Groundwater from a well is analyzed for basicity

CHEMISTRY · Multi-part · A Level · Chemistry · Acids and bases · Acids and bases

Problem

Groundwater from a well is analyzed for basicity. The analysis shows 4.0 mg4.0\,\text{mg} of hydroxide ions per litre of water at 25∘C25^{\circ}\text{C}. Assume the molar mass of the hydroxide ion is 17.0 g mol−117.0\,\text{g}\,\text{mol}^{-1} and the density of the water sample is 1.00 g mL−11.00\,\text{g}\,\text{mL}^{-1}. (a) Convert the reported hydroxide‐ion concentration to molarity (mol L−1)(\text{mol}\,\text{L}^{-1}), showing your dimensional analysis. (b) Using your answer from part (a), calculate the pOH of the groundwater sample. Show all steps and report the value with the appropriate significant figures. (c) Determine the pH of the groundwater and state whether the water is acidic, neutral, or basic at 25∘C25^{\circ}\text{C}. Support your conclusion quantitatively.

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