A solution has a hydroxide-ion concentration of 0.0040 M. What is the pOH of the solution? A solution has a pH value of 3.66. What is the pOH for this solution? What is the pH of a 0.0072 M hydrochloric acid solution?

1. pOH = 2.4

2. pOH = 10.34

3. pH = 2.14

Explanation:

1. Determination of the pOH.

Concentration of Hydroxide ion, [OH-] = 0.004 M

pOH =?

pOH = - log [OH-]

pOH = - log (0.004)

pOH = 2.4

Therefore, the pOH of the solution is 2.4

2. Determination of the pOH.

pH = 3.66

pOH =?

pH and pOH are related by the following equation:

pH + pOH = 14

With the above formula, we can obtain the pOH of the solution as follow:

pH = 3.66

pOH =?

pH + pOH = 14

3.66 + pOH = 14

Collect like terms

pOH = 14 - 3.66

pOH = 10.34

Therefore, the pOH of the solution is 10.34

3. Determination of the pH.

Molarity of HCl = 0.0072 M

Concentration of Hydrogen ion, [H+] =?

Thus, we can obtain the concentration of Hydrogen ion, [H+] as follow:

HCl(aq) —> H+(aq) + Cl-(aq)

From the balanced equation above,

1 mole of HCl produced 1 mole of H+.

Therefore, 0.0072 M HCl will also produce 0.0072 M H+.

Therefore, the concentration of Hydrogen ion, [H+] in the solution is 0.0072 M.

Finally, we shall determine the pH of the solution as follow:

Concentration of Hydrogen ion, [H+] = 0.0072 M.

pH =?

pH = - log [H+]

pH = - log (0.0072)

pH = 2.14

Therefore, the pH of the solution is 2.14

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