using the information how do you solve the questions on the bottom B. ENTHALPY C

Question

using the information how do you solve the questions on the bottom

B. ENTHALPY CHANGES FOR REACTIONS Mg+H and MgopH ( Mgo Mass of weighing paper Mass of weighing paper plus sample Mass of sample Moles of sample Initial temperature of HCI and calorimeter Final temperature of solution (extrapolated from graph) Change of temperature lo 5750 OAs5O 0.0203 Or 23,13 Calculations Use 4.07 J/g C as specific heat for HCI solution and 1.01 g/mL as its density BL Calculate the enthalpy change AH! in kJ/mole, for Mg + H. B2 Calculate the enthalpy change, AH2, in kJ/mole, for Mgo + H.· ,- C. Calculate the enthalpy of formation of MgO D. Given , (MgO) as-602 kJ/mole, calculate your percentage error. % Error

Explanation / Answer

Mg + 2H+ ---> Mg2+ + H2

since volume of HCl solution is not mentioned, for calculation we would assume volume of HCl = 100 ml

density = 1 g/ml

mass of HCl solution = 100 ml x 1 g/ml = 100 g

Enthalpy change dH1 = -100 g x 4.07 J/g.oC x 14.1 oC/0.0189 mol x 1000 = -303.635 kJ/mol

MgO + 2H+ ---> M2+ + H2O

Enthalpy change dH2 = -100 g x 4.07 J/g.oC x 2.3 oC/0.0203 mol x 1000 = -46.11 kJ/mol

we know,

H2 + 1/2O2 --> H2O    dH3 = -286 kJ/mol

So,

Mg + 1/2O2 ---> MgO

Enthalpy for formation for MgO = dH1 - dH2 + dH3

                                                  = -303.635 + 46.11 - 286

                                                  = -543.33 kJ/mol

%error = (-602 + 543.33) x 100/-602 = 9.74%

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