Magnesium metal reacts with HCl solution, liberating H2 gas and generating Mg2+ cations in solution. A 1.890-g sample of Mg metal is added to 125.0 mL of a 4.00 M HCl solution, and the reaction goes to completion. How many grams of H2 are formed?
To determine the number of grams of H2 formed in the reaction, we need to calculate the amount of H2 gas produced using stoichiometry.
Let's start by writing the balanced chemical equation for the reaction:
Mg + 2HCl -> MgCl2 + H2
From the equation, we can see that 1 mole of magnesium reacts with 2 moles of hydrochloric acid to produce 1 mole of H2 gas.
Next, let's calculate the number of moles of HCl used in the reaction:
moles of HCl = concentration of HCl x volume of HCl solution
moles of HCl = 4.00 M x (125.0 mL / 1000 mL/1 L)
moles of HCl = 0.500 moles
Since the reaction goes to completion, all the moles of HCl will react with magnesium in a 1:2 ratio. Therefore, the number of moles of magnesium required is twice the moles of HCl used:
moles of Mg = 2 x moles of HCl
moles of Mg = 2 x 0.500 moles
moles of Mg = 1.000 moles
Now, we need to calculate the molar mass of H2 to convert moles to grams:
Molar mass of H2 = 2.016 g/mol (approximately)
Finally, we can calculate the grams of H2 formed:
grams of H2 = moles of H2 x molar mass of H2
grams of H2 = 1.000 moles x 2.016 g/mol
grams of H2 = 2.016 g
Therefore, approximately 2.016 grams of H2 are formed in this reaction.