Question

What is the $ pH $ of a $ 0.025M $ $ HCl $ solution ?

Answer 1

Hint: For solving the given problem, we should have information regarding neutralization reaction and $ pH $ . Neutralization is a reaction that occurs between acid and base and produce . Water and salt as a result . $ pH $ basically determines the power of hydronium ions . It is inversely proportional to the concentration of hydronium ( $ H^+ $) ion . It can also be regarded as the potential of hydrogen .
To find the $ pH $ of given acid, we have :
 $ pH = -log[ H^+ ] $
Where,
$  [H^+ ] \rightarrow $ Concentration of acid.

Complete Step By Step Answer:
Step-1:
We have given $ 0.025M $ $ HCl $ solution. We know that $ HCl $ is a strong acid or electrolyte which releases $ H^+ $ ion on dissociation and dissociates almost completely. So, $ [ H^+ ] = 0.025M $ .
Step-2:
Using the given formula we have :
 $ pH = -log[ H^+ ] $
 $ pH = -log ( 25 \times 10^{ -3 }) $
Now we have to solve $ log (25 \times 10^{ -3 } ) $ .
Some rules are $ log(a \times b) = log a + log b $ .
So, $ log(25 \times 10^{ -3 }) = log25 + log10^{ -3 } $ .
Another rule is $ loga ^m = m log a $.
So, $ log(5)^2 + log(10^{ -3 }) = 2log5 - 3log10 $ .
Applying value of $ log5 $ and $ log10 $ , we get ;
 $ pH = -log(25 \times 10^{ -3 }) $
 $ =1.6 $

Note:
The reactants can be of different types in neutralization reactions like strong acid and strong base, weak acid and strong base or vice versa. The $ pH $ change in any reaction basically depends upon the relative strength of the reactants. In case of neutralization, the $ pH $ is always nearly $ 7 $ or equal to $ 7 $ .The $ pH $ for acids is less than seven. The lesser the value, the stronger is the acid. The $ pH $ for base is greater than seven. The greater the value, the stronger the base. The $ pH $ range is from $ 0-14 $ .