Question #d4fbe

1 Answer
Ernest Z.
May 11, 2017

It depends on the nature of the chemical.

Explanation:

(a) If the solution contains a weak base and its conjugate acid

The solution is a buffer.

Its pH will not change on the addition of water because the relative concentrations of the acid and its conjugate base do not change on dilution.

(b) If the solution contains a strong base

If #"pH" = 11.4#,

#"pOH = 14.00 - 11.4 = 2.6"#

#["OH"^"-"] = 10^"-2.6" color(white)(l)"mol/L" = 2.5 × 10^"-3" color(white)(l)"mol/L"#

If you dilute 4 oz of the solution with 1 gal (128 oz) of water, the new concentration is

#["OH"^"-"] = 2.5 × 10^"-3"color(white)(m) "mol/L" × (4 color(red)(cancel(color(black)("oz"))))/(129 color(red)(cancel(color(black)("oz")))) = 7.5 × 10^"-5"color(white)(l) "mol/L"#

#"pOH = -log"(7.5 × 10^"-5") = 4.1#

#"pH =14.00 - 4.1 = 9.9"#

The pH will decrease to 9.9.

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