Answer :
Final answer:
To calculate the mass of reactant that will produce a specific amount of heat, convert the desired heat output to the same units as the given energy per unit mass (specific heat), then use ratio and proportion to calculate the mass.
Explanation:
To calculate the mass of reactant that will produce a specific amount of heat, you need to use the known ratio of energy per unit mass or specific heat. In this case, it is noted that 35.9 kJ/g of heat is released for each gram of reactant consumed. However, the heat you want to produce is given in Joules (J), so you need to convert it to Kilojoules (kJ) first because the given specific heat is in kJ. To do this, remember that 1 kJ = 1000 J. Therefore, 820 J = 820/1000 kJ = 0.82 kJ.
Now use the basic principle of proportion for the calculations. If 35.9 kJ is produced by 1 g, then 0.82 kJ will be produced by how many grams? Here is how you set it up:
1 g / 35.9 kJ = X g / 0.82 kJ
By cross-multiplying and isolating X, you can figure out the mass of the reactant needed to produce 820 J (or 0.82 kJ) of heat.
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