PAG 2.2 Questions and Answers | Latest Version | 2024/2025 | Graded A+

PAG 2.2 Questions and Answers | Latest Version | 2024/2025 | Graded A+ How can you determine the molar mass of an acid? Weigh the container with H3X.nH2O, transfer the solid to a 250 cm3 beaker, and re-weigh the container. Dissolve the solid in 100 cm3 of distilled water and stir. Transfer the solution to a 250 cm3 volumetric flask, rinse the beaker, and add the rinsings to the flask. Fill the flask just below the mark, insert the stopper, and mix well. Transfer 25 cm3 of NaOH solution into a conical flask and add 3-4 drops of phenolphthalein. Fill a burette with the prepared solution and titrate the NaOH solution until the end point is reached. Repeat until you obtain two concordant results. What equipment is required for this procedure? A balance (2 d.p.), goggles, burette, white tile, 25 cm3 pipette and filler, filter funnel, glass rod, 100 cm3 measuring cylinder, volumetric flask, two 250 cm3 conical flasks, distilled water, 0.1 mol dm3 NaOH, phenolphthalein indicator, and the unknown hydrated acid. How do you calculate the mean titre from concordant results? Mean titre = (T1 + T2) / 2 How do you calculate the moles of NaOH used? Moles (n) = concentration (C) x volume (V) 0.100 x 25 / 1000 = 0.0025 moles What is the stoichiometric equation, and how does it determine the moles of H3X? The equation is H3X + 3NaOH → Na3X + 3H2O. The ratio of H3X to NaOH is 1:3. Therefore, moles of H3X = 0.0025 / 3 = 8.33 x 10−4 moles. How do you calculate the molar mass of H3X in 250 cm3? Molar mass = moles / mean titre x 250 How do you determine the molar mass of H3X.nH2O? Molar mass = mass / X What is the percentage uncertainty for the balance with ±0.01 g uncertainty in each reading? Percentage uncertainty = (2 x 0.01) / (mass - mass1) x 100 What is the percentage uncertainty for a burette with ±0.05 cm3 uncertainty in each reading? Percentage uncertainty = (2 x 0.05) / titre x 100