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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Q19: Step 1: Identify the given values for the initial concentration (M_1), initial volume (V_1), and final volume (V_2). The dilution formula is M_1V_1 = M_2V_2. M_1 = 2.0 mol/dm^3 V_1 = 50 cm^3 V_2 = 200 cm^3 Step 2: Rearrange the formula to solve for the new concentration (M_2) and substitute the values. M_2 = (M_1V_1)/(V_2) M_2 = (2.0 mol/dm^3)(50 cm^3)200 cm^3 Step 3: Calculate the new concentration. M_2 = 100 mol/dm^3 · cm^3200 cm^3 M_2 = 0.5 mol/dm^3 The new concentration is B. 0.5 mol/dm³. Q20: The pH scale is a measure of the acidity or alkalinity of a solution. The pH scale ranges from D. 1 to 14. (Note: While 0-14 is common, 1-14 is also considered a valid range in some contexts, especially for general chemistry questions where 0 is extremely acidic and 14 is extremely basic). Given the options, 1 to 14 is the most appropriate choice. Q21: Step 1: Identify the given values for the initial concentration (M_1), final concentration (M_2), and final volume (V_2). The dilution formula is M_1V_1 = M_2V_2. M_1 = 0.5 mol/dm^3 M_2 = 0.1 mol/dm^3 V_2 = 500 cm^3 Step 2: Rearrange the formula to solve for the original volume (V_1) and substitute the values. V_1 = (M_2V_2)/(M_1) V_1 = (0.1 mol/dm^3)(500 cm^3)0.5 mol/dm^3 Step 3: Calculate the original volume. V_1 = 50 mol/dm^3 · cm^30.5 mol/dm^3 V_1 = 100 cm^3 The original volume was B. 100 cm³. Q22: To distinguish between a weak acid and a strong acid, an indicator that shows a range of pH values is needed. Litmus paper only indicates if a solution is acidic or basic, not the strength. Phenolphthalein changes color in a basic range (pH 8.2-10), making it unsuitable for distinguishing between acids. Universal indicator paper changes color over a wide pH range, allowing for a more precise estimation of pH and thus distinguishing between strong and weak acids. The most suitable indicator is C. Universal indicator paper. Q23: Step 1: Identify the chemical formula for calcium carbonate, which is CaCO₃. Step 2: List the atomic masses of each element: Ca = 40 C = 12 O = 16 Step 3: Calculate the molar mass by summing the atomic masses of all atoms in the formula. Molar mass of CaCO_3 = (1 × Ca) + (1 × C) + (3 × O) Molar mass of CaCO_3 = (1 × 40) + (1 × 12) + (3 × 16) Molar mass of CaCO_3 = 40 + 12 + 48 Molar mass of CaCO_3 = 100 g/mol The molar mass of calcium carbonate is C. 100 g/mol. Q24: When a strong acid is diluted by adding water, the concentration of hydrogen ions (H^+) decreases. A decrease in H^+ concentration means the solution becomes less acidic. Since pH is inversely related to acidity (lower pH means higher acidity), a decrease in acidity will cause the pH to increase. The pH will B. increase (become less acidic). Send me the next one 📸