- #1
Sythe777
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Picture to show more clearly: http://i.imgur.com/JmARtQM.png
1. Homework Statement
What is the molar enthalpy of combustion ΔH(c) of magnesium?
Mg(s) + 2HC(aq) → H2(g) + MgCl2(aq)
MgO(s) + 2HCl(aq) → H2O(l) + MgCl2(aq)
m(Mg) = 0.5 g
m(MgO) = 1.0 g
V(HCl) = 100.0 mL
C(HCl) = 1.0 mol/L
T(HCl) = 19° C
T(rxn1) = 38° C
T(rxn2) = 25° C
rxn1 relates to Mg(s) + 2HCl(aq)
rxn2 relates to MgO(s) + 2HCl(aq)2. Homework Equations
n(Mg) = m/M
q = mcΔT
ΔH(C) = -q/n
3. The Attempt at a Solution
n(Mg) = m/M
n(Mg) = (0.5 g)/(24.31 g/mol)
n(Mg) = 0.02056766762649115590292060880296 mol
n(Mg) = 0.021 mol
q = mcΔT
q = (3.6 g)(4.18 J/g °C)(38° C – 19° C)
q = 285.912 J
q = 285.9 J
ΔHC = -q/n
ΔHC = -285.9 J/0.021 mol
ΔHC = 13614.285714285714285714285714286
ΔHC = 13.6 kJ/mol
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If anyone can help me with this it would be greatly appreciated!
1. Homework Statement
What is the molar enthalpy of combustion ΔH(c) of magnesium?
Mg(s) + 2HC(aq) → H2(g) + MgCl2(aq)
MgO(s) + 2HCl(aq) → H2O(l) + MgCl2(aq)
m(Mg) = 0.5 g
m(MgO) = 1.0 g
V(HCl) = 100.0 mL
C(HCl) = 1.0 mol/L
T(HCl) = 19° C
T(rxn1) = 38° C
T(rxn2) = 25° C
rxn1 relates to Mg(s) + 2HCl(aq)
rxn2 relates to MgO(s) + 2HCl(aq)2. Homework Equations
n(Mg) = m/M
q = mcΔT
ΔH(C) = -q/n
3. The Attempt at a Solution
n(Mg) = m/M
n(Mg) = (0.5 g)/(24.31 g/mol)
n(Mg) = 0.02056766762649115590292060880296 mol
n(Mg) = 0.021 mol
q = mcΔT
q = (3.6 g)(4.18 J/g °C)(38° C – 19° C)
q = 285.912 J
q = 285.9 J
ΔHC = -q/n
ΔHC = -285.9 J/0.021 mol
ΔHC = 13614.285714285714285714285714286
ΔHC = 13.6 kJ/mol
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If anyone can help me with this it would be greatly appreciated!