What is the concentration of hydroxide ions in pure water at 30.0°C, if Kw at this temperature is 1.47⋅10−14?

1 Answer
anor277
Feb 12, 2017

We interrogate the equilibrium: 2H2O(l)⇌H3O++HO−.

[HO−]=1.21×10−7⋅mol⋅L−1

Explanation:

We interrogate the equilibrium:

2H2O(l)⇌H3O++HO−,

where the ion product, Kw=1.47×10−14, at 303⋅K. Note that this is slightly higher than Kw=10−14 at 298⋅K, and given that this is a bond breaking reaction this is perhaps reasonable.

From the equation, [H3O+][HO−]=1.47×10−14.

Given that this is a neutral solution, [H3O+]=[HO−].

Thus [HO−]2=1.47×10−14

And [HO−]=√1.47×10−14=1.21×10−7⋅mol⋅L−1

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