Calculate the hydroxide ion concentration.............

Calculate the hydroxide ion concentration, [OH-], in 1.90 M HNO3.

Calculate the hydrogen ion concentration, [H+], in 0.00968 M NaOH.

Calculate the hydrogen ion concentration, [H+], in 0.00612 M Ba(OH)2. Careful!

In all strong acids, [acid]= [H+]

In all strong bases, [base]= [OH-]

1) pH= -lg[H+]
= -lg(1.90)
= -0.279

pOH= 14-pH
= 14.27
-lg[OH-]= 14.27
lg(1/[OH-])= 14.27
[OH-]= 1/(10^14.27)
= 5.37x10^-15M

2) pOH= -lg[OH-]
= -lg(0.00968)
= 2.01

pH= 14-pOH
= 11.99
-lg[H+]= 11.99
lg(1/[H+]= 11.99
[H+]= 1/(10^11.99)
= 1.02x10^-12M

3) pOH= -lg[OH-]
= -lg(0.00612)
= 2.21

pH= 14-pOH
= 11.79
-lg[H+]= 11.79
lg(1/[H+])= 11.79
[H+]= 1/(10^11.79)
= 1.62x10^-12M

I hope this helps. Good luck!!