Sulphuric acid (H_{2}SO_{4}) is a colourless, viscous liquid and phosphorus pentoxide (P_{2}O_{5}) is a strong dehydrating agent. Let us take a glance at how these two react to each other.

**Phosphorus oxide is not as strong an acid as much as sulphuric acid; it is an acidic oxide that works well as a desiccating agent.**

We will dive deep into the facts about reactions between H_{2}SO_{4} and P_{2}O_{5}, like reaction enthalpy, type of reaction, conjugate pairs, intermolecular forces etc.,

**What is the product of H**_{2}SO_{4} and P_{2}O_{5}

_{2}SO

_{4}and P

_{2}O

_{5}

**Sulphur trioxide and meta-phosphoric acids are formed when sulphuric acid (H _{2}SO_{4}) is heated in the presence of phosphorus pentoxide, which has to be taken in excess. **

**H _{2}SO_{4} + P_{2}O_{5} = SO_{3} + HPO_{3}**

**What type of reaction is H**_{2}SO_{4} and P_{2}O_{5}

_{2}SO

_{4}and P

_{2}O

_{5}

**The reaction between H**_{2}**SO**_{4} **and P _{2}O_{5} is a double-displacement reaction. **

**How to balance H**_{2}SO_{4} and P_{2}O_{5}

_{2}SO

_{4}and P

_{2}O

_{5}

** The reaction between H_{2}SO_{4} and P_{2}O_{5} can be balanced using the steps mentioned below**,

**Writing the general chemical equation:****H**_{2}SO_{4}+ P_{2}O_{5}= SO_{3}+ HPO_{3}**We need to check whether the number of atoms on the reactant and product side is equal.****But as we can see, the number of hydrogens, oxygens and phosphorus need to be balanced throughout the equation.****Therefore we will multiply a coefficient of 2 with metaphosphoric acid to get the new equation.****H**_{2}SO_{4}+ P_{2}O_{5}= SO_{3}+ 2HPO_{3}**Counting down the number of atoms present on both sides of the chemical equation;**

Atoms | Number on reactant side | Number on product side |
---|---|---|

H | 2 | 2 |

S | 1 | 1 |

O | 9 | 9 |

P | 2 | 2 |

**Number of Atoms**

**As the number of atoms gets equated, the new balanced chemical equation is****H**_{2}SO_{4}+ P_{2}O_{5}= SO_{3}+ 2HPO_{3}

**H**_{2}SO_{4} and P_{2}O_{5} titration

_{2}SO

_{4}and P

_{2}O

_{5}titration

**The titration between H _{2}SO_{4} and P_{2}O_{5} is not feasible as both are acids and thus the end-point during the titration cannot be determined.**

**H**_{2}SO_{4} and P_{2}O_{5} net ionic equation

_{2}SO

_{4}and P

_{2}O

_{5}net ionic equation

**The net ionic equation for H_{2}SO_{4} + P_{2}O_{5} reaction is**,

**SO _{4}^{2-} (aq.) + P_{2}O_{5} (aq.) = SO_{3} (g) + PO_{3}^{–} (aq.)**

**The general balanced equation for****H**_{2}SO_{4}+ P_{2}O_{5}**is****H**_{2}SO_{4}+ P_{2}O_{5}= SO_{3}+ 2HPO_{3}**Indicating the chemical states of each molecule****H**_{2}SO_{4}(aq.) + P_{2}O_{5}(aq.) = SO_{3}(g) + 2HPO_{3}**(aq.)**- S
**plit the soluble compounds into their respective ions.** **2H**^{+}(aq.) + SO_{4}^{2-}(aq.) + P_{2}O_{5}(aq.) = SO_{3}(g) + 2H^{+}(aq.) + PO_{3}^{–}(aq.)**Cancel out the ions which are present on both sides to get the net ionic equation.****SO**_{4}^{2-}(aq.) + P_{2}O_{5}(aq.) = SO_{3}(g) + PO_{3}^{–}(aq.)

