Discover The 15 Incredible Facts On HNO3 + I2 Reaction

Nitric acid (HNO₃) is a strong acid and Iodine (I₂) is an oxidizing agent. Let us learn some amazing information about how HNO₃ and I₂ react.

HNO₃, also known as the spirit of niter, is an important laboratory reagent for nitration. It can be synthesized by the Ostwald process. I₂ is a non-metallic halogen. It is a purple-black color solid. It sublimes with a noxious stench and violet vapor at room temperature.

In the following article, we will go over the reaction enthalpy, type of reaction, product generation, and other aspects of the reaction of HNO₃ + I₂.

1. What is the product of HNO₃ and I₂?

When HNO₃ and I₂ are react together, Iodic acid (HIO₃) and nitrogen dioxide (NO₂) are formed as a major product, along with water as a by-product. 

• HNO₃ + I₂ -> HIO₃ + NO₂ +H₂O

2. What type of reaction is HNO₃ + I₂?

HNO₃ + I₂ reaction falls under the category of a redox reaction.

3. How to balance HNO₃ + I₂?

The reaction of HNO₃ + I₂ → HIO₃ + NO₂ + H₂O is not yet balanced. Thus we must balance the equation as follows:

• Since this reaction produces five different molecules and, we first label all the reactants and products with the letters A, B, C, D, and E.
• A HNO₃ + B I₂ = C HIO₃ +D NO₂ + E H₂O
• When the coefficients of the same elements are rearranged according to their stoichiometric proportion, we obtain,
• H = A = C+ 2E, N = A = D, O = 3A =3C+2D+E, I = 2B =C
• By applying the Gaussian elimination and equating each equation, we arrive at the following solutions:
• A = 10, B = 1, C = 2, D = 10, and E = 4.
• The overall balanced equation will be, 10 HNO₃ + I₂ = 2 HIO₃ +10 NO₂ + 4 H₂O

4. HNO₃ + I₂ titration

HNO₃ + I₂ titration is not feasible under normal conditions because

• Concentrated HNO₃ is very hard to handle. It is highly corrosive.
• HNO₃ gives ambiguous products like NO, NO₂, N₂O, and even mixture of them during redox titration. So, it is nearly impossible to calculate the desired result.
• HNO₃ and I₂ both have oxidizing capabilities. Endpoint detection will be hard to achieve.

5. HNO₃+ I₂ net ionic equation

The net ionic equation between HNO₃ + I₂ is as follows,

H⁺(aq) + NO₃^–(aq) + I₂(s) = H⁺(aq) + IO₃^–(aq) + H⁺(l) + OH^–(l)

• The strong electrolyte HNO₃ will ionize into H⁺ and nitrate as a counter ion.
• I₂ cannot be ionized since it is always solid and remains undissociated.
• Due to HIO₃‘s strong electrolyte properties, it ionizes into H⁺ and IO₃^– in the product portion.
• When water was in a liquid condition, it ionizes into a proton and hydroxide ions.
• Thus, the net ionic equation becomes,
• H⁺(aq) + NO₃^–(aq) + I₂(s) = H⁺(aq) + IO₃^–(aq) + H⁺(l) + OH^–(l)

6. HNO₃+ I₂ conjugate pairs

In the reaction, HNO₃ + I₂ conjugate pairs will represent the respective deprotonated and protonated forms of each of the following species:

• NO₃^– is conjugate base of HNO₃.
• H₂O is conjugate acid of OH^–.

7. HNO₃ and I₂ intermolecular forces

The intermolecular forces in HNO₃ + I₂ are as follows:

• The intermolecular force in HNO₃ is the electrostatic attraction between protons and nitrate ions.
• London dispersion force exists in I₂.
• The Coulombic force and electronic interactions are present in HIO₃.
• Hydrogen bonding, covalent force, dipole-induced dipole, and London dispersion forces exist in H₂O.

8. HNO3 + I₂ reaction enthalpy

HNO₃ + I₂reaction enthalpy is  933.04 kJ/mol which can be obtained by the formula:

• ΔH⁰_f (reaction) = ΣΔH⁰_f (product) – ΣΔH⁰_f (reactants)  

• Enthalpy of reaction is: {2 *(-221.33) + 10* (33.18)+ 4*(-241.8)}- (-{10* (-207.36) + 1* (62.50)} kJ/mol = 933.04 kJ/mol.

9. Is HNO₃ + I₂ a buffer solution?

HNO₃ + I₂ does not result in a buffer solution, given that both HNO₃ is a potent mineral acid and I₂  is a Lewis acid. As a buffer system, the acid-salt equilibrium cannot be kept up.

10. Is HNO₃ + I₂ a complete reaction?

The HNO₃ + I₂ reaction is complete since it yields three main products: potent electrolyte HIO₃, gas NO₂, a water molecule.

11. Is HNO₃ + I₂ an exothermic or endothermic reaction?

The reaction of HNO₃ + I₂ is endothermic following the thermodynamics first law. This reaction absorbs more energy and temperature, where δH is highly positive.

12. Is HNO₃ + I₂ a redox reaction?

HNO₃ + I₂ reaction is redox because the nitrogen atom is reduced from the +5 to the +4 oxidation state. Iodine oxidizes from a zero to a +5 oxidation state. Thus, I₂ and concentrated HNO₃ work as reducing and oxidizing agents, respectively.

13. Is HNO₃ + I₂ a precipitation reaction

HNO₃ + I₂ is not a precipitation reaction because HIO₃ is a strong electrolyte, NO₂ is a brown gas, and water remains in liquid form in the solution.

14. Is HNO₃ + I₂ reversible or irreversible reaction?

The reaction between HNO₃ + I₂ is irreversible because it produces acid, water, and a gas. That acid is a strong electrolyte, also. The equilibrium shifts towards the right-hand side or forward directions only.

15. Is HNO₃ + I₂ displacement reaction?

HNO₃ + I₂ is not an illustration of a displacement reaction because no ions has replaced other ions. They have mutually rearranged to give three final products.

Conclusion

The reaction between concentrated HNO₃ and I₂ gives a redox and irreversible reaction. Nitrogen dioxide, produced from this reaction gas, can be used as a catalyst in various chemical reactions.

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Ishita Ghosh

Hey readers, I am Ishita Ghosh. I have done my Master’s in Chemistry. My area of specialization is Inorganic Chemistry. The true way to comprehend chemistry is to understand it from its grassroots level. My effort is to share every bit of knowledge in chemistry I have so that it helps you for a better grasp on this subject.