Calculating Molarity of KOH Solution: Discrepancy in Reported Results

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Discussion Overview

The discussion revolves around the calculation of the molarity of a KOH solution, specifically addressing a discrepancy between the participant's calculated molarity of 0.52 M and a colleague's reported value of 0.78 M. The scope includes technical calculations related to solution preparation and molarity determination.

Discussion Character

  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant calculates the final molarity of their KOH solution to be 0.52 M based on adding 40.69 lb of 90% anhydrous KOH to 561.86 liters of water.
  • Another participant questions the accuracy of the reported molarity of 0.78 M, suggesting that it seems incorrect based on their calculations.
  • A participant mentions that "anhydrous KOH" is K2O, prompting further discussion about the implications of this definition on the calculations.
  • One participant calculates that the molarity for K2O would be 0.62 M, assuming a solution density of 1.0247 g/mL, and notes that the ratio of the two molarities (0.52/0.78) is exactly 2/3, indicating a potential simple error in conversions.

Areas of Agreement / Disagreement

Participants do not reach a consensus on the correct molarity, with multiple competing views on the calculations and definitions involved. The discussion remains unresolved regarding the accuracy of the reported molarity.

Contextual Notes

There are limitations regarding the assumptions made in the calculations, such as the density of the solution and the definition of "anhydrous KOH." These factors may influence the final molarity results but are not fully resolved in the discussion.

pmason61
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I'm trying to verify the final molarity of my solution.

I'm adding 40.69 lb of 90% anhydrous KOH to 148.43 (561.86L) gallons of water . I get a final molarity of 0.52. The report I'm reading arrives at a molarity of 0.78. Is this an error?

Thanks to anyone who can provide the calcs.
 
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Is this homework? If so, we can move it to the correct subforum.
 
No it's not homework. I'm checking the calcs in a report by a colleague in nthe alkaline hydrolysis business and his stated 0.78 M KOH seems off to me. I get 297.01 moles in 561.86 liters to be 0.52 molarity
 
pmason61 said:
I'm adding 40.69 lb of 90% anhydrous KOH to 148.43 (561.86L) gallons of water . I get a final molarity of 0.52. The report I'm reading arrives at a molarity of 0.78. Is this an error?
"Anhydrous KOH" is K2O; any thoughts?
 
What's the other 10% of the anhydrous KOH?
 
Bystander said:
"Anhydrous KOH" is K2O; any thoughts?

Doesn't change the result enough. I am getting 0.52 M for KOH and 0.62 M for K2O (assuming the density of the solution to be 1.0247 g/mL, which is more or less OK for 0.52 M, should be a bit higher for 0.62 M).

Note 0.52/0.78 is exactly 2/3, such coincidences often mean some simple error in conversions.
 

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