15 Facts on HI + CsOH: What, How To Balance & FAQs

Chemical reactivities involving acids and bases react in specific temperature and pressure conditions to give salt and water. Let us look at the chemistry between HI and CsOH.

Hydrogen iodide (HI) functions both as a catalyst and a reducing agent in organic synthesis and organometallic catalysis reactions. Cesium hydroxide (CsOH) is a strong base comprised of highly reactive alkali metal which is hygroscopic in nature. The metal hydroxide is very corrosive towards metals.

The reactivity of HI and CsOH can be a source of efficient photocathodes and scintillators. Thus, some important reactive activities of the reactants and products are explored in detail:

What is the product of HI and CsOH?

HI and CsOH interacts to produce cesium iodide (CsI) and water (H2O). The complete chemical reaction is given as:

HI + CsOH = CsI + H2O

What type of reaction is HI + CsOH?

HI + CsOH is a substitution reaction where hydrogen and cesium cation gets substituted with iodide and hydroxide anion to form new compounds namely CsI and H2O.

How to balance HI + CsOH?

The following algebraic steps are used to equationally balance the chemical reaction

HI + CsOH = CsI + H2O,

  • Characterize different reactants or product species in the given chemical equation with different variables (A, B, C, and D) to deduce unknown coefficients.
  • A HI + B CsOH = C CsI + D H2O
  • Illustrate a simplified equation for each molecule in the reacting compound signifying the atom number of every element in given reactant or product species, so as to solve the equation.
  • H = A + B = 2D, I = A = C, Cs = B = C, O = B = D
  • The Gaussian elimination and substitution method is applied to solve all the variables and coefficients, and the answers are
  • A = 1, B = 1, C = 1, and D = 1
  • Hence, the overall chemical reaction is balanced as,
  • HI + CsOH = CsI + H2O

HI + CsOH titration

HI + CsOH system is considered as strong acid strong base titration under suitable conditions. The given steps are followed to proceed with the titration:

Apparatus Used

Burette, holder, pipette, stands, conical flask, volumetric flask, beakers, measuring cylinder


Phenolphthalein is used as an indicator for HI + CsOH titration system


  • Standard solution of CsOH is prepared by dissolving in distilled water in a volumetric flask.
  • An unknown solution of CsOH is pipetted out in a flask.
  • To the flask containing an unknown solution, HI is added.
  • After the addition of acid onto the base, the reaction is tested by adding phenolphthalein as an indicator.
  • The flask is swirled gently to mix all the contents in regular intervals.
  • Fill the burette with HI and observe the starting mark on the burette.
  • Titrate the CsOH solution filled in the flask.
  • Light pink color is produced on addition of the few drops of indicator decides the endpoint of the reaction.
  • The final volume is calculated on the basis of the calibration scale of the burette.
  • The process is repeated in triplicate to deduce concordant readings.
  • The strength of the solution can be calculated as per the formulae
  • M2 = (V1 * M1)/V2
  • where M2 : strength of the acid, V1 : volume of added base, M1 : strength of the added base, V2 : volume of the used acid.

HI + CsOH net ionic equation

The net ionic equation of HI + CsOH is

H+ (aq) + OH (aq) = H2O (l)

  • Write the balanced reaction equation and consider the physical states of reactants and products species accordingly
  • HI (aq) + CsOH (aq) = CsI (aq) + H2O (l)
  • Then after, strong acids, bases, as well as salts dissociate completely into ions whereas pure solid substances and molecules do not dissociate
  • H+ (aq) + I (aq) + Cs+ (aq) + OH (aq) = Cs+ (aq) + I (aq) + H2O (l)
  • Thus, the net ionic equation is
  • H+ (aq) + OH (aq) = H2O (l)

HI + CsOH conjugate pairs

  • The conjugate base of the strong acid HI is I.
  • The conjugate pair of CsOH is formed as H2O.

HI + CsOH intermolecular forces

Intermolecular forces acting on HI and CsOH are:

  • HI interact via strong hydrogen bonds, weak London dispersion forces, and dipole-dipole bonds among the molecules.
  • An ionic compound, CsOH interacts via London dispersion forces between Cs+ and OH ions.

HI + CsOH reaction enthalpy

HI + CsOH is observed as a positive reaction enthalpy of +243.45 kJ/mol. The reaction enthalpy is calculated as per the following formula:

ΔH⁰f (reaction) = Σ ΔH⁰f (products) – Σ ΔH⁰f (reactants)

  • Enthalpy of formation for reactant HI: +25.95 kJ/mol
  • Enthalpy of formation for reactant CsOH: -416.44 kJ/mol
  • Enthalpy of formation for product CsI: -348.14 kJ/mol
  • Enthalpy of formation for product H2O: -285.80 kJ/mol

Is HI + CsOH a buffer solution?

HI + CsOH cannot work as a buffer solution as the buffer is constituted of a weak acid and salt of its conjugate base. In this given case, HI is a strong acid and CsOH is a strong base.

Is HI + CsOH a complete reaction?

HI + CsOH is a complete reaction because CsI and H2O formed in the reaction are stable products.   

Is HI + CsOH an exothermic or endothermic reaction?

HI + CsOH is an exothermic reaction because the negative reaction enthalpy is calculated which shows liberation of heat to complete the reaction.

Is HI + CsOH a redox reaction?

HI + CsOH is not a redox reaction because hydrogen and cesium element do not change their +1 oxidation state at both the reactant and product sides in the given reaction.

Is HI + CsOH a precipitation reaction?

HI + CsOH is not a precipitation reaction as CsI formed in the reaction is highly soluble in water thus showing no precipitate development in the reaction.

Is HI + CsOH reversible or irreversible reaction?

HI + CsOH is an irreversible reaction as the products formed in the reaction do not convert themselves back into the original reactants until the conditions are kept unchanged.

Is HI + CsOH displacement reaction?

HI + CsOH is a displacement reaction because the hydrogen cation is displaced by the cesium cation to produce new ionic compound CsI in the given reaction.


The HI + CsOH forms cesium iodide as the major compound. The cesium iodide crystals have high utility as scintillators due to their relatively low light yield and fast cooling features. CsI is hygroscopic and does have high temperature gradient. The photocathodes of CsI are also efficient at high UV wavelengths.

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