This chemistry question involves key chemical concepts and calculations. The detailed solution below walks through each step, from identifying the reaction type to computing the final answer.
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Morning Abiodun😍😍😍 — let's get this done. a) For the titration of a strong base (NaOH) with an acid (HX), a suitable indicator is phenolphthalein. It changes color from colorless in acid to pink in alkaline solution at the endpoint. b) The titration was repeated three times to obtain concordant results and ensure accuracy. Repeating the titration helps to minimize random errors and obtain a reliable average titre. c) i) Calculate the concentration of B (NaOH) in mol dm⁻³: Step 1: Calculate the molar mass of NaOH. Molar mass of NaOH = 22.99\, g/mol (Na) + 15.999\, g/mol (O) + 1.008\, g/mol (H) = 39.997\, g/mol ≈ 40.0\, g/mol Step 2: Calculate the moles of NaOH in 250 cm³ of solution. Moles of NaOH = Mass of NaOHMolar mass of NaOH = 0.98\, g40.0\, g/mol = 0.0245\, mol Step 3: Calculate the concentration of NaOH in mol dm⁻³. Concentration of B (NaOH) = Moles of NaOHVolume of solution (dm^3) = 0.0245\, mol0.250\, dm^3 = 0.098\, mol dm^-3 ii) Calculate the concentration of A (HX) in mol dm⁻³: Step 1: Identify the concordant titres and calculate the average titre. The concordant titres are 22.20 cm³ and 22.10 cm³. The average titre given is 22.15 cm³. Average volume of A used = 22.15\, cm^3 = 0.02215\, dm^3 Step 2: Calculate the moles of NaOH used in the titration. Moles of NaOH = Concentration of B × Volume of B Moles of NaOH = 0.098\, mol dm^-3 × 0.0250\, dm^3 = 0.00245\, mol Step 3: Determine the moles of HX from the stoichiometry. From the equation HX_(aq) + NaOH_(aq) NaX_(aq) + H_2O_(l), the mole ratio of HX : NaOH is 1:1. Moles of HX = Moles of NaOH = 0.00245\, mol Step 4: Calculate the concentration of HX. Concentration of A (HX) = Moles of HXVolume of A used (dm^3) = 0.00245\, mol0.02215\, dm^3 = 0.1106\, mol dm^-3 iii) Calculate the molar mass of A (HX): Step 1: Use the given mass of HX in 1.0 dm³ and its calculated concentration. Molar mass of HX = Mass of HX in 1.0 dm^3Concentration of A (HX) Molar mass of HX = 6.90\, g0.1106\, mol dm^-3 = 62.39\, g/mol iv) Calculate the relative atomic mass of X: Step 1: Subtract the molar mass of hydrogen from the molar mass of HX. Relative atomic mass of X = Molar mass of HX - Molar mass of H Relative atomic mass of X = 62.39\, g/mol - 1.008\, g/mol = 61.38 d) i) THREE precautions taken during the titration: • Ensure the burette is filled below the eye level to avoid splashing and ensure accurate reading. • Read the burette at eye level to avoid parallax error. • Rinse the burette with the acid (solution A) and the pipette with the base (solution B) before use to prevent dilution or contamination. • Ensure no air bubbles are present in the burette tip. • Add the titrant dropwise near the endpoint and swirl the flask constantly. ii) TWO laboratory apparatus used for the titration: • Burette (for dispensing the titrant, solution A) • Pipette (for accurately measuring a fixed volume of solution B) • Conical flask (for holding solution B and the indicator) • Retort stand and clamp (to hold the burette) Send me the next one 📸