Question

how many gram of sodium hydroxide must be dissolved in 1 litre of solution to give in a pH of 12​

Answer 1

Answer: As we know,

pH + pOH = 14

Given the pH of solution is 12, so pOH would be :

14-12 = 2

pOH = -log[OH-]

2 = -log[OH-]

[OH-] = 10-2 M = 0.01 M =0.01 mol L-1

0.01 mol of OH- ion will obtain from 0.01 mol of NaOH

Mass corresponding to 0.01 mol NaOH = number of moles x molar mass of NaOH

                                                             = 0.01 mol x 40 g mol-1

                                                             = 0.4 g

So, correct answer is 0.4 g NaOH per Liter.