Two Questions on Form 4 Chemistry (about pH)

用戶205586

2008-06-15 6:52 am

1. Would a compound with acidity other than pH 7 be neutral?
2. It is known that pH is the measurement of H+(aq) concentration in an acid, but it does not represent the concentration of OH-(aq) in a substance. So, could pH show whether a compound is alkaline or not, if no information about its concentration of OH-(aq) is given?

回答 (1)

Uncle Michael

2008-06-15 7:54 am

✔ 最佳答案

1.
In practice, all pH measurements are made at 25oC (or assumed to be 25oC).

At 25oC, all neutral solutions have pH 7. If the pH of a solution is not 7 at 25oC, the solution is NOT neutral.

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2.
There is also a value called pOH to show the concentration of OH-(aq) ions. At 25oC, pH + pOH = 14.
For example, the pH of 0.1 M NaOH is 13, and the pOH is 14 - 13 = 1.

For a neutral solution at 25oC, pH = pOH = 7.
For an acidic solution at 25oC, pH < 0 and pOH > 0.
For an alkaline solution at 25oC, pH > 0 and pOH < 0.
(PH + pOH = 14)
=

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