15 Facts on HF + Na2SO3: What, How To Balance & FAQs

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Sodium sulphite, Na2SO3, is a base that easily reacts with strong acids like hydrofluoric acid (HF). Let us know more about the chemical reactivity of HF and Na2SO3.

Na2SO3 is a white crystalline ionic solid soluble in water. It works as an oxygen scavenger and is used in developing photographs. HF is a colorless inorganic gas, completely soluble in water, and used for etching metals and glass.

In this section, let us discuss certain reaction-based facts like the products formed, type of reaction, balancing method etc.

What is the product of HF and Na2SO3?

HF and Na2SO3 interact to produce sodium fluoride (NaF) and water (H2O) along with the evolution of sulphur dioxide (SO2) gas.

 2HF + Na2SO3 ———-> 2NaF + H2O + SO2            

What type of reaction is HF + Na2SO3?

HF + Na2SO3 is an acid-base neutralization reaction where strong acid (HF) and a weak base (Na2SO3) react to form a salt (NaF) and water.

How to balance HF + Na2SO3?

Na2SO3 + HF = NaF + SO2 + H2O

The steps to balance the above equation are:

  • Note the number of each element involved in the reaction, in both the reactant and product side.
ElementsReactant sideProduct side
Na21
F11
S11
O33
H12
Number of elements on each side of the reaction
  • We find that the numbers of sodium and hydrogen atoms in the reactant and product side are unequal.
  • Multiply HF in the reactant side and NaF in the product side by 2 to create a balance.
  • Hence, the overall balanced reaction is given by –
  • Na2SO3 + 2HF = 2NaF + SO2 + H2O

HF + Na2SO3 titration

HF + Na2SO3 system is an acid-base titration and is carried out in the following simple steps.

Apparatus

Burette, burette stand, pipette, measuring cylinders, conical flask, beakers, and volumetric flask.

Indicator

Methyl red is used as the indicator while titrating HF and Na2SO3.

Procedure

  • Na2SO3  solution is prepared by weighing the required amount and dissolving it in distilled water in a volumetric flask.
  • Standardized HF solution is then pipetted out into a clean conical flask.
  • The burette is filled with unknown strength of Na2SO3.
  • Na2SO3 solution is then slowly added from the burette into the conical flask containing standard HF solution.
  • Now add 2 drops of methyl red indicator to the conical flask and stir well.
  • Continue adding  Na2SO3 slowly from the burette into the conical flask until the color of the solution changes from orange to light pink.
  • The color change marks the endpoint and the completion of the neutralization reaction.
  • Note the burette reading and repeat the procedure to get 3 concurrent readings.
  • Using NHF VHF = NNa2SO3VNa2SO3, the strength of Na2SO3 is determined.

HF + Na2SO3 net ionic equation

The net ionic equation between HF + Na2SO3 is –

2H+ (aq) + SO32- (aq)  =  H2O (l) + SO2 (g)   

To derive the net ionic equation, the following steps are followed:

  • Write the balanced chemical equation along with the physical states of each compound involved in the reaction.
  • 2HF (aq) + Na2SO3 (aq) = 2NaF (aq) + H2O (l)+ SO2 (g)
  • Aqueous forms of strong acids, bases, and salts dissociate into ions, whereas substances in liquid and gaseous states do not dissociate.
  • Now, write the complete ionic equation of HF + Na2SO3 as –
  • 2H+ (aq)+ 2F– (aq) + 2Na+ (aq) + SO32- (aq) = 2Na+ (aq) + 2F–  (aq) + H2O (l) + SO2 (g)
  • Cancel the spectator ions (2F–, 2Na+), which appear on both sides of the equation, to arrive at the net ionic equation as –
  • 2H+ (aq)+ SO32- (aq) =  H2O (l) + SO2 (g)

HF+ Na2SO3 conjugate pairs

  • Conjugate pair of acid HF is F–.
  • Basic Na2SO3 does not form a conjugate pair, as no proton is available for donation or acceptance.

HF + Na2SO3 intermolecular forces

HF + Na2SO3 reaction enthalpy

HF + Na2SO3 reaction enthalpy is -1049.7 KJ/mol, and the enthalpy values are listed below:

Reactants and ProductsEnthalpy in KJ/mol
HF-332.63
Na2SO3-13.24
NaF-572.8
H2O-285.8
SO2-296.8
Enthalpy values
  • ∆Hf°(reaction) = ∆Hf°(products) – ∆Hf°(reactants)

= -1728.2  – (-678.5)

= -1049.7 KJ/mol

Is HF + Na2SO3 a buffer solution?

HF + Na2SO3 is not a buffer solution because the reaction mixture contains HF, which is a strong acid, and Na2SO3 is not the salt of the conjugate base of HF.

Is HF + Na2SO3 a complete reaction?

HF + Na2SO3 is a complete reaction, as aqueous hydrofluoric acid completely neutralizes sodium sulphite and the products formed are completely stable.

Is HF + Na2SO3 an exothermic reaction?

HF + Na2SO3 is an exothermic reaction, as the reaction enthalpy is negative due to the formation of ionic NaF.

Is HF + Na2SO3 a redox reaction?

The reaction between HF and Na2SO3 is not a redox reaction, as the oxidation state of the elements remains the same throughout the reaction.

Is HF + Na2SO3 a precipitation reaction?

The reaction HF + Na2SO3 is not a precipitation reaction as the product, sodium fluoride formed, is completely soluble in water.

Is HF + Na2SO3 irreversible reaction?

HF + Na2SO3 is an irreversible reaction because, at equilibrium, the reactants are completely converted into NaF and H2O, along with the liberation of SO2 gas.

Is HF + Na2SO3 a displacement reaction?

The reaction between HF + Na2SO3 is an example of a double displacement reaction; both the cationic component (H and Na) of the reactants is displaced with the respective anionic part (F and SO3).                                                      

Conclusion

HF + Na2SO3 is a typical exothermic and double displacement reaction. Na2SO3 is commercially used as a food preservative, while HF is used as an industrial agent. The product, NaF formed, is an ionic salt that crystallizes in cubic crystals similar to NaBr and NaCl.