"What is the percent yield of H2O from a reaction if only 40g of water was recovered by reacting H2 and O2 gas in a reaction where 50 g of water was expected to be formed as the product?" a. 0.8%
b. 80%
c. 125%
d. 75%

Just took the quiz on edgenuity and the correct answer is "c.  4.54 x  10–12  j"

It is a product

Sorry im just trying to get answers like you are 

Answer is:     molar solubility of  yttrium fluorid is 4.23·10⁻⁶ m. balanced chemical reaction: yf₃(s)  → y³⁺(aq) + 3f⁻(aq). ksp = 8.62·10⁻²¹. ksp = [y³⁺]  · [f⁻]³.[y³⁺] = [yf₃] = s.[f⁻] = 3[yf₃] = 3s.ksp(yf₃)  = s  · (3s)³.8.62·10⁻²¹ = 27s⁴.s(yf₃)  =  ⁴√(8.62·10⁻²¹  ÷ 27).s(yf₃)  = 0.00000423 m.s(yf₃) = 4.23·10⁻⁶ m.