Question

Find pH of 0.1M NaOH solution.
A. 1
B. 2
C. 13
D. 17

Answer 1

Hint: pH is a scale used to specify how acidic or basic a water-based solution is. Acidic solutions have a lower pH, while basic solutions have a higher pH.

Complete answer:
You will need to know the molarity of the NaOH. Let's assume the solution is 0.1M. NaOH is a strong base, so this will produce 0.1mol/L of OH ions in solution. This will produce a pH of 13.
pOH = -log $$\left[1\times {10}^{-1}\right]$$
$$=-\log 1+\left(-\log {10}^{-1}\right)$$
$$\text{ = 0 + ( - ( - 1)) log 10}$$
$$\text{ = 0 + 1 x 1}$$
$$\text{ = 0 + 1}$$
$$\text{ = 1}$$
Now we know that,
pH +pOH = 14
pH + 1 = 14
pH = 14 – 1
pH = 13

Therefore, the pH of 0.1 M NaOH solution is 13.

Note: The pH scale, which ranges from 0 to 14, tells you how acidic or alkaline a solution is. A pH lower than 7 is acidic, while a pH higher than 7 is alkaline. In mathematical terms, pH is the negative logarithm of the molar concentration of hydrogen ions in the solution. A pH testing strip will tell you that NaOH is a strong alkaline, but to calculate its exact pH, you have to work out its molarity first.