Question

When magnesium metal and an aqueous solution of hydrochloric acid combine, they produce an aqueous solution of magnesium chloride and hydrogen gas. Using the equation, Mg (s) + 2HCl (aq) Imported Asset MgCl2 (aq) + H2 (g), if 36.5 g of Mg and 2 moles of HCl are supplied, identify the limiting reagent.

I don't understand how to reach the answer ???

thank you !!!

Answer 1

The limiting reagent is HCl

Step-by-step explanation

Mg(s) +2 HCl (aq) → MgCl₂ (aq) +H₂ (g)

Step 1:Find the moles of Mg used

moles = mass /molar mass

from periodic table the molar mass of Mg = 24.3 g

moles = 36.5 g/24.3 g/mol = 1.502 moles

Step 2: Use the mole ratio to determine the moles of MgCl₂ produced from each reactant .

Mg: MgCl₂ is 1:1 therefore 1.502 moles of mg reacted to produce 1.502 moles of MgCl₂

HCl: MgCl₂ is 2:1 therefore 2 moles of HCl reacted to produce

2 mole x 1/2 = 1 moles of MgCl₂

Since HCl produce least amount of MgCl₂, HCl is the limiting reagent

Answer 2

The balanced chemical reaction is:

Mg(s) + 2HCl(aq) = MgCl2(aq) + H2(g)

We are given the amounts of reactants to be used for the reaction. This will be the starting point of the calculations.

36.5 g Mg ( 1 mol / 24.31 g ) = 1.50 mol Mg
2 mol HCl

From the reaction, the mole ratio of the reactants is 1:2. In every 1 mole of magnesium 2 mol of hydrochloric acid is required. Therefore, from the amount supplied the limiting reactant is the hydrochloric acid.