Question

Write balanced chemical equation:
Sodium thiosulphate is reacted with dilute hydrochloric acid.
A. \[2N{a_2}{S_2}{O_3} + HCl \to 2NaCl + {H_2}O + S{O_2} + S\]
B. \[N{a_2}{S_2}{O_3} + 2HCl \to NaCl + {H_2}O + S{O_2} + S\]
C. \[N{a_2}{S_2}{O_3} + 2HCl \to 2NaCl + {H_2}O + S{O_2} + S\]
D. \[2N{a_2}{S_2}{O_3} + HCl \to NaCl + {H_2}O + 2S{O_2} + S\]

Answer 1

Hint: To balance the reaction, we can use the law of conservation of mass. Hit and trial method is used to balance the number of atoms on both, left and right side of the reaction. The mass of products in a chemical reaction must be equal to the mass of reactants.

Complete step by step answer:
-According to the law of conservation of mass, in an isolated system, mass is neither created nor destroyed by any chemical or physical transformations.
-A chemical equation represents the substances that are involved in a chemical reaction i.e. reactants and products. The balanced chemical equation is the one which has the same number of atoms on both sides of a reaction.
-When sodium thiosulphate reacts with dilute hydrochloric acid, they produce a cloudy precipitate. Although both the reactant chemicals are clear solutions yet on reacting, they form yellow precipitate of sulphur. It's a common reaction used to study reaction rates.
-Sodium thiosulphate reacts with dilute hydrochloric acid to produce sulphur dioxide, sodium chloride, sulphur and water. Sulphur dioxide is a soluble gas and has the ability to dissolve completely in aqueous solutions. The sulphur formed in this reaction is insoluble and present in the mixture as a white or pale-yellow precipitate or a colloid that gives a milky appearance and thus makes the solution opaque.
-We know now the reactants and products involved in the chemical reaction, we can write the equation as
 \[N{a_2}{S_2}{O_3} + 2HCl \to 2NaCl + {H_2}O + S{O_2} + S\]

Type of Atom	No. of atoms on left side	No. of atoms on right side
Na	2	2
C	2	2
O	3	3
H	2	2
Cl	2	2

Hence, the correct option is (C).

Note:
These balancing numbers are called stoichiometric coefficients. It is the number written in front of atoms, ions and molecules in a chemical reaction to balance the number of each element on both the sides. It gives the ratio of moles of reactants and products. It can be a fraction value too.