Calculate the mass of Mg needed to produce ~40 mL of H2. how do I do this?
write a balanced chemical equation.
Mg+2HCl>>MgCl2 + H2
so for each mole of H2, one mole of Mg is required.
how do i figure out the moles of H2? Do I convert the mL to L and then divide that by the mass of H2?
To calculate the mass of Mg needed to produce a certain volume of H2 gas, you need to use the stoichiometry of the balanced chemical equation.
First, write the balanced equation for the reaction between Mg and H2O to produce H2 gas:
Mg + 2H2O -> Mg(OH)2 + H2
From the balanced equation, you can see that one mole of Mg reacts to produce one mole of H2 gas. Also, one mole of any gas occupies 22.4 liters at STP (standard temperature and pressure).
Given that you have 40 mL of H2 gas, you need to convert it to liters:
40 mL = 0.04 L (since 1 liter = 1000 mL)
Next, use the molar volume of a gas at STP to determine the number of moles of hydrogen gas:
1 mole H2 gas = 22.4 L
So, the number of moles of H2 gas produced from 40 mL can be calculated as:
moles of H2 gas = volume of H2 gas / molar volume of H2 gas at STP
= 0.04 L / 22.4 L/mol
= 0.00179 mol
Now, based on the balanced equation, the molar ratio between magnesium and hydrogen gas is 1:1. Therefore, the number of moles of magnesium required is also 0.00179 mol.
Lastly, to calculate the mass of magnesium needed, you need to multiply the number of moles by the molar mass of magnesium (24.31 g/mol):
mass of Mg = moles of Mg × molar mass of Mg
= 0.00179 mol × 24.31 g/mol
= 0.0437 g
Therefore, approximately 0.0437 grams of magnesium (Mg) is needed to produce around 40 mL of hydrogen gas (H2).