I need help with finding the theoretical yield of Mg(s) + 2HCl(aq) → MgCl2(aq) + H2(g). So far I have 24.305 + 37.4688 = 61.7738 g based on the weight of MgCl2 + H2, but I'm not exactly sure what to do or if I've even started it properly. Also, if you could help me with the percent yield of that equation. Any help would be greatly appreciated.
Here is just what you need? This is a worked example of a stoichiometry problem.
http://www.jiskha.com/science/chemistry/stoichiometry.html
To find the theoretical yield of a reaction, you need to know the balanced chemical equation and the amount (in moles) of the limiting reactant. In this case, the balanced equation is:
Mg(s) + 2HCl(aq) → MgCl2(aq) + H2(g)
To determine the limiting reactant, you need to compare the amount (in moles) of each reactant to the stoichiometric ratio in the balanced equation. The stoichiometric ratio states that one mole of magnesium will react with two moles of hydrochloric acid to produce one mole of magnesium chloride and one mole of hydrogen gas.
Now, let's assume you have 24.305 grams of magnesium (Mg). To convert this mass into moles, you need to divide it by the molar mass of magnesium (24.305 g/mol). Thus:
24.305 g / 24.305 g/mol = 1 mole
Since you have exactly one mole of magnesium, you can conclude that magnesium will not be the limiting reactant.
Next, let's calculate the moles of HCl. You have 37.4688 grams of HCl. Similar to what we did for magnesium, divide the mass of HCl by its molar mass (36.461 g/mol):
37.4688 g / 36.461 g/mol ≈ 1.027 moles
Since we need two moles of HCl to react with one mole of magnesium, the molar ratio is 1:2. Hence, the number of moles of HCl is twice as much as the number of moles required for the reaction.
Therefore, from the stoichiometry, we know that only one mole of magnesium is necessary to react, while two moles of HCl are present. This means that one mole of magnesium (24.305 grams) will react with one mole of HCl (36.461 grams).
The molar mass of MgCl2 is 95.211 g/mol. So, the mass of magnesium chloride produced in this reaction would be:
1 mole × 95.211 g/mol = 95.211 grams of MgCl2
However, you also need to take into account the production of hydrogen gas (H2). According to stoichiometry, one mole of magnesium will produce one mole of H2. The molar mass of hydrogen gas is 2.016 g/mol. Considering this, the mass of hydrogen gas produced in this reaction would be:
1 mole × 2.016 g/mol = 2.016 grams of H2
Therefore, the theoretical yield of magnesium chloride is 95.211 grams, and the theoretical yield of hydrogen gas is 2.016 grams.
To calculate the percent yield, you need to compare the actual yield (the amount of product obtained in the lab) with the theoretical yield (the amount of product calculated). The percent yield formula is:
Percent Yield = (Actual Yield / Theoretical Yield) × 100
If you have the actual yield from the lab, you can substitute it into the formula to calculate the percent yield.