A sample of water was known to contain chloride ions. To determine the concentration of chloride ions in the water sample, a student added a solution of silver nitrate to 500mL of the water. 1.26g of silver chloride percipitate formed. What was the concentration of chloride ions in the water sample?
Convert g AgCl to mols. mols = grams/molar mass
There is 1 mol Cl to 1 mol AgCl; therefore, mols Cl is the same as mols AgCl.
Then M = mols/L soln.
To determine the concentration of chloride ions in the water sample, we need to use the given information about the mass of the precipitate formed.
First, let's write the balanced chemical equation for the reaction:
AgNO3 + Cl- → AgCl + NO3-
From the equation, we can see that each mole of AgNO3 reacts with one mole of Cl- ions to form one mole of AgCl precipitate.
Next, we need to calculate the number of moles of AgCl precipitate formed. To do this, we need to know the molar mass of AgCl. The molar mass of AgCl is 143.32 g/mol (107.87 g/mol for Ag + 35.45 g/mol for Cl).
Using the given mass of the precipitate (1.26g) and the molar mass of AgCl, we can calculate the number of moles of AgCl:
moles of AgCl = mass of AgCl / molar mass of AgCl
= 1.26g / 143.32 g/mol
≈ 0.0088 mol
Since one mole of AgCl corresponds to one mole of Cl- ions, the moles of Cl- ions in the water sample is also 0.0088 mol.
Now, we need to find the concentration of chloride ions in the water sample. Concentration is defined as the amount of solute (in moles) divided by the volume of solution (in liters).
Given:
Volume of water sample = 500mL = 0.5 L
Concentration of chloride ions = moles of Cl- ions / volume of water sample
= 0.0088 mol / 0.5 L
≈ 0.0176 mol/L
Therefore, the concentration of chloride ions in the water sample is approximately 0.0176 mol/L.