Question

Calculate the standard enthalpy change for the reaction that occurs when 4.50 grams of magnesium oxide reacts with excess hydrochloric acid, given the following information:2HCl(aq) + MgO(s) → MgCl2(aq) + H2O(l) ΔH = -120.3 kJ/molMolar mass of MgO = 40.31 g/molRound your answer to two decimal places.

Answer 1

First, we need to determine the number of moles of magnesium oxide  MgO  in the given mass:moles of MgO = mass / molar massmoles of MgO = 4.50 g / 40.31 g/molmoles of MgO = 0.1117 molNow, we can use the stoichiometry of the reaction and the given standard enthalpy change to calculate the enthalpy change for the reaction with 0.1117 mol of MgO:H = -120.3 kJ/mol  0.1117 molH = -13.43 kJThe standard enthalpy change for the reaction with 4.50 grams of magnesium oxide and excess hydrochloric acid is -13.43 kJ  rounded to two decimal places .