Answer
approximately 4.8 to 6.4
Work Step by Step
(see p.381)
The $\mathrm{p}\mathrm{H}$ scale measures the acidity of a solution:$ \quad \mathrm{p}\mathrm{H}=-\log[\mathrm{H}^{+}]$
where $[\mathrm{H}^{+}]$ is the hydrogen ion concentration (in moles per liter, M).
Solutions are
neutral if $pH=7$
acidic if $pH < 7$
basic if $pH > 7$
------------------
$[\mathrm{H}^{+}]=4.0\times 10^{-7}\Rightarrow$
$pH=-\log(4.0\times 10^{-7})\approx 6.4$
$[\mathrm{H}^{+}]=1.6\times 10^{-5}\Rightarrow$
$pH=-\log(1.6\times 10^{-5})\approx 4.8$
The range of pH readings:
approximately 4.8 to 6.4
