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The pH scale is a measure used to determine the acidity or basicity of a solution. Calculating the pH involves understanding its relationship with pOH, the power of hydroxide ions concentration. The core formula linking them is: \[ \text{pH} + \text{pOH} = 14 \] Consequently, once you know the pOH, you can easily find the pH by subtracting the pOH from 14. For instance, part (a) of the problem demonstrated this: after computing a pOH of 2.52, the pH is simply \( 14 - 2.52 = 11.48 \). The pH value helps classify solutions as acidic (pH < 7), neutral (pH = 7), or basic (pH > 7). With substances like Sr(OH)\(_2\), LiOH, and NaOH, you would expect basic pH values as they are known bases.

Hydroxide ion concentration, denoted by \( [\text{OH}^{-}] \), is a critical factor in determining the basicity of a solution. To find it, first consider the dissociation of the base in water. For example, in Sr(OH)\(_2\), each mole provides two moles of \( \text{OH}^{-} \) ions. Therefore, you multiply the molarity of Sr(OH)\(_2\) by 2 for the \( [\text{OH}^{-}] \).In the exercise:- Begin with a base's molarity or moles (calculated from mass).- Remember dissociation ratios: Sr(OH)\(_2\) provides two \( \text{OH}^{-} \) ions per unit, while LiOH offers one.Calculated \( [\text{OH}^{-}] \) directly links to pOH, using the formula:\[ \text{pOH} = -\log_{10}([\text{OH}^{-}]) \] This highlights how greater \( [\text{OH}^{-}] \) signifies a more substantial base tendency, visibly lowering the pOH and, in turn, raising the pH.

Dilution refers to reducing the concentration of a solution by increasing its volume, often by adding more solvent. To find the new concentration after dilution, apply:\[ C_1V_1 = C_2V_2 \] where \( C_1 \) and \( C_2 \) are the initial and final concentrations, and \( V_1 \) and \( V_2 \) are the initial and final volumes.For example, in part (c), when diluting 1.00 mL of 0.175 M NaOH to 2.00 L, solve:\[ (0.175)(0.001) = (C_2)(2.00) \] Resulting in:\[ C_2 = \frac{0.175 \times 0.001}{2.00} = 8.75 \times 10^{-5} \text{ M} \]This lowering of concentration means fewer \( \text{OH}^{-} \) ions per unit volume, reflecting on the pH and solution properties. Understanding dilution is crucial for accurately depicting a solution's strength post-adjustment.