Chemistry

posted by .

A solution has a pH of 3.90. What is the hydroxide ion concentration? I know that I need to find H30+ first but my teacher doesn't allow calculators on the test. So how would I find the answer WITHOUT a calculator?

  • Chemistry -

    First off, hydroxide ion is OH-. H3O+ is actually the hydrogen ion concentration. Ummm...without a calculator, this is a tough one. You can estimate, by first finding the pOH:

    pOH = 14-pH = 10.10

    Then you can extrapolate into how the log was formed:

    So if the pOH = 10 then the concentration of OH- in the solution would be 1E-10 M, and if the pOH = 11 then the concentration of OH- in the solution would be 1E-11.

    However, the only way to do this without a calculator is to know the math behind logs and anti-logs...or memorize the tables for values. For example:

    Lets say pH = 3.50, you know that if the pH was 3 then the concentration of H+ would be 1E-3 M. Also, if it was 4 then H+ concentration would be 1E-4 M. Here's where memorizing is helpful, once you know the range you can just memorize some numbers:

    pH = 3.50; H+ conc = 3.16E-4
    pH = 4.50; H+ conc = 3.16E-5
    pH = 10.50; H+ conc = 3.16E11

    As you might notice, it doesn't matter what the pH is, if it is xx.50 then you can guarantee that the answer will look like 3.16E-xx.

    So having a table of these values memorized is helpful and thus a pOH = 10.10 gives you a concentration of about 7.94E-11 M

    If you have any more questions or are confused about a certain part then just ask.

  • Chemistry -

    Let me clarify something:

    As you might notice, it doesn't matter what the pH is, if it is x.50 (where x= 1,2,3,4,5,6,7,8,9,etc) then you can guarantee that the answer will look like: 3.16E-(x+1).

Respond to this Question

First Name
School Subject
Your Answer

Similar Questions

  1. Chemistry

    If a solution of Ca(OH)2 has a pH of 12.31 how can I calculate the concentration of calcium hydroxide in mol L-1 ?
  2. Physics

    I just wanted to clarify anwsers. Question 23. Nucleotides contain phosphate groups bonded to the.. A) C3' or c5' atoms B). C3 or C3' atoms C). N1 or N9 Atoms D). C3 or N9 atoms E). C3 or C5 atoms The anwser that I chosen in A. QUESTION …
  3. biochemistry

    I just wanted to clarify anwsers. Question 23. Nucleotides contain phosphate groups bonded to the.. A) C3' or c5' atoms B). C3 or C3' atoms C). N1 or N9 Atoms D). C3 or N9 atoms E). C3 or C5 atoms The anwser that I chosen in A. QUESTION …
  4. College Chemistry

    1) The concentration of the aluminum ion in a test solution is 0.10M. Using the Ksp for aluminum hydroxide (3. x 10^-34), calculate the concentration of hydroxide needed to precipitate aluminum hydroxide. From the concentration of …
  5. Physical Chem

    A student added solid K2O to a 750.0 mL volumetric flask. The solid was dissolved in water and then the flask filled with water to the mark. This formed 750.0 mL of the initial KOH solution. 20.0 mL of the initial solution was transferred …
  6. chemistry

    what are the hydronium-ion and the hydroxide ion concentration of a solution at 25 C that is 0.0050 M strontium hydroxide, Sr(OH)2?
  7. Chemistry

    What happens to the hydroxide ion concentration in aqueous solutions when we increase the hydrogen ion concentration by adding an acid?
  8. Chemistry

    The pH of a solution is 1. Which of the following statements are also true for the solution?
  9. Chemistry

    The hydronium ion concentration for a solution is determined to be 4.5 x 10^-7 M. What is the concentration of the hydroxide ion?
  10. Physical Science

    Find the hydroxide-ion concentration in an aqueous solution when the hydronium-ion concentration is 1×10^−10M. Recall that 10^a×10^b=10^(a+b). Express your answer to one significant figure and include the appropriate units.

More Similar Questions