How many moles Cl ion were present in the sample? (Use Eqs. 2 and 3.)
a. moles Cl
b. How many grams Cl ion were present? (Use Eq. 4.)
What was the mass percent Cl ion in the sample? (Use Eq. 5.)
c. % C
The Correct Answer and Explanation is:
To answer this question thoroughly, I need to know the values in Equations 2, 3, 4, and 5, or details from the experiment/sample you’re referring to (e.g., volume, molarity, or titration data). However, I can walk you through a general step-by-step method using standard chemical principles and formulas based on typical usage of such equations for calculating moles, grams, and mass percent of chloride (Cl⁻) ions.
Assumptions and General Formulas
Let’s assume you’re analyzing a sample for chloride ion (Cl⁻) using Mohr titration with silver nitrate (AgNO₃), where:
Eq. 2:
$\text{mol AgNO}_3 = M \times V$
This gives the moles of AgNO₃ used.
Eq. 3:
$\text{mol Cl}^- = \text{mol AgNO}_3$
Since Ag⁺ reacts with Cl⁻ in a 1:1 molar ratio:
$\text{Ag}^+ + \text{Cl}^- \rightarrow \text{AgCl} \downarrow$
Eq. 4:
$\text{mass of Cl}^- = \text{mol Cl}^- \times \text{molar mass of Cl}^-$
Molar mass of Cl⁻ = 35.45 g/mol.
Eq. 5:
$\text{Mass percent Cl}^- = \left( \frac{\text{mass of Cl}^-}{\text{mass of sample}} \right) \times 100$
Sample Calculation
Let’s say:
- Volume of AgNO₃ used = 0.02500 L (25.00 mL)
- Molarity of AgNO₃ = 0.100 mol/L
- Mass of sample = 0.5000 g
a. Moles of Cl⁻
Using Eq. 2 and 3:
$$
\text{mol AgNO}_3 = 0.100 \, \text{mol/L} \times 0.02500 \, \text{L} = 0.002500 \, \text{mol}
$$
$$
\text{mol Cl}^- = \text{mol AgNO}_3 = 0.002500 \, \text{mol}
$$
b. Mass of Cl⁻
Using Eq. 4:
$$
\text{mass Cl}^- = 0.002500 \, \text{mol} \times 35.45 \, \text{g/mol} = 0.08863 \, \text{g}
$$
c. Mass Percent of Cl⁻
Using Eq. 5:
$$
\text{mass percent Cl}^- = \left( \frac{0.08863}{0.5000} \right) \times 100 = 17.73\%
$$
Explanation (300+ words)
In chemical analysis, determining the amount of a specific ion in a sample is crucial for understanding composition and purity. Here, we calculate the amount of chloride ion (Cl⁻) in a given sample using a titration approach with silver nitrate (AgNO₃), a classic method known as Mohr titration. Silver nitrate reacts with chloride ions to form an insoluble precipitate of silver chloride (AgCl), and this stoichiometric 1:1 reaction forms the basis of the calculation.
First, we determine the number of moles of silver nitrate added during titration using molarity (mol/L) multiplied by the volume (L), as described in Equation 2. Since each mole of AgNO₃ reacts with exactly one mole of Cl⁻, the moles of AgNO₃ used equals the moles of Cl⁻ in the sample (Equation 3).
Next, the moles of Cl⁻ are converted to grams using the molar mass of Cl⁻ (35.45 g/mol), a standard atomic value from the periodic table (Equation 4). This gives the actual mass of chloride ion present in the sample.
Lastly, to determine the mass percent, we divide the mass of Cl⁻ by the total sample mass and multiply by 100 (Equation 5). This value reflects the proportion of chloride ion in the entire sample, a critical parameter in quality control and chemical formulations.
These steps illustrate the essential role of stoichiometry and unit conversions in analytical chemistry. Whether in water quality testing, food analysis, or industrial processes, knowing how to compute the mass percent of ions like Cl⁻ ensures accurate labeling and regulatory compliance.
If you provide the actual values or equations used in your specific scenario, I can tailor the answer further.