You need to know the delta H for the reaction. That isn't listed in the problem but you can look it up.
How much heat do you need? That's
q = mass H2O x specific heat H2O x (Tfinal-Tintial)
You have the data to calculate q needed.
Then 24.3 g Mg x (q in kJ/delta H iin kJ) = g Mg needed.
5. 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) + 2H2O(l) --> Mg(OH)2(s) + H2(g) Calculate the number of grams of Mg needed for this reaction to release enough energy to increase the temperature of 25 mL of water from 17 to 87 degrees Celcius.
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