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Question: The pH of 0.1M ammonium hydroxide is. A. 14 B. \[ < 13\] C. \[ > 13\] D. \[ < 7\]...

The pH of 0.1M ammonium hydroxide is.
A. 14
B. <13 < 13
C. >13 > 13
D. <7 < 7

Explanation

Solution

pH is a way of measuring the acidity or basicity of a given compound. It represents the number of H+{H^ + } ions present in the given compound. The acidic character of a compound is dependent on the concentration of the H+{H^ + } ions present in it.

Formula used: pOH=−log⁡[OH−]pOH = - \log \left[ {O{H^ - }} \right]

Complete step by step answer:
The higher the number of H+{H^ + } ions present, the greater is the acidic character of that compound. Mathematically, it is equivalent to the negative logarithmic value of the concentration of the H+{H^ + } ions in a compound. It can be represented as:
pH=−log[H+]pH = - log[{H^ + }]
in case of concentration of OH−O{H^ - } , pOH=−log⁡[OH−]pOH = - \log \left[ {O{H^ - }} \right] .
pH is measured on a scale of 1 to 14, where 1 means the most acidic while 14 means most basic. Chemically neutral substances lie at the center of this scale, i.e. at 7. This is because the acidic character of a neutral substance is balanced by its basic character. To put it in simpler terms, let us understand another small concept: the basic character of a substance is determined by the concentration of OH−O{H^ - } ions in the compound and is put in perspective by a measure known as the pOH scale.
There is a relation between pH and pOH, which is, pH  +pOH=14pH\,\, + pOH = 14
Now, moving back to the question, ammonium hydroxide is a weak base.
Now, for 0.1M ammonium hydroxide, the pOH is,

pOH=−log⁡[OH−] pOH=−log⁡0.1 pOH=log⁡10 pOH=1  pOH = - \log \left[ {O{H^ - }} \right] \\\ pOH = - \log 0.1 \\\ pOH = \log 10 \\\ pOH = 1 \\\

But as ammonium hydroxide is a weak base complete dissociation will not ben taken. So the pH of this solution will be almost 7.
Therefore, the correct answer is, B.

Note: In neutral substances, the concentration of OH−O{H^ - } and H+{H^ + } is equivalent and they cancel each other out to give the neutral characteristic. we know that water is a neutral substance and hence its pH is 7. And as per the explanation above, the number of H+{H^ + } ions is equal to the number of OH−O{H^ - } ions and hence they cancel out their acidic and basic properties to give water its neutral nature.