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

Potassium(K), an alkali metal, is highly reactive, and H2SO3 (sulphurous acid) is a weak inorganic acid. Let us examine their reaction in detail.

K is a soft, silvery-white metal, solid at room temperature, and is an excellent conductor of electricity. Its reaction with water is violent and highly exothermic. H2SO3 is a colorless and corrosive acid, with a pungent-burning sulphur smell. K is a good reducing agent, as seen in its reaction with H2SO3.

In this article, let us discuss the reaction of H2SO3 + K, the type of reaction, the forces involved, buffer solution, and other related facts.

What is the product of H2SO3 and K?

Potassium sulphite and hydrogen gas are the products formed when H2SO3 reacts with K.

H2SO3 + 2K ———> K2SO3 + H2

What type of reaction is H2SO3 + K?

H2SO3 + K is a single displacement reaction.

How to balance H2SO3 + K?

The equation H2SO3 + K is balanced by the following steps.

 H2SO3 + 2K = K2SO3 + H2

  • Identify and count the number of moles of each element involved in both the sides of the reaction.
ElementReactant sideProduct side
Count of the elements on each side of the reaction
  • We find that the number of moles of all elements in the reactant and product side are equal except potassium (K).
  • A coefficient of 2 is added before K in the reactant side so that the number of moles of K are same on both sides of the equation.
  • The overall balanced equation is given by –
  • H2SO3 + 2K  = K2SO3 + H2

H2SO3 + K  titration

H2SO3 + K will not undergo titration as K being a metal, will not be used in the titration.

H2SO3 + K  net ionic equation

The net ionic equation between H2SO3 + K is:

H2SO3 (aq)+ K (s) = 2K+  (aq) + SO32- (aq) + H2 (g)

The following are the steps to derive the net ionic equation:

  • Write the balanced molecular equation along with its physical state.
  • H2SO3 (aq) + K (s)  =  K2SO3 (aq)  + H2 (g)
  • The electrolytes, which are strong, are split into their respective ions. H2SO3 is a weak electrolyte, K is a solid and H2 is a gas, so will not split. The equation now becomes,
  • H2SO3 (aq)+ K (s) = 2K+  (aq) + SO32- (aq) + H2 (g)
  • The charge in the above equation is also conserved. Therefore, the net ionic equation is –
  • H2SO3 (aq)+ K (s) = 2K+  (aq) + SO32- (aq) + H2 (g)

H2SO3 + K  conjugate pairs

  • Conjugate base of H2SO3 as HSO3
  • K is a metal, so there is no conjugate pair for K.

H2SO3 + K  intermolecular forces

  • In H2SO3, Electrostatic forces, London dispersion forces, Van der Waals forces, and dipole-dipole interactions are the intermolecular forces that hold the hydrogen and sulphite ions together.
  • Metallic bonding is seen in K, as it is a metal.

H2SO3 + K  reaction enthalpy

H2SO3 + K reaction enthalpy is -467.87 KJ/mol. The enthalpy of the reaction is calculated using the values listed below,

Reactants and ProductsEnthalpy in KJ/mol
Enthalpy values
  • The enthalpy of formation of elements or molecules existing in their original state is taken as zero.
  • ∆Hf°(reaction) = ∆Hf°(products) – ∆Hf°(reactants)

= -1123.37 – (-655.5)

= -467. 87 KJ/mol

Is H2SO3 + K a buffer solution?

H2SO3 + K will not form a buffer solution due to the presence of a metal (K) and weak sulphurous acid.

Is H2SO3 + K a complete reaction?

H2SO3 + K  is a complete reaction since one of the products formed is hydrogen gas that gets evolved during the reaction.

Is H2SO3 + K an exothermic reaction?

H2SO3 + K is an exothermic reaction, as the reaction enthalpy is found to be negative.

Is H2SO3 + K a redox reaction?

H2SO3 + K is a redox reaction where,

  • Potassium is oxidized from 0 to +1 oxidation state.
  • Hydrogen is reduced from +1 to 0 oxidation state.

Is H2SO3 + K a precipitation reaction?

H2SO3 + K is not a precipitation reaction as the product formed is completely soluble in water, and no precipitate is observed.

Is H2SO3 + K an irreversible reaction?

H2SO3K is an irreversible reaction as the forward reaction is more favorable due to increased entropy associated with the liberation of gaseous hydrogen.

Is H2SO3 + K a displacement reaction?

H2SO3 + K  is an example of a single displacement reaction, as potassium is more reactive than hydrogen and will displace it from its salt solution to form potassium sulphite.

Screenshot 2022 11 30 192052
Single Displacement Reaction


The reaction of K with H2SO3 is less violent than with H2SO4, as sulphurous acid is a weak acid. The reaction proceeds with a violet-colored flame. Potassium is a very vital nutrient for human and plant growth.

Read more about following H2SO3 facts

H2SO3 + Al
H2SO3 + Al(OH)3
H2SO3 + CuS
H2SO3 +KClO3
H2SO3 + O2
H2SO3 + BaCl2
H2SO3 + Ba(OH)2
H2SO3 + K2O
H2SO3 + CaO
H2SO3 + Ca(OH)2
H2SO3 + CaCl2
H2SO3 + HgO
H2SO3 + BaCO3
H2SO3 + Mn(OH)2
H2SO3 + AgOH
H2SO3 + Fe(OH)3
H2SO3 + K
H2SO3 + LiOH
H2SO3 + Fe2O3
H2SO3 + NaHCO3
H2SO3 + Ca
H2SO3 + CsOH
H2SO3 + Ag2S Reaction
H2SO3 + Hg(OH)2
H2SO3 + AL2O3
H2SO3 + KIO3
H2SO3 + FeCO3
H2SO3 + Zn(OH)2
H2SO3 + NH3
H2SO3 + Na2CO3
H2SO3 + CaCO3
H2SO3 + CuO
H2SO3 + KMnO4
H2SO3 + FeCl2
H2SO3 + AlBr3
H2SO3 + NaHSO3
H2SO3 + Na
H2SO3 + Br2