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 hydrogen - ion concentration into the pH formula

Given $\text{pH}=-\log[\text{H}^+]$ and $[\text{H}^+]=2\times 10^{-9}$. So $\text{pH}=-\log(2\times 10^{-9})$.

Step2: Use the logarithm property $\log(ab)=\log a+\log b$

$-\log(2\times 10^{-9})=-(\log 2+\log(10^{-9}))$.

Step3: Recall the logarithm property $\log(10^n)=n$

We know that $\log(10^{-9})=-9$ and $\log 2\approx0.3010$. Then $-(\log 2+\log(10^{-9}))=- (0.3010 - 9)$.

Step4: Simplify the expression

$- (0.3010 - 9)=-0.3010 + 9=8.699\approx8.7$.

Answer:

C. 8.7