Question

Identify the balance reaction between Aluminium and hydrochloric acid from the following reactions:
$
  {\text{A}}{\text{. }}2Al + 5HCl \to 2AlC{l_3} + 3{H_2} \\
  {\text{B}}{\text{. 2}}Al + 7HCl \to 2AlC{l_3} + 3{H_2} \\
  {\text{C}}{\text{. }}2Al + 8HCl \to 2AlC{l_3} + 3{H_2} \\
  {\text{D}}{\text{. 2}}Al + 6HCl \to 2AlC{l_3} + 3{H_2} \\
$

Answer 1

Hint: To answer this question first we have to understand what is balance reaction and we should have knowledge of how we can make an unbalanced reaction into a balance reaction. Here we have to only find a balanced reaction.

Complete step-by-step answer:
So first we have to understand what is a balanced reaction.
Balance reaction:
A balanced chemical equation occurs when the number of the atoms involved in the reactants side is equal to the number of atoms in the products side.
A balanced equation obeys the Law of Conservation of Mass. This is an important guiding principle in science. Finally, a balanced equation lets up predict the amount of reactants needed and the amount of products formed.
Now we have to check option wise that in which option all atoms of reactant are equal to atoms in the product.
We have option A.
$
  2Al + 5HCl \to 2AlC{l_3} + 3{H_2} \\
    \\
 $
Here on the reactant side we have two atoms of aluminium same as on the product side that means aluminium is balanced.
On the reactant side we have five atoms of hydrogen but on the product side we have six atoms of hydrogen that means hydrogen is not balanced. And hence option A is wrong because it is not a balanced reaction.
Now we will check option B.
$
  {\text{2}}Al + 7HCl \to 2AlC{l_3} + 3{H_2} \\
    \\
 $
Here on the reactant side we have two atoms of aluminium same as on the product side. And hence aluminium is balanced.
On the reactant side we have seven atoms of hydrogen but on the product side we have six atoms of hydrogen and hence hydrogen is not balanced. And that’s why option B is wrong. Means this is also an unbalanced reaction.
Now we will check option C.
$
  2Al + 8HCl \to 2AlC{l_3} + 3{H_2} \\
    \\
$
Here on the reactant side we have two atoms of aluminium and on the product side two atoms of aluminium to aluminium is balanced.
Now we have eight atoms of hydrogen on the reactant side but on the product side we have only six atoms of hydrogen that means hydrogen is not balanced and that’s why option C is also wrong.
Now at last we have to check option D.

${\text{2}}Al + 6HCl \to 2AlC{l_3} + 3{H_2}$
Here we can see we have two atoms of aluminium on the reactant side and also two atoms on the product side and hence aluminium is balanced.
Now we check hydrogen. We have six hydrogen on reactant side and on product side we have the same six hydrogen so hydrogen is also balanced.
Now we will check calcium and we have six atoms of calcium on reactant side and on product side also and that’s why calcium is also balanced that means option D is balanced.
Hence option D is the correct option.
Note: Whenever we get this type of question the key concept of solving is we have to check that means we have to count number of atoms on both side of reaction that means on reactant side and on product side and when we get same number of atoms on both side then we can say reaction is balanced equation.