# What is the pH of a 0.0001 M solution of HNO3? pOH?

May 30, 2016

$p H = - {\log}_{10} {H}_{3} {O}^{+}$;
in water $p O H = 14 - p H$
${\log}_{10} \left\{0.0001\right\}$ $=$ ${\log}_{10} \left({10}^{-} 4\right) = - 4$, by definition of the log function. Thus $p H$ $=$ $4$, and, necessarily, $p O H = 10$.
Note that you should understand $\log$ functions. When I write ${\log}_{a} B = c$, I specify that ${a}^{c} = B$; thus ${\log}_{10} 100 = 2 , {\log}_{10} 1000 = 3$, and ${\log}_{10} {10}^{- 1} = - 1$. What are ${\log}_{10} 1 , 000 , 000$, and ${\log}_{10} {10}^{-} 6$?