The following substances are considered "basic." Which one has the most disassociated "OH^- ions? Review U4L7 p. 2-4 (1 point) Responses Great Salt Lake, milk of magnesia pH 10 Great Salt Lake, milk of magnesia pH 10 Baking soda pH 9 Baking soda pH 9 Ammonia solution pH 11 Ammonia solution pH 11 Soapy Water pH 12

1 answer

To determine which substance has the most dissociated \( \text{OH}^- \) ions, we can look at the pH values provided. The pH scale ranges from 0 to 14, where lower values indicate acidic solutions and higher values indicate basic solutions. For basic solutions, as the pH increases, the concentration of hydroxide ions \( \text{OH}^- \) also increases.

The relationship between pH and the concentration of hydroxide ions is given by the formula:

\[ \text{pOH} = 14 - \text{pH} \]

From this, we can calculate the pOH for each substance and determine the corresponding concentration of hydroxide ions:

  1. Great Salt Lake, milk of magnesia (pH 10):

    • pOH = 14 - 10 = 4
    • \([ \text{OH}^- ] = 10^{-4} , \text{M}\)
  2. Baking soda (pH 9):

    • pOH = 14 - 9 = 5
    • \([ \text{OH}^- ] = 10^{-5} , \text{M}\)
  3. Ammonia solution (pH 11):

    • pOH = 14 - 11 = 3
    • \([ \text{OH}^- ] = 10^{-3} , \text{M}\)
  4. Soapy Water (pH 12):

    • pOH = 14 - 12 = 2
    • \([ \text{OH}^- ] = 10^{-2} , \text{M}\)

Comparing the concentrations of \( \text{OH}^- \) ions:

  • \( 10^{-4} , \text{M} \) for Milk of Magnesia
  • \( 10^{-5} , \text{M} \) for Baking Soda
  • \( 10^{-3} , \text{M} \) for Ammonia
  • \( 10^{-2} , \text{M} \) for Soapy Water

Soapy Water, with a pH of 12, has the highest concentration of \( \text{OH}^- \) ions, making it the substance with the most disassociated \( \text{OH}^- \) ions.

Answer: Soapy Water (pH 12)