Question

ph=1.72
express your answer using two significant figures.
oh⁻ = m
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part b
ph=13.68
express your answer using two significant figures.
oh⁻ =

Explanation:

Part A

Step1: Find pOH from pH

We know that \( \text{pH} + \text{pOH} = 14 \). Given \( \text{pH} = 1.72 \), so \( \text{pOH} = 14 - 1.72 = 12.28 \).

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

The formula relating pOH and \([\text{OH}^-]\) is \( \text{pOH} = -\log_{10}[\text{OH}^-] \), which can be rearranged to \( [\text{OH}^-] = 10^{-\text{pOH}} \). Substituting \( \text{pOH} = 12.28 \), we get \( [\text{OH}^-] = 10^{-12.28} \). Calculating this, \( 10^{-12.28} \approx 5.248\times 10^{-13} \). Rounding to two significant figures, we get \( 5.2\times 10^{-13} \) M.

Step1: Find pOH from pH

Using \( \text{pH} + \text{pOH} = 14 \), with \( \text{pH} = 13.68 \), we have \( \text{pOH} = 14 - 13.68 = 0.32 \).

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

Using \( [\text{OH}^-] = 10^{-\text{pOH}} \), substitute \( \text{pOH} = 0.32 \). So \( [\text{OH}^-] = 10^{-0.32} \). Calculating this, \( 10^{-0.32} \approx 0.479 \). Rounding to two significant figures, we get \( 0.48 \) M (or \( 4.8\times 10^{-1} \) M).

Answer:

\( 5.2\times 10^{-13} \)

Part B