Chem Lab – Heat of Combustion of Magnesium

hot up of Combustion of Magnesium Background The students were given unspoilt instructions on how to experimentally determine the total heat of response (? Hrxn) for the combustion of magnesium ribbon, using Hesss Law. Data Collection Reaction 1 Reaction 2 (MgO) (Mg) Trial 1 Trial 2 Trial 1 Trial 2 Volume of 1. 00 M HCl 50. 0 mL 0. 5 mL 50. 0 mL 0. 5 mL 50. mL 0. 5 mL 50. 0 mL 0. 5 mL Final temperature, t2 28. 9(C 0. 1(C 28. 8(C 0. 1(C 44. 8(C 0. 1(C 44. 4( C 0. 1(C Initial temperature, t1 22. 5(C 0. 1(C 22. 3( C 0. 1(C 21. 9(C 0. 1(C 21. 8( C 0. 1(C trade of solid 0. 50 g 0. 01g 0. 50 g 0. 01g 0. 25 g 0. 01g 0. 25 g 0. 01g Data Processing Reaction 1 (MgO) Trial 1 Trial 2 Change in final temperature sign temperature final temperature initial temperature temperature, (t 28. (C 22. 5(C = 6. 4(C 28. 8(C 22. 3(C = 6. 3(C precariousness of temperature 0. 1(C + 0. 1(C = 0. 2(C doubtfulness of temperature 0. 1(C + 0. 1(C = 0. 2(C Change in temperature = 6. (C 0. 2(C Change in temperature = 6. 3(C 0. 2(C Heat of HCl set of 1. 0 M HCl pic specific heat of HCl pic variegate in Mass of 1. 0 M HCl pic specific heat of HCl pic change in solution, q temperature temperature To find book of 1. 0 M HCl Density of 1. M HCl pic volume To find mass of 1. 0 M HCl Density of 1. 0M HCl pic volume of 1. 0M HCl of 1. 0M HCl 1. 005 pic pic 50. 0 mL = 50. 3 g 1. 005 pic pic 50. 0 mL = 50. 3 g 50. 3 g pic . 00418 pic pic 6. 4(C = 1. 3 kJ 50. g pic . 00418 pic pic 6. 3(C = 1. 3 kJ % incertitude of Heat (0. 5mL ? 50 mL) + (0. 2(C ? 6. 4(C) % hesitation of Heat (0. 5mL ? 50 mL) + (0. 2(C ? 6. 3(C) pic degree Celsius% = 4% pic cytosine% = 4% Uncertainty of Heat 4% of 1. 3 kJ = 0. 5 kJ Uncertainty of Heat 4% of 1. kJ = 0. 5 kJ Heat of HCl = 1. 3 kJ 0. 5 kJ Heat of HCl = 1. 3 kJ 0. 5 kJ total heat change, henry change of reaction = -heat of HCl solution Enthalpy change of reaction = -heat of HCl solution (H Enthalpy of MgO = -1. kJ 0. 5 kJ Enthalpy of MgO = -1. 3 kJ 0. 5 kJ Moles of MgO Mass of MgO ? hoagy mass of MgO Mass of MgO ? molar mass of MgO 0. 50 g MgO ? 40. 30pic = 0. 0120 mol 0. 50 g MgO ? 40. 30pic = 0. 0120 mol % Uncertainty of moles (0. 01g ? 0. 0g) pic 100% = 2% % Uncertainty of moles (0. 01g ? 0. 50g) pic 100% = 2% Uncertainty of moles 2% of 0. 0120 mol = 0. 0002 mol Uncertainty of moles 2% of 0. 0120 mol = 0. 0002 mol Moles of MgO = 0. 0120 mol 0. 0002 mol Moles of MgO = 0. 0120 mol 0. 0002 mol Molar enthalpy Enthalpy of MgO ? moles of MgO Enthalpy of MgO ? oles of MgO change, (H/mol -1. 3 kJ ? 0. 0120 mol = -110 pic -1. 3 kJ ? 0. 0120 mol = -110 pic % Uncertainty (0. 5 kJ ? 1. 3 kJ) + (0. 0002 mol ? 0. 0120 mol) % Uncertainty (0. 5 kJ ? 1. 3 kJ) + (0. 0002 mol ? 0. 