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 answers to question 5 and 8.a. Question 5: Step 1: Calculate the moles of NaOH used. The volume of NaOH is 38.7 mL = 0.0387 L. The molarity of NaOH is 0.600 M. Moles of NaOH = Molarity × Volume Moles of NaOH = 0.600 molL × 0.0387 L = 0.02322 mol Step 2: Determine the moles of the unknown monoprotic acid. A monoprotic acid (HA) reacts with NaOH in a 1:1 mole ratio: HA(aq) + NaOH(aq) NaA(aq) + H_2O(l) Since 0.02322 mol of NaOH was needed to neutralize "the acid", we assume this refers to the total moles of acid present in the solution. Moles of HA = Moles of NaOH = 0.02322 mol Step 3: Calculate the molarity of the acid solution. The 0.02322 mol of acid was dissolved in 1.00 L of water. Molarity of acid = Moles of HAVolume of solution Molarity of acid = 0.02322 mol1.00 L = 0.02322 M Rounding to three significant figures: Molarity of acid = 0.0232 M Step 4: Calculate the molar mass of the unknown acid. The mass of the unknown acid is 4.00 g. Molar mass of acid = Mass of acidMoles of acid Molar mass of acid = 4.00 g0.02322 mol ≈ 172.26 gmol Rounding to three significant figures: Molar mass of acid = 172 g/mol Question 8.a: Step 1: Write the electronic configuration for Se²⁻. Selenium (Se) is element 34. Its neutral electron configuration is [Ar] 3d^10 4s^2 4p^4. To form Se²⁻, two electrons are gained, filling the 4p subshell. Se^2- : [Ar] 3d^10 4s^2 4p^6 Step 2: Write the electronic configuration for Fe²⁺. Iron (Fe) is element 26. Its neutral electron configuration is [Ar] 3d^6 4s^2. To form Fe²⁺, two electrons are lost. For transition metals, electrons are removed from the highest principal energy level first, which is the 4s subshell. Fe^2+ : [Ar] 3d^6 3 done, 2 left today. You're making progress.