Determine the amount of NaOH and Sr(OH)2 based on pOH

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SUMMARY

The discussion focuses on calculating the amounts of NaOH and Sr(OH)2 in a 4.00-L solution with a pOH of 1.51, indicating a hydroxide ion concentration of 0.100 moles. The participant correctly identifies that the total moles of hydroxide ions produced by both strong bases must equal the total moles present in the solution. The confusion arises from the relationship between the dissociation of Sr(OH)2, which produces two moles of OH- per mole, compared to NaOH, which produces one mole of OH- per mole. The solution requires a systematic approach to balance the contributions of both bases to the total hydroxide concentration.

PREREQUISITES
  • Understanding of pOH and pH concepts
  • Knowledge of strong base dissociation, specifically NaOH and Sr(OH)2
  • Ability to perform stoichiometric calculations
  • Familiarity with molarity and volume relationships in solutions
NEXT STEPS
  • Review the dissociation equations for NaOH and Sr(OH)2
  • Learn how to calculate pOH and its relationship to hydroxide ion concentration
  • Practice stoichiometric problems involving multiple solutes
  • Explore the concept of equilibrium in strong base solutions
USEFUL FOR

Chemistry students, educators, and anyone involved in analytical chemistry or solution chemistry who seeks to deepen their understanding of strong base behavior and stoichiometric calculations.

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Homework Statement


Hello!
I am trying to solve the following problem:
A 4.00-L base solution contains 0.100 mol total of

NaOH and Sr(OH)2 . The pOH of the solution is 1.51.

Determine the amounts (in moles) of NaOH and

Sr(OH)2 in the solution.

Homework Equations


3. The Attempt at a Solution [/B]
I am stuck because I am not sure I correctly constructing the solution path:

We have pOH = 1.51, which means that there are 10^(-1.51) moles of OH in solution, i.e. 0.0309 moles per one liter of solution. If I have 4 liters, then shouldn't there be 0.1236 moles of OH in this solution?
But according to the problem there are only 0.100 moles of NaOH and Sr(OH)2; both are strong bases, therefore there 0.100 moles of OH in the 4 liters of solution. How can that be?
Where is my mistake?
Thank you very much!
 
Physics news on Phys.org
How many moles of OH- are produced per 1 mole of dissociating Sr(OH)2?
 
Borek said:
How many moles of OH- are produced per 1 mole of dissociating Sr(OH)2?
2 moles. There are 3 moles of OH- produced by dissociating both NaOH and Sr(OH)2, and two of those come from dissociating Sr(OH)2
 
What does it mean

ducmod said:
solution contains 0.100 mol total of NaOH and Sr(OH)2
 

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