Given....#2Mg(s) + O_2(g) rarr 2MgO(s)# #; DeltaH_"rxn"=-1203kJmol^-1# What enthalpy is associated with the combustion of FOUR moles of magnesium metal?

Answer 1

#DeltaH=-2406*kJ...........#

#2Mg(s) + O_2(g) rarr 2MgO(s)# # DeltaH_"rxn"=-1203*kJ*mol^-1#

Enthalpy terms are written per mole of reaction as written. We combust 4 moles of magnesium metal, and should therefore generate #2xx-1203*kJ=-2406*kJ#.

Note that given these data we could write #DeltaH_f^@(MgO)=-601.5*kJ#. Why?

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Answer 2

Cooper Anderson

Since the given reaction is for the formation of 2 moles of magnesium oxide (MgO), and the enthalpy change for the reaction is -1203 kJ/mol, the enthalpy change for the formation of 1 mole of magnesium oxide is -1203 kJ/mol.

To find the enthalpy change for the formation of 2 moles of magnesium oxide, we multiply the enthalpy change for 1 mole by 2:

(2 \times -1203 , \text{kJ/mol} = -2406 , \text{kJ})

Therefore, the enthalpy associated with the combustion of four moles of magnesium metal is -2406 kJ.

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Answer from HIX Tutor

When evaluating a one-sided limit, you need to be careful when a quantity is approaching zero since its sign is different depending on which way it is approaching zero from. Let us look at some examples.

Given....#2Mg(s) + O_2(g) rarr 2MgO(s)# #; DeltaH_"rxn"=-1203*kJ*mol^-1# What enthalpy is associated with the combustion of FOUR moles of magnesium metal?

Given....#2Mg(s) + O_2(g) rarr 2MgO(s)# #; DeltaH_"rxn"=-1203kJmol^-1# What enthalpy is associated with the combustion of FOUR moles of magnesium metal?