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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21. a) State and explain the observations made when burning magnesium is lowered into a glass jar of carbon (IV) oxide. Observations: The magnesium continues to burn with a bright white flame. A white solid (magnesium oxide) and black specks* (carbon) are formed on the inside of the jar. Explanation: Magnesium is a highly reactive metal that is able to reduce carbon (IV) oxide (CO_2) to elemental carbon, while itself being oxidized to magnesium oxide. The reaction is highly exothermic, allowing the magnesium to continue burning despite the absence of oxygen. b) Write an equation for the reaction that takes place in (a) 2Mg(s) + CO_2(g) → 2MgO(s) + C(s) 22. (Assuming the atomic mass of Hydrogen (H) is 1.0, as H=10. is a likely typo.) Step 1: Calculate the molar mass of sodium hydroxide (NaOH). M_r(NaOH) = Na + O + H = 23.0 + 16.0 + 1.0 = 40.0 g/mol Step 2: Calculate the molarity of the sodium hydroxide solution. The concentration is 4.0 g/L. Molarity of NaOH = Mass concentrationMolar mass = 4.0 g/L40.0 g/mol = 0.1 mol/L Step 3: Calculate the moles of sodium hydroxide used. Volume of NaOH solution = 22.2 cm^3 = 0.0222 L. Moles of NaOH = Molarity × Volume = 0.1 mol/L × 0.0222 L = 0.00222 mol Step 4: Determine the moles of the dibasic acid. A dibasic acid (H_2A) reacts with sodium hydroxide in a 1:2 mole ratio: H_2A(aq) + 2NaOH(aq) → Na_2A(aq) + 2H_2O(l) Moles of acid = Moles of NaOH2 = 0.00222 mol2 = 0.00111 mol Step 5: Calculate the relative formula mass of the dibasic acid. Mass of dibasic acid = 0.1 g. Relative formula mass = Mass of acidMoles of acid = 0.1 g0.00111 mol ≈ 90.09 Rounding to three significant figures: Relative formula mass = 90.1 3 done, 2 left today. You're making progress.