17 Facts on HCl + K2CrO4: What, How To Balance & FAQs


Hydrochloric acid is a strong inorganic acid, and Potassium chromate is an inorganic crystalline compound. Let us look at how their reaction proceeds.

Hydrochloric acid, also known as muriatic acid, is a colorless gas that can exist in both aqueous and gaseous forms. It can be prepared (industrially) by dissolving Hydrogen chloride in water. Potassium chromate, a yellow solid, is a strong oxidizing agent and is water-soluble in nature.

This article shall discuss important facts such as the products formed, reaction enthalpy, and the redox mechanism of the reaction between HCl and K2CrO4.

What is the product of HCl and K2CrO4

HCl and K2CrO4 react to form Potassium Dichromate, Potassium Chloride, and Water. The reaction takes place in an aqueous medium. The reaction is as follows:

2HCl + 2K2CrO4 = K2Cr2O7 + 2KCl + H2O

What type of reaction is HCl + K2CrO4

The reaction of HCl with K2CrO4 is an acid-base reaction wherein HCl is a strong acid and K2CrO4 acts as a weak base.

How to balance HCl + K2CrO4

The steps to equate the above-mentioned reaction is as follows:

The skeletal unbalanced chemical equation is: HCl + K2CrO4 = K2Cr2O7 + KCl + H2O

  • In order to balance the reaction, the number of atoms of elements present on both the reactant and product side must be equal.
AtomsReactant SideProduct Side
Hydrogen1 2
Chlorine1 1
Potassium2 3
Chromium1 2
Oxygen4 8
Table showing the count of Atoms of Elements from the unbalanced equation

In the next step, The number of Hydrogen atoms on both sides of the reaction is first equalized. In order to do so, coefficient 2 is added to the HCl molecule as there are 2 atoms of Hydrogen on the product side.

Similarly, to balance Potassium, a coefficient of 2 is added to the KCl molecule, resulting in a total of 4 Potassium atoms on the product side. Now, Potassium on the reactant side is balanced further by adding 2 to the K2CrO4 molecule, resulting in an equal number of Potassium atoms on both sides of the reaction.

The above two steps are repeated until all of the atoms of the elements reacting are equivalent on both the reactant and product sides.

Thus, the balanced chemical reaction is:

2HCl + 2K2CrO4 = K2Cr2O7 + 2KCl + H2O

HCl + K2CrO4 Titration

HCl + K2CrO4 falls under the category of strong acid weak base titration where HCl is a strong acid and K2CrO4 behaves as a weak base,

Apparatus

Burette, Pipette, Conical flask, Beakers, Burette stand, Funnel, and measuring flask 

Indicator

Methyl orange is used as an indicator for this titration.

Procedure

  • The burette is washed, rinsed, and filled with a standardized HCl solution.
  • A clean, washed conical titration flask is filled with K2CrO4 solution, and 2 drops of methyl orange indicator are introduced to it.
  • The titration is carried out by drop-wise addition of the HCl solution to the titration flask till a color change is observed,
  • Once the solution in the titration flask turns reddish-orange, it marks the end point of the reaction. The reading is noted down.
  • The above steps are repeated till concordant readings are obtained.
  • The volume of the required chemical is determined by using the formula N1V1 = N2V2.

HCl + K2CrO4 Net Ionic Equation

The net ionic equation comprises only those species that are participating in the reaction eliminating the spectator ions. The balanced net ionic equation between HCl + K2CrO4 is as follows:

2CrO42- (aq) + 2H+ (aq) = Cr2O72- (aq) + H2O (l)

HCl + K2CrO4 Conjugate Pairs

The conjugate pair formed during the reaction between HCl + K2CrO4 are as follows:

  • Conjugate base of HCl (donates a proton) = Cl
  • Conjugate base of H2O = OH

HCl + K2CrO4 Intermolecular Forces

  • HCl shows ionic interactions in its aqueous phase. However, dipole-dipole interaction (arises due to the charge separation between Hydrogen and chlorine) and London dispersion forces are the intermolecular forces present between the HCl molecules.
Intermolecular forces in HCl
  • The bond that holds together the molecule K2CrO4 is ionic bonding. Thus, strong electrostatic forces of attraction exist between the ions K+ and CrO42-.

HCl + K2CrO4 Reaction Enthalpy

The enthalpy of the reaction HCl + K2CrO4 is found to be -1236.2 kJ/mol. The enthalpy information of the reaction is tabulated as follows:

Compounds (aq.)Bond Enthalpy, ΔH⁰f (kJ/mol)
HCl428
K2CrO4-1388.7
K2Cr2O7-2033
KCl-419.4
H2O-285.8
Bond enthalpy values

The Reaction enthalpy is calculated using the formula, ΔH⁰f (reaction) = ΣΔH⁰f (products) ΣΔH⁰f (reactants).

Is HCl + K2CrO4 a Buffer Solution

The HCl + K2CrO4 mixture will not form a strong buffer solution because its chromate ions have a poor buffering capacity, and its pH range does not remain constant when a strong acid such as HCl is added. The presence of a weak acid is suitable for a solution to make it a good buffer.

