Question

\(0.3780 \mathrm{~g}\) of an organic chloro compound gave \(0.5740 \mathrm{~g}\) of silver chloride in Carius estimation. Calculate the percentage of chlorine present in the compound.

Short answer

The percentage of chlorine in the compound is approximately 37.62%.

Step-by-step solution

Determine Molar Mass of Silver Chloride

The molar mass of silver chloride (AgCl) is the sum of the molar mass of silver (Ag) which is approximately 107.87 g/mol and chlorine (Cl) which is about 35.45 g/mol. Therefore, the molar mass of AgCl is approximately 143.32 g/mol.

Calculate Moles of Silver Chloride Formed

To find the moles of AgCl, use the formula: \( \text{moles} = \frac{\text{mass}}{\text{molar mass}} \). Hence, the moles of AgCl = \( \frac{0.5740 \, \text{g}}{143.32 \, \text{g/mol}} \approx 0.00401 \, \text{mol} \).

Determine Moles of Chlorine in Silver Chloride

The reaction producing silver chloride involves equal moles of chlorine, so the moles of chlorine also equal 0.00401 mol as there is a 1:1 mole ratio between chlorine and AgCl in the product.

Calculate Mass of Chlorine in Original Compound

Calculate the mass of chlorine using: \( \text{mass} = \text{moles} \times \text{molar mass of Cl} \). Therefore, the mass of chlorine = \( 0.00401 \, \text{mol} \times 35.45 \, \text{g/mol} = 0.1422 \, \text{g} \).

Calculate Percentage of Chlorine in the Compound

To find the percentage of chlorine, use the formula: \( \frac{\text{mass of chlorine}}{\text{mass of compound}} \times 100 \). Thus, the percentage of chlorine = \( \frac{0.1422 \, \text{g}}{0.3780 \, \text{g}} \times 100 \approx 37.62\% \).

Key concepts

Percentage Composition

Percentage composition is a way of expressing the mass of a specific element in a compound as a percentage of the entire mass. This is crucial in chemistry because it helps in determining how much of each element is present in a compound.

To calculate the percentage composition of chlorine in a compound, we first need to find the mass of the chlorine in the sample. Here, we were given that 0.3780 g of the organic chloro compound was used. Then, the mass of silver chloride formed, 0.5740 g, allowed us to determine the moles of chlorine by using the formula:

• Moles of AgCl = \( \frac{\text{mass}}{\text{molar mass}} \)
• Moles of Cl in AgCl is equal due to the 1:1 stoichiometry.

By calculating the moles, we further determine the mass of chlorine itself. Finally, the percentage composition formula:

• \( \text{Percentage} = \frac{\text{mass of chlorine}}{\text{mass of compound}} \times 100 \)

helps us find that 37.62% of chlorine is present in the compound, which is a vital step in understanding the sample's chemical makeup.

Chlorine Determination

Chlorine determination allows chemists to pinpoint how much chlorine is in a substance. This example uses Carius estimation, a classic method to measure the chlorine content in organic compounds.

The process begins with the organic compound being burned with silver nitrate, forming silver chloride (AgCl). The key part of the method is understanding the stoichiometric relationship between chlorine and silver chloride. Each chlorine atom in the original compound results in one mole of AgCl according to the reaction. Thus, by weighing the AgCl, we indirectly determine the chlorine content.

• We found 0.00401 moles of AgCl from a mass of 0.5740 g.
• This is directly converted to chlorine moles because of the 1:1 ratio.

Once the moles of chlorine are known, they are converted to mass using the chlorine molar mass. This allows precise determination of chlorine percentage, offering insights into the compound structure and elemental makeup.

Molar Mass Calculation

Calculating the molar mass is a fundamental concept in chemistry that aids in converting between mass and moles. Molar mass is the mass of one mole of a substance; it is necessary for determining proportions in chemical reactions.

• The molar mass of silver chloride (AgCl) is calculated as the sum of its constituent elements: silver (Ag) and chlorine (Cl).
• Ag has a molar mass of 107.87 g/mol, and Cl is 35.45 g/mol.
• Adding these gives AgCl a molar mass of approximately 143.32 g/mol.

In real-world chemistry, this calculation is used as a conversion factor. For our exercise, it was essential to determine how many moles of silver chloride were formed from a given mass. By obtaining the moles of AgCl through:

• \( \text{Moles} = \frac{\text{Mass}}{\text{Molar Mass}} \)

Scientists could accurately calculate the respective moles of chlorine. Understanding and performing molar mass calculations is thus critical in analyzing compounds and reactions.