15 Facts on HI + K2S what, How to Balance & FAQs

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Hydrogen iodide is a strong acid; its aqueous form is called a hydroiodic acid, and K2S is potassium sulfide. Let us understand a few facts about this reaction.

HI is a diatomic molecule and is a very strong acidic gas. Hydrogen iodide is a gas under standard conditions, whereas hydroiodic acid is an aqueous gas solution. K2S is a brownish-red solid and is ionic. It is readily reactive to water.

This article will discuss hydrogen iodide and potassium sulfide reactions, like the product formed, its buffer solution, enthalpy, entropy, molecular forces and so on.

What is the product of HI and K2S?

Potassium iodide (KI) and hydrogen sulfide (H2S) are the products of the reaction between HI and K2S.

2HI + K2S ——–> 2KI + H2S

What type of reaction is HI + K2S

HI + K2S is a double displacement reaction.

How to balance HI + K2S

Reaction between HI + K2S is balanced in the following steps:

HI + K2S————>KI + H2S

  • The number of hydrogen and potassium atoms in this reaction are not same on left hand side and right hand side.
  • The reaction between gets balanced by arranging the same number of atoms by multiplying 2 with HI and 2 with KI.
  • 2HI + K2S ———–>2KI + H2S
  • Now, the number of atoms of each element on the reactant side equals that on the product side. Thus the overall balanced reaction is-
  • 2HI + K2S ———->2KI + H2S    

HI + K2S titration

HI + K2S titration comes under strong acid Vs weak base titration. In this reaction, acidic salt, i.e., potassium iodide, is formed, and the amount formed during the reaction is calculated.

Apparatus

Burette, pipette, conical flask, round bottom flask, burette stand, wash bottle.

Indicator

In the strong acid versus weak base titration, phenolphthalein as an indicator is used and we get colorless observation as an endpoint.

Procedure

  • The burette is filled with a standardized hydrogen iodide solution.
  • The conical flask is with basic solution along few drops of indicator.
  • The process of titration is done till the solution becomes colorless.
  • This color change is the equivalent point.
  • Then the volume of KI is found by the formula V1S1 = V2S2. 

HI + K2S net ionic equation

The net ionic equation of the reaction HI+K2S is

2H+(aq) + S2-(aq)———>H2S(g)

To obtain the net ionic equation following steps are followed:

  • Write the balanced molecular equation.
  • 2HI (aq) + K2S(aq)———->2KI(aq) + H2S(g)  (molecular equation)
  • Mention the state for each substance.
  • Split electrolytes into ions and finally cross out the spectator ions.
  • Thus the net ionic equation for HI and K2S is-
  • 2H+(aq) + S2-(aq)———>H2S(g)  

HI + K2S conjugate pairs

HI + K2S reaction has the following conjugate pairs-

  • I – is the conjugate base of strong acid HI.
  • K2S conjugate pair is S2-.

HI and K2S intermolecular forces.

  • In HI, a strong dipole-dipole interaction between the ions exists.
  • In potassium sulfide, ion-ion interactions are present because potassium is a metal and the sulfur atom is a non-metal, so they combine to form an ionic bond.

HI + K2S reaction enthalpy

The enthalpy for HI + K2S reaction is -276.96KJ, which indicates energy is released. It is determined by the formula given below-

Change in reaction enthalpy= sum of enthalpies on the product side- the sum of enthalpies on the reactant side.

MoleculeEnthalpy Value
HI-52.96KJ
K2S471.5KJ
KI-655.8KJ
H2S-39.7KJ
Change in reaction enthalpy-276.96KJ
Enthalpy Value

Is HI + K2S a buffer solution

The reaction between HI + K2S do not form a buffer solution because the strong acid, i.e., hydrogen iodide conjugate base is I– (the anion of potassium iodide is weak salt).

Is HI + K2S a complete reaction

The reaction HI + K2S is complete because the product formed-potassium iodide is water soluble.

Is HI + K2S an exothermic or endothermic reaction

The reaction HI + K2S is exothermic as energy is released in the form of heat.  

Is HI + K2S a redox reaction

The reaction HI + K2S is not a redox reaction because electron transfer does not take place.

Is HI + K2S a precipitation reaction

HI + K2S is not a precipitation reaction because no precipitate is formed, and the product (potassium iodide) formed is soluble in water.

Is HI + K2S reversible or irreversible reaction

The reaction HI + K2S is irreversible because of the formation of H2S, as its formation helps to increase the reaction entropy.

Is HI + K2S displacement reaction

HI + K2S is a double displacement reaction because both the reactants are ionic; an interchange of ions occurred to form a new compound.

Conclusion

The formed product potassium iodide is ionic compound and can be used in organic synthesis as a good source of iodide. Hydrogen iodide is widely used as reducing agent.