Hi! I need some help with this one;

"Which values are correct for a 0.010 mol dm− solution of NaOH (aq) at 298 K? (Kw =1.0×10−14 mol2 dm−6 at 298 K)

A. [H+] = 1.0*10^-12 mol dm^-3 and pH = 12.00
B. [OH-] = 1.0*10^-12 mol dm^-3 and pH = 12.00
C. [H+] = 1.0*10^-12 mol dm^-3 and pOH = 12.00
D. [OH-] = 1.0*10^-12 mol dm^-3 and pOH = 12.00"

The mark scheme says A. Anyone that can explain this for me? Why is it not D?

Question

Hi! I need some help with this one;

"Which values are correct for a 0.010 mol dm− solution of NaOH (aq) at 298 K? (Kw =1.0×10−14 mol2 dm−6 at 298 K)

A. [H+] = 1.0*10^-12 mol dm^-3 and pH = 12.00
B. [OH-] = 1.0*10^-12 mol dm^-3 and pH = 12.00
C. [H+] = 1.0*10^-12 mol dm^-3 and pOH = 12.00
D. [OH-] = 1.0*10^-12 mol dm^-3 and pOH = 12.00"

The mark scheme says A. Anyone that can explain this for me? Why is it not D?

cuanchi · Answer

pH = -log [H+]
in the strong base the concentration of [OH-] is equal to the concentration of the base.
In the problem you are given the concentration of the base.
then Kw= [H+][OH-]=1 x10^(-14)

alphabeta · Answer

Thank you so much, Cuanchi! Now I understand:-)