Synthesis and Analysis

Exp. No. 9 Experiment/Subject [Lab] - Synthesis and Analysis Date 3-25-25 PSU CHEM 34 Name Nobu Emesda Lab Partner Gray Drawer/Desk No. 57 Course & Section No. 002 [Q1] Reaction: 2 Al(s) + 2 KOH(aq) + 6 H2O(l) -> 2 KAl (OH)4(aq) + 3 H2(g) I observed bubbling as aluminum dissolved in KOH. This indicates hydrogen gas was released supporting the above reaction. Aluminum formed a soluble complex ion, KAl(OH)4. [Q2] I saw a white precipitate (Al(OH)3) form and then gradually dissolved after acid addition, showing that aluminum hydroxide formed and redissolved consistently with both reactions above. [Q3] - A) Theoretical Yield Moles Al = 0.7320 g / 26.98 g/mol = .027 mol From balanced equation: 2 Al -> 2 KAlC SO4)2 12 H2O Moles alum = .0271 mol Mass alum = .0271 mol x 474.39 g/mol = 12.872 B) Percent Yield. Y. Yield = (9.044 g / 12.87 g) x 100 = 71.06% [Q4] Observation: White precipitate forms with BaCl2. Net Ionic Equation: Ba^2+(aq) + SO4^2-(aq) -> BaSO4(s) [Q5] Bubbling and hissing when heated indicate release of water hydration confirming alum is a hydrate. [Q6] Step 9: Al^3+(aq) + 3 OH^-(aq) -> Al(OH)3(s) Step 10: Al(OH)3(s) + OH^-(aq) -> Al(OH)4^-(aq) [Q7] Table Evidence for Alum Formation Test Evidence Supports BaCl2 added white precipitate SO4^2- present Flame test Purple flame K+ present Heated alum Bubbling & sound Water present KOH test Precipitate Al^3+ present Melting Point Close to known Confirms purity/ value 91-92.5°C identity [Q8] Claim: Sample is mostly pure Evidence: Literature Mp 92.5°C our range was from 87.1°C to 97.2°C. Reasoning: A narrow Mp range close to 92.5°C indicates purity. Broader or lower range suggest impurities, likely unreacted salts or excess KOH.