Problem 83P

Determine the pH of each solution and classify it as acidic, basic, or neutral.

(a) pOH = 8.5

(b) pOH = 4.2

(c) pOH = 1.7

(d) pOH = 7.0

Solution: Here, we are going to determine the pH of the given solution and classify them as acidic, basic or neutral.

Step1:

pH is the negative logarithm to base 10 of hydrogen ion concentration whereas pOH is the negative logarithm to base 10 of hydroxyl ion concentration, i.e.,

pOH = - log[OH- ] and pH = - log[H+ ]

And pH + pOH =14

We can distinguish acidic, neutral and basic aqueous solutions by the relative values of their pH

Acidic: pH < 7

Neutral: pH = 7

Basic: pH > 7

Step2:

- Given, pOH = 8.5

Therefore pH = 14 - pOH

= 14 - 8.5

= 5.5

Since, pH < 7, therefore, the solution is acidic.

b) Given, pOH = 4.2

Therefore pH = 14 - pOH

= 14 - 4.2

= 9.8

Since, pH > 7, therefore, the solution is basic.

c) Given, pOH = 1.7

Therefore pH = 14 - pOH

= 14 - 1.7

= 12.3

Since, pH > 7, therefore, the solution is basic.

d) Given, pOH = 7.0

Therefore pH = 14 - pOH

= 14 - 7.0

= 7.0

Since, pH = 7, therefore, the solution is neutral.

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