Question

How many grams of naoh must be dissolved in litre of the solution to give it a ph of 12?

Answer 1

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 L

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