15 Facts on HCl + HCN: How To Balance & FAQs

Chemical components interact during chemical reactions to create new compounds with unique compositions. Let us investigate the chemical interactions of HCl and HCN.

The reaction between HCl and HCN is in general an addition reaction giving rise to formation of an adduct. Hydrochloric acid is a monoprotic and strong acid. Hydrogen cyanide is a not a recommended gas as it interferes with human body oxygen content.

The reaction dynamics between HCl and HCN has to be studied using quasiclassical trajectory principles due to the similar energetics shown by both reactant species. Here, we discuss more mechanistic with an explanation in the following article.

1. What is the product of HCl and HCN?

An adduct of hydrogen and hydrogen chloride is formed together with pseudohalide cyanide when hydrochloric acid reacts with hydrogen cyanide.

HCl + 2HCN = H2(HCl) + 2CN

2. What type of reaction is HCl + HCN?

HCl + HCN is an example of addition reaction in which both the reactants add together to form an intermediate.

3. How to balance HCl + HCN?

We can balance the reaction HCl + HCN = H2(HCl) + CN using algebraic method as follows,

  • Each reactant or product in the equation is labeled with a variable (A, B, C, and D) to represent unknown coefficients.
  • A HCl + B HCN = C H2(HCl) + D CN
  • Now, the equation is solved by an appropriate number, considered to be the coefficient of reactants and products.
  • H = A + B = 3C, C = A = D, N = A = D, Cl = B = C
  • All the variables and coefficients are calculated by the Gauss elimination method, and lastly, we get
  • A = 1, B = 2, C = 1, and D = 2
  • So, the overall balanced equation will be,
  • HCl + HCN = H2(HCl) + CN

4. HCl + HCN titration

HCl + HCN titration system is an example of conductometric titration of a mixture of acids (HCl and HCN) against a strong base (NaOH). Below are discussed several conditions, apparatus, and procedures for the titration.

Apparatus used

Burette, burette clamps, conical flask, magnetic stirrer, and beakers.

Indicator

Conductivity measurement is used as an indicator of the titration endpoint. Thus, eliminates requirement of specific colored indicators.

Procedure

The general process for conductometric titration of the mixture of a strong acid with a base is as follows:

  • The combination of acids must be diluted with distilled water so that the changes in the conductance value can be brought on by adding drops of base i.e., NaOH.
  • A burette must be filled with NaOH and the initial volume is noted.
  • Here in this step, a conductivity cell is kept into the diluted acid solution by completely immersing the electrodes.
  • The strong acid will react first, followed by the weak acid.
  • In this titrating system HCl will react with NaOH at the start and get neutralized.
  • The conductivity cell is connected to a conductometer to obtain an initial reading.
  • As the volume of base is added into the acid mixture, corresponding change in the values of conductance are recorded.
  • H+ ions split off from the strongly ionised HCl, steadily decreasing the conductance of the solution
  • After the HCl is consumed, HCN and NaOH begin to react.
  • The neutralisation of weak acid causes slight increase in conductance.
  • The additional OH ions cause the conductance to increase significantly after the equivalence point.
  • Thus, the conductance will decrease steeply, then increase marginally and steeply.
  • The sharp increase in the conductance of the solution suggests the attainment of endpoint. Hereon, a few more concordant readings are important to be recorded after the endpoint of the titration.
  • The observed values are then after graphically plotted and the equivalence point is obtained from the intersection point between the two different lines achieved.
  • The strength of the acid can be calculated using the formulae
  • S2 = (V1 * S1)/V2 where S2 is the strength of the acid, V1 is the volume of base added, and S1 is the strength of the base and V2 is the volume of the acid used.

5. HCl + HCN net ionic equation

The net ionic equation for HCN + HCl is

  • H+ (aq) + Cl (aq)+ HCN (s) = Cl (aq) + CN (aq) + H2 (g)

Following steps are used to derive the net ionic equation:

  • Firstly, write the balanced chemical equation and represent the physical states of reactants and products
  • HCl (aq) + HCN (s) = H2(HCl) (s) + CN (aq)
  • Now, strong acids, bases and salts dissociates into ions whereas the pure solid substances and molecules do not dissociate
  • H+ (aq) + Cl (aq)+ HCN (s) = Cl (aq) + CN (aq) + H2 (g)

6. HCl + HCN conjugate pairs

HCN + HCl being strong acids, will form conjugate bases by losing a proton. Thus, no conjugate pair can exist between the two.

  • Conjugate pair of HCl = Cl
  • Conjugate pair of HCN = CN

7. HCl and HCN intermolecular forces

HCN and HCl are linear molecules with a permanent dipole moment. The dispersion forces and dipole-dipole forces are observed in both the molecules.

8. HCl + HCN reaction enthalpy

HCN + HCl do not report reaction enthalpy. Therefore, it is impossible to comment on whether the reaction can dissipate energy and is feasible.

9. Is HCl + HCN a buffer solution?

HCN + HCl do not form a buffer in an aqueous solution because both are acids.

10. Is HCl + HCN a complete reaction?

HCN + HCl is incomplete reaction as no stable product forms on the right-hand side.

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

HCN + HCl cannot be answered for its exothermic or endothermic behavior because of no reports on heat utilization or liberation during the mix-up of the reactants.

12. Is HCl + HCN a redox reaction?

HCN + HCl do not show redox reaction because reduction and oxidation of reactants do not occur

13. Is HCl + HCN a precipitation reaction?

HCN + HCl is not a precipitation reaction as no precipitates are observed at the end of the reactions.

14. Is HCl + HCN reversible or irreversible reaction?

HCN + HCl is irreversible reaction because the formed pseudohalide cyanide cannot react with H2(HCl) to produce the original reactants.

15. Is HCl + HCN displacement reaction?

HCN + HCl is not a displacement reaction as no multiple displacements of molecules from the reactants were noticed.

Conclusions

The reaction of hydrochloric acid with hydrogen cyanide produces an important intermediate in the presence of a free catalyst. With increasing catalyst concentration, it can be seen that the HCl rate increases rapidly.