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


The reaction of strong acid (HCl) with lead (II) sulfide leads to the formation of solid cotunnite and a colorless chalcogen hydride gas. Let us find out in detail the reaction.

Muriatic acid or HCl is a strong colourless acid, prepared from hydrogen and chloride elements. Lead II sulfide (PbS) also referred to as Galena is a semiconducting material, the principal ore, and the most important compound of lead.

The following article studies the reaction mechanism, and type of reaction, in detail steps for balancing the reaction and calculates the reaction enthalpy and the net ionic equation.

What is the product of HCl and PbS?

The reaction of hydrochloric acid (HCl) with lead (II) sulfide (PbS)) forms lead (II) chloride and hydrogen sulfide.

PbS + 2HCl → PbCl2 + H2S

What type of reaction is HCl + PbS?

The reaction of HCl+PbS is classified as a neutralization reaction due to the formation of lead (II) chloride, which is a slightly soluble salt.

How to balance HCl + PbS?

A chemical reaction is balanced by following steps –

  • The unbalanced chemical reaction is written down as:
  • PbS + HCl → PbCl2 + H2S
  • The number of moles of each compound on the reactant side and product side is tabulated down as:
CompoundReactant SideProduct Side
Pb11
S21
Cl12
H12
The number of moles of each compound in the reaction
  • A reaction is balanced when the number of moles on the reactant side equals the number of moles on the product side. Here, moles of H2 and Cl atoms are not equal on either side of the reaction.
  • The given reaction is balanced by multiplying 2 with HCl on the reactant side
  • The Balanced chemical reaction is –
  • PbS + 2HCl → PbCl2 + H2S
Balanced Chemical Reaction

HCl + PbS titration

There is no such titration performed between them, due to the absence of a base compound.

HCl + PbS net ionic equation

The net ionic equation is – PbS(s) + 2H+(aq) + 2Cl(aq) = PbCl2(aq) + H2S(g). The steps followed are as follows –

  • The phase or state of each element is determined as shown below
  • PbS(s) + 2HCl(aq) = PbCl2(aq) + H2S(g)
  • The complete ionic equation is determined by separating all soluble ionic compounds into their respective ions – PbS(s) + 2H+(aq) + 2Cl(aq) = PbCl2(aq) + H2S(g)
  • The ions present in both the reactant and product sides are removed.
  • The net ionic equation includes only the species involved in the reaction.
  • The net ionic equation is – PbS(s) + 2H+(aq) + 2Cl(aq) = PbCl2(aq) + H2S(g)

HCl + PbS conjugate pairs

The conjugate acid-base pair is not written in the case of PbS, while for HCl it is:

  • The conjugate base of HCl= Cl

HCl and PbS intermolecular forces

The intermolecular forces acting on HCl and PbS are-

HCl + PbS reaction enthalpy

The reaction enthalpy is 76.45 KJ/mol, when HCl reacts with PbS. The number of moles and respective enthalpy of each compound present in the reaction is tabulated below. The reaction enthalpy is calculated as:

Reaction Enthalpy = [1*(-336) + 1*(-20.17)] – [1*(-98.32) + 2*(-167.15)] = 76.45 KJ/mol.

CompoundsNumber of MolesEnthalpy (KJ/mol)
PbS1-98.32
HCl2-167.15
PbCl21-336
H2S1-20.17
The number of moles and respective enthalpy of each compound

Is HCl + PbS a buffer solution?

HCL + PbS is not a buffer solution due to the presence of HCl which is a strong acid.

Is HCl + PbS a complete reaction?

HCl + PbS is a complete reaction since complete moles of reactant are consumed into the product at equilibrium.

Is HCl + PbS an exothermic or endothermic reaction?

HCl + PbS is an endothermic reaction since the enthalpy is +76.45 KJ/mol, decreasing the reaction temperature.

Is HCl + PbS a redox reaction?

HCl + PbS is not a redox reaction, since the oxidation state of elements remains unchanged during the reaction.

Is HCl + PbS a precipitation reaction?

HCl + PbS is a precipitate reaction due to the formation of precipitate PbCl2 which is a slightly soluble salt.

Is HCl + PbS reversible or irreversible reaction?

HCl + PbS is a irreversible reaction and can be reversed only if there is a drastic change in pressure or temperature.

Is HCl + PbS displacement reaction?

HCl + PbS exhibits a double displacement (metathesis) reaction. In this reaction, hydrogen is traded with Sulphur atoms to form hydrogen sulfide (H2S), and chlorine (Cl) is traded with lead (II) to lead (II) chloride (PbCL2).

Double Displacement Reaction

Conclusion

Hydrochloric acid reacts with lead (II) sulfide to form lead (II) chloride and hydrogen sulfide which has a variety of uses. PbCl2 is used in the production of aurene glass, infrared transmitting glass, lead salts etc. H2S is primarily used in the production of sulphuric acid and to create a variety of inorganic sulfides.

Pratham Shah

Hi....I am Pratham Manish Shah, Pursuing an Integrated MTech degree in Chemical Engineering from the Institute of Chemical Technology Mumbai Marathwada Jalna. With Lamdageeks, I am Interested in learning ongoing education opportunities to maintain knowledge of emerging technologies and methods. Let's connect via LinkedIn: www.linkedin.com/in/pratham-shah-07

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