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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here are the solutions for the chemistry practical paper: Q1 (a): Prepare 0.10 mole dm^-3 of HNO_3 as solution D. Step 1: Determine the volume of concentrated HNO_3 needed. To prepare 1 dm^3 (1000 cm^3) of 0.10 mol dm^-3 HNO_3 solution, we first need to find the molarity of concentrated HNO_3. Assuming concentrated HNO_3 is 68\% w/w with a density of 1.42 g/cm^3 and molar mass of HNO_3 is 63.01 g/mol: Molarity of conc. HNO_3 = 68 × 1.42 g/cm^3 × 1000 cm^3/dm^363.01 g/mol × 100 = 15.33 mol/dm^3 Using the dilution formula C_1V_1 = C_2V_2: 15.33 mol/dm^3 × V_1 = 0.10 mol/dm^3 × 1 dm^3 V_1 = 0.10 mol/dm^3 × 1 dm^315.33 mol/dm^3 = 0.00652 dm^3 = 6.52 cm^3 Step 2: Outline the preparation procedure. • Carefully measure out 6.52 cm^3 of concentrated HNO_3 using a measuring cylinder or pipette. • Pour about 500 cm^3 of distilled water into a 1 dm^3 volumetric flask. • Slowly add the measured concentrated HNO_3 to the water in the volumetric flask, swirling gently. (Always add acid to water). • Add more distilled water until the solution is just below the calibration mark. • Stopper the flask and invert several times to mix. • Add distilled water dropwise until the bottom of the meniscus aligns with the 1 dm^3 calibration mark. • Stopper and invert the flask several times to ensure thorough mixing. • Label the solution as Solution D (0.10 mol dm^-3 HNO_3). This stock solution can then be dispensed in 200 cm^3 portions to each student. Q1 (b): Prepare 0.04 mole dm^-3 of Na_2CO_3 · 10H_2O as solution E. Step 1: Calculate the mass of Na_2CO_3 · 10H_2O needed. To prepare 1 dm^3 (1000 cm^3) of 0.04 mol dm^-3 Na_2CO_3 · 10H_2O solution. Molar mass of Na_2CO_3 · 10H_2O: (2 × 22.99) + 12.01 + (3 × 16.00) + (10 × (2 × 1.008 + 16.00)) = 286.15 g/mol. Mass needed = Molarity × Volume × Molar mass Mass = 0.04 mol/dm^3 × 1 dm^3 × 286.15 g/mol = 11.446 g Step 2: Outline the preparation procedure. • Weigh out 11.45 g of Na_2CO_3 · 10H_2O accurately using a digital balance. • Transfer the weighed solid into a beaker and dissolve it in about 200 cm^3 of distilled water. Stir to ensure complete dissolution. • Carefully transfer the solution into a 1 dm^3 volumetric flask using a funnel. • Rinse the beaker and funnel with small portions of distilled water and add the rinsings to the volumetric flask to ensure all solute is transferred. • Add distilled water until the solution is just below the calibration mark. • Stopper the flask and invert several times to mix. • Add distilled water dropwise until the bottom of the meniscus aligns with the 1 dm^3 calibration mark. • Stopper and invert the flask several times to ensure thorough mixing. • Label the solution as Solution E (0.04 mol dm^-3 Na_2CO_3 · 10H_2O). This stock solution can then be dispensed in 125 cm^3 portions to each student. Q1 (c): Prepare 0.08 mole dm^-3 of KOH as solution F. Step 1: Calculate the mass of KOH needed. To prepare 1 dm^3 (1000 cm^3) of 0.08 mol dm^-3 KOH solution. Molar mass of KOH: 39.10 + 16.00 + 1.008 = 56.108 g/mol. Mass needed = Molarity × Volume × Molar mass Mass = 0.08 mol/dm^3 × 1 dm^3 × 56.108 g/mol = 4.48864 g ≈ 4.49 g Step 2: Outline the preparation procedure. • Weigh out 4.49 g of KOH pellets quickly, as it is hygroscopic, using a digital balance. • Transfer the weighed solid into a beaker and dissolve it in about 200 cm^3 of distilled water. Stir to ensure complete dissolution. (Note: Dissolution of KOH is exothermic). • Allow the solution to cool to room temperature. • Carefully transfer the cooled solution into a 1 dm^3 volumetric flask using a funnel. • Rinse the beaker and funnel with small portions of distilled water and add the rinsings to the volumetric flask. • Add distilled water until the solution is just below the calibration mark. • Stopper the flask and invert several times to mix. • Add distilled water dropwise until the bottom of the meniscus aligns with the 1 dm^3 calibration mark. • Stopper and invert the flask several times to ensure thorough mixing. • Label the solution as Solution F (0.08 mol dm^-3 KOH). This stock solution can then be dispensed in 125 cm^3 portions to each student. Q1 (d): Prepare methyl orange and phenolphthalein indicators. Step 1: Prepare Methyl Orange indicator. • Dissolve 0.1 g of methyl orange powder in 100 cm^3 of distilled water. Stir until completely dissolved. Step 2: Prepare Phenolphthalein indicator. • Dissolve 1 g of phenolphthalein powder in 100 cm^3 of ethanol (or industrial methylated spirit). Stir until completely dissolved. Q2: Provide samples and reagents. • Provide 2 g of Tin(II) Chloride labeled as SAMPLE B1. • Provide 2 g of 2-Hydrobenzoic Acid (Salicylic Acid) labeled as SAMPLE B2. • Ensure that all necessary test reagents for inorganic and organic qualitative analysis are provided in the laboratory benches as instructed. What's next? 📸