Suppose that a 0.6123-g unknown chloride-containing sample was dissolved, and and AgCl precipitated by adding a AgNO3 solution. The precipitate was filtered, ignited, and found to weigh 0.3324 g. What was the percent chloride in the unknown?
moles AgCl = mass AgCl/molar mass AgCl.
moles Cl^- is the same as moles AgCl since there is 1 Cl ion in 1 molecule of AgCl.
Then grams Cl = moles Cl x atomic mass Cl.
%Cl = (mass Cl/mass sample)*100 = ?%
13.39%
To find the percent chloride in the unknown sample, we can use the concept of stoichiometry and mass percent composition.
Step 1: Determine the mass of silver chloride precipitate.
Given that the mass of the precipitate (AgCl) is 0.3324 g.
Step 2: Convert the mass of AgCl to moles.
The molar mass of AgCl is 143.32 g/mol (atomic mass of Ag = 107.87 g/mol + atomic mass of Cl = 35.45 g/mol).
We can use this molar mass to convert the mass of AgCl to moles by dividing the mass by the molar mass:
0.3324 g / 143.32 g/mol = 0.002316 mol.
Step 3: Determine the number of moles of chloride ions (Cl-) in the sample.
Since AgCl is a 1:1 ratio compound between silver (Ag+) and chloride (Cl-) ions, we can conclude that the moles of chloride ions are the same as the moles of AgCl.
Therefore, the moles of chloride ions in the sample are 0.002316 mol.
Step 4: Determine the mass of chloride.
To find the mass of chloride, we use the atomic mass of chlorine, which is 35.45 g/mol.
The mass of chloride can be calculated by multiplying the moles of chloride by the molar mass of chlorine:
0.002316 mol × 35.45 g/mol = 0.08206 g.
Step 5: Calculate the percent chloride in the sample.
To find the percent chloride, divide the mass of chloride by the mass of the unknown sample and multiply by 100:
Percent chloride = (0.08206 g / 0.6123 g) × 100% ≈ 13.4%.
Therefore, the percent chloride in the unknown sample is approximately 13.4%.