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 = ?
2.4 g H2
To determine the theoretical yield of hydrogen, we need to convert the given mass of sodium (Na) and water (H2O) into moles and then use the balanced chemical equation to find the stoichiometric ratio between sodium and hydrogen.
Step 1: Convert the mass of Na to moles.
The molar mass of Na is 22.99 g/mol.
moles of Na = mass of Na / molar mass of Na
moles of Na = 13.8 g / 22.99 g/mol
Step 2: Convert the mass of water (H2O) to moles.
The molar mass of H2O is 18.02 g/mol.
moles of H2O = mass of H2O / molar mass of H2O
moles of H2O = 21.6 g / 18.02 g/mol
Step 3: Determine the limiting reactant.
To find the limiting reactant, compare the moles of Na and H2O and identify the one with the smaller number of moles. The reactant with fewer moles is the limiting reactant.
Step 4: Use the stoichiometric ratio to calculate the moles of H2 produced.
From the balanced chemical equation of the reaction between Na and H2O:
2 Na + 2 H2O → 2 NaOH + H2
The stoichiometric ratio between Na and H2 is 2:1. This means that 2 moles of Na react to produce 1 mole of H2.
If Na is the limiting reactant, the moles of H2 produced will be:
moles of H2 = moles of Na * (1 mole of H2 / 2 moles of Na)
If H2O is the limiting reactant, the moles of H2 produced will be:
moles of H2 = moles of H2O * (1 mole of H2 / 2 moles of H2O)
Step 5: Calculate the theoretical yield of hydrogen in grams.
Using the moles of H2 calculated in Step 4, we can convert moles to grams using the molar mass of H2.
theoretical yield of H2 = moles of H2 * molar mass of H2
To calculate the % yield, we can use the formula:
% yield = (actual yield / theoretical yield) * 100
Since the actual yield is given as 0.500 g of H2, we can substitute this value into the formula to calculate the % yield.