15 Facts on HI + CH3OH: What, How To Balance & FAQs

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The reaction between HI and CH3OH is a classic example of Substitution Nucleophilic Bimolecular reaction (SN2).

Hydrogen iodide (HI) is a very strong acid while methanol (CH3OH) can act as both acid and base (amphoteric). The molar mass of HI is 128g/mol and that of CH3OH is 32.04g/mol. Both HI and CH3OH are polar molecules capable of forming intermolecular hydrogen bonding.

Let us now look into the reaction between these two compounds and discuss the properties and outcomes in detail.

What is the product of HI and CH3OH

Methyl iodide (CH3I) and water (H2O) is the product of reaction between HI and CH3OH.

  • CH3OH + HI → CH3I + H2O

What type of reaction is HI + CH3OH

The reaction between HI and CH3OH is Substitution reaction where –OH is replaced by iodide of HI.

How to balance HI + CH3OH

The reaction between HI and CH3OH is balanced by following steps,

CH3OH + HI → CH3I + H2O

  • If we compare the number of moles of carbon, hydrogen , iodine and oxygen on both left and right side for the reaction we will see that the number is same and hence the reaction is balanced.

HI + CH3OH titration

The titration between HI and CH3OH cannot be carried out as CH3OH is amphoteric in nature while HI is a strong acid.

HI + CH3OH net ionic equation

The net ionic equation for HI + CH3OH is represented as,

H+ + I– + CH3O– + H+ → CH3I + H2O

  • HI dissociates into H+ and I– while CH3OH breaks down to CH3O– + H+.
  • Lastly all combine to yield CH3I and H2O.

HI + CH3OH conjugate pairs

The conjugate pairs of HI and CH3OH are given by,

  • The conjugate base of HI = I–
  • The conjugate base of CH3OH = CH3O–

HI and CH3OH intermolecular forces

The following intermolecular forces occur in case of both HI and CH3OH,

  • The dipole-dipole interaction due to electronegativity difference between Hydrogen and Iodine in case of HI and Carbon and Hydrogen in case of CH3OH.
  • Intermolecular hydrogen bonding also takes place for both the molecules.

HI + CH3OH reaction enthalpy

The Enthalpy of reaction for HI + CH3OH was found to be -48.24kJ/mol. The enthalpy of formation for both reactants and product is listed below,

  • Enthalpy of formation for CH3OH = -239kJ/mol
  • Enthalpy of formation for HI = 26 kJ/mol
  • Enthalpy of formation for CH3I = 24.46kJ/mol
  • Enthalpy of formation for H2O = -285.7kJ/mol
  • Enthalpy of reaction = [24.46-285.7]-[26-239] = -48.24 kJ/mol

Is HI + CH3OH a buffer solution

HI and CH3OH cannot form a buffer solution as HI is a strong acid while CH3OH being amphoteric in nature cannot maintain the pH of the solution.

Is HI + CH3OH a complete reaction

HI + CH3OH is a complete reaction as HI is a strong acid capable of undergoing complete dissociation to give CH3I and H2O as products.

Is HI + CH3OH an exothermic or endothermic reaction

The reaction between HI and CH3OH is exothermic as the enthalpy of reaction is having a negative value and releases energy.

exothermic reaction
Energy level diagram of Exothermic reaction

Is HI + CH3OH a redox reaction

HI + CH3OH reaction is not a redox reaction because there is no change in the oxidation state of the atoms.

Is HI + CH3OH a precipitation reaction

HI + CH3OH reaction is not a precipitation reaction because CH3I is not a solid compound rather it is a dense liquid insoluble in water.

Is HI + CH3OH reversible or irreversible reaction

The reaction between HI and CH3OH is an irreversible reaction because the CH3I is a stable product and cannot be reversed back to CH3OH by disturbing the equilibrium.

Is HI + CH3OH displacement reaction

The reaction HI + CH3OH is a displacement reaction as the ions of both the reactants are exchanged with each other.

  • OH of CH3OH is replaced by I– of HI.
  • Hydride ions combine with the OH– ions to form water.

Conclusion

Equimolar quantities of HI and CH3OH combine with each other to form CH3I and H2O as products. CH3OH is a water insoluble liquid and hence can be easily separated from the reaction mixture. This is an exothermic reaction where OH of methanol is displaced by I– of hydrogen iodide.