120 mol) pic 100% = 40% pic 100% = 40% Uncertainty 40% of -110 pic = 40 pic Uncertainty 40% of -110 pic = 40 pic Molar enthalpy change = -110 pic 40 pic Molar enthalpy change = -110 pic 40 pic fair(a) molar (molar enthalpy change of Trial 1 + molar enthalpy change of Trial 2) ? enthalpy change ( -110 pic + -110 pic ) ? 2 = -110 pic Uncertainty (40 pic + 40 pic ) ? 2 = 40 pic Average molar enthalpy change = -110 pic 40 pic Reaction 2 (Mg) Trial 1 Trial 2 Change in final temperature initial temperature final temperature initial temperature temperature, (t 44. 8(C 21. 9(C = 22. 9(C 44. 4(C 21. 8(C = 22. (C Uncertainty of temperature 0. 1(C + 0. 1(C = 0. 2(C Uncertainty of temperature 0. 1(C + 0. 1(C = 0. 2(C Change in temperature = 22. 9(C 0. 2(C Change in temperature = 22. 6(C 0. 2(C Heat of HCl Mass of 1. M HCl pic specific heat of HCl pic change in Mass of 1. 0 M HCl pic specific heat of HCl pic change in solution, q temperature temperature To find mass of 1. 0 M HCl Density of 1. 0M HCl pic volume To find mass of 1. 0 M HCl Den sity of 1. 0M HCl pic volume of 1. 0M HCl of 1. M HCl 1. 005 pic pic 50. 0 mL = 50. 3 g 1. 005 pic pic 50. 0 mL = 50. 3 g 50. 3 g pic . 00418 pic pic 22. 9(C = 4. 81 kJ 50. 3 g pic . 00418 pic pic 22. 6(C = 4. 75 kJ % Uncertainty of Heat (0. 5mL ? 0 mL) + (0. 2(C ? 22. 9(C) % Uncertainty of Heat (0. 5mL ? 50 mL) + (0. 2(C ? 22. 6(C) pic 100% = 1. 9% pic 100% = 1. 9% Uncertainty of Heat 1. 9% of 4. 81 kJ = 0. 09 kJ Uncertainty of Heat 1. 9% of 4. 75 kJ = 0. 09 kJ Heat of HCl = 4. 81 kJ 0. 09 kJ Heat of HCl = 4. 75 kJ 0. 9 kJ Enthalpy change,Enthalpy change of reaction = -heat of HCl solution Enthalpy change of reaction = -heat of HCl solution (H Enthalpy of Mg = -4. 81 kJ 0. 09 kJ Enthalpy of Mg = -4. 75 kJ 0. 09 kJ Moles of Mg Mass of Mg ? molar mass of Mg Mass of Mg ? molar mass of Mg 0. 25 g ? 24. 30pic = 0. 010 mol 0. 25 g ? 24. 30pic = 0. 10 mol % Uncertainty of moles (0. 01g ? 0. 25g) pic 100% = 4% % Uncertainty of moles (0. 01g ? 0. 25g) pic 100% = 4% Uncertainty of moles 4% of 0. 0100 mol = 0. 0004 mol Uncertainty of moles 4% of 0. 0100 mol = 0. 0004 mol Moles of Mg = 0. 0100 0. 0004 mol Moles of Mg = 0. 0100 0. 0004 mol Molar enthalpy Enthalpy of Mg ? oles of Mg Enthalpy of Mg ? moles of Mg change, (H/mol -4. 81kJ ? 0. 0100 mol = -481 pic -4. 75 kJ ? 0. 0100 mol = 475pic % Uncertainty (0. 09 kJ ? 4. 81 kJ) + (0. 0004 mol ? 0. 0100 % Uncertainty (0. 09 kJ ? 4. 75 kJ) + (0. 0004 mol ? 0. 100 mol) pic 100% = 6% mol) pic 100% = 6% Uncertainty 6% of -481 pic = 29 pic Uncertainty 6% of -475 pic = 29 pic Molar enthalpy change = -481 pic 29 pic Molar enthalpy change = -475 pic 29 pic Average molar (molar enthalpy change of Trial 1 + molar enthalpy change of Trial 2) ? enthalpy change (-481 pic + -475 pic ) ? 2 = -478 pic Uncertainty (29 pic + 29 pic ) ? 2 = 29 pic Average molar enthalpy change = -478 pic 29 pic