Multiple Choice
On the pH scale, pH is defined as . What concentration does pH measure?
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17. Acid and Base Equilibrium
The pH Scale
Multiple Choice
Typical human stomach acid has a pH around 1–2. Approximately what is the hydronium ion concentration, , for a pH of 1.5?
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Verified step by step guidance1
Recall the definition of pH, which is given by the formula: \(\mathrm{pH} = -\log_{10} [\mathrm{H}_3\mathrm{O}^+]\), where \([\mathrm{H}_3\mathrm{O}^+]\) is the hydronium ion concentration in moles per liter (M).
To find the hydronium ion concentration from the pH, rearrange the formula to solve for \([\mathrm{H}_3\mathrm{O}^+]\): \([\mathrm{H}_3\mathrm{O}^+] = 10^{-\mathrm{pH}}\).
Substitute the given pH value of 1.5 into the equation: \([\mathrm{H}_3\mathrm{O}^+] = 10^{-1.5}\).
Calculate \$10^{-1.5}\( by recognizing that \(10^{-1.5} = 10^{-1} \times 10^{-0.5}\), which can be expressed as \(0.1 \times 10^{-0.5}\), and then evaluate \)10^{-0.5}\( as the square root of \)10^{-1}$.
Express the final hydronium ion concentration in scientific notation, which will be approximately \(3.2 \times 10^{-2}\) M, matching the correct answer choice.
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