Question

$pH$ of $NaOH$ solution is $10$. What is the concentration of $NaOH$?

Answer 1

Hint: In order to obtain the concentration of NaOH, we can make use of the relationship between \[pH\] and \[pOH\], i.e.
\[pH + pOH = 14\]
By using the above equation, we can obtain\[pOH\]value, which will help us to find the concentration of NaOH easily.

Complete step by step solution:
 In order to solve the above question, we must first convert the \[pH\]value into \[pOH\]. As it would be more convenient to obtain the concentration of NaOH. Because NaOH contains \[O{H^ - }\]ions. So, finding \[pOH\] will make it easy to obtain the concentration.
Consider the equation,
\[pH + pOH = 14\]
We know that \[pH\] of NaOH is given as 10, therefore equating in the above equation we get,
\[10 + pOH = 14\]
\[pOH = 14 - 10 = 4\]
\[pOH = - \log [O{H^ - }]\]
\[4 = - \log [O{H^ - }]\]
\[ - 4 = \log [O{H^ - }]\]
Taking the antilog of the above equation will help us to get the concentration of NaOH.
\[{\rm{antilog[ - 4] = }}[O{H^ - }]\]
\[[O{H^ - }] = 0.0001M\]

Therefore, the concentration of NaOH is 0.0001M.

Additional information:
- \[pH\] is a convenient way to measure the acidity and basicity of the solution.
- \[pH\] is a negative logarithm scale.
- Logarithm means for every one-unit change in the \[pH\] scale, the concentration of
 \[{H^ + }\] changes by 10 factors.
- For a temperature at \[25^\circ C\], the \[pH\] is below 7 for acidic solution, \[pH\] is above 7 for basic solution and \[pH\]is equal to 7 for neutral solution.

Note: - The \[pH\] and \[pOH\] values are not the same for acidic solution. When \[pH\] is below 7 for acidic solution, then \[pOH\] will be below 7 for acidic solution.
- The \[pH\] is above 7 for basic solution while \[pOH\] is below 7 for basic solution.