Question

what is the ph of a solution with h⁺ = 1.25 × 10⁻¹⁰ m? use ph = -logh₃o⁺.
○ -10.1
○ -9.90
○ 7.90
○ 9.90

Explanation:

Step1: Recall the pH formula

The formula for pH is \( \text{pH} = -\log[\text{H}_3\text{O}^+] \), and we know that \( [\text{H}^+] = [\text{H}_3\text{O}^+] \), so we can use \( [\text{H}^+] = 1.25\times 10^{-10}\ \text{M} \) in the formula.

Step2: Calculate the logarithm

First, calculate \( \log(1.25\times 10^{-10}) \). We can use the property of logarithms \( \log(ab)=\log(a)+\log(b) \), so \( \log(1.25\times 10^{-10})=\log(1.25)+\log(10^{-10}) \). We know that \( \log(10^{-10})=- 10 \) and \( \log(1.25)\approx0.0969 \). So \( \log(1.25\times 10^{-10})=0.0969 - 10=-9.9031 \).

Step3: Apply the pH formula

Now, substitute into the pH formula: \( \text{pH}=-\log(1.25\times 10^{-10})=-(-9.9031)\approx9.90 \) (rounded to two decimal places).

Answer:

9.90