15 Facts About HNO3 + Ag2S: How This Combination Works

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Silver Sulfide (Ag2S) is a dense black inorganic solid. Let us see how it reacts with Nitric acid (HNO3) through this article.

Nitric Acid (HNO3) is a highly corrosive mineral acid. Nitric acid is mainly produced by reaction of Nitrogen Dioxide with water. It is a primary agent used in nitration reaction and synthesis of many organic compounds. The reaction between Nitric acid and silver sulfide is very rapid.

This article will provide an in depth details regarding the interaction of HNO3 with Ag2S.

What is the product of HNO3 and Ag2S

The reaction of Silver Sulfide with Nitric Acid produces Silver Nitrate, Nitric Oxide, Solid Sulfur and water. Solid Silver Sulfide (Ag2S) is soluble in Nitric acid. The balanced Chemical reaction for this reaction is:

Ag2S + 4HNO3 → 2AgNO3 + 2NO + S + 2H2O

What type of reaction is HNO3 and Ag2S

The reaction of Nitric acid (HNO3) with Silver sulfide (Ag2S) is a Redox type of reaction.

How to balance HNO3 and Ag2S

  • The general chemical reaction can be represented as:
  • Ag2S + HNO3 → AgNO3 + NO + S + H2O
  • Now, identifying the number of elements at each side.
  • There are 2Ag, 1S, 1H, 1N and 3O at reactant side and Ag, 1S, 2H, 2N and 5O at product side.
  • By including relevant coefficients on both the side we obtain a following balanced chemical equation.
  • Ag2S + 4HNO3  →   2AgNO3 + 2NO + S + 2H2O

HNO3 + Ag2S titration

HNO3 + Ag2S do not represent any titration reaction. HNO3 is strong acid but, Ag2S is neither strong nor weak base as it is a metal sulfide. Therefore, titration is not possible for this reaction.

HNO3 + Ag2S net ionic equation

  • The balanced molecular equation is
  • Ag2S + 4HNO3  →   2AgNO3 + 2NO + S + 2H2O
  • Then writing (s, l, aq, g) for each of the molecule.
  • Ag2S(s) + 4HNO3 (l)  → 2AgNO3(s) + 2NO(g) + S(s) + 2H2O(s)
  • Now, breaking strong electrolytes into ions.
  • 2Ag+ + S2- + 4H+ + 4NO3 – → 2Ag+ +  2NO3– + 2NO + S + 2H2O
  • After breaking we will cross out the common ions from both the sides we will obtain the net ionic equation as follows:
  • The final net ionic equation is:
  • S2- + 4H+ + 2NO3 – → 2NO + S + 2H2O

HNO3 + Ag2S conjugate pairs

HNO3 + Ag2S Conjugate pairs are as follows:

  • The conjugate base for HNO3 is NO3– .
  • The conjugate acid for HNO3 is H+.
  • The conjugate base for Ag2S is S2-.
  • The conjugate acid for Ag2S is Ag+.

HNO3 + Ag2S intermolecular forces

HNO3 + Ag2S intermolecular forces are as follows

  • Nitric acid is strong acid and there is large electronegative difference between H and NO3. Hence, HNO3 is a polar molecule.
  • The intermolecular interaction in HNO3 molecule is dipole-dipole interactions and dispersion interactions.
  • London dispersion forces happen when the electrons in HNO3 + Ag2Sare drawn to one another by their transient and erratic charges.

HNO3 + Ag2S reaction enthalpy

HNO3 + Ag2S reaction enthalpy is around (-309.69). The enthalpy information is as follows:

  • The formation enthalpy of HNO3= -207.36kJ/mol.
  • The formation enthalpy of Ag2S = -31.8kJ/mol.
  • The formation enthalpy of AgNO3 = -124.39kJ/mol.
  • The formation enthalpy of NO = 90.25kJ/mol.
  • The formation enthalpy of H2O = -241.8kJ/mol.
  • The formation enthalpy of S = 0.33kJ/mol.
  • The Reaction Enthalpy is (-31.8 + 4(-207.36))-(2(-124.39)+2×90.25+0.33+2(-241.8))

Is HNO3 + Ag2S a buffer solution

HNO3 + Ag2S is not a Buffer solution because for a buffer solution there has to be weak acid or base but HNO3 is strong acid hence buffer solution is not possible.

Is HNO3 + Ag2S a complete reaction

HNO3 + Ag2S is a complete reaction since all of the reactant’s moles of HNO3 and Ag2S are completely converted and consumed by the product at equilibrium.

Is HNO3 + Ag2S an exothermic or endothermic reaction

HNO3 + Ag2S is an Exothermic reaction. The formation enthalpy is negative that means some amount of heat is released during the formation of this bond. The exothermic reaction graph is as follows.

Exothermic reaction graph
Exothermic Reaction Graph

Is HNO3 + Ag2S a redox reaction

HNO3 + Ag2S is Oxidation-Reduction i.e., Redox type of reaction. In this reaction Ag2S is reducing agent. It donates 2 electrons in the reaction process. HNO3 is strong oxidizing agent and gets reduced during the reaction process thereby, making stable products.

Is HNO3 + Ag2S a precipitation reaction

The reaction of HNO3 + Ag2S is a precipitate reaction. Yellow colored solid of Sulfur is formed as product of this reaction. The product of Sulfur formed in this reaction is precipitate for this reaction and it is insoluble in water.

Is HNO3 + Ag2S reversible or irreversible reaction

The reaction of HNO3 + Ag2S is irreversible type of reaction. The Nitric Oxide formed in this reaction is in gaseous state and is liberated as product thereby making this reaction irreversible. The equilibrium in this reaction cannot be moved backward.

Is HNO3 + Ag2S displacement reaction

The reaction of HNO3 + Ag2S is a displacement reaction. Here S2- ions of Ag2S is replaced by NO3– ions hence making it a displacement reaction.

Conclusion

Fuming Nitric acid dissolves Silver Sulfide precipitate to form Silver nitrate, Nitric oxide and Sulfur as a product. Sulfur being insoluble in water can be easily separated. This is an exothermic redox reaction. And the products obtained in this reaction are of great use in the synthetic industry.