Sulfurous acid(H2SO3) is a water-soluble acid, and Bromine(Br2) is a volatile diatomic molecule. Let us explore more about their reaction.
Sulfurous acid is also known as trioxo-sulfuric acid, it is a colourless liquid and weaker acid than sulfuric acid. Bromine appears to be a reddish-brown liquid at room temperature, having a density of 3.1028 g/cm3.
The article below will cover some important aspects of the reaction between H2SO3 and Br2.
What is the product of H2SO3 and Br2?
H2SO3 reacts with Br2 to give Dithionic acid(H2S2O6) and Hydrobromic acid (HBr).
2H2SO3 + Br2 → H2S2O6 + 2HBr
What type of reaction is H2SO3 + Br2?
The reaction of H2SO3 + Br2 is an oxidation-reduction reaction.
How to balance H2SO3 + Br2?
To balance the H2SO3 + Br2 reaction, the following steps are to be followed.
H2SO3 + Br2 → H2S2O6 + HBr
- Count the number of atoms present on the reactant and product sides.
| Elements involved | Reactants side | Products side |
|---|---|---|
| H | 2 | 3 |
| O | 1 | 2 |
| S | 3 | 6 |
| Br | 2 | 1 |
- Multiply with significant numbers to the specific reactants and products such that the number of each atom on the reactant side and the product side becomes equal.
- 2× H2SO3 on reactant side and 2 × HBr on the product side.
- Count the number of atoms after the multiplication process to ensure an equal number of atoms on both sides.
| Elements involved | Reactants side | Products side |
| H | 4 | 4 |
| S | 2 | 2 |
| O | 6 | 6 |
| Br | 2 | 2 |
- write the complete balanced chemical equation.
- The balanced chemical equation is
- 2H2SO3 + Br2 = H2S2O6 + 2HBr
H2SO3 + Br2 titration
Titration of H2SO3 + Br2 is not possible because H2SO3 is an acid so it will be titrated only by a strong base like NaOH, not with Br2.
H2SO3 + Br2 net ionic equation
The net ionic equation of the reaction is-
Br2(aq) + 2SO32- (aq) = 2Br–(aq)+ S2O62-(aq)
The net ionic equation is obtained by using the steps below.
- Write the balanced chemical reaction
- 2H2SO3 + Br2 = H2S2O6 + 2HBr
- H2SO3, HBr and H2S2O6 dissociates in aqueous media as
- H2SO3 = 2H+(aq) + SO32-(aq)
- HBr = H+(aq) + Br–(aq) and
- H2S2O6 = 2H+ (aq)+ S2O62- (aq).
- So, the complete ionic equation is
- Br2(aq) +4H+(aq) + 2SO32- (aq) = 2Br–(aq)+ S2O62-(aq) + 4H+(aq)
- 4H+ gets cancelled out from both sides.
- And the net ionic equation becomes:
- Br2(aq) + 2SO32- (aq) = 2Br–(aq)+ S2O62-(aq)
H2SO3 + Br2 conjugate pairs
The conjugate pairs of H2SO3 + Br2 reaction are
| Compounds | Conjugate acid | Conjugate base |
| H2SO3 + H2O → | H3O+ (aq) | HSO3–(aq) |
| HSO3––+ H2O → | H3O+ (aq) | SO32-(aq) |
| H2S2O6 + H2O → | H3O+ (aq) | S2O62– (aq) |
| HBr + H2O → | H3O+ (aq) | Br- |
H2SO3 and Br2 intermolecular forces
The intermolecular forces of the reaction H2SO3 + Br2 are:
- H2SO3 molecule has hydrogen bonding tendency, dipole-dipole interaction and ion-dipole interaction.
- Br2 is a nonpolar molecule and thus possesses London dispersion force.
- HBr is an ionic molecule and has ionic interaction.
- H2S2O6 shows dipole-dipole interaction and Hydrogen bonding interaction.
H2SO3 + Br2 reaction enthalpy
The enthalpy of the reaction H2SO3 + Br2 is not available in literature. For dithionic acid(H2SO3) ΔH0f (enthalpy of formation) value is not experimentally calculated.
Is H2SO3 + Br2 a buffer solution?
H2SO3 + Br2 is not a buffer solution because H2SO3 + Br2 is a mixture of a weak acid(H2SO3) and a Lewis acid ( Br2) whereas buffer solution is made by mixing weak acid and its conjugate base or weak base and its conjugate acid.
Is H2SO3 + Br2 a complete reaction?
The H2SO3 + Br2 reaction is a complete reaction, no further reaction is possible here.
Is H2SO3 + Br2 an exothermic or endothermic reaction?
The exothermic and endothermic nature of the H2SO3 + Br2 reaction can not be specified without knowing the reaction enthalpy.
Is H2SO3 + Br2 a redox reaction?
H2SO3 + Br2 reaction is a redox reaction because here, sulfur of H2SO3 is oxidized from +4 to +5 oxidation state, and H2SO3 reduces bromine from 0 to -1 oxidation state.
Is H2SO3 + Br2 a precipitation reaction?
H2SO3 + Br2 reaction is not a precipitation reaction because the products dithionic acid(H2SO3) and hydrobromic acid(H2SO3) are soluble in water and so do not form precipitate.
Is H2SO3 + Br2 reversible or irreversible reaction?
The H2SO3 + Br2 reaction is a reversible reaction because it can undergo the reverse reaction also:
H2S2O6(aq) + 2HBr(aq) = 2H2SO3(aq) + Br2(aq)
Is H2SO3 + Br2 displacement reaction?
The H2SO3 + Br2 reaction is not a displacement reaction as no accountable ion displacement has taken place there.
Conclusion
Sulfurous acid is a weak acid and is used in pigments, dyes, and as a reducing agent. Bromine-bearing chemicals are used in agriculture industries. Dithionic acid is water soluble and used as a gentle oxidizing and reducing agent.
Hello….I am Soumak Mahato. I have completed my M.Sc in Chemistry from Banaras Hindu University in 2022, specializing in Inorganic Chemistry. I have joined Lambdageeks as an SME in Chemistry. Trying to explain chemistry in easy way. My hobbies include Sports and music.
Let’s connect through LinkedIn
Hi Fellow Reader,
We're a small team at Techiescience, working hard among the big players. If you like what you see, please share our content on social media. Your support makes a big difference. Thank you!