How many grams of H2(g) can theoretically be produced from a 5-g sample of magnesium metal and excess HCl(aq)?
Here is a worked example. Just follow the steps.
http://www.jiskha.com/science/chemistry/stoichiometry.html
To determine the amount of H2(g) that can be produced from the given sample of magnesium metal, we need to use stoichiometry to calculate the theoretical yield.
1. Write the balanced equation for the reaction between magnesium (Mg) and hydrochloric acid (HCl):
Mg(s) + 2HCl(aq) → MgCl2(aq) + H2(g)
From the equation, we can see that 1 mole of magnesium reacts with 2 moles of hydrochloric acid to produce 1 mole of hydrogen gas.
2. Convert the mass of magnesium to moles:
Given that the mass of magnesium is 5 g, we need to determine the number of moles of magnesium. To do this, we need to divide the mass by the molar mass of magnesium (24.31 g/mol):
Number of moles of magnesium = 5 g / 24.31 g/mol
3. Use the stoichiometry from the balanced equation:
Since 2 moles of hydrochloric acid react with 1 mole of magnesium to produce 1 mole of hydrogen gas, we can determine the moles of H2 produced by dividing the moles of magnesium by 2:
Number of moles of H2 = (Number of moles of magnesium) / 2
4. Convert moles of H2 to grams:
Finally, to determine the mass of hydrogen gas, multiply the moles of hydrogen by the molar mass of hydrogen (2.02 g/mol):
Mass of H2 = (Number of moles of H2) x (Molar mass of H2)
By following these steps, you can calculate the theoretical yield of hydrogen gas based on the given sample of magnesium and excess hydrochloric acid.