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iPad 1:43 PM D UVU Login Servic × 'MyLab and Mast: × ' D Cours MasteringChemis × https/session.masteringchemistry.com/myct/itemvie.. my110 ±Enthalpy ± Enthalpy Enthalpy H is a measure of the energy content of a system at constant pressure chemical reactons involve changes in enthalpy H which can be measured where thbscript "ren° is for "entalpy of roaction" and is for "erealpy of formason" and m ard n fepresent the appropriate stoei metric coeficients for each substance The following table lists some enthalpy of formation values for selected substances , . (kJ/mol) NaOH(aq) MgCl:(s) NaCl(ag) Mg(OH)2(s) H,O(U) -641.8 407.3 924.5 285.8 Part A Determine the enthalpy for this reaction MgCl2(s) + 2NaOH(aq)Mg(OH)2(s) + 2NaC (aq) Express your answer in killejoules per mole to one decimal place Hints He k.J/mol My Answers Give Up Part B Consider the reaction Mg(OH)2 (8) Mg0(s) +HO(l) with enthalpy of reaction ar.w' = 37.5k//rnol What the enthalpy of formation of MgO(s)? Express your answer in kilojoules per mole to one decimal place kJ/mol My Answers Give Up

Explanation / Answer

A)

we have:

Hof(MgCl2(s)) = -641.8 KJ/mol

Hof(NaOH(aq)) = -469.1 KJ/mol

Hof(Mg(OH)2(s)) = -924.5 KJ/mol

Hof(NaCl(aq)) = -407.3 KJ/mol

we have the Balanced chemical equation as:

MgCl2(s) + 2 NaOH(aq) ---> Mg(OH)2(s) + 2 NaCl(aq)

deltaHo rxn = 1*Hof(Mg(OH)2(s)) + 2*Hof(NaCl(aq)) - 1*Hof( MgCl2(s)) - 2*Hof(NaOH(aq))

deltaHo rxn = 1*(-924.5) + 2*(-407.3) - 1*(-641.8) - 2*(-469.1)

deltaHo rxn = -159.1 KJ/mol

Answer: -159.1 KJ/mol

B)

we have:

deltaHo rxn = -37.5 KJ/mol

Hof(Mg(OH)2(s)) = -924.5 KJ/mol

Hof(H2O(l)) = -285.5 KJ/mol

we have the Balanced chemical equation as:

Mg(OH)2(s) ---> MgO(s) + 2 H2O(l)

deltaHo rxn = 1*Hof(MgO(s)) + 2*Hof(H2O(l)) - 1*Hof( Mg(OH)2(s))

-37.5 = 1*Hof(MgO(s)) + 2*(-285.5) - 1*(-924.5)

Hof(MgO(s)) = -391 KJ/mol

Answer: -391 KJ/mol

Feel free to comment below if you have any doubts or if this answer do not work. I will edit it if you let me know

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