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 to your questions: 7.1 Define the term weak base. A weak base is a base that partially ionizes in an aqueous solution, meaning it does not fully dissociate to produce hydroxide ions. 7.2 Write down the formula of the conjugate acid of the carbonate ion, CO_3^2-(aq). When the carbonate ion (CO_3^2-) accepts a proton (H^+), it forms its conjugate acid. HCO_3^- 7.3 Determine the value of: 7.3.1 p Step 1: Use the formula: Volume used = Final burette reading - Initial burette reading. 20.05 cm^3 = p - 6.5 cm^3 Step 2: Solve for p. p = 20.05 cm^3 + 6.5 cm^3 p = 26.55 cm^3 7.3.2 q Step 1: Use the formula: Volume used = Final burette reading - Initial burette reading. 20.15 cm^3 = 48.3 cm^3 - q Step 2: Solve for q. q = 48.3 cm^3 - 20.15 cm^3 q = 28.15 cm^3 7.4 METHYL ORANGE is used as the indicator. Explain why methyl orange is the most suitable indicator for this titration by referring to the pH at the equivalence point. The titration involves a strong acid (HCl) and a weak base (K_2CO_3). At the equivalence point of such a titration, the resulting solution will be acidic (pH < 7). Methyl orange changes color in the pH range of 3.1 to 4.4, which is suitable for detecting the equivalence point in an acidic medium. 7.5 Calculate the concentration of the K_2CO_3 solution. Given: Concentration of HCl (C_A) = 0.1 mol·dm^-3 Volume of HCl (V_A) = 25 cm^3 = 0.025 dm^3 Balanced equation: K_2CO_3(aq) + 2HCl(aq) → 2KCl(aq) + CO_2(g) + H_2O(l) Mole ratio K_2CO_3 : HCl is n_B : n_A = 1:2. Step 1: Calculate the average volume of K_2CO_3 (V_B) used. V_B = 20.05 cm^3 + 20.15 cm^32 = 40.20 cm^32 = 20.10 cm^3 Convert to dm^3: V_B = 20.10 cm^3 × 1 dm^31000 cm^3 = 0.02010 dm^3. Step 2: Use the titration formula (C_A V_A)/(n_A) = (C_B V_B)/(n_B) to find C_B. (0.1 mol·dm^-3)(0.025 dm^3)2 = C_B (0.02010 dm^3)1 Step 3: Solve for C_B. 0.00125 = C_B (0.02010) C_B = (0.00125)/(0.02010) C_B ≈ 0.062189 mol·dm^-3 The concentration of the K_2CO_3 solution is 0.0622 mol·dm^-3. 7.6 Calculate the value of x in the formula K_2CO_3 · xH_2O. The solution from 7.5 was prepared by dissolving 6.525 g of K_2CO_3 · xH_2O in 600 cm^3 (0.600 dm^3) water. Concentration of K_2CO_3 (C_B) = 0.062189 mol·dm^-3 (from 7.5). Step 1: Calculate the moles of anhydrous K_2CO_3 in the 600 cm^3 solution. Moles of K_2CO_3 = C_B × Volume of solution Moles of K_2CO_3 = 0.062189 mol·dm^-3 × 0.600 dm^3 Moles of K_2CO_3 = 0.0373134 mol Step 2: Calculate the molar mass of anhydrous K_2CO_3. M(K_2CO_3) = 2(39.10) + 12.01 + 3(16.00) = 78.20 + 12.01 + 48.00 = 138.21 g/mol Step 3: Calculate the mass of anhydrous K_2CO_3 in the 6.525 g sample. Mass of K_2CO_3 = Moles of K_2CO_3 × M(K_2CO_3) Mass of K_2CO_3 = 0.0373134 mol × 138.21 g/mol = 5.1569 g Step 4: Calculate the mass of water in the hydrated sample. Mass of H_2O = Total mass of hydrated salt - Mass of K_2CO_3 Mass of H_2O = 6.525 g - 5.1569 g = 1.3681 g Step 5: Calculate the moles of water. M(H_2O) = 2(1.01) + 16.00 = 18.02 g/mol Moles of H_2O = Mass of H_2OM(H_2O) = 1.3681 g18.02 g/mol = 0.07592 mol Step 6: Determine the value of x. x = Moles of H_2OMoles of K_2CO_3 x = 0.07592 mol0.0373134 mol ≈ 2.034 Rounding to the nearest whole number, the value of x is 2. That's 2 down. 3 left today — send the next one.