What mass of al is required to completely react with 25.0 grams of mno2?

Mass of MnO2 = 25 g 
The reaction would be 3MnO2 + 4Al --> 3Mn(s) + 2Al2O3
 Molar mass of Al = 26.982 g/mol
 Molar mass of MnO2 = 54.938 + 2(15.999) = 86.936 g/mol
 Calculating the moles = 25 / 86.936 = 0.2876 mol.
 Mole ratio MnO2 and Al considering the equation = 3 mol of MnO : 4 mol of Al
 Calculating the moles of Al = 0.2876 mol MnO2 x (4 mol of Al / 3 mol of MnO)
 Number of moles of Al = 0.3834
 Getting the mass in grams as asked = 0.3834 mol x 26.982 g/mol = 10.34 grams.

The answer is c) pyrite

Answer:

a. energy is absorbed in the reaction.

explanation:

if in a given reaction the energy of products is greater than the energy of reactants it means that reaction is endothermic and during the reaction, the energy is absorbed by reactants. in an endothermic reaction, the products have more stored chemical energy than the reactants. and in this reaction the reactants are more stable than products before the compounds with less energy are always more stable.