【Daily Question】Chemical Analysis Edition, 11.5.2021
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The label concentration of the NaOH solution is 0.300 mol/L. This solution has absorbed a small amount of CO2 from the air. Using phenolphthalein as an indicator, it was standardized with standard HCl solution, and the resulting concentration was higher than the label value. A. Higher; B. Lower; C. Unchanged; D. Unable to determine. B
B. CO2 is an acidic gas; its absorption lowers the pH value