posted by Anonymous .
Suppose 13.8 g Na and 21.6 g of water are mixed. What is the theoretical yield in grams of hydrogen from this mixture. what is the % yield if 0.500 g of H2 is formed
This is a limiting reagent (LR) problem.
You know that because amounts are given for BOTH reactants.
2Na + 2H2O ==> 2NaOH + H2
mols Na = grams/atomic mass
mols H2O = grams/molar mass
Using the coefficients in the balanced equation, convert mols Na to mols H2.
Do the same for mols H2O to mols H2.
It is likely that these two values will not agree which means one of them is wrong. The correct value to use in LR problems is ALWAYS the smaller value and the reagent producing that value is th LR. Then grams = mols x molar mass. This is the theoretical yield(TY).
%yieled = (actual yield/TY)*100 = ?