Question

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

Answer 1

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 $0-14$ .