\) (c) \(41.05 \%\) (d) \(5.06 \%\)

Short answer

The percentage of nitrogen is 10.3%, option (b).

Step-by-step solution

Determine the Molar Mass of the Molecule

Calculate the molar mass of the compound \( \mathrm{C}_{5} \mathrm{H}_{10} \mathrm{ONCl} \) by adding the atomic masses of all the atoms in the formula. Use the atomic masses: C=12 g/mol, H=1 g/mol, O=16 g/mol, N=14 g/mol, Cl=35.5 g/mol. First, carbon: \(5 \times 12 = 60\) g/molSecond, hydrogen: \(10 \times 1 = 10\) g/molNext, oxygen: \(1 \times 16 = 16\) g/mol Then, nitrogen: \(1 \times 14 = 14\) g/mol Finally, chlorine: \(1 \times 35.5 = 35.5\) g/mol The total molar mass is \(60 + 10 + 16 + 14 + 35.5 = 135.5\) g/mol.

Calculate the Mass Percentage of Nitrogen

Now, calculate the percentage by mass of nitrogen in the compound using the formula,\[\text{Percent by mass of N} = \left(\frac{\text{Mass of N in the formula}}{\text{Molar Mass of the compound}}\right) \times 100\]The mass of nitrogen is 14 g/mol. Substituting the values:\[\left(\frac{14}{135.5}\right) \times 100 = 10.33\%\]

Key concepts

Molar Mass Calculation

Calculating the molar mass is the first step in finding the percent composition of any element within a compound. Molar mass represents the mass of one mole of a substance, which you find by adding the atomic masses of each element in the molecular formula. For instance, for the compound \(\mathrm{C}_{5}\mathrm{H}_{10}\mathrm{ONCl}\), you calculate the molar mass as follows:

• Carbon (\(C\)): There are 5 carbon atoms, each with an atomic mass of 12 g/mol, resulting in \(5 \times 12 = 60\) g/mol.
• Hydrogen (\(H\)): With 10 hydrogen atoms at 1 g/mol each, the total is \(10 \times 1 = 10\) g/mol.
• Oxygen (\(O\)): 1 oxygen atom at 16 g/mol, contributing \(1 \times 16 = 16\) g/mol.
• Nitrogen (\(N\)): 1 nitrogen atom at 14 g/mol, so \(1 \times 14 = 14\) g/mol.
• Chlorine (\(Cl\)): 1 chlorine atom at 35.5 g/mol, making \(1 \times 35.5 = 35.5\) g/mol.

Combine all these contributions to get the total molar mass of the compound, which is \(60 + 10 + 16 + 14 + 35.5 = 135.5\) g/mol. This is crucial for further calculations, as described in the next section.

Organic Compounds

Organic compounds primarily consist of carbon atoms, along with hydrogen, oxygen, nitrogen, and sometimes other elements. They form the basis of all known life due to their versatility and variety. Carbon is known as the backbone of organic chemistry because of its ability to form stable bonds with many elements.The compound \(\mathrm{C}_{5}\mathrm{H}_{10}\mathrm{ONCl}\) is a classic example of an organic compound consisting of different elements.

• The carbon and hydrogen atoms form a hydrocarbon skeleton.
• Elements like oxygen, nitrogen, and chlorine add functional groups, providing specific chemical properties and reactions.

Organic chemistry studies these compounds and their transformations, understanding how different atoms respond within the structure, and exploring the endless possibilities of molecular architecture. Identifying the unique elements in an organic compound, like nitrogen in this exercise, is essential for understanding its behavior and composition.

Atomic Mass

Atomic mass is the weight of a single atom of an element, typically measured in atomic mass units (amu) or grams per mole (g/mol). It reflects the number of protons and neutrons in the nucleus, as electrons have negligible mass. Each element on the periodic table has a unique atomic mass, which is used in various chemical calculations.For instance, consider nitrogen in our compound \(\mathrm{C}_{5}\mathrm{H}_{10}\mathrm{ONCl}\). Nitrogen has an atomic mass of 14 g/mol, which means each mole of nitrogen atoms weighs 14 grams.

• This atomic mass helps determine how much each atom contributes to the overall molar mass of a compound.
• It is crucial in calculating the percentage composition of specific elements within a compound, such as the 10.33% composition of nitrogen found.

Correctly understanding atomic mass ensures precise molar mass calculations and accurate determination of element compositions in compounds.