Al alloy analysis
...wn # 19 Analytical Balance # 3 Top loading scale # 2 Vapor pressure of water at 20.09oC: 18.536 torr Ref: Handbook of Chem. and Physics, 63rd Edition, pp D196-197 Density of water at 20.09oC: 0.998014 g/mL Ref: Handbook of Chem. and Physics. 1984, pp F4-5 Molarity of HCl: 6M Barometric pressure: 755.9 mmHg Observations: The capsules became sticky to the touch if held to long. There was no immediate change when HCl was added. After approximately 1 minute and 15 seconds the sample began to foam. The foam was a brown/ grey color. The reaction was exothermic and warm to the touch. The HCl and Alloy solution turned pink-brown. Calculations: 1. Pressure of H2 gas 755.9 mmHg – 18.536mmHg = 737.4 mmHg 2. Moles H2 gas (0.970atm x 0.12286L)/(0.08206 x 290.24K) = 5.00 x10-3 mol H2 (0.970atm x 0.12140L)/(0.08206 x 290.24K) = 4.94 x10-3 mol H2 3. Moles gas per gram sample 5.00 x10-3 mol H2 / 0.1068g = 0.0469mol/g 4.94 x10-3 mol H2 / 0.1090g = 0.0453mol/g 4. Percent Al 0.0469 = 0.0004030 (%Al) + 0.01529 78.4% 0.0453 = 0.0004030 (%Al) + 0.01529 74.5% 5. Average Percent Al (78.4% + 74.5%)/2 = 76.5% Report Table: Unknown # 19 Component Experimental % Accepted value % Error % Al 76.5% 72.0% 6.25 % High % Error of (%Al) = (72.0% - 76.5%)/72.0% x 100% = 6.25% Discussion questions: 1. If the barometric pressure had been recorded in cm instead of mm it would have raised each calculation by 100 making the % error much higher. It would be obvious that something was wrong when the %Al came out to be over 100%. 2. By following procedure the temperature should have been taken after the reaction took place. The H2 and water should have come to equilibrium by the time the Temp was taken so there should be no change in results. 3. If the vapor pressure of water w...