If 5.0 grams of Zinc were added to 35.0 grams of H2SO4, how many grams of hydrogen gas would be evolved?
This is a limiting reagent (LR) problem. I know that because amounts for BOTH reactants are given.
Zn + H2SO4 ==> H2 + ZnSO4
mols Zn = grams/molar mass
mols H2SO4 = grams/molar mass
Using the coefficients in the balanced equation, convert mols Zn to mols H2.
Do the same for mols H2SO4 to mols H2.
It is quite likely that you will obtain two different values for the mols H2 and that means one of them is wrong; the correct value in LR problems is ALWAYS the smaller value and the reagent producing that value is the LR.
Now convert mols H2 to g H2 by g = mols x molar mass.
Thank you so much!
To find the number of grams of hydrogen gas evolved, we need to determine the balanced chemical equation for the reaction between Zinc (Zn) and sulfuric acid (H2SO4), and then calculate the stoichiometry of the reaction.
The balanced chemical equation for the reaction between zinc and sulfuric acid is as follows:
Zn + H2SO4 → ZnSO4 + H2
According to the balanced equation, 1 mole of zinc (Zn) reacts with 1 mole of sulfuric acid (H2SO4) to produce 1 mole of hydrogen gas (H2).
To calculate the number of moles of zinc (Zn) and sulfuric acid (H2SO4) in the given masses, we need to use their respective molar masses. The molar mass of zinc (Zn) is 65.38 g/mol, and the molar mass of sulfuric acid (H2SO4) is 98.08 g/mol.
For zinc (Zn):
Number of moles = Mass / Molar mass
Number of moles of zinc (Zn) = 5.0 g / 65.38 g/mol
For sulfuric acid (H2SO4):
Number of moles = Mass / Molar mass
Number of moles of sulfuric acid (H2SO4) = 35.0 g / 98.08 g/mol
Next, we need to determine the limiting reagent, which is the reactant that gets completely consumed in the reaction. The reactant that produces the minimum amount of product is the limiting reagent. To determine this, we compare the calculated number of moles of zinc (Zn) and sulfuric acid (H2SO4) and see which one is smaller.
The stoichiometry of the reaction between zinc and sulfuric acid tells us that 1 mole of zinc reacts with 1 mole of sulfuric acid to produce 1 mole of hydrogen gas. Therefore, the limiting reagent will be whichever reactant has the smaller number of moles.
Finally, based on the stoichiometry of the balanced equation, we can determine the number of moles of hydrogen gas (H2) produced, and then convert it to grams.
Number of moles of hydrogen gas = Number of moles of limiting reagent (either zinc or sulfuric acid)
To convert the number of moles of hydrogen gas to grams, we multiply by the molar mass of hydrogen gas, which is 2.02 g/mol.
Number of grams = Number of moles of hydrogen gas * Molar mass of hydrogen gas
By following these steps, you should be able to find the number of grams of hydrogen gas evolved in the given chemical reaction.