Chapter 4.3, Problem 98PE

Scientists use the p11 scale to represent the level of acidity or alkalinity of a liquid. This is based on the molar concentration of hydrogen ions, $\left[{\text{H}}^{\text{+}}\right]$ . Since the values of $\left[{\text{H}}^{\text{+}}\right]$ vary over a large range, ${\text{1×10}}^0$ mole per liter to ${\text{1×10}}^{-14}$ mole per liter (mol/L), a logarithmic scale is used to compute pH. The formula $\text{pH}=-\log \left[{\text{H}}^{\text{+}}\right]$ represents the pH of a liquid as a function of its concentration of hydrogen ions, $\left[{\text{H}}^{\text{+}}\right]$ . The pH scale ranges from 0 to 14. Pure water is taken as neutral having a pH of 7. A p11 less than 7 is acidic. A pH greater than 7 is alkaline (or basic). For Exercises 97-98, use the formula for pH. Round pH values to 1 decimal place.

98. Bleach and milk of magnesia are both bases. Their $\left[{\text{H}}^{\text{+}}\right]$ values are 2.0 ×10-13 mol/L and 4.1 × 10-10 mol/L, respectively.
a. Find the pH for bleach.
b. Find the pH for milk of magnesia.
c. Which substance is more basic?