Thermochemical Stoichiometry

Question

The following thermochemical equation is for the reaction of tetraphosphorus decaoxide(s) with water(l) to form phosphoric acid(aq).

1. P₄O₁₀(s) + 6H₂O(l)4H₃PO₄(aq)    H = -453 kJ

How many grams of P₄O₁₀(s) would have to react to produce 101 kJ of energy?

______grams

Answer 1

The balanced equation tells us that 453 kJ are produced from reaction of ONE mole P₄O₁₀.

Thus...

101 kJ x 1 mol P₄O₁₀/453 kJ = 0.223 moles P₄O₁₀ needed to generate 101 kJ

Converting this to grams, we have...

0.223 mol P₄O₁₀ x 284 g/mol = 63.3 g P₄O₁₀ required