When a $pH$ paper is dipped in an aqueous solution,it turns blue. What is the approximate $pH$ value of that solution?

How is an aqueous solution with $pH$ $12$ compared to an aqueous solution with $pH$ $9$?

Which of the following is a strong acid?

What will be the $OH^{-}$ concentration in an aqueous solution having $pH = 8$?

Five solutions $A, B, C, D$ and $E$ when tested with universal indicator showed $pH$ values of $4, 1, 11, 7$ and $9$,respectively. Which solution is:
$(a)$ neutral?
$(b)$ strongly alkaline?
$(c)$ strongly acidic?
$(d)$ weakly acidic?
$(e)$ weakly alkaline?
Arrange the $pH$ values in increasing order of hydrogen-ion concentration.

As the concentration of $[H_{3}O^{+}]$ ions increases in an acidic aqueous solution,what happens to the nature of the solution?