Can't seem to match the answer help

  • Thread starter laker_gurl3
  • Start date
  • Tags
In summary, the concentration of Sr(OH)2 in a solution with a pH of 11 is 5.0 x 10^-4. This can be calculated by finding the pOH, which is 3, and then dividing the concentration of OH- (0.001) by 2 due to the stoichiometric ratio. This gives a concentration of 5.0 x 10^-4 for Sr(OH)2.
  • #1
What is the concentration of Sr(OH)2 in a solution with a pH of 11?

The answer is SUPPOSED to be 5.0 x 10^-4...buuut i keep getting 0.001..
i didnt think this would be a complicated question.. all i did was found the pOH to be 3..and found the concentration of OH, giving me .001
what am i doing wrong?:S
Physics news on
  • #2
I'm not completely sure (I should be sure though! :P)

Equation is:

Sr(OH)2 + H2O <==> 2OH- + Sr((OH)O <---??

But anyways, the important thing is that there the hydroxide anion has a subscript of 2. You have to pay attention to the stoichiometric rations; therefore the molar ratio of the concentration of Sr(OH)2 to OH is 1:2.

Your 0.001 concentration of OH- present in solution is correct, but then you have to divide it to two to get the concentration of the Sr(OH)2.

[tex]0.001 \div 2 = 0.0005 or 5.0 \times 10^{-4}[/tex]

Last edited:
  • #3

It's possible that you may be making a calculation error or using the wrong formula. The correct way to find the concentration of Sr(OH)2 in a solution with a pH of 11 is to first find the pOH, which is 14 - pH, giving you a pOH of 3. Then, use the formula [OH-] = 10^-pOH to find the concentration of hydroxide ions. In this case, [OH-] would be 10^-3 or 0.001. Since Sr(OH)2 dissociates into two hydroxide ions, the concentration of Sr(OH)2 would be half of the concentration of hydroxide ions, which is 0.0005 or 5.0 x 10^-4. Double check your calculations and make sure you are using the correct formula to get the correct answer.

What do I do if I can't seem to match the answer?

If you are having trouble matching the answer, try breaking down the problem into smaller parts and tackling them one at a time. It may also be helpful to review any relevant notes or material to better understand the concept.

Why am I having difficulty matching the answer?

There could be several reasons why you are having difficulty matching the answer. It could be due to a lack of understanding of the concept, not reading the question carefully, or making a simple mistake. Take a moment to review your approach and try again.

Is there a specific method I should use to match the answer?

The method for matching the answer will depend on the type of problem you are trying to solve. It is important to understand the concept and choose a method that is appropriate for the problem. If you are unsure, consult with your teacher or a classmate for guidance.

What should I do if I am consistently unable to match the answer?

If you are consistently unable to match the answer, it may be helpful to seek additional resources such as a tutor or online tutorials. It may also be beneficial to review your study habits and make sure you are giving yourself enough time to understand the material.

What should I do if I think the answer is correct, but it doesn't match?

If you are confident that your answer is correct but it doesn't match, double check your work for any mistakes or miscalculations. It may also be helpful to consult with a classmate or your teacher to get a second opinion.