15 Facts on H2SO3 + KIO3: What, How To Balance & FAQs

H2SO3 is a strong acid that can easily react with the salt of a strong base like KIO3. Let us see the reaction mechanism between the H2SO3 and KIO3.

H2SO3 or sulfurous acid is an inorganic acid of S and it is a very strong acid having a pka value is 1.81. the acid has one double-bonded oxygen and two -OH group present around the central sulfur atom. Whereas potassium iodate is a salt of strong acid and strong base having strong electrolytic properties.

The reaction between H2SO3 and KIO3 does not require any kind of catalyst, both are enough reactive for proceeds the reaction. Let us discuss the mechanism of the reaction between sulfurous acid and potassium iodate, the reaction enthalpy, the type of reaction, product formation, etc. in the following part of article.

1. What is the product of H2SO3 and KIO3?

Potassium iodide and sulfuric acid are formed as major product formed when H2SO3 and KIO3 are reacted together.

H2SO3 + KIO3 = H2SO4 + KI

2. What type of reaction is H2SO3 + KIO3?

H2SO3 + KIO3 reaction is an example of an acid formation reaction and single displacement reaction along with redox and precipitation reactions. Here, acid compounds are formed in the course of the reaction.

3. How to balance H2SO3 + KIO3?

H2SO3 + KIO= H2SO4 + KI this reaction is not balanced yet, we have to balance the equation in the following way-

  • First, we label all the reactants and products by A, B, C, and D as there are four different molecules obtained for this reaction and the reaction looks like this,
  • A H2SO4 +B KIO3 = C H2SO4 + D KI
  • Equating the coefficients for the same type of elements by rearranging them.
  • After the rearrangement of coefficients of the same elements by their stoichiometric proportion, we get,
  • H = 2A = 2C, S = A = C, O = 4A = 3B = 4C, K = B= D, I = B = D,
  • Using the Gaussian elimination and equating all the equations we get, A = 3, B = 1, C = 3, and D =1,
  • The overall balanced equation will be,
  • 3H2SO3 + KIO3 = 3H2SO4 + KI

4. H2SO3 + KIO3 titration

To estimate the quantity of iodide or strength of acid we can perform a titration between KIO3 and H2SO3.

Apparatus used

We need a burette, conical flask, burette holder, volumetric flask, and beakers for this titration.

Titre and titrant

H2SOversus KIO3, H2SO3 acts as a titrant which is taken in the burette and the molecule to be analyzed is KIO3 which is taken in a conical flask.

Indicator

The whole titration is done in an acidic medium or acidic pH so the best suitable indicator will be phenolphthalein which gives perfect results for this titration at given pH.

Procedure

The burette is filled with standardized H2SO3. KIO3 is taken in a conical flask along with respective indicators. H2SO3 is added dropwise to the conical flask and the flask is shaken constantly. After a certain time, when the endpoint arrives, the indicator changes its color and the reaction is done.

5. H2SO3+ KIO3 net ionic equation

The net ionic equation between H2SO3 + KIO3 is as follows,

SO2 + H+ + OH + K+ + IO3 = 2H+ + SO42- + K+ + I

To derive the net ionic equation, the following steps are required,

  • H2SO3 will be broken into sulfur dioxide and water and water ionized as proton and hydroxide ions.
  • After that KIO3 also dissociates into K+ ion and IO3 ion as it is also a strong electrolyte
  • In the product part H2SO4 ionized into H+ and SO42-as it is a strong electrolyte and strong acid.
  • KI is also ionized as K+ and I as it is a salt.

6. H2SO3+ KIO3 conjugate pairs

In the reaction, H2SO3 + KIO3 conjugate pairs will be the corresponding de-protonated and protonated form of that particular species which are listed below-

  • Conjugate pair of H2SO3 = SO32-
  • Conjugate pair of OH = H2O
  • Conjugate pair of SO42- = H2SO4

7. H2SO3 and KIO3 intermolecular forces

The intermolecular force present in H2SO3 is the strong electrostatic force between protons and sulfite ions. In KIO3 there are electronic interactions and coulumbic force present. It is also an electrostatic and covalent force present in H2SO4, also van der waal’s attraction.

MoleculeActing
force
H2SO3 / H2SO4Electrostatic,
van der waal’s
Dipole
interaction
KIO3Strong electrostatic
force and
ionic interaction,
Coulumbic force
KIElectrostatic force,
ionic interaction,
Intermolecular Forces

8. H2SO3 + KIO3 reaction enthalpy

H2SO3 + KIO3 reaction enthalpy is -2713.3 KJ/mol which can be obtained by the formula: enthalpy of products – enthalpy of reactants.

MoleculeEnthalpy
(KJ/mol)
KIO3+34.63
H2SO3+52.89
H2SO4-814
KI-78
Enthalpy of Reactants
and Products

9. Is H2SO3 + KIO3 a buffer solution?

H2SO3 + KIO3 gives a buffer solution of strong acid H2SO4 and KI which can control the pH of the reaction.

10. Is H2SO3 + KIO3 a complete reaction?

H2SO3 + KIO3 is complete because it gives two major one is a strong acid and the other is ionic salt.

11. Is H2SO3 + KIO3 an exothermic or endothermic reaction?

H2SO3 + KIO3 is exothermic in terms of thermodynamics first law. This reaction released more energy and temperature to the surroundings, where δH is always negative.

12. Is H2SO3 + KIO3 a redox reaction?

H2SO3 + KIO3 reaction is a redox reaction because in this reaction sulfur gets oxidized and iodine gets reduced. Here H2SO3 acts as a reducing agent whereas KIO3 acts as an oxidizing agent.

Screenshot 2022 12 01 145420
Redox Schematic of the
H2SO3 and KIO3 Reaction

13. Is H2SO3 + KIO3 a precipitation reaction

The reaction between H2SO3 + KIO3 is a precipitation reaction because KI gets precipitated in the solution at certain pH which can be removed by using rare earth metal.

14. Is H2SO3 + KIO3 reversible or irreversible reaction?

The reaction between H2SO3+ KIO3 is irreversible because it produced salt and acid. The equilibrium shifts towards the right-hand side only or forward directions.

H2SO3 + KIO3 —-> H2SO4 + KI

15. Is H2SO3 + KIO3 displacement reaction?

The reaction between H2SO3+ KIO3 is an example of a single displacement reaction. Because in the above reaction H+ displaced oxygen from KIO3.

Screenshot 2022 12 01 145845
Single Displacement Reaction

Conclusion

The reaction between H2SO3 and KIO3 gives us an electrolytic salt potassium iodide along with sulfuric acid, where we can estimate the amount of iodine. This reaction is an acid-base and irreversible reaction. This reaction is used for the production of sulfuric acid.