Calculate the theoretical volume of gas you would expect to be evolved
from your experiment if X moles of magnesium were reacted with an
excess of HCl at standard conditions (STP).
Mg + 2HCl ==> MgCl2 + H2
mols Mg = X
mols H2 produced = X (look at the coefficients; 1 mol H2 produced for 1 mol Mg used)
Volume = mols*22.4L/mol
volume 22.4X liters.
To calculate the theoretical volume of gas evolved from the reaction between magnesium and hydrochloric acid, we need to use the ideal gas law. The ideal gas law equation is:
PV = nRT
where:
P = pressure (in atmospheres)
V = volume (in liters)
n = number of moles of gas
R = ideal gas constant (0.0821 L·atm/(mol·K))
T = temperature (in Kelvin)
At standard conditions (STP), the pressure is 1 atm and the temperature is 273 K.
In this case, you have X moles of magnesium reacted with an excess of HCl. Assuming the reaction goes to completion and all the magnesium reacts, all the limiting reactant (HCl) will react, and X moles of magnesium will generate X moles of gas.
Let's say X is the number of moles of magnesium.
Therefore, the number of moles of gas (n) is also X.
Now, substitute the values into the equation:
PV = nRT
(1 atm) * V = X * (0.0821 L·atm/(mol·K)) * (273 K)
Simplifying the equation:
V = (X * 0.0821 * 273) / 1
V = (22.4583X) / 1
Therefore, the theoretical volume of gas (V) in liters would be 22.4583 times the number of moles of magnesium (X).