Final answer:
To calculate the percentage acidity of lemonade with a pH of 2.9, find the hydrogen ion concentration from the given pH, and then convert that to a mass percentage accounting for the volume and molar mass of the acidic solute.
Step-by-step explanation:
To calculate the percentage acidity of lemonade with a pH of 2.9, first, understand that pH is a measure of the hydrogen ion concentration in a solution. The equation pH = -log[H₃O⁺] allows us to find the molarity of hydrogen ions, then we can convert that to percentage. Since lemonade has a pH of 2.9, we calculate the hydrogen ion concentration using the anti-logarithm (inverse of the log), which is 10^2.9 M or 1.258 x 10⁻³ M.
To find the percentage, we would need the volume of the lemonade solution and its total solute mass or molarity of the acid being used. If we assume the acid in lemonade is citric acid, which has a molar mass of 192.12 g/mol, we could calculate mass using molarity and then convert that to a percentage by mass.
However, this is not a direct percentage acidity as found in Liquid Intelligence. To correlate this to a percentage similar to the range presented by David Arnold (0.7-0.9%), it would involve comparing the molarity to the concentration of a reference solution (such as 0.1M citric acid) and expressing this as a percentage.