Determine the theoretical and percent yield of hydrogen gas if 80.5 g water undergoes electrolysis to produce hydrogen and oxygen and 2.81 g hydrogen is collected.
theoretical yield
% yield = (exp.yield)/(theoretical) x 100%
exp. yield = 2.81g
to find theoretical yield;
1. Construct a balance equation for water electrolysed into H2 and O2. Note the mole ratio between H2O and H2.
2. calculate the mole of H2O using n = m/Mr where m is 80.5g and Mr is molar mass of water.
3. Use the mole in 2 to find the mole of H2 using the mole ratio from the balance equation in 1.
4. Use the mole in 3 to find the mass of H2 using m = nMr where n is the mole in 3 and Mr is the molar mass of H2.
the mass you find will be your theoretical yield.
plug in your values and calculate for % yield.
hope that helps..
To determine the theoretical yield of hydrogen gas, we need to calculate the amount of hydrogen that can be produced based on the balanced chemical equation for the electrolysis of water.
The balanced chemical equation for the electrolysis of water is:
2H2O → 2H2 + O2
From this equation, we can see that for every 2 moles of water (H2O), we get 2 moles of hydrogen gas (H2).
Now let's calculate the number of moles of water (H2O) present in 80.5 g of water:
molar mass of water (H2O) = 2 * (mass of hydrogen) + mass of oxygen
= 2 * (1.008 g/mol) + 16.00 g/mol
= 2.016 g/mol + 16.00 g/mol
= 18.016 g/mol
moles of water (H2O) = mass of water / molar mass of water
= 80.5 g / 18.016 g/mol
= 4.467 mol
Since the balanced equation shows that for every 2 moles of water, we get 2 moles of hydrogen gas, the theoretical yield of hydrogen gas is also 4.467 mol.
Now let's convert the moles of hydrogen gas to grams, since the measured yield is given in grams:
molar mass of hydrogen gas (H2) = 2 * (mass of hydrogen)
= 2 * (1.008 g/mol)
= 2.016 g/mol
mass of hydrogen gas (H2) = moles of hydrogen gas * molar mass of hydrogen gas
= 4.467 mol * 2.016 g/mol
= 9.015 g
Therefore, the theoretical yield of hydrogen gas is 9.015 grams.
To calculate the percent yield, we use the formula:
percent yield = (actual yield / theoretical yield) * 100
In this case, the actual yield is given as 2.81 g. Substituting the values into the formula:
percent yield = (2.81 g / 9.015 g) * 100
= 31.15%
Therefore, the percent yield of hydrogen gas is approximately 31.15%.