15 Facts on H2SO4 + K2S: What, How To Balance & FAQs

There are certain reactions which show certain colour change in the product. Let us look at such beautiful reactions and their properties.

Sulphuric acid, hygroscopic and colourless, is a lab reagent that is corrosive in nature. Potassium Sulphide is also hygroscopic and a toxic compound having high solubility in water but low in organic solvents. Dusts of sulphide are harmful for our eyes and skin. The reaction produces products in different states.

This article will show how the reaction of two dangerous compound give products of varying properties.

What is the product of H₂SO₄ and K₂S?

H₂SO₄ and K₂S are reacted to form Potassium sulphate, sulphur dioxide gas, sulphur and water molecule respectively. The reaction equation is:

• 2H₂SO₄ + K₂S → K₂SO₄ + SO₂ + S + 2H₂O

What type of reaction is H₂SO₄ + K₂S?

The reaction of H₂SO₄ and K₂S is a dissociation reaction as products formed dissociate to ions in the solution.

How to balance H₂SO₄ + K₂S?

These are the rules to equal the H₂SO₄ + K₂S reaction scheme:

• H₂SO₄ + K₂S → K₂SO₄ + SO₂ + S + H₂O
• Here, both the reaction and product side must be equal in atoms; multiply H₂SO₄ with 2 to equal with the sulphur atoms of H₂SO₄.
• 2H₂SO₄ + K₂S → K₂SO₄ + SO₂ + S + 2H₂O

H₂SO₄ + K₂S Titration

H₂SO₄ + K₂S titration is possible and should be carried out with caution.

Apparatus

• Graduated burette
• Conical flask
• Volumetric flask
• Burette stands
• Sample beakers

Titre and Titrant

• K₂S is used as the titrant, whose concentration is known.
• H₂SO₄ is the titre, the concentration is to be measured.

Indicator

Thymol Blue indicator is used for strong acid-base titrations as it turns yellowish in an acidic medium while bluish in a basic medium.

Procedure 

• Standardised solution of K₂S of known concentration is filled in the burette and clamped to the stand.
• In the conical flask, the unknown sulphuric acid is added after washing.
• Few drops of thymol blue indicator(pH= 8.0-9.6) is added in the solution.
• At the equivalence point, equal moles of acid and base have reacted, signifying the end of the titration with suitable colour change.
• The volume of base used is applied to measure the strength of the acid by the formula:
• V_K2S S_K2S = V_H2SO4 S_H2SO4

H₂SO₄ + K₂S Net Ionic Equation

H₂SO₄ + K₂S reaction has the net ionic equation,

• 2H⁺(aq) + 2SO₄^2-(aq) + 2K⁺(aq) + S^2-(aq) → 2K⁺(aq) + SO₄^2-(aq) + SO₂(g) + S(g) + H⁺(aq) + OH^–(aq)

H₂SO₄ + K₂S Conjugate Pairs

H₂SO₄ + K₂S reaction has the following conjugate pairs:

• Conjugate base of H₂SO₄= HSO₄^–
• Conjugate base of H₂O= OH^–

H₂SO₄ + K₂S Intermolecular Forces

H₂SO₄ + K₂S reaction has the following intermolecular forces,

• H₂SO₄ shows an ionic character in an aqueous medium.
• K₂S show weak intermolecular forces like Van der Waals forces.
• K₂S is more prone to reaction with water.
• S consists of allotropes in rhombic and monoclinic form.

H₂SO₄ + K₂S Reaction Enthalpy

H₂SO₄ + K₂S reaction enthalpy is around -272 kJ/mol. The enthalpy information is as follows:

• Enthalpy of Formation of K₂S = -406.2 kJ/mol
• Enthalpy of Formation of H₂SO₄ = -814 kJ/mol
• Enthalpy of Formation of H₂O = -285.8 kJ/mol
• Enthalpy of Formation of K₂SO₄ = -1437.7 kJ/mol
• Enthalpy of Formation of S = 0 (element)
• Enthalpy of Formation of SO₂ = -296.8 kJ/mol

Is H₂SO₄ + K₂S a Buffer Solution?

H₂SO₄ + K₂S cannot be a strong buffer solution because it strong acids like sulphuric acid cannot make a buffer.

Is H₂SO₄ + K₂S a Complete Reaction?

The H₂SO₄ + K₂S reaction can be called complete as, once equilibrium is reached, products are completely formed.

Is H₂SO₄ + K₂S an Exothermic Reaction?

H₂SO₄ + K₂S reaction is exothermic in nature as the value is negative.

Is H₂SO₄ + K₂S a Redox Reaction?

The reaction of H2SO4 and K₂S is an actual redox reaction because:

• Oxidation state of Sulphur changes from -2 to 0 in the products.
• K₂S(-2) → S(0)

Is H₂SO₄ + K₂S a Precipitation Reaction?

H₂SO₄ + K₂S is not a precipitation reaction because no precipitate is obtained. Instead, gaseous products are obtained.

Is H₂SO₄ + K₂S a Reversible Reaction?

H₂SO₄ + K₂S reaction is not reversible in nature as final products obtained are gases that cannot revert.

Is H₂SO₄ + K₂S a Displacement Reaction?

H₂SO₄ + K₂S reaction is not a displacement reaction as no ions are replaced in the products while reactants have decomposed.

Conclusion

H₂SO₄ is both a good oxidising and dehydrating agent that is non-flammable in nature. K_2­S, insoluble in ether, is another useful lab reagent that loves to react with water. The acid-base titration reflects the usage of indicators to form the desired product.

Neeloy Bhattacharya

Hello….Neeloy here! I have pursued a Master’ in Chemistry and am currently a Subject Matter Expert in this community. Science and reasoning feed my curiosity and I love to express whatever I see, in my words. Quiz addict. Let’s connect at LinkedIn.