The Chemistry Behind HCl + Ag2CrO4: 15 Facts You Should Know

HCl is a strong acid and it can easily react with basic salt silver chromate without any catalyst. Let us discuss the chemistry behind this reaction.

Ag2CrO4 or silver chromate is mainly used for the mohr’s salt titration in analytical chemistry. It is a metallic salt and reacts with water to form a base so it is a basic salt and reacts with a diluted or concentrated form of acid. HCl or hydrochloric acid is a strong mineral acid that easily donates a proton.

Although there will be some parameters and limitations present in this reaction. Now we can discuss more the mechanism of the reaction like enthalpy, redox reaction, intermolecular force, conjugate pairs, etc with an explanation in the following part of the article.

1. What is the product of HCl and Ag2CrO4?

H2CrO4 (Chromic acid) and AgCl (silver chloride) are formed when diluted HCl and Ag2CrO4 are reacted together but when we use conc. HCl and Ag2CrO4 then dichromic acid (H2CrO7) and water are also formed along with silver chloride.

HCl(dil.) + Ag2CrO4 = AgCl + H2CrO4

HCl(Conc.) + Ag2CrO4 = H2CrO7 + AgCl + H2O

2. What type of reaction is HCl + Ag2CrO4?

HCl + Ag2CrO4 reaction is an example of a double displacement reaction, and a redox and precipitation reaction. It is also a hydrolysis reaction because, in the course of the reaction, water is formed.

3. How to balance HCl + Ag2CrO4?

HCl + Ag2CrO4 = H2CrO7 + AgCl + H2O, we have to balance the equation in the following way-

  • First, we label all the reactants and products by A, B, C, D, and E as there are five different molecules obtained for this reaction and the reaction looks like this,
  • A HCl + B Ag2CrO4 = C H2CrO7 + D AgCl + E H2O
  • Equating the coefficients for the same type of elements by rearranging them.
  • After the rearrangement of coefficients of the same elements by their stoichiometric proportion, we get,
  • H = A = 2C = 2E, Cl = A = D, O = 4B = 7C = E, Ag = 2B = D, Cr = B = C.
  • Using the Gaussian elimination and equating all the equations we get, A = 4, B = 2, C = 1, D =4, and E = 1
  • The overall balanced equation will be,
  • 4HCl + 2Ag2CrO4 = H2CrO7 +4 AgCl + H2O
  • And another balanced equation will be, Ag2CrO4 + 2HCl = H2CrO4 + 2AgCl

4. HCl + Ag2CrO4 titration

To estimate the quantity of chromate or acid strength, we can titrate Ag2CrO4 and HCl.

Apparatus used

We need a burette, conical flask, burette holder, volumetric flask, and beakers for this titration.

Titre and titrant

HCL versus Ag2CrO4, HCl acts as a titrant taken in the burette and the molecule to be analyzed is Ag2CrO4 taken in a conical flask.


The whole titration is done in an acidic medium or acidic pH so the best suitable indicator will be phenolphthalein which gives perfect results for this titration at given pH.


The burette is filled with standardized HCl. Ag2CrO4 is taken in a conical flask along with respective indicators. HCl is added dropwise to the conical flask and the flask is shaken constantly. After a certain time, when the endpoint arrives, the indicator changes its color and the reaction is done.

5. HCl+ Ag2CrO4 net ionic equation

The net ionic equation between HCl + Ag2CrO4 is as follows,

H+(aq.) + Cl(aq.) + Ag+(aq.) + CrO42-(aq.) = 2H+(aq.) + CrO72-(aq.) + H+(aq.) + OH(aq.) + Ag+(aq.) + Cl(aq.)

  • HCl will be ionized as proton and chloride as it is strong acid and electrolyte.
  • After that Ag2CrO4 also dissociates into Ag+ ion and CrO42-ion as it is also a strong electrolyte
  • In the product part, AgCl is ionized into Ag+ and Clas it is a strong electrolyte and salt in the aqueous form.
  • H2O ionized into proton and hydroxide ion.
  • H2CrO7 is also ionized into di protonic form and CrO72- as counter ion as it is an acidic molecule and can be dissociated into an aqueous medium.

6. HCl+ Ag2CrO4 conjugate pairs

In the reaction, HCl+ Ag2CrO4 conjugate pairs will be the corresponding de-protonated and protonated form of that particular species which are listed below-

  • Conjugate pair of HCl = Cl
  • Conjugate pair of OH = H2O
  • Conjugate part of CrO72- = HCrO7
  • Conjugate part of HCrO7 = H2CrO7
  • Conjugate part of H2CrO4 = CrO42-

7. HCl and Ag2CrO4 intermolecular forces

 HCl + Ag2CrO4 has the following intermolecular reactions,

van der waal’s
Ag2CrO4Strong electrostatic
force and
ionic interaction,
Coulumbic force,
metallic bond
AgClElectrostatic force,
ionic interaction,
H2CrO4 / H2CrO7Covalent force, ionic
dipole interaction
H2OIonic interaction and
Intermolecular Forces

8. HCl + Ag2CrO4 reaction enthalpy

HCl + Ag2CrO4 reaction enthalpy is +1001.24 KJ/mol which can be obtained by the formula: enthalpy of products – enthalpy of reactants. Here the change in enthalpy is positive.

Enthalpy of Reactants
and Products

9. Is HCl + Ag2CrO4 a buffer solution?

In the reaction between HCl + Ag2CrO4, there is no such buffer formed but the mixture of H2CrO7 can control the pH even added base in the solution.

10. Is HCl + Ag2CrO4 a complete reaction?

The reaction between HCl + Ag2CrO4 is complete because it gives two major ones: an electrolytic salt and an acidic molecule along with water as a by-product.

11. Is HCl + Ag2CrO4 an exothermic or endothermic reaction?

The reaction of HCl + Ag2CrO4 is endothermic in terms of thermodynamics first law. This reaction released more energy and temperature to the surroundings, where δH is always positive.

Energy profile Diagram of Endothermic Reaction

12. Is HCl + Ag2CrO4 a redox reaction?

HCl + Ag2CrO4 reaction is a redox reaction because in this reaction chromium gets reduced and also silver gets oxidized. Where HCl acts as a reducing agent and Ag2CrO4 acts as an oxidizing agent.

13. Is HCl + Ag2CrO4 a precipitation reaction

The reaction between HCl + Ag2CrO4 is a precipitation reaction because AgCl gets precipitated in the solution at certain pH.

14. Is HCl + Ag2CrO4 reversible or irreversible reaction?

The reaction between HCl+ Ag2CrO4 is irreversible because it produces an acid molecule. Due to the production of the acidic molecule, the equilibrium shifts towards the right-hand side only or forward directions.

HCl + Ag2CrO4 —-> AgCl+ H2CrO7 + H2O

15. Is HCl + Ag2CrO4 displacement reaction?

The reaction between HCl+ Ag2CrO4 is an example of a double displacement reaction. Because in the above reaction, H+ was displaced by Ag+ from HCl, and Ag+ was displaced by proton from the Ag2CrO4.

Screenshot 2023 01 06 195126
Double Displacement Reaction


The reaction between HCl and Ag2CrO4 is important because it can produce dichromic acid. In the course of reaction silver chloride is also produced so it is an industrially important reaction for the production of AgCl and H2CrO7. When we use diluted HCl acid then it forms H2CrO4.