The Chemistry Behind H2SO4 + Cl2: 13 Facts You Should Know

Sulfuric acid (H2SO4) is a powerful mineral acid, and Cl2 is a diatomic gaseous molecule. Let us explore more about their reaction.

Sulfuric acid is also known as the oil of vitriol. The central atom sulfur is in +6 oxidation state here. It is a highly viscous hygroscopic liquid having a density of 1.8302g/cm3. At room temperature, Cl2 appears to be a greenish-yellow gas with a pungent odor. It is oxidizing in nature.

In this article, we will discuss some important properties and parameters of the reaction H2SO4 + Cl2.

What is the product of H2SO4 and Cl2?

Sulfur dioxide (SO2), perchloric acid (HClO4) and H2O are the products of the reaction H2SO4 + Cl2.

H2SO4(aq) + Cl2(g)→ HClO4 + SO2(g) + H2O

What type of reaction is H2SO4 + Cl2?

The reaction H2SO4 + Cl2 is an oxidation-reduction reaction.

How to balance H2SO4 + Cl2?

To balance the H2SO4 + Cl2 reaction, the following steps are to be followed.

H2SO4 + Cl2 → HClO4 + SO2 + H2O

  • Count the number of atoms present on the reactant side and on the product side.
Elements involved Reactants side Products side
H 2 3
S 1 1
O 4 5
Cl 2 1
Atom Counts
  • 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.
  • 7× H2SO4 on reactant side and 6×H2O, 7 × SO2 and 2×HClO4 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 14 14
S 7 7
O 28 28
Cl 2 2
Atom Counts after multiplication
  • Thus the balanced chemical equation is
  • Cl2 + 7H2SO4  = 2HClO4 + 7 SO2 + 6H2O

H2SO4 + Cl2 titration

Titration is not possible in the reaction H2SO4 + Cl2, because H2SO4 is a very strong acid and Chlorine is a gas at room temperature.

H2SO4 + Cl2 net ionic equation

The net ionic equation of the reaction is-

Cl2(g) + 12H+(aq)+ 7SO42- (aq) = 2ClO4 (aq)+ 7 SO2(g) + 6H2O

The net ionic equation is obtained by using the steps below.

  • Write the balanced chemical reaction
  • Cl2 + 7H2SO4 = 2HClO4 + 7 SO2 + 6H2O
  • H2SO4 and HClO4 dissociates in aqueous media as:
  • H2SO4 = 2H+(aq) + SO42- (aq) and HClO4 = H+ (aq)+ ClO4(aq).
  • So, the complete ionic equation is
  • Cl2(g) + 14H+(aq)+ 7SO42- (aq) = 2H+ (aq)+ 2ClO4 (aq)+ 7 SO2(g) + 6H2O       
  • 2H+ gets canceled out from both sides.
  • Thus the net ionic equation is
  • Cl2(g) + 12H+(aq)+ 7SO42- (aq) → 2ClO4 (aq)+ 7 SO2(g) + 6H2O

H2SO4 + Cl2 conjugate pairs

The conjugate pairs of H2SO4 + Cl2 reaction are:

Compounds Conjugate acid Conjugate base
H2SO4 +   H2O  →     H3O+ (aq)     HSO4(aq)
HSO4+   H2O  →     H3O+ (aq)     SO42-(aq)
HClO4+   H2O  →     H3O+ (aq)     ClO4 (aq)
 Conjugate acid-base pairs

H2SO4 and Cl2 intermolecular forces

The intermolecular forces of H2SO4 + Cl2 reaction are:

  • H2SO4 molecule has Hydrogen bonding tendency, dipole-dipole interaction and Dispersion forces.
  • Cl2 has London dispersion force as it is a nonpolar molecule.
  • HClO4 possesses dipole–dipole force.
  • H2O participates in hydrogen bonding, dipole-induced dipole interactions.
  • SO2 shows dipole-dipole interaction as it is a polar molecule.

Is H2SO4 + Cl2 a buffer solution?

H2SO4 + Cl2 is not a buffer solution because sulfuric acid is a very strong acid and does not constitute a buffer solution.

Is H2SO4 + Cl2 a complete reaction?

The H2SO4 + Cl2 reaction is not a complete reaction. Because the so-formed product SO2 can react with Cl2 gas further (if provided in excess) to form SO2Cl2 which can react with H2O to form H2SO4 and HCl.

  • SO2  + Cl2 → SO2Cl2
  • SO2Cl2 + H2O →H2SO4 + HCl

Is H2SO4 + Cl2 a redox reaction?

The H2SO4 + Cl2 reaction is a redox reaction. Here, Sulfur gets reduced from +6 to +4 oxidation state, and chlorine gets oxidized from 0 to +7 oxidation state.

Screenshot 20221228 194828 1
Simultaneous oxidation reduction process

Is H2SO4 + Cl2 a precipitation reaction?

The reaction of H2SO4 + Cl2 is not a precipitation reaction as no precipitate is formed in the reaction mixture.

Is H2SO4 + Cl2 reversible or irreversible reaction?

The H2SO4 + Cl2 is an irreversible reaction because of the formation of gaseous product SO2(g), which will not participate in the reverse reaction. And also, the forward reaction is thermodynamically more favorable due to release of SO2(g), so no question of being reversible arises.

Is H2SO4 + Cl2 displacement reaction?

The H2SO4 + Cl2 reaction is not a displacement reaction as no ion displacement takes place.

Conclusion

The sodium salt of Perchloric acid named sodium perchlorate (NaClO4) is used as rocket fuel. Chlorine-containing compounds are used as bleaching agent and sulfuric acid is an essential component of every laboratories.