How does the pKa value of certain weak acids present in food (2.85, 2.99, 3.13, 4.10, 4.76) affect the loss in mass of calcium carbonate (in grams, measured using an electronic balance, ±0.01 g), and how does the addition of sodium fluoride solution affect this reaction, keeping the concentration and temperature of the acid solutions and sodium fluoride solutions, the time taken for the reaction and the surface area of the calcium carbonate chips controlled?