Question

the equation for the ph of a substance is ph = -logh+, where h+ is the concentration of hydrogen ions. what is the approximate ph of a solution whose hydrogen ion concentration is 2×10^-9? 1.0 2.9 8.7 9.3

Explanation:

Step1: Substitute the value of \([H^{+}]\) into the formula

Given \(pH = -\log[H^{+}]\) and \([H^{+}]=2\times 10^{-9}\), then \(pH=-\log(2\times 10^{-9})\).
Using the logarithm property \(\log(ab)=\log a+\log b\), we get \(pH = -(\log2+\log(10^{-9}))\).
Since \(\log(10^{-9})=- 9\) (because \(\log_{10}10^{n}=n\)) and \(\log2\approx0.3\), then \(pH=- (0.3 - 9)\).

Step2: Simplify the expression

\(pH=-0.3 + 9=8.7\)

Answer:

8.7 (corresponds to the third option)