**H**_{2}SO_{4} and P_{2}O_{5} conjugate pairs

_{2}SO

_{4}and P

_{2}O

_{5}conjugate pairs

**In the following reaction,**

**H**_{2}**SO**_{4}** + P**_{2}**O**_{5}** = SO**_{3}** + 2HPO**_{3}

**The Conjugate pair for reactant H**_{2}**SO**_{4}**is HSO**_{4}^{–}**The Conjugate pair for HPO**_{3}**is PO**_{3}^{–}

**The other two, i.e., P _{2}O_{5} and SO_{3}, do not have any conjugate pairs because they lack hydrogen in their chemical formula.**

**H**_{2}SO_{4} and P_{2}O_{5} intermolecular forces

_{2}SO

_{4}and P

_{2}O

_{5}intermolecular forces

**The H _{2}SO_{4} + P_{2}O_{5} reaction has the following intermolecular forces between the molecules,**

Molecules | Intermolecular forces |
---|---|

H_{2}SO_{4} | 1. Van der Waals dispersion forces 2. dipole-dipole interactions |

P_{2}O_{5} | Weak van der waal forces |

SO_{3} | London-dispersion forces |

**Intermolecular forces between**

**H**_{2}SO_{4}and P_{2}O_{5}**Is H**_{2}SO_{4} and P_{2}O_{5} a buffer solution

_{2}SO

_{4}and P

_{2}O

_{5}a buffer solution

**H _{2}SO_{4} + P_{2}O_{5} reaction** cannot yield a buffer solution as both chemicals have an acidic nature having variations in the strength of acidity. That is why if more acid is added to the solution, the pH value will decrease further, which should not happen in the case of a buffer solution.

**Is H**_{2}SO_{4} and P_{2}O_{5} a complete reaction

_{2}SO

_{4}and P

_{2}O

_{5}a complete reaction

**H _{2}SO_{4} + P_{2}O_{5} reaction** is a complete reaction as sulphuric acid, and phosphorus pentoxide is completely used to form meta-phosphoric acid with sulphur trioxide.

**Is H**_{2}SO_{4} and P_{2}O_{5} an exothermic or endothermic reaction

_{2}SO

_{4}and P

_{2}O

_{5}an exothermic or endothermic reaction

**H _{2}SO_{4} + P_{2}O_{5} reaction** is an endothermic chemical reaction because heat is needed at the beginning of the reaction to initiate the process.

**Is H**_{2}SO_{4} and P_{2}O_{5} a redox reaction

_{2}SO

_{4}and P

_{2}O

_{5}a redox reaction

**H _{2}SO_{4} + P_{2}O_{5} reaction is not a redox reaction because the oxidation states of atoms have remained unchanged throughout the process.**

**Is H**_{2}SO_{4} and P_{2}O_{5} a precipitation reaction

_{2}SO

_{4}and P

_{2}O

_{5}a precipitation reaction

**H _{2}SO_{4} + P_{2}O_{5} reaction** is not a precipitation reaction as H

_{2}SO

_{4}and P

_{2}O

_{5}reaction do not yield any precipitates.

**Is H**_{2}SO_{4} and P_{2}O_{5} reversible or irreversible reaction

_{2}SO

_{4}and P

_{2}O

_{5}reversible or irreversible reaction

**H _{2}SO_{4} + P_{2}O_{5} reaction** is irreversible reaction because the SO

_{3}released cannot be added back to the reaction until an immense high pressure is applied, which is not possible normally.

**Is H**_{2}SO_{4} and P_{2}O_{5} displacement reaction

_{2}SO

_{4}and P

_{2}O

_{5}displacement reaction

**H _{2}SO_{4} + P_{2}O_{5} reaction** is a double-displacement reaction.

**Here, P**

_{2}O_{5}acting as a dehydrator removes water from sulphuric acid to form meta-phosphoric acid.**Conclusion**

The article concludes that both sulphuric acid and phosphorus pentoxide are reacting with each other being acids and P_{2}O_{5} is a stronger dehydrating agent than sulphuric acid. These chemicals have several industrial and laboratory importance.