Chemical reactions result in the conversion of key reactant species to economical and stable products for industrial growth. Let us know about the chemical reactivity of H_{2}SO_{3} and CaCl_{2}.

**H _{2}SO_{3} is a reducing agent formed as an intermediate component during acid rain formation from SO_{2}. CaCl_{2} a hygroscopic deliquescent inorganic compound is used for the de-icing process. The reaction between H_{2}SO_{3} and CaCl_{2} forms calcium sulfite.**

The reactivity of H_{2}SO_{3} and CaCl_{2} was assessed for its flue gas desulphurization conditions. Moreover, the following chemical characteristics of the reacting species can be discussed.

**What is the product of H**_{2}SO_{3} and CaCl_{2}?

_{2}SO

_{3}and CaCl

_{2}?

**H _{2}SO_{3} and CaCl_{2}**

**react to form calcium sulfite and hydrogen chloride.**

**H _{2}SO_{3} + CaCl_{2} = CaSO_{3} + HCl**

**What type of reaction is H**_{2}SO_{3} + CaCl_{2}?

_{2}SO

_{3}+ CaCl

_{2}?

**H _{2}SO_{3} + CaCl_{2} is a substitution reaction where sulfite and chloride anion interchange their respective cation species to form new compounds.**

**How to balance H**_{2}SO_{3} + CaCl_{2}?

_{2}SO

_{3}+ CaCl

_{2}?

**The following algebraic method can be used to balance the reaction**

**H _{2}SO_{3} + CaCl_{2} = CaSO_{3} + HCl,**

**Each reactant and product in the equation is labelled with a variable (A, B, C, and D) to represent unknown coefficients.****A H**_{2}SO_{3}+ B CaCl_{2}= C CaSO_{3}+ D HCl**Now, an appropriate quantity thought of as the coefficient of reactants and products, is used to solve the equation.****H = 2A = 2D, S = A = C, O = 3A = 3C, Ca = B = C, Cl = 2B = D****The Gaussian elimination method is used to determine all the variables and coefficients, and the results are****A = 1, B = 1, C = 1, and D = 2****Accordingly, the overall balanced equation is,****H**_{2}SO_{3}+ CaCl_{2}= CaSO_{3}+ 2 HCl

**H**_{2}SO_{3} + CaCl_{2 }titration

_{2}SO

_{3}+ CaCl

_{2 }titration

**The titration of H _{2}SO_{3} + CaCl_{2} is not possible as H_{2}SO_{3} normally exists as a gas and CaCl_{2} is a salt and there is no base present in this system. **

**H**_{2}SO_{3} + CaCl_{2 }net ionic equation

_{2}SO

_{3}+ CaCl

_{2 }net ionic equation

**The net ionic equation of Ca + H _{2}SO_{4} is**

**SO _{3}^{-2} (aq) + Ca^{+2} (aq) = CaSO_{3} (s)**

**Write the balanced chemical equation and represent the physical states of reactants and products accordingly**

**H**_{2}SO_{3}(aq) + CaCl_{2}(aq) = CaSO_{3}(s) + 2 HCl (aq)**Now, strong acids, bases, and salts dissociate into ions whereas pure solid substances and molecules do not dissociate****Thus, the net ionic equation is****SO**_{3}^{-2}(aq) + Ca^{+2}(aq) = CaSO_{3}(s)

**H**_{2}SO_{3} + CaCl_{2 }conjugate pairs

_{2}SO

_{3}+ CaCl

_{2 }conjugate pairs

**Ca Cl_{2} + H_{2}SO_{4} reaction has the following conjugate pairs,**

**H**_{2}SO_{3}forms HSO_{3}^{–}as conjugate base.**CaCl**_{2}does not form conjugate pair because it does not contain any proton.

**H**_{2}SO_{3} and CaCl_{2 }intermolecular forces

_{2}SO

_{3}and CaCl

_{2 }intermolecular forces

**Ca Cl_{2} + H_{2}SO_{4} reaction has the following intermolecular forces,**

**H**_{2}SO_{3}molecules are bonded together via strong covalent bonds.**CaCl**_{2}interacts using ion-dipole forces.

**H**_{2}SO_{3} + CaCl_{2 }reaction enthalpy

_{2}SO

_{3}+ CaCl

_{2 }reaction enthalpy

**H _{2}SO_{3} + CaCl_{2} reaction enthalpy is -1206.9 kJ/mol.**

**Is H**_{2}SO_{3} + CaCl_{2 }a buffer solution?

_{2}SO

_{3}+ CaCl

_{2 }a buffer solution?

**H _{2}SO_{3} + CaCl_{2} is not a buffer solution because H_{2}SO_{3 }is a strong acid that cannot be a part of the buffer.**

**Is H**_{2}SO_{3} + CaCl_{2 }a complete reaction?

_{2}SO

_{3}+ CaCl

_{2 }a complete reaction?

**H _{2}SO_{3} + CaCl_{2} is a complete reaction as calcium sulfite and hydrogen chloride are formed as stable products.**

**Is H**_{2}SO_{3} + CaCl_{2 }an exothermic or endothermic reaction?

_{2}SO

_{3}+ CaCl

_{2 }an exothermic or endothermic reaction?

**H _{2}SO_{3} + CaCl_{2} is an exothermic reaction due to the liberation of heat with the addition of strong sulfurous acid.**

**Is H**_{2}SO_{3} + CaCl_{2 }a redox reaction?

_{2}SO

_{3}+ CaCl

_{2 }a redox reaction?

**H _{2}SO_{3} + CaCl_{2} is not a redox reaction because the oxidation states of elements do not change during the reaction.**

**Is H**_{2}SO_{3} + CaCl_{2 }a precipitation reaction?

_{2}SO

_{3}+ CaCl

_{2 }a precipitation reaction?

**H _{2}SO_{3} + CaCl_{2} is a precipitation reaction because solid calcium sulfite precipitates at the end of the reaction.**

**Is H**_{2}SO_{3} + CaCl_{2 }reversible or irreversible reaction?

_{2}SO

_{3}+ CaCl

_{2 }reversible or irreversible reaction?

**H _{2}SO_{3} + CaCl_{2} is an irreversible reaction because the formed products (CaSO_{3} and HCl) cannot convert back into the original reactants.**

**Is H**_{2}SO_{3} + CaCl_{2 }displacement reaction?

_{2}SO

_{3}+ CaCl

_{2 }displacement reaction?

**H _{2}SO_{3} + CaCl_{2} is a double displacement reaction because both the anion component of the reactants is displaced with the respective cationic part.**

**Conclusions**

The reactivity of H_{2}SO_{3} + CaCl_{2} forms calcium sulfite which is the product of flue gas desulphurization. It is widely used as preserving canned edibles, and wines acting as an oxygen scavenger. Another application involves the production of wood pulp by dissolving lignin from the woods.

Hi…..This is Avneesh Rawat, I have done my Ph.D. in Chemistry from Govind Ballabh Pant University of Agriculture and Technology. Currently, I am working as Project Associate in CSIR, CIMAP, Pantnagar. I am specializing in handling sophisticated GC/MS, GC, HPLC, FTIR instrumentation.