PAG 2.1 Questions and Answers | Latest Version | 2024/2025 | Graded A+

PAG 2.1 Questions and Answers | Latest Version | 2024/2025 | Graded A+ **How do you prepare a standard solution of sodium hydrogen carbonate (NaHCO3) for determining the concentration of HCl?** Weigh 2.1g of solid sodium hydrogen carbonate into a beaker using a weighing boat. Rinse the boat with distilled water into the beaker. Dissolve the solid in distilled water and transfer to a 250cm3 volumetric flask. Rinse the beaker and include the rinsing in the flask. Fill the flask just below the mark with distilled water, stopper, and invert to mix thoroughly. **What equipment is necessary for preparing the standard solution?** Weighing boat, balance (2 decimal places), distilled water, glass rod, volumetric flask (250cm3), 100cm3 beaker. **How do you determine the concentration of the HCl solution through titration with your standard solution?** Transfer the standard solution to a beaker and pipette 25cm3 into a 250cm3 conical flask. Add methyl orange indicator and fill a burette with HCl using a funnel. Titrate the NaHCO3 until the endpoint (yellow to orange). Repeat for concordant results. **What equipment is required for this titration?** Dropping pipette (25cm3), methyl orange, beaker, conical flask (250cm3), safety goggles, white tiles, burette, filter funnel, glass rod, spatula, HCl, NaHCO3. **How do you calculate the mean titre?** Mean titre = (t1 + t2) / 2 **Calculate the amount of moles in 25cm3 of 0.1 mol dm-3 standard solution.** Moles = (25/1000) x 0.1 = 2.5 x 10^-3 moles **What is the chemical equation between HCl and NaHCO3?** HCl + NaHCO3 -> NaCl + H2O + CO2 **Calculate the amount, in moles, of HCl present in the mean titre.** Since the stoichiometry is 1:1, moles of HCl = 2.5 x 10^-3 moles **Calculate the concentration of HCl.** Concentration = moles of HCl / mean titre (in dm3) **The balance has an uncertainty of ±0.01g. Calculate the percentage uncertainty.** Percentage uncertainty = (2 x 0.01 / 2.1) x 100 = 0.95% **Explain why hydrated sodium carbonate