Is HCl + K2CrO4 a Complete Reaction

HCl + K2CrO4 is a complete because the compounds formed are highly stable and complete, allowing them to be used in other organic studies and experiments.

Is HCl + K2CrO4 an Exothermic or Endothermic Reaction

HCl + K2CrO4 reaction is observed to be exothermic in nature since the enthalpy of the reaction is negative, thus, releasing heat to the surroundings and increasing the temperature of the system.

Is HCl + K2CrO4 a Redox Reaction

  • HCl + K2CrO4 is a redox (oxidation-reduction) reaction, as a change in the oxidation state of ions takes place from reactants to products.
  • HCl acts as a reducing agent, and K2CrO4 acts as an oxidizing agent.

6 Cl-1 – 6 e = 6 Cl0 —————-> (Oxidation)

2 Cr+6 + 6 e = 2 Cr+3 ————–> (Reduction)

Is HCl + K2CrO4 a Precipitation Reaction

HCl + K2CrO4 is not a precipitation reaction, as no insoluble product formation takes place.

Is HCl + K2CrO4 Reversible or Irreversible Reaction

  • The reaction HCl + K2CrO4 is moderately reversible in nature, which implies that the extent of reversibility is considerably small.
  • The reversible nature arises as the dichromate ions (Cr2O72-) formed in the product can be converted back to the chromate ions (CrO42-) of K2CrO4 by increasing the H+(aq) concentration. The increase is made possible by the addition of a source of H+(aq), in this case, Hydrochloric acid.

Is HCl + K2CrO4 Displacement Reaction

The reaction HCl + K2CrO4 is a double displacement (metathesis) reaction as the two compounds reacting exchange their ions to form completely new products.

How to balance K2CrO4 + BaCl2 + HCl = BaCr2O7 + KCl + H2O

Following are the steps to balance the given reaction:

  • The number of atoms of each element for this reaction is counted and tabulated as given below:
AtomsReactant SideProduct Side
Hydrogen1 2
Chlorine31
Potassium21
Chromium1 2
Oxygen4 8
Barium11
Table showing the count of Atoms of Elements from the unbalanced equation
  • The next step is to equalize unbalanced atoms of elements by multiplying or adding coefficients. Adding coefficient 2 to the K2CrO4 and 4 to the KCl molecules balances Potassium, chromium, and oxygen on either side of the reaction.
  • The only unbalanced atoms are Hydrogen and chlorine. Coefficient 2 is added to the HCl molecule to balance these two elements.
  • Thus, the resultant balanced chemical reaction is:

2K2CrO4 + BaCl2 + 2HCl  = BaCr2O7 + 4KCl + H2O

How to balance K2CrO4 + HCl + NaOH = KO + NaCrO + H2O + Cl

  • The number of atoms of each element in this reaction is counted and tabulated similarly, as discussed in the preceding section.
  • The next step is to equalize unbalanced atoms of elements by multiplying or adding coefficients. In order to balance Hydrogen on both sides, coefficient 3 is added to HCl, and simultaneously coefficients 2 and 3 are multiplied to molecules H2O and Cl, respectively.
  • Finally, Potassium and Oxygen are the remaining unbalanced atoms required to be equalized. Adding coefficient 2 to the compound KO balances the whole equation.
  • Thus, the resultant balanced chemical reaction is:

2K2CrO4 + BaCl2 + 2HCl  = BaCr2O7 + 4KCl + H2O

How to balance K2CrO4 + Na2SO3 + HCl = KCl + Na2SO4 + CrCl3 + H2O

  • The number of atoms of each element in this reaction is counted in the same manner as was tabulated in the preceding sections.
  • The next step is to equalize unbalanced atoms of elements by multiplying or adding coefficients to them. The compounds containing chromium and sulfur are multiplied by coefficients 2 and 3, respectively.
  • The Hydrogen and oxygen are further balanced by multiplying compounds HCl and H2O by coefficients 10 and 5, respectively.
  • The above two steps are repeated until all of the atoms of the elements (chlorine and Potassium in this case) reacting are equivalent on both the reactant and product sides.
  • Thus, the balanced chemical reaction is:

2K2CrO4 + 3Na2SO3 + 10HCl = 4KCl + 3Na2SO4 + 2CrCl3 + 5H2O

Conclusion

The reaction of K2CrO4 with HCl forms an important red-orange colored reagent, K2Cr2O7, which is used as an oxidizing agent primarily in industrial and laboratory applications. The second product is a colorless to white inorganic halide KCl which finds its use in fertilizer, medicinal, culinary, and industrial applications.

Padmakshi Kotoky

Hello, I am Padmakshi Kotoky working as a Subject Matter Expert on this platform. I have completed my post-graduation from the Institute of Chemical Technology, Mumbai. I have always found Chemistry an intriguing subject and enjoy exploring more on it. I would like to utilize this platform to explain the subject in an easy and precise manner making it simpler for the readers to understand the concepts with clarity. I engage myself in Singing, Dancing, and nature photography during my leisure time. Let's connect through LinkedIn - https://www.linkedin.com/in/padmakshi-k-b54679132

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