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

Caustic potash, another name for potassium hydroxide, is an extremely potent base that reacts with sulfurous acid. Let us talk about what will happen when these two react.

Potassium hydroxide is highly corrosive but not combustible. It is extensively used in the production of chemicals, cleaning agents, and petroleum refining. H₂SO₃ is a colorless liquid with a strong sulfuric burning odor which corrodes both metals and tissue.

We will discuss the product formed when H₂SO₃ reacts with KOH, the type of reaction, the net ionic equation and many other related topics in this article.

What is the product of H₂SO₃ and KOH ?

Potassium sulfite and water are produced when sulfurous acid reacts with potassium hydroxide.

H₂SO₃ + KOH = K₂SO₃ + H₂O

What type of reaction is H₂SO₃ + KOH ?

H₂SO₃ + KOH is an acid-base reaction because salt and water are produced when acid (H₂SO₃) and base (KOH) interact with each other.

How to balance H₂SO₃ + KOH

H₂SO₃ + KOH is balanced using the following steps-

H₂SO₃ + 2KOH = K₂SO₃ + H₂O

• Record the moles of each element on the reactant and product sides.

ELEMENT	REACTANT	PRODUCT
H	3	2
S	1	1
O	4	4
K	1	2

• From the table it is observed that number of the elements on the product and reactant sides are not equal. So to equate them following actions are made-
• KOH in the reactant side must ne multiplied by 2.
• H₂O in the product side must be multiplied by 2.
• Finally, the balanced chemical equation is,
• H₂SO₃ + 2KOH = K₂SO₃ + 2H₂O

H₂SO₃ + KOH titration

H₂SO₃ + KOH is titrated as a weak acid versus strong base titration reaction. To estimate the quantity or strength of acid H₂SO₃ titration is performed against KOH.

Apparatus

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

Indicator

The phenolphthalein or methyl orange indicator is used whose endpoint is pink to colorless.

Procedure

• Standardized H₂SO₃ and KOH are added dropwise to the conical flask while the flask is being shaken.
• The mixture is then poured into the burette along with the appropriate indicator.
• When the endpoint arrives after a certain amount of time, the indicator changes color, signaling that the reaction is complete.
• We repeat the titration several times and then we estimate potassium sulfite quantity by the formula V₁S₁ = V₂S₂.

H₂SO₃ + KOH net ionic equation

The net ionic equation for the of reaction H₂SO₃ + KOH is :

• OH^– = K⁺ + O^2- + SO₃^2-

The steps below are used to derive this net ionic equation:

• Ionize the strong electrolytes, H2SO3, K2SO3, and KOH are strong electrolytes in this reaction.

• 2H⁺ + SO₃^2- + 2K⁺ + OH^– = 2K⁺ + 2SO₃^2- + 2H⁺ + 2OH^–

• Write down the net ionic equation after canceling the spectator ions on both sides.

• The net ionic equation after canceling the spectator ions is:

• OH^– = K⁺ + O^2- + SO₃^2-

H₂SO₃ + KOH conjugate pairs

The conjugate acid-base pairs of the reaction H₂SO₃ + KOH are:

• H₂SO₃(Conjugate base) = HSO₃^–
• H₂O (Conjugate base) = OH^–

H₂SO₃ and KOH intermolecular forces

The intermolecular forces acting on H₂SO₃ + KOH  are-

• Columbic force is the electrostatic force of attraction in KOH. In the lattice of Potassium hydroxide, the potassium ion (K⁺), and hydroxyl ion (OH^–) are attracted by each other by this strong interionic forces of attraction.
• The dipole-dipole interaction and London dispersion forces are present in H₂SO₃. It also forms a very strong intermolecular hydrogen bonding with itself.

H₂SO₃ + KOH reaction enthalpy

The enthalpy of the reaction H₂SO₃ + KOH is 55.83KJ/mol.

CHEMICAL COMPOUND	ENTHALPY
H2SO3	-552 KJ/mol
K2SO3	-313 KJ/mol
KOH	-102.83KJ/mol
H2O	-286KJ/mol

• Rection Enthalpy = Enthalpy of product – Enthalpy of reactant

• Rection Enthalpy = (-286-313) – (-552-102.83) KJ/mol

• Rection Enthalpy = (-599) – (-654.83) KJ/mol = 55.83 KJ/mol.

Is H₂SO₃ + KOH a buffer solution ?

H₂SO₃ + KOH is not a buffer solution due to the presence of the weak acid H₂SO₃.

Is H₂SO₃ + KOH a complete reaction ?

The reaction between H₂SO₃ and KOH is complete because all of the moles of reactants are completely converted and consumed by the product at equilibrium.

Is H₂SO₃ + KOH an exothermic or endothermic reaction ?

H₂SO₃ + KOH is an exothermic reaction because the energy released due to the formation of water molecules is greater than the energy absorbed for the progress of the reaction. And being a neutralization reaction the enthalpy of the neutralization is always exothermic.

Is H₂SO₃ + KOH a redox reaction ?

H₂SO₃ + KOH is not a redox reaction because in this reaction no electron transfer takes place, and all the elements- K, H, O, and S maintain their oxidation state throughout the reaction.

Is H₂SO₃ + KOH a precipitation reaction ?

H₂SO₃ + KOH is not a precipitation reaction because none of the two products potassium sulfite (K₂SO₃) and water are obtained as a precipitate after the completion of the reaction.

Is H₂SO₃ + KOH reversible or irreversible reaction ?

H₂SO₃ + KOH is an irreversible reaction because the product side is more stable than the reactant side. In addition, it is a neutralization reaction, and because more stable salt and water are produced, the entire neutralization reaction becomes irreversible.

Is H₂SO₃ + KOH displacement reaction ?

H₂SO₃ and KOH is a double displacement reaction because the sulfate ion is transferred from H₂SO₃ to K₂SO₃ and the Hydrogen ion is transferred from H₂SO₃ to H₂O.

Conclusion

K₂SO₃ which is a byproduct of the reaction of H₂SO₃ + KOH is widely used for preserving food and beverages. It is an inorganic compound which is in white crystalline form, it is formed by the thermal decomposition of potassium meta bisulfite.