Question

Input Data Reactant Mg MgO Mass (9) 2300 104 Volume (mL) 100.0 1000 AT (C) 10.4 9.6 Calculated Enthalpies of Reaction Mg(s) + 2 HCl(aq) --> MgCl, (aq) + H29) AH = -459.83 kJ/mol MgO(s) + 2 HCl(aq) -> MgCl2(aq) + H20(0) AH = -155.66 kJ/mol Mg(s) + 4029) -> Mg(s) AH = -589.99 kJ/mol Problem: Solve for the following enthalpy changes 1) When 6.07 g NaOH(s) is reacted with 200.0 mL 0.759 M HCl(aq), the temperature increases 18.14 Celsius degrees. NaOH(s) + H+(aq) --> Na (aq) + H2OU AH = ? 2) When 5.84 g NaOH(s) is dissolved in 2000 mL of water, the temperature increases 7.54 Celsius degrees NaOH(s) --> Na (aq) + OH (aq) AH = ? 3. calculate AH for the reaction', ttay) + OH -> H2O

help me solve 1-3

Answer 1

1) The reagent moles are calculated:

n NaOH = g / MM = 6.07 / 40 = 0.151 mol

n HCl = M * V = 0.759 M * 0.2 L = 0.151 mol

Both are limit reagents, the reaction enthalpy is calculated:

ΔH = - m * cp * ΔT solution / n = - 200 g * 0.00418 * 18.14 / 0.151 = - 100.43 kJ / mol

2) The enthalpy change is calculated:

ΔH = - m * cp * ΔT * MM / m NaOH = - 200 * 0.00418 * 7.54 * 40 / 5.84 = - 43.17 kJ / mol

3) The change of enthalpy of the reaction is calculated:

ΔH = ΔHf H2O - ΔHf H + - ΔHf OH- = - 285.8 - 0 - 0 = -285.8 kJ / mol

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