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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1. (a) (i) A standard solution is a solution with an accurately known concentration. It is prepared by dissolving a precise mass of a primary standard substance in a specific volume of solvent. 1. (a) (ii) Step 1: Calculate the molar mass of Na_2CO_3. Molar mass of Na_2CO_3 = (2 × 23.0) + 12.0 + (3 × 16.0) = 106.0 g/mol Step 2: Calculate the number of moles of Na_2CO_3 needed. Convert volume to dm^3: 500 cm^3 = 0.500 dm^3 Use the formula Moles = Concentration × Volume: Moles = 0.2 moldm^-3 × 0.500 dm^3 = 0.1 mol Step 3: Calculate the mass of Na_2CO_3 needed. Use the formula Mass = Moles × Molar mass: Mass = 0.1 mol × 106.0 g/mol = 10.6 g The mass of sodium carbonate needed is 10.6 g. 1. (a) (iii) Step 1: Use the dilution formula M_1V_1 = M_2V_2. Given: M_1 = 0.2 moldm^-3 V_1 = 500 cm^3 M_2 = 0.04 moldm^-3 Step 2: Calculate the final volume V_2. V_2 = (M_1V_1)/(M_2) = 0.2 moldm^-3 × 500 cm^30.04 moldm^-3 = 2500 cm^3 Step 3: Calculate the volume of water to be added. Volume of water added = V_2 - V_1 = 2500 cm^3 - 500 cm^3 = 2000 cm^3 The volume of water needed is 2000 cm^3. 1. (b) (i) The titration involves NaCl and AgNO_3, which forms AgCl precipitate. This is a precipitation titration. The suitable indicator is Potassium chromate (K_2CrO_4). 1. (b) (ii) Step 1: Write the balanced chemical equation. NaCl(aq) + AgNO_3(aq) → AgCl(s) + NaNO_3(aq) The mole ratio of NaCl to AgNO_3 is 1:1. Step 2: Calculate the moles of AgNO_3 reacted. Convert volume to dm^3: 20 cm^3 = 0.020 dm^3 Moles of AgNO_3 = Concentration × Volume = 0.1 moldm^-3 × 0.020 dm^3 = 0.002 mol Step 3: Determine the moles of NaCl reacted. From the 1:1 mole ratio: Moles of NaCl = 0.002 mol Step 4: Calculate the molarity of the NaCl solution. Convert volume to dm^3: 25 cm^3 = 0.025 dm^3 Molarity of NaCl = Moles of NaClVolume of NaCl solution = 0.002 mol0.025 dm^3 = 0.08 moldm^-3 The molarity of the sodium chloride solution is 0.08 moldm^-3. 1. (c) | Type of unit cell | Coordination number | Number of particles per unit cell | | :---------------------------- | :------------------ | :-------------------------------- | | Cubic close pack or face centered cubic | 12 | 4 | | Body centered cubic | 8 | 2 | 1. (d) (i) Lattice energy is the energy change that occurs when one mole of an ionic compound is formed from its gaseous ions under standard conditions. It represents the strength of the electrostatic forces between ions in a crystal lattice.