Question

A new well is discovered in West Texas with a bicarbonate concentration of \(225 \mathrm{ppm}\). According to the line of best fit, which of the following best approximates the \(\mathrm{pH}\) of the well water? A) \(7.1\) B) \(7.3\) C) \(7.4\) D) \(8.4\)

Short answer

The best approximation for the pH of the well water with a bicarbonate concentration of 225 ppm is: C) 7.4

Step-by-step solution

Analyze the Answer Choices

Upon examining the answer choices, we notice that they are all clustered around a pH value of 7, which is considered neutral on the pH scale. This observation suggests that the well water is likely to have a pH close to, but not exactly at, neutrality. It may be slightly acidic (below 7) or slightly basic (above 7).

Consider the Relationship Between Bicarbonate Concentration and pH

Bicarbonate (\(HCO_3^-\)) is the conjugate base of carbonic acid (\(H_2CO_3\)). When bicarbonate concentration increases in water, this tends to increase the pH of the water, making it more basic. This relationship is governed by the following equilibrium reaction: \[H_2CO_3\rightleftharpoons H^+ + HCO_3^-\] Since the water has a bicarbonate concentration of 225 ppm, we can expect that increasing bicarbonate will result in an increase in pH, moving away from the neutral value of 7.

Estimate the Best Approximation for the pH

Knowing that the pH is likely to be above 7 due to the presence of bicarbonate, we can eliminate choices A and B, leaving us with the two most plausible options, C and D: C) 7.4 D) 8.4 Since the line of best fit was not explicitly given, we cannot make an accurate calculation, but we can still make an informed choice. Given that the bicarbonate concentration, while significant, is not very high, we can hypothesize that the well water's pH would not increase dramatically away from neutrality. Therefore, we can reasonably estimate that the best approximation for the pH of the well water is option C, 7.4.

Choose the Best Approximation for the pH

Based on our reasoning, we can conclude that the best approximation for the pH of the well water with a bicarbonate concentration of 225 ppm is: C) 7.4