Could someone please walk me through how to solve this problem:
A sample that is 63.9 % chloride by mass is dissolved in water and treated with an excess of AgNO3. If the mass of the AgCl precipitate is 1.045g, what was the mass of the original sample?
1.045 g AgCl x (atomic mass Cl/molar mass AgCl) = about 0.26 but you need a closer answer than that. Then
[(0.26)/(mass sample)]*100 = 63.9%
Solve for mass sample.
To solve this problem, we need to use the concept of mass percent composition and stoichiometry.
Step 1: Determine the mass percent composition of chloride in the original sample.
The problem states that the sample is 63.9% chloride by mass. This means that in every 100 grams of the sample, 63.9 grams is chloride.
Step 2: Determine the mass of chloride in the original sample.
Let's assume the mass of the original sample is "x" grams. Since the sample is 63.9% chloride, we can calculate the mass of chloride in the sample by multiplying the mass of the sample (x grams) by the mass percent composition of chloride (63.9% or 0.639):
Mass of chloride = (0.639)(x) grams
Step 3: Determine the mass of silver chloride (AgCl) formed.
The problem states that an excess of AgNO3 was added, which reacts with chloride to form AgCl. The mass of AgCl formed is given as 1.045 grams.
Step 4: Set up and solve an equation to find the mass of the original sample.
Using stoichiometry, we can set up the following equation, which relates the moles of AgCl formed to the moles of chloride in the original sample:
1 mole of AgCl corresponds to 1 mole of chloride.
We know the molar mass of AgCl is 143.32 g/mol, which allows us to convert the 1.045 grams of AgCl to moles:
Moles of AgCl = 1.045 grams of AgCl / 143.32 g/mol
Since 1 mole of AgCl corresponds to 1 mole of chloride, the moles of chloride in the sample are the same as the moles of AgCl formed:
Moles of chloride = Moles of AgCl
Finally, we can find the mass of the original sample using the mass of chloride:
Mass of original sample = Mass of chloride / (mass percent composition of chloride / 100)
Mass of original sample = (Mass of chloride) / (0.639)
By substituting the values into the equation, you can find the mass of the original sample.