Question

How would you balance: \[AlB{r_3} + {K_2}S{O_4} \to KBr + A{l_2}{\left( {S{O_4}} \right)_3}?\]

Answer 1

Hint: We need to know the concept of law of conservation of masses in order to balance any chemical equation. The Law of Conservation of Mass was given by Antoine Lavoisier in 1789 with the discovery that mass is neither created nor destroyed in chemical reactions. Thus an equation (chemical equation to be more specific) needs to be balanced so that it obeys the law of conservation of masses.

Complete step by step answer:
The following points must be kept in mind in order to balance a chemical equation:
The law of conservation of mass states that mass in an isolated system is neither created nor destroyed by chemical reactions or physical transformations.
According to the law of conservation of mass, the mass of the products in a chemical reaction must equal the mass of the reactants.
The law of conservation of mass is useful for a number of calculations and can be used to solve for unknown masses, such as the amount of gas consumed or produced during a reaction.
Let us take the example of an unbalanced reaction to explain the need of balancing a reaction. An unbalanced equation has an unequal number of atoms on either side of the reaction. For example,
\[KMn{O_4} \to {K_2}Mn{O_4} + Mn{O_2} + {O_2}\]
In this reaction of decomposition of potassium permanganate, the equation is unbalanced since the number of atoms of \[K\] , $Mn$ and \[O\] is unequal before and after the reaction, thus disobeying the law of conservation of mass. After balancing the reaction, we have
\[2KMn{O_4} \to {K_2}Mn{O_4} + Mn{O_2} + {O_2}\]
The above equation obeys the law of conservation of masses since the number of atoms of all the elements taking part in the reaction are equal before and after the reaction.
Using the same logic, we can balance the given unbalanced equation \[AlB{r_3} + {K_2}S{O_4} \to KBr + A{l_2}{\left( {S{O_4}} \right)_3}\]
The balanced chemical equation is \[2AlB{r_3} + 3{K_2}S{O_4} \to 6KBr + A{l_2}{(S{O_4})_3}\]

Note: It must be noted that in case of ionic reactions, law of conservation of masses holds true along with law of conservation of charges as well. It states that the net charge of either side of the reactions must be equal before and after the reaction. In other words, all chemical reactions (ionic or non-ionic) must obey both the laws of conservation of mass and charge.