Potassium(K), an alkali metal, is highly reactive, and H_{2}SO_{3} (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. H _{2}SO_{3 }is a colorless and corrosive acid, with a pungent-burning sulphur smell. K is a good reducing agent, as seen in its reaction with **

**H**

_{2}SO_{3.}In this article, let us discuss the reaction of H_{2}SO_{3 }+ K, the type of reaction, the forces involved, buffer solution, and other related facts.

## What is the product of H_{2}SO_{3} and K?

**Potassium sulphite and hydrogen gas are the products formed when H _{2}SO_{3}**

**reacts with K.**

**H _{2}SO_{3} + 2K ———> K_{2}SO_{3} + H_{2}**

**↑**

## What type of reaction is H_{2}SO_{3} + K?

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

**+**

**K**

**is a single displacement reaction.**

## How to balance H_{2}SO_{3} + K?

**The equation**** ****H _{2}SO_{3}**

**+**

**K is balanced by the following steps.**

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

**+ 2K**

_{ }**= K**

_{2}**SO**

_{3}+ H_{2}**Identify and count the number of moles of each element involved in both the sides of the reaction.**

Element | Reactant side | Product side |
---|---|---|

S | 1 | 2 |

K | 1 | 1 |

O | 3 | 3 |

H | 2 | 2 |

**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 –****H**_{2}SO_{3}+ 2K_{ }= K_{2}SO_{3}+ H_{2}

## H_{2}SO_{3} + K _{ }titration

**H**_{2}**SO**_{3} **+ K will not undergo titration as K being a metal, will not be used in the titration.**

## H_{2}SO_{3} + K _{ }net ionic equation

**The net ionic equation between H _{2}SO_{3} + K**

_{ }**is:**

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

**(aq)**

**+ K**

_{ }**(s) =**

_{ }**2K**

^{+}_{ }**(aq)**

**+ SO**

_{3}^{2-}**(aq)**

**+ H**

_{2 }**(g)**

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

**Write the balanced molecular equation along with its physical state.****H**_{2}SO_{3 }(aq) + K (s)**= K**_{2}SO_{3 }(aq)_{ }+**H**_{2}(g)**The electrolytes, which are strong, are split into their respective ions.****H**_{2}SO_{3 }is a weak electrolyte,**K is a solid and H**_{2}**is a gas, so will not split. The equation now becomes,****H**_{2}SO_{3}**(aq)****+ K**_{ }**(s) =**_{ }**2K**^{+}_{ }**(aq)****+ SO**_{3}^{2-}**(aq)****+ H**_{2 }**(g)****The charge in the above equation is also conserved. Therefore, the net ionic equation is –****H**_{2}SO_{3}**(aq)****+ K**_{ }**(s) =**_{ }**2K**^{+}_{ }**(aq)****+ SO**_{3}^{2-}**(aq)****+ H**_{2 }**(g)**

## H_{2}SO_{3} + K _{ }conjugate pairs

**Conjugate base of H**_{2}SO_{3 }as HSO_{3}^{– }**K is a metal, so there is no conjugate pair for K.**

## H_{2}SO_{3} + K _{ }intermolecular forces

**In H**_{2}SO_{3}, 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.**

## H_{2}SO_{3} + K _{ }reaction enthalpy

**H _{2}SO_{3} + K reaction enthalpy is -467.87 KJ/mol. The enthalpy of the reaction is calculated using the values listed below,**

Reactants and Products | Enthalpy in KJ/mol |
---|---|

K(s) | 0.0 |

H_{2}SO_{3}(aq) | -655.5 |

K_{2}SO_{3}(aq) | -1123.37 |

H_{2}(g) | 0.0 |

**Enthalpy values**

**The enthalpy of formation of elements or molecules existing in their original state is taken as zero.****∆H**_{f}^{°}(reaction) = ∆H_{f}^{°}(products) – ∆H_{f}^{°}(reactants)

**= -1123.37 – (-655.5)**

**= -467. 87 KJ/mol**

## Is H_{2}SO_{3} + K a buffer solution?

**H _{2}SO_{3} + K will not form a buffer solution due to the presence of a metal (K) and weak sulphurous acid.**

## Is H_{2}SO_{3} + K a complete reaction?

**H _{2}SO_{3} + K _{ }is a complete reaction since one of the products formed is hydrogen gas that gets evolved during the reaction.**

## Is H_{2}SO_{3} + K an exothermic reaction?

**H _{2}SO_{3} + K is an exothermic reaction, as the reaction enthalpy is found to be negative.**

## Is H_{2}SO_{3} + K a redox reaction?

**H _{2}SO_{3} + 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 H_{2}SO_{3} + K a precipitation reaction?

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

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

## Is H_{2}SO_{3} + K an irreversible reaction?

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

**K is an irreversible reaction as**

**the forward reaction is more favorable due to increased entropy associated with the liberation of gaseous hydrogen.**

## Is H_{2}SO_{3} + K a displacement reaction?

**H _{2}SO_{3} + 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.**

**Conclusion**

The reaction of K with H_{2}SO_{3} is less violent than with H_{2}SO_{4}, 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

Hi Everyone. I am Vishnupriya T. I have pursued a Master’s in Chemistry and a PG Diploma in Quality Management. Currently working as an SME in Chemistry, aiming to enrich my curiosity and knowledge. I would love to share knowledge and connect with others at my LinkedIn profile:

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