15 Facts on HCl + P4O10: What, How To Balance & FAQs

HCl is an inorganic acid and P4O10 is one of the oxides of phosphorous. Let us inspect how these two compounds react to each other.

In the reaction HCl+P4O10, HCl is reacting with a non-metal oxide, tetraphosphorus decaoxide (P4O10) by absorbing heat to generate the products. HCl is one of the important mineral acids in chemistry and P4O10 is a deliquescent white solid.

In this article, essential features of the reaction between HCl and P4O10 will be brought to light.

What is the product of HCl and P4O10

Phosphorous oxychloride (POCl3) and phosphoric acid (H3PO4) also known as orthophosphoric acid are produced in the reaction between HCl and P4O10.

HCl + P4O10  =  POCl3 + H3PO4

What type of reaction is HCl + P4O10

The reaction HCl + P4O10 does not belong to any particular category of reaction as listed below.

  • HCl + P4O10 is not a combination reaction as the two compounds are not combining together to form a single compound.
  • HCl + P4O10 is not a decomposition reaction as a single compound is not decomposed into two simpler compounds.
  • HCl + P4O10 is not a combustion reaction as it is not involving a reaction with O2 producing CO2 and H2O.
  • HCl + P4O10 is not a neutralization reaction as it is not a reaction between acid and base.

How to balance HCl + P4O10

The reaction written below is unbalanced.

HCl + P4O10  =  POCl3 + H3PO4

Following steps is to be followed for getting the balanced equation for this reaction.

  • The formulas of the compound present should be multiplied by the smallest possible figure when the number of atoms of every element is not the same.
  • The number of P atoms on reactant and product side is 4 and 2 respectively.
  • So, we will multiply both POCl3 and H3PO4 with 2 as shown below.
  • HCl + P4O10  =  2POCl3 + 2H3PO4
  • Here, the number of H and Cl atoms on reactant and product side is 1 and 6 respectively.
  • So, we will multiply HCl by 6.
  • The number of O atoms is now the same on left hand side and right hand side.
  • Thus the balanced equation is-
  • 6HCl + P4O10 =  2POCl3 + 2H3PO4

HCl + P4O10 titration

For the reaction HCl + P4O10, titration cannot be performed as this reaction does not fulfill some basic criteria for titration.

HCl + P4O10 net ionic equation

The ionic equation for the reaction HCl + P4O10  is not possible because, except for HCl, the other three compounds cannot be written as dissociated ions.

HCl + P4O10 conjugate pairs

  • The conjugate base of HCl is Cl.
  • P4O10 has no conjugate pair as it is neither an acid nor a base.

HCl + P4O10  intermolecular forces

  • Dipole-dipole and London dispersion forces; are the two intermolecular forces present in HCl, where the former one is significant as there is some polar nature present in HCl.
  • P4O10 has weak van der Waals forces as intermolecular force.

HCl + P4O10  reaction enthalpy

The reaction enthalpy of HCl + P4O10 is 215.32 kJ/mole.

CompoundsEnthalpy of formation (kJ/mole)
HCl (aq)-167.16
P4O10 (s)-2984.0
Table representing enthalpy of formation values of all compounds

The reaction enthalpy is calculated as follows.

Reaction enthalpy = [Enthalpy of formation values of POCl3 and H3PO3] – [Enthalpy of formation values of HCl and P4O10]

= [(-597.0*2) + (-1288.3*2)] – [(-167.16*6) + (-2984.0)] = 215.32

Is HCl + P4O10 a buffer solution

The mixture of HCl and P4O10 is not a buffer solution as HCl is a strong acid.

Is HCl + P4O10 a complete reaction

HCl + P4O10 is a complete reaction as further reaction is impossible after product formation.

Is HCl + P4O10 an exothermic or endothermic reaction

The reaction HCl + P4O10 is endothermic in nature as the reaction enthalpy value is 215.32 kJ/mole.

Is HCl + P4O10 a redox reaction

The reaction HCl + P4O10 is not a redox reaction, because the oxidation states of all the atoms H, Cl, P, and O present in the reactant and product molecules are the same before and after the reaction.

Is HCl + P4O10 a precipitation reaction

HCl and P4O10 is not a precipitation reaction as the product POCl3 is liquid and the another product H3POis a water-soluble solid.

Is HCl + P4O10 reversible or irreversible reaction

HCl + P4O10 is an irreversible reaction as it is unidirectional.

Is HCl + P4O10 displacement reaction

The reaction HCl and P4O10 is not a displacement reaction as a more reactive ion of one molecule is not displacing a less reactive ion from another molecule.


In conclusion, when HCl reacts with tetraphosphorus decaoxide, the products are POCl3 and H3PO4. H3PO4 appears as a clear colorless liquid or transparent solid. On the other hand, POCl3 is a fuming, oily type of liquid used for chlorination purposes.

Tuluma Das

Hello, I am Tuluma Das, Completed my Ph.D. in Organic Chemistry from the Indian Association for the Cultivation of Science. I have a total of 9 years of research experience including a Ph.D. and Postdoc and 3 years of teaching experience. I have published 7 papers so far in international journals. Let’s connect through Linkedin : https://www.linkedin.com/in/tuluma-das-90887a99/

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