Calculating Molarity of Cr(III) Sulfate and Sulfate Ion

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Discussion Overview

The discussion revolves around calculating the molarity of chromium(III) sulfate and the sulfate ion concentration after dilution in a chemistry homework context. Participants are addressing the steps necessary to solve the problem, particularly focusing on the dilution process and the relevant volumes involved.

Discussion Character

  • Homework-related
  • Technical explanation
  • Conceptual clarification

Main Points Raised

  • One participant has successfully calculated the molarity of Cr(III) sulfate in the original solution but is uncertain about how to proceed with calculating the molarity of sulfate ions in the diluted solution.
  • Another participant suggests reviewing the process of diluting and mixing solutions to aid in understanding the calculations.
  • Multiple participants express confusion regarding the initial and final volumes needed for the calculations, questioning whether the molarity from part (a) should be used for part (b).
  • A participant clarifies that the final volume is explicitly stated in the problem as 250 mL, indicating that the density is not necessary for this specific problem.

Areas of Agreement / Disagreement

Participants generally agree on the need to clarify the initial and final volumes for the dilution calculation. However, there is disagreement and confusion about how to interpret the problem statement and apply the information correctly.

Contextual Notes

Some participants note that the problem description provides specific volumes, which should simplify the calculations. There is uncertainty about the application of density in this context, as it has not been discussed in class.

Who May Find This Useful

Students working on similar chemistry problems involving dilution and concentration calculations may find this discussion helpful.

Zhalfirin88
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Homework Statement


21.76g Cr(III) Sulfate is dissolved in enough water to give 500.0 mL of solution. 10.00 mL of this solution is pipetted into a 250.0mL volumatric flask and diluted to the mark.

a) Calculate the molarity of Cr(III) Sulfate in original solution
b) Calculate the molarity of sulfate ion in the diluted solution.

The Attempt at a Solution


I figured out a) but I'm having trouble with b) where do I start?
 
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I don't get it, what's the final and initial volumes for this problem? And for the molarity, would it be the one I solved for in a) ?
 
Zhalfirin88 said:
I don't get it, what's the final and initial volumes for this problem? And for the molarity, would it be the one I solved for in a) ?

Those are literally in the problem description.
 
symbolipoint said:
Those are literally in the problem description.

That doesn't help.

The link he posted said the final volume is the sum of all volumes. Now, the sum of all what volumes? In class, there hasn't been a single mention of densities so I don't understand your link.
 
From the question: you take 10 mL of the solution and add enough pure water to fill it up to 250 mL. What is the final volume?

Note: densities are used when you are not given final volume and you have to calculate it. In your case final volume is given verbatim in the question so you can use equation 12.2 from the linked page, no need to go any further.

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