Question

Identify the following as acids, bases, or neutral solutions:

contains more hydronium ions than hydroxide ions

H2O

[H3O+] = 3.4 × 10-5 M

[OH-] = 2.8 × 10-2 M

Ca(OH)2

[H3O+] = 1.0 × 10-7 M

Answer 1

The solution is acidic if it contains more hydronium ions than hydroxide ions.

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H₂O is neutral as in H₂O the [H₃O⁺] = [OH^-] = 10^-7 M, pH = 7.

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[H₃O⁺] = 3.4 × 10^-5

or, -log[H₃O⁺] = -log(3.4 × 10^-5)

or, pH = 4.5

The pH of the solution is less than 7. Hence, the solution is acidic.

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[OH^-] = 2.8 × 10^-2 M

or, -log[OH^-] = -log(2.8 × 10^-2)

or, pOH = 1.6

or, 14 - pH = 1.6

or, pH = 12.4

The pH of the solution is more than 7. Hence, the solution is basic.

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Ca(OH)₂ is a strong base. The solution of Ca(OH)₂ is basic.

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[H₃O+] = 1.0 × 10^-7 M

or, -log[H₃O⁺] = -log(1.0 × 10^-7)

or, pH = 7

The pH of the solution is 7. Hence, the solution is neutral.