Question

Fill in the blank space and then balance the chemical equations.

___________ + dil.HCl $\to$MgCl₂ + _______

Answer 1

Step 1: The completed equation:

$\underset{\mathrm{Magnesium}}{\mathrm{Mg}\left(\mathrm{s}\right)}+\underset{\mathrm{Hydrochloric}\mathrm{acid}}{\mathrm{dil}.\mathrm{HCl}\left(\mathrm{aq}\right)}\to \underset{\mathrm{Magnesium}\mathrm{chloride}}{{\mathrm{MgCl}}_2\left(\mathrm{aq}\right)}+\underset{\mathrm{Hydrogen}}{{\mathrm{H}}_2\left(\mathrm{g}\right)}$

Step 2: Calculating the number of atoms on the reactants and product side:

Elements	Number of atoms on the reactant side	Number of atoms on the product side
Mg	1	1
H	1	2
Cl	1	2

Step 3: Balancing the uneven numbers of atoms on the reactants and product side:

• The number of hydrogen and chlorine atoms is unequal on the reactant and product sides.
• The balancing of the equation can be done by multiplying the required coefficients. ie, HCl in the reactant side should be multiplied by 2.

Elements	Number of atoms on the reactant side	Number of atoms on the product side
Mg	1	1
H	2	2
Cl	2	2

Now the numbers of atoms are equal on both sides.

$\underset{\mathrm{Magnesium}}{\mathrm{Mg}\left(\mathrm{s}\right)}+\underset{\mathrm{Hydrochloric}\mathrm{acid}}{2\mathrm{HCl}\left(\mathrm{aq}\right)}\to \underset{\mathrm{Magnesium}\mathrm{chloride}}{{\mathrm{MgCl}}_2\left(\mathrm{aq}\right)}+\underset{\mathrm{Hydrogen}}{{\mathrm{H}}_2\left(\mathrm{g}\right)}$

Therefore, the equation is balanced.