Question

ph = 1.72
express your answer using two significant figures.
oh⁻ = .48 m
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Explanation:

Step1: Find pOH from pH

We know that \( \text{pH} + \text{pOH} = 14.00 \). Given \( \text{pH} = 1.72 \), we calculate pOH as:
\( \text{pOH} = 14.00 - \text{pH} = 14.00 - 1.72 = 12.28 \)

Step2: Calculate \([\text{OH}^-]\) from pOH

The formula relating pOH and \([\text{OH}^-]\) is \( \text{pOH} = -\log_{10} [\text{OH}^-] \), so we can rearrange it to \( [\text{OH}^-] = 10^{-\text{pOH}} \).
Substituting \( \text{pOH} = 12.28 \) into the formula:
\( [\text{OH}^-] = 10^{-12.28} \)
Calculating \( 10^{-12.28} \), we know that \( 10^{-12.28} = 10^{-12 - 0.28} = 10^{-12} \times 10^{-0.28} \).
\( 10^{-0.28} \approx 0.5249 \), so \( 10^{-12.28} \approx 5.249 \times 10^{-13} \)

Step3: Round to two significant figures

\( 5.249 \times 10^{-13} \) rounded to two significant figures is \( 5.2 \times 10^{-13} \) (or \( 5.2e - 13 \))

Answer:

\( 5.2 \times 10^{-13} \) (or \( 5.2e - 13 \)) M