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 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.

Answer 2

 The limiting reagent   is   HCl

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