15 Facts on HF + CH3COOH: What, How to Balance & FAQs

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Hydrogen Fluoride (HF) is an inorganic compound . Acetic acid or ethanoic acid (CH3COOH) is a weak inorganic acid with the common name vinegar. Let us look into their reaction.

HF in an aqueous solution produces hydrofluoric acid, a weak acid, unlike other hydrohalides. HF is used in synthetic chemistry, for preparing herbicides, refrigerants etc. On the other hand, CH3COOH is used in homes as food preservative and in producing methyl acetate, acetic anhydride, cellulose acetate etc.

In this article, HF and CH3COOH reaction will be studied.

What is the product of HF and CH3COOH?

In HF + CH3COOH reaction, acetyl fluoride (CH3COF) and water (H2O) are formed .

HF (aq) + CH3COOH = CH3COF + H2O

What type of reaction is HF + CH3COOH?

HF + CH3COOH reaction is an example of a double displacement reaction.

How to balance HF + CH3COOH?

HF + CH3COOH reaction is-

HF (aq) + CH3COOH = CH3COF + H2O

The number of Hydrogen, Carbon, Oxygen and Fluorine atoms on the reactant and product sides are 5, 2, 2 and 1, respectively. Thus the reaction is balanced.

HF + CH3COOH titration

HF + CH3COOH titration is a acid-base titration, because the acidic HF undergoes neutralization with CH3COOH, where HF act as a strong acid, and CH3COOH as a weak base. 

Apparatus used

Burette, Pipette, Beaker, Dropper.

Indicator

Methyl orange is used as an indicator in HF + CH3COOH titration, the pH range of which is 3 (red) to 5 (yellow in basic).

Procedure

  • Take HF with known normality in the burette
  • A particular volume of CH3COOH is taken in a beaker using a pipette
  • Drops of methyl orange are added
  • Titrate against HF
  • A color change from yellow to red indicates an equivalence point. Note it down
  • Repeat the procedure for concordant values
  • Normality of CH3COOH is calculated using equation; NHFVHF=NCH3COOHVCH3COOH

HF + CH3COOH net ionic equation

The net ionic equation of HF + CH3COOH reaction is-

H+ (aq) + F– (aq) + CH3COOH (aq) = CH3COF (l) + H2O (l)

Steps included in deriving ionic equation are as follows;

  • Consider the balanced equation with physical states;
  • HF (aq) + CH3COOH (aq) = CH3COF (l) + H2O (l)
  • Only comparatively strong electrolyte, HF is dissociating into proton and fluoride ions. Then, equation becomes;
  • H+ (aq) + F– (aq) + CH3COOH (aq) = CH3COF (l) + H2O (l)
  • Acetic acid is not completely dissociated as it is a weak electrolyte.
  • No common ions are present to cancel out in this reaction.
  • Thus, net ionic eqution is;
  • H+ (aq) + F– (aq) + CH3COOH (aq) = CH3COF (l) + H2O (l)

HF + CH3COOH conjugate pairs

Conjugate acid-base pairs of HF + CH3COOH reaction are-

HF (l)+ CH3COOH = CH3COOH2+ + F–

  • The conjugate base of HF is F-
  • CH3COOH2 acts as the conjugate acid of CH3COOH

HF and CH3COOH intermolecular forces

The intermolecular forces in HF + CH3COOH are-

  • In HF + CH3COOH, hydrogen bonding is present as an intermolecular force. Because, HF is a polar molecule due to electronegativity differences between H and Br.
  • Strong hydrogen bonding is present in HF.
  • Dipole-dipole interaction is also present, because, CH3COOH is a dipole molecule. 
2 3
Intermolecular interactions between HF and CH3COOH

HF + CH3COOH reaction enthalpy

In HF + CH3COOH reaction, the enthalpy is +99.67 KJ/mol, where-

  • Enthalpy of formation of HF, H1= -320.13 KJ/mol
  • Enthalpy of formation of CH3COOH, H2= -484.13 KJ/mol
  • Enthalpy of formation of CH3COF, H3= -463.71 KJ/mol
  • Enthalpy of formation of H2O, H4=-285.83 KJ/mol
  • Thus, reaction enthalpy is calculated as-
  • Hr = [H4+ H3]-[H1+ H2]
  • = [-285.83 +-463.71]-[-320.13 + -484.13] KJ/mol
  • = +99.67 KJ/mol

Is HF + CH3COOH a buffer solution?

HF + CH3COOH is not a buffer solution, because HF is highly acidic, whereas CH3COOH acts as a base and decreases its acidity.

Is HF + CH3COOH a complete reaction?

HF + CH3COOH is a complete reaction. It is because one molecule of each reactant undergoes a complete reaction to form CH3COF and H2O as products.

Is HF + CH3COOH an exothermic or endothermic reaction?

HF + CH3COOH is an endothermic reaction. It is because the reaction takes place by consuming energy, as indicated by the positive value of reaction enthalpy (+99.67 KJ/mol).

Is HF + CH3COOH a redox reaction?

HF + CH3COOH is not a redox reaction due to no change in the oxidation states of species.

Is HF + CH3COOH a precipitation reaction?

HF + CH3COOH reaction is not precipitation as no precipitate is formed as a product.

Is HF + CH3COOH reversible or irreversible reaction?

HF + CH3COOH is a reversible reaction when liquid HF is used and it reaches equilibrium after a time, t. The equilibrium reaction is-

HF (Liq) + CH3COOH <=> CH3COOH2+ + F–

Is HF + CH3COOH displacement reaction?

HF + CH3COOH is a displacement reaction because the F– and OH– ions are getting displaced in this reaction.

Conclusion

In the reaction of HF and CH3COOH, the acetic acid acts as a basic substance when liquid HF is present as solvent. The reaction attains equilibrium. With aqueous HF, acyl fluoride (CH3COF) and water are formed as a product.