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

by

HCl is a strong acid and Hg is a shiny silvery liquid of d-block (transition metal) element. Let us learn more about their chemical concept.

HCl is also known as Chlorane and is a colorless acid. It completely dissociates in aqueous media as H+ and Cl– ions. Hg is also known as quicksilver and is the dense metallic liquid at standard temperature and pressure. The reaction between HCl and Hg is only possible when the HCl is present in the concentrated form.   

What is the product of HCl and Hg?

The product of HCl + Hg are HgCl2 and H2 gas. HgCl2 is present in white precipitated form and H2 gas is evolved from this reaction.

2HCl (aq) +Hg (s) → HgCl2 (s) + H2 (g)

What type of reaction is HCl + Hg?

HCl + Hg reaction is a single displacement reaction.

How to balance HCl+Hg?

  • Write the reactants and products of the reaction
  • HCl + Hg = HgCl + H2
  • As two atoms of hydrogen gas evolved in the product side, in order to balance the reaction side, 2 is multiplied with HCl. Now, hydrogen is balanced.
  • 2HCl + Hg = HgCl + H2
  • In the above step, on the product side one Cl atom is present, whereas on the reactant side two Cl atoms are present. In order to balance Cl atoms on the product side, 2 is multiplied to Cl.
  • The balanced chemical equation can be written as follows:
  • 2HCl (aq) +Hg (s) → HgCl2 (s) + H2 (g)

HCl+Hg titration?

HCl + Hg titration is not possible, as the Hg metal is treated with aqua-regia (3 HCl : 1 HNO3) forms a white precipitate of HgCl2.

HCl+Hg net ionic equation?

HCl+Hg reaction has the following net ionic equation,

HgCl2 = Hg2+ + 2Cl–

  • The storng electrolyte, HCl dissociates into H+ and Cl– in water.
  • The mercury ion (Hg+) combines with Cl2–  and displaces H+ in hydrochloric acid.

HCl+Hg conjugate pairs?

HCl+Hg reaction has the following conjugate pairs,

  • HCl = H+ + Cl–
  • HCl removes one proton to form Cl–, so here the pair HCl and Cl– acts as a conjugate acid base pair.

HCl and Hg intermolecular forces?

HCl+Hg reaction has the following intermolecular forces,

  • HCl is a polar compound in which H+ and Cl– are connected through ionic bonding.
  • The product contains a salt HgCl2, in which Hg2+ and 2Cl– ions are connected through ionic bonds and H2 gas contains covalent bonds.

HCl+Hg reaction enthalpy?

HCl+Hg reaction has the reaction enthalpy of -45.38 KJ/mol.

  • The enthalpy change for HCl+Hg is -45.38 KJ/mol.
  • The enthalpy for the reactant HCl is -92.31 KJ/mol, and for the product (HgCl2) is -230 KJ/mol.
  • The enthalpy for H2 (g) is zero. The enthalpy change for the reaction is (Products-reactants), which is equal to -230 – (-92.31)×2 = -45.38 KJ/mol.

Is HCl+Hg a buffer solution?

HCl+Hg reaction is not a buffer solution because HCl is a strong acid and it completely dissociates into its ions and is hence unable to form a buffer solution.

Is HCl+Hg a complete reaction?

HCl+Hg reaction is not a complete reaction, as there are no products in the product side. The complete balanced equation is 2HCl+Hg → HgCl2 + H2

Is HCl+Hg an exothermic or endothermic reaction?

HCl+Hg reaction is an exothermic reaction, as the enthalpy of the reaction is negative. In HCl+Hg, a large amount of heat is evolved in the reaction system.   

Is HCl+Hg a redox reaction?

HCl+Hg reaction, is a redox reaction where there is a change in the oxidation state of the reaction system. In, this reaction, the Hg is oxidized and H is reduced.

Is HCl+Hg a precipitation reaction?

HCl+Hg reaction is a precipitation reaction as the product of this reaction is a white precipitate of HgCl2.

Is HCl+Hg a reversible or irreversible reaction?

HCl+Hg reaction is an irreversible reaction. This reaction is an example of precipitation reaction and precipitation reactions are generally irreversible because the formed precipitates cannot be converted back to the solution.

Is HCl+Hg displacement reaction?

HCl+Hg is a displacement reaction. The Hydrogen ion in hydrochloric acid is displaced by the Hg metal ion and forms a white HgCl2 precipitate and the evolution of H2 gas occurs.

Conclusion

The reaction of HCl and Hg produces a white precipitate and the reaction is exothermic in nature. The product, Hg2Cl2 is also known as calomel. This calomel is used extremely as a reference electrode in electrochemistry.