Water (H2O) can ionize into two ions, the hydronium ion (H3O+) and the hydroxide ion (OH-). Where are these two ions always found?
Answers
Answer:
Explanation:
Water can undergo autoionization to form \text{H}_3\text{O}^+H
3
O
+
start text, H, end text, start subscript, 3, end subscript, start text, O, end text, start superscript, plus, end superscript and \text{OH}^-OH
−
start text, O, H, end text, start superscript, minus, end superscript ions.
The equilibrium constant for the autoionization of water, K_\text{w}K
w
K, start subscript, start text, w, end text, end subscript, is 10^{-14}10
−14
10, start superscript, minus, 14, end superscript at 25\,^\circ\text{C}25
∘
C25, degrees, start text, C, end text.
In a neutral solution, [\text{H}_3\text{O}^+]=[\text{OH}^-][H
3
O
+
]=[OH
−
]open bracket, start text, H, end text, start subscript, 3, end subscript, start text, O, end text, start superscript, plus, end superscript, close bracket, equals, open bracket, start text, O, H, end text, start superscript, minus, end superscript, close bracket
In an acidic solution, [\text{H}_3\text{O}^+]>[\text{OH}^-][H
3
O
+
]>[OH
−
]open bracket, start text, H, end text, start subscript, 3, end subscript, start text, O, end text, start superscript, plus, end superscript, close bracket, is greater than, open bracket, start text, O, H, end text, start superscript, minus, end superscript, close bracket
In a basic solution, [\text{OH}^-]>[\text{H}_3\text{O}^+][OH
−
]>[H
3
O
+
]open bracket, start text, O, H, end text, start superscript, minus, end superscript, close bracket, is greater than, open bracket, start text, H, end text, start subscript, 3, end subscript, start text, O, end text, start superscript, plus, end superscript, close bracket
For aqueous solutions at 25\,^\circ\text{C}25
∘
C25, degrees, start text, C, end text, the following relationships are always true:
K_\text{w}=[\text{H}_3\text{O}^+][\text{OH}^-]=10^{-14}K
w
=[H
3
O
+
][OH
−
]=10
−14
K, start subscript, start text, w, end text, end subscript, equals, open bracket, start text, H, end text, start subscript, 3, end subscript, start text, O, end text, start superscript, plus, end superscript, close bracket, open bracket, start text, O, H, end text, start superscript, minus, end superscript, close bracket, equals, 10, start superscript, minus, 14, end superscript
\text{pH}+\text{pOH}=14pH+pOH=14start text, p, H, end text, plus, start text, p, O, H, end text, equals, 14
The contribution of the autoionization of water to [\text{H}_3\text{O}^+][H
3
O
+
]open bracket, start text, H, end text, start subscript, 3, end subscript, start text, O, end text, start superscript, plus, end superscript, close bracket and [\text{OH}^-][OH
−
]open bracket, start text, O, H, end text, start superscript, minus, end superscript, close bracket becomes significant for extremely dilute acid and base solutions.