7. Meals-ready-to-eat (MREs) are military meals that can be heated on a flameles

Question

7.  Meals-ready-to-eat (MREs) are military meals that can be heated on a flameless heater. The heat is

     produced by the following reaction:   Mg(s) + 2 H2O(l)  ?  Mg(OH)2(s) + H2(g)

a)     Calculate the standard enthalpy change for this reaction using DHof values from Appendix C.

b)    Suppose this reaction is used to heat a sample of water. Calculate the heat required to raise the temperature of 125 mL of water from 22.3 ?C to 74.8 ?C.   

c)     Calculate the grams of Mg needed to supply this amount of heat.

please show me all the steps thanks.

Meals-ready-to-eat (MREs) are military meals that can be heated on a flameless heater. The heat is produced by the following reaction: Mg(s) + 2 H2O(l) ? Mg(OH)2(s) + H2(g) Calculate the standard enthalpy change for this reaction using DHof values from Appendix C. Suppose this reaction is used to heat a sample of water. Calculate the heat required to raise the temperature of 125 mL of water from 22.3 ?C to 74.8 ?C. Calculate the grams of Mg needed to supply this amount of heat.

Explanation / Answer

a)

Enthalpy of reaction= DHof of Mg(OH)2(s) -2*DHof of H2O(l)

=-924.7 - 2*(-285.8)=-353.1 kJ

b)

Heat required=mcdT=0.125*4.186*(74.8-22.3)=27.47 kJ

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