Question

1. Consider the unbalanced equation:

Mg (s) + HCl (aq) ---> MgCl2 (s) + H2 (g)

If 4.59 mol of Mg and 4.59 mol of HCl are reacted, how many moles of MgCl2 are produced?

Hint: Write the balanced equation first.

Answer 1

2.30 moles MgCl₂

Step-by-step explanation:

First, you need to balance the chemical equation. An equation is balanced when there is an equal amount of each element on both sides of the reaction. These values can be modified by adding coefficients in front of the molecules.

The unbalanced equation:

Mg (s) + HCl (aq) ---> MgCl₂ (s) + H₂ (g)

Reactants: 1 magnesium, 1 hydrogen, 1 chlorine

Products: 1 magnesium, 2 hydrogen, 2 chlorine

The balanced equation:

Mg (s) + 2 HCl (aq) ---> MgCl₂ (s) + H₂ (g)

Reactants: 1 magnesium, 2 hydrogen, 2 chlorine

Products: 1 magnesium, 2 hydrogen, 2 chlorine

Now, you need to use the mole-to-mole ratios from the balanced equation to convert between moles. Since we were not given a limiting reactant, the easiest way to find the actual moles of MgCl₂ is to start from both reactants.

4.59 moles Mg 1 mole MgCl₂
------------------------- x ------------------------ = 4.59 moles MgCl₂
1 mole Mg

4.59 moles HCl 1 mole MgCl₂
------------------------- x ------------------------ = 2.30 moles MgCl₂
2 moles HCl

Since HCl produces the smaller amount of product, it must be the limiting reactant. In other words, HCl runs out before all of the Mg is completely used up. Therefore, the actual amount of MgCl₂ produced in 2.30 moles.