Question

please give detailed solution

Answer 1

Given Volume of solution = 100lits.
Mass of NaOH = 4

To know the pH we have to calculate the concentration of the H+ ions.

But NaOH is a base so we have to find the concentration of OH- ions.

Molar mass of NaOH = molar mass of Na + Molar mass of O + molar mass of H

=> Molar mass of NaOH = 23+16+1 = 40g/mole

No. of moles of NaOH in 4g = 4/40 = 0.1moles

Now, Concentration of OH- ions= no of moles/volume of solution

=0.1/100= 0.001moles/litre=10^-3moles/litre

therefore pOH= -log[OH- ions concentration]
=> pOH= -log[10^-3]= 3
so pH = 14-3= 11.