Question

A 25.0 g sample of garden compost was analyzed for chloride content. The sample was dissolved in water and the chloride was precipitated as silver chloride. 1.58 g of dried precipitate was obtained. Calculate the percent chloride in the sample.

Answer 1

The percent chloride in the sample is 1.56%

Explanation:

Hi there!

The molecular formula of silver chloride is AgCl. Its molar mass (the mass of a mol of AgCl) is 143.32 g/mol. Then the number of moles of AgCl obtained in the precipitated will be:

1.58 g · (1 mol/143.32 g) = 0.0110 mol

Then, since 1 mol AgCl contains 1 mol Cl⁻ (chloride), in the sample of compost there will be 0.0110 mol Cl⁻.

The mass of 0.0110 mol Cl⁻ is:

0.0110 mol Cl⁻ · (35.453 g /mol) = 0.390 g Chloride.

Then, the percent chloride in the sample will be:

0.390 g · (100 % / 25.0 g) = 1.56%

The percent chloride in the sample is 1.56%