# Concentration of an original solution

• apbuiii
In summary, when 38 mL of 0.1250 M H2SO4 (sulfuric acid) is added to 100 mL of solution of PbI2 (Lead(II) Iodide) a precipitate of PbSO4 forms. The PbSO4 (Lead(II) Sulfate) is then filtered from the solution, dried, and weighed. If the recovered PbSO4 is found to have a mass of 0.0471 g, the concentration of iodide ions in the original solution is 0.00225 M.
apbuiii

## Homework Statement

When 38 mL of 0.1250 M H2SO4 (sulfuric acid) is added to 100 mL of solution of PbI2 (Lead(II) Iodide) a precipitate of PbSO4 forms. The PbSO4 (Lead(II) Sulfate) is then filtered from the solution, dried, and weighed. If the recovered PbSO4 is found to have a mass of 0.0471 g, what was the concentration of iodide ions in the original solution?

## Homework Equations

So I started with an equation: H2SO4 + PbI2 = PbSO4 + 2HI; Molarity(M)= Moles of solute/moles of solution

## The Attempt at a Solution

I treated this problem like a limiting reagent. I assumed that the amount recovered was 100% yield (Perfect world. I know haha)

If Sulfuric acid was the limiting reagent, then the amount of moles of Lead(II) Sulfate would be 1.44 grams; which is 0.00475 moles of Lead(II) Sulfate. So that means sulfuric acid is in excess and the Lead(II) Iodide was the limiting reagent. To figure out the Molarity of the PbI2 I worked backwards from moles of PbSO4 recovered: 0.1L "X" = 1.553X10-4 moles. This gave me 1.553X10-3 M PbI2. Then, I changed this from M of PbI[/sup]2[/sub] to M of Iodine: (1.553X10-3 M PbI2) (2mol I/ 1mol PbI2) = 3.11X10-3 M I. To get moles of I, I multiplied by 0.1 L PbI2 solution, and I got 3.11X10-4 moles I. finally, I divided that by Liters of beginning solution which was 100mL + 38mL: (3.11X10-4 moles I)/(.138L) = 0.00225 M of Iodine.

Are my steps correct? I know this was a kind of a long process, but if you could please give me feedback that would be much appreciated!

apbuiii said:
To figure out the Molarity of the PbI2 I worked backwards from moles of PbSO4 recovered: 0.1L "X" = 1.553X10-4 moles. This gave me 1.553X10-3 M PbI2. Then, I changed this from M of PbI[/sup]2[/sub] to M of Iodine: (1.553X10-3 M PbI2) (2mol I/ 1mol PbI2) = 3.11X10-3 M I.

I have not checked numbers, but seems to me like here you already have your answer. Original solution was the one before acid was added.

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Okay, I see. So I don't have to add the 38mL of Sulfuric acid for the liters of solution. I kind of thought so. I guess the information about Sulfuric acid was superfluous...

Well, it would be useful if you were expected to calculate concentration taking solubility products into account.

--

Your steps appear to be correct. The approach you took, treating the problem like a limiting reagent, is a good way to solve it. However, it is important to note that in a real-world scenario, the yield may not be 100%, so the calculated concentration of iodine ions may not be completely accurate. Also, it would be helpful to include units in your final answer (0.00225 M iodine ions). Overall, your solution is well thought out and shows a good understanding of the concepts involved. Keep up the good work!

## What is the definition of concentration of an original solution?

The concentration of an original solution refers to the amount of solute (substance being dissolved) present in a given amount of solvent (substance doing the dissolving).

## How is concentration of an original solution measured?

The concentration of an original solution can be measured in various units, such as molarity (moles of solute per liter of solution), molality (moles of solute per kilogram of solvent), or mass percent (mass of solute per 100 grams of solution).

## Why is knowing the concentration of an original solution important?

Knowing the concentration of an original solution is important because it allows for the accurate preparation of solutions for experiments or industrial processes. It also helps in determining the amount of solute needed to achieve a desired concentration.

## How does the concentration of an original solution affect the properties of a solution?

The concentration of an original solution directly affects the properties of a solution, such as its density, boiling point, and freezing point. As the concentration increases, these properties also increase.

## How can the concentration of an original solution be changed?

The concentration of an original solution can be changed by adding more solute or solvent to the solution, or by diluting the solution with a solvent. It can also be changed through various chemical reactions that involve the solute.

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