Avneesh Rawat

The chemical reaction between nitric acid and carbon produces components that are primarily oxidative and responsible for the decomposition of organic substances. Let us explore the chemical reactivity of HNO₃ and C. 

HNO₃ is a colorless corrosive mineral acid that finds various applications in the fertilizer industry. Carbon denoted as C due to its sp2 hybridization can form a variety of interesting compounds. 

The reactivity of HNO₃ and C can be a source of various important compounds with agricultural benefits. Thus, these important reaction-based incredible facts are presented below in detail: 

What is the product of HNO₃ and C?

HNO₃ and C interact to produce nitrogen dioxide (NO₂), Carbon dioxide (CO₂), and water (H₂O). The complete chemical equation is given as:

HNO₃ + C = NO₂ + CO₂ + H₂O

What type of reaction is HNO₃ + C?

HNO₃ + NaOH is a reduction-oxidation reaction where carbon (C) oxidizes itself to carbon dioxide (CO₂), and nitric acid (HNO₃) gets reduced to nitrogen dioxide (NO₂). 

How to balance HNO₃ + C?

The following algebraic methodology can be used as an explanation to balance the chemical reaction 

HNO₃ + C = NO₂ + CO₂ + H₂O,

• Label each species (reactant or product) given in the chemical equation with a respective variable (A, B, C, D, and E) to illustrate unknown coefficients.
• (A) C + (B) HNO₃ = (C) CO₂ + (D) NO₂ + (E) H₂O
• Deduce a suitable equation for each element in the reacting species representing the number of atoms of an element in each reactant or product species, applied to solve the equation.
• C = A = C, H = B = 2E, N = B = D, O = 3B = 2C + 2D + E
• The Gaussian elimination and substitution methodology is applied to simplify all the variables and coefficients, and the outcomes are
• A = 1, B = 4, C = 1, D = 4, and D = 2
• Hence, the overall balanced equation is, 
• 4 HNO₃ + C = 4 NO₂ + CO₂ + 2 H₂O

HNO₃ + C titration

HNO₃ + C system is not performed as titration as carbon as an element cannot work either as a titre or as a titrant. A specific indicator cannot also be thought of to demonstrate the end point of the titration.

HNO₃ + C net ionic equation

The net ionic equation of HNO₃ + C is 

C (s) + 4 H⁺ (aq) = 2 H₂O (l) + CO₂ (g)

The net ionic equation is obtained using the following steps

• Write the balanced chemical equation and designate the physical states of reactants and products accordingly
• HNO₃ (aq) + C (s) = 4 NO₂ (g) + CO₂ (g) + 2 H₂O (l)
• Now, strong acids, bases, and salts dissociate into ions whereas pure solid substances and molecules do not dissociate
• H⁺ + NO₃^– + C = H⁺ + NO₂^– + C+ CO₂ + OH^– 
• Thus, the net ionic equation is
• C (s) + 4 H⁺ (aq) = 2 H₂O (l) + CO₂ (g)

HNO₃ + C conjugate pairs

• Conjugate pair of strong acid HNO₃ is H₂NO₃⁺.
• Conjugate pair of C cannot be formed due to unavailability of free hydrogen ions in it. 

HNO₃ and C intermolecular forces

Intermolecular forces acting on HNO₃ and C are: 

• HNO₃ interacts using strong hydrogen bonds, weak London dispersion forces, and dipole-dipole interactions between the molecules. 
• C oxidizes to form CO₂ where the movement of the electron causes instantaneous dipoles to form London dispersion forces.
• NO₂ register formation of dipole dipole and ion-dipole interactions due to negative and positive charges being found in equilibrium in the molecule.

HNO₃ + C reaction enthalpy

HNO₃ + C exhibits a negative reaction enthalpy of -631.62 kJ/mol. Enthalpy information for the reactants and products involved are as follows: 

• Enthalpy of formation for reactant HNO₃: -207.36 kJ/mol
• Enthalpy of formation for reactant C: 716.68 kJ/mol
• Enthalpy of formation for product NO₂: 33.18 kJ/mol
• Enthalpy of formation for product CO₂: -393.50 kJ/mol
• Enthalpy of formation for product H₂O: -241.80 kJ/mol

Is HNO₃ + C a buffer solution?

HNO₃ + C does not form a buffer because the buffer is prepared by the addition of weak acid to the salt of its conjugate base whereas HNO₃ is not a weak acid and C is an amphoteric element and not a salt of the conjugate base of HNO₃. 

Is HNO₃ + C a complete reaction?

HNO₃ + C is a complete reaction as the stable products namely nitrogen dioxide (NO₂), carbon dioxide (CO₂), and water (H₂O). are produced in the reaction.   

Is HNO₃ + C an exothermic or endothermic reaction?

HNO₃ + C is an exothermic reaction because the calculated reaction enthalpy is observed to be negative. The enthalpy oof formation of reactants is greater than that of products which justifies that heat is released in the process. 

Is HNO₃ + C a redox reaction?

HNO₃ + C is a redox reaction because carbon (C) oxidizes itself to carbon dioxide (CO₂), and nitric acid (HNO₃) gets reduced to nitrogen dioxide (NO₂). 

Is HNO₃ + C a precipitation reaction?

HNO₃ + C is not a precipitation reaction as NO₂ and CO₂ produced in the reaction are gases that do not settle as a solid precipitate in the reaction. 

Is HNO₃ + C reversible or irreversible reaction?

HNO₃ + C is an irreversible reaction because the formed products in the reaction do not change back into original reactants till the conditions remain similar. 

Is HNO₃ + C displacement reaction?

HNO₃ + C is not a displacement reaction because no new compounds are observed to be formed due to the displacement of a single component or due to double displacement between both the reacting species.

Conclusions

The chemical reaction of HNO₃ + C forms nitrogen dioxide and carbon dioxide as the major products that have huge beneficial properties in the production of fertilizers, pesticides, and related industries. The chemicals have been used in the manufacturing of synthetic dyes, fibres and plastics.