Given:
Mg + 2HCl --> H2 + MgCl2
0.250 g of magnesium reacts with 10.00 mL of 1.5 M HCl.
What volume (in mL) of H2 gas is produced?
This is a limiting reagent problem BECAUSE BOTH reactants are given.
1. Calculate moles Mg. moles = g/molar mass.
2. Calculate moles HCl. moles = M x L
3. Using the coefficients in the balanced equation, determine how many moles of H2 will be produced by EACH reactant.
4. Choose the lower number of moles of H2, the reactant producing that number will be the limiting reagent, then multiply by 22.4 L/mol to determine the volume (then change to mL)
To find the volume of H2 gas produced, we need to use the stoichiometry of the balanced chemical equation, as well as the given information.
First, let's determine the number of moles of magnesium (Mg) using its molar mass. The molar mass of Mg is 24.31 g/mol.
Given that you have 0.250 g of magnesium, we can calculate the number of moles using the formula:
moles = mass / molar mass
moles of Mg = 0.250 g / 24.31 g/mol
Now let's use the molar ratio between Mg and H2 from the balanced equation, which is 1:1. This means that for every 1 mole of Mg, we should obtain 1 mole of H2.
moles of H2 = moles of Mg
Now we need to find the volume of H2 gas produced. To do that, we'll use the Ideal Gas Law equation:
PV = nRT
Where:
P = pressure (in atm)
V = volume (in L)
n = number of moles
R = ideal gas constant (0.0821 L.atm/mol.K)
T = temperature (in Kelvin)
In this case, we don't have the information about the pressure or temperature, but we can assume that the experiment is done at room temperature and that the pressure is atmospheric pressure.
So, we can simplify the equation to:
V = n * 22.4 L/mol
Now, plug in the value of moles of H2 from the step above into the equation:
V = moles of H2 * 22.4 L/mol
Since the volume is usually measured in milliliters (mL), we can convert the answer by multiplying by 1000:
volume of H2 gas = moles of H2 * 22.4 L/mol * 1000 mL/L
Now you have all the values required to calculate the volume of H2 gas produced. Just substitute the value of moles of H2 into the equation and calculate the answer.