What is the volume at STP of hydrogen gas in mL that is produced when 4.32 g of magnesium reacts with 205 mL of 0.118 M hydrochloric acid?
convert grams to moles and see how many moles of H2 are generated.
1 mole occupies 22.4L at STP
To find the volume of hydrogen gas produced, we need to determine the moles of hydrogen gas first using stoichiometry.
The balanced chemical equation between magnesium and hydrochloric acid is:
Mg + 2HCl → MgCl2 + H2
From the equation, we can see that one mole of magnesium reacts with two moles of hydrochloric acid to produce one mole of hydrogen gas.
Step 1: Calculate the moles of magnesium:
We are given the mass of magnesium, which is 4.32 g. To find the moles, we can use the molar mass of magnesium, which is 24.31 g/mol.
Moles of magnesium = Mass of magnesium / Molar mass of magnesium
Moles of magnesium = 4.32 g / 24.31 g/mol
Step 2: Calculate the moles of hydrochloric acid:
We are given the volume of hydrochloric acid, which is 205 mL, and the molarity, which is 0.118 M. The molarity formula is Molarity (M) = Moles / Volume (L).
Moles of hydrochloric acid = Molarity × Volume (L)
Convert the volume from mL to L: 205 mL = 205/1000 L
Moles of hydrochloric acid = 0.118 M × (205/1000) L
Step 3: Determine the limiting reactant:
To find the limiting reactant, we compare the moles of magnesium and hydrochloric acid. The reactant that produces fewer moles of hydrogen gas is the limiting reactant.
Since the balanced equation shows that one mole of magnesium reacts with two moles of hydrochloric acid, we can calculate the theoretical moles of hydrogen gas produced from both reactants.
Theoretical moles of hydrogen gas from magnesium = Moles of magnesium
Theoretical moles of hydrogen gas from hydrochloric acid = 2 × Moles of hydrochloric acid
Step 4: Find the moles of hydrogen gas:
To determine the moles of hydrogen gas produced, we use the limiting reactant. The limiting reactant is the one that produces fewer moles of hydrogen gas.
Moles of hydrogen gas = Theoretical moles of hydrogen gas from limiting reactant
Step 5: Calculate the volume of hydrogen gas:
To find the volume of hydrogen gas produced, we need to use the ideal gas law. The ideal gas law equation is:
PV = nRT
Where:
P = Pressure (at STP, it is 1 atm)
V = Volume (which we need to find)
n = Moles of gas
R = Ideal gas constant (0.0821 L.atm/mol.K)
T = Temperature in Kelvin (at STP, it is 273.15 K)
Rearranging the ideal gas law equation, we get:
V = (n × R × T) / P
At STP, the pressure is 1 atm and the temperature is 273.15 K.
Substitute the values and solve for V.
Finally, convert the volume from liters to milliliters by multiplying by 1000 since 1 L is equal to 1000 mL.
By following these steps, you can find the volume of hydrogen gas produced in mL.