Question

2. Classify the following solutions as acidic, basic, or neutral at 25OC.
a.         pH = 13.00
  b.         [H3O+] = 1.0 x 10-12 M
  c.         pOH = 5.00
  d.         [OH-]= 1.0 x 10-9M
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Answer 1

Answer: a) pH = 13.00 : basic

b) $[H_3O^+]=1.0\times 10^{-12}$: basic

c) pOH = 5.00 : basic

d) $[OH^-]=1.0\times 10^{-9}$: acidic

Explanation:

pH or pOH is the measure of acidity or alkalinity of a solution.

pH is calculated by taking negative logarithm of hydrogen ion concentration.

$pH=-\log [H_3O^+]$

Acids have pH ranging from 1 to 6.9 and bases have pH ranging from 7.1 to 14.Neutral substances have pH of 7.

a) pH = 13.00

As pH is more than 7, the solution is basic.

b)  $[H_3O^+]=1.0\times 10^{-12}$

Putting in the values:

$pH=-\log[1.0\times 10^{-12}]$

$pH=12$

As pH is more than 7, the solution is basic.

c) pOH = 5.00

$pH+pOH=14.0$

$pH=14.0-5.00=9.00$

As pH is more than 7, the solution is basic.

d) $[OH^-]=1.0\times 10^{-9}$

Putting in the values:

$pOH=-\log[1.0\times 10^{-9}]$

$pOH=9.00$

$pH+pOH=14.0$

$pH=14.0-9.00=5.00$

As pH is less than 7, the solution is acidic.