15 Facts on H2SO4 + Na2S2O3: What, How To Balance & FAQs

Sulfuric acid (H2SO4) is a strong dibasic acid and Sodium thiosulphate (Na2S2O3) is a colorless or white crystalline substance. Let us learn about the reaction H2SO4 + Na2S2O3.

Sulfuric acid is also known as hydrogen sulfite, It is a colorless and odorless liquid with high viscosity of about 26.7 cP(200C). Na2S2O3 is a hydrated compound and highly soluble in water. Sodium thiosulphate solution is also known as Hypo solution.

The article will provide some informative discussion over the reaction of H2SO4 + Na2S2O3.

What is the product of H2SO4 and Na2S2O3?

Sulfur(S), sodium sulfate (Na2SO4), and sulfurous acid(H2SO3) are the products of the reaction H2SO4 + Na2S2O3.

Na2S2O3 + H2SO4 → S + Na2SO4 + H2SO3

What type of reaction is H2SO4 + Na2S2O3?

The H2SO4 + Na2S2O3 reaction is a disproportionation reaction where the sulfur of Na2S2O3 is getting oxidized and reduced simultaneously.

S2IIO32-+ 2e → S0 (Reduction of sulfur)

S2IIO32- – 2e → SIVO32- (Oxidation of sulfur)

How to balance H2SO4 + Na2S2O3?

The H2SO4 + Na2S2O3 reaction is balanced using the procedure below:

  • List the Number of atoms of both the reactant and products side
Elements involvedReactants sideProducts side
H22
S33
Na22
O77
Atom Counts
  • The number of atoms is already the same on both sides.
  • So, the equation is balanced.
  • The balanced chemical equation is
  • Na2S2O3 + H2SO4 = S + Na2SO4 + H2SO3

H2SO4 + Na2S2O3 titration

The H2SO4 + Na2S2O3 titration is performed to determine the rate of the reaction by varying the concentration of sodium thiosulphate in the reaction mixture.

Apparatus used:

  • 50 ml beakers
  • 250ml beaker
  • Two measuring cylinders(10ml)
  • Measuring cylinder(100ml)
  • Stopwatch
  • Glass rod

Chemicals used:

  • Dilute H2SO4
  • Na2S2O3 of different molar concentrations (0.1M, 0.2M, 0.3M, 0.4M)
  • Distilled water.

Indicator:

The indicator has no role in the H2SO4 + Na2S2O3 titration process.

Titration Procedure:

  • Prepare 100ml 1M Na2S2O3 by adding 25g of Na2S2O3 in 100 ml distilled water in 250 ml beaker.
  • Take four beakers and prepare 0.1M Na2S2O3 by adding 1ml 1M Na2S2O3 and 9 ml water.
  • Similarly, for 0.2M 2ml Na2S2O3 + 8ml water, for 0.3 M 3ml Na2S2O3 + 7ml water and for 0.4M 4ml Na2S2O3+ 6ml water in four different beakers.
  • Now, label another four 50 ml beakers as 1,2,3,4 and place them on clean white paper.
  • Add 10ml dilute H2SO4 solution in each beaker.
  • Then add 5ml 0.1M Na2S2O3 solution in Beaker-1, start the stopwatch immediately while adding the thiosulphate solution, and stir the solution until a yellowish-white precipitate of sulfur appears, then stop the stopwatch and note the time taken in seconds.
  • Similarly, add 5 ml 0.2, 0.3,0.4 M Na2S2O3 to beaker number 2,3 and 4, respectively, following the first procedure.
  • Note the time taken by other thiosulphate solutions similarly.
  • You will notice that 0.4M Na2S2O3 solution has taken the least time and 0.1M Na2S2O3 has taken the highest time to form the precipitate of sulfur.
  • Note down all the concentrations, volumes and time taken by different solutions carefully in tabular form.
  • Using the values, plot two graphs concentration of Na2S2O3 vs time and concentration of Na2S2O3 vs rate of the reaction.

H2SO4 + Na2S2O3 net ionic equation

The net ionic equation of the H2SO4 + Na2S2O3 reaction is

S2O32- (aq) = S + SO32-(aq)

The net ionic equation is derived by using the following steps

  • Write the balanced chemical equation.
  • Na2S2O3 + H2SO4 S + Na2SO4 + H2SO3
  • Na2S2O3, H2SO4, Na2SO4 and H2SO3 dissociates as:
  • Na2S2O3= 2Na+(aq) + S2O32- (aq)
  • H2SO4= 2H+(aq) + SO42-(aq)
  • Na2SO4= 2Na+(aq) + SO42-(aq)
  • H2SO3=2H+(aq) + SO32- (aq)
  • Add all the above equations to get the complete ionic equation.
  • 2Na+(aq) + S2O32- (aq)+ 2H+(aq) + SO42-(aq) = S +2Na+(aq) + SO42-(aq)+ 2H+(aq) + SO32- (aq)
  • Similar ions 2Na+(aq), 2H+(aq) and SO42-(aq) are cancelled out from both sides.
  • So, the net ionic equation is
  • S2O32- (aq) = S + SO32-(aq).

H2SO4 + Na2S2O3 conjugate pairs

The conjugate pairs of the H2SO4 + Na2S2O3 reaction is:

  • H2SO4 has conjugate base HSO4 and SO42-.
  • H2SO3 is the conjugate acid of Na2S2O3.

H2SO4 and Na2S2O3 intermolecular forces

The intermolecular forces of the H2SO4 + Na2S2O3 are:

  • H2SO4 exhibits dipole-dipole interaction due to the presence of permanent dipole, hydrogen bonding force between electropositive hydrogen and electronegative oxygen and dispersion force.
  • Na2S2O3 possesses ion-dipole interaction force.

H2SO4 + Na2S2O3 reaction enthalpy

The enthalpy of the H2SO4 + Na2S2O3 reaction is = -619.83 KJ/mol.

CompoundsNumber of MolesEnthalpy of formation, ΔH0f (KJ/mol)
H2SO41-814
Na2S2O31-586.2
Na2SO41-1384.48
H2SO31-635.55
S10
ΔH0values of the reactants and products
  • Reaction enthalpy =ΔH0f (reaction) = ΣΔH0f (product) – ΣΔH0f (reactants)
  • ΔH0f (reaction)= [1×(-1384.48) + 1×(0)+ 1×(-635.55)] – [1×(-814) + 1×(-586.2)] KJ/mol.
  • ΔH0f (reaction) = -619.83 KJ/mol.

Is H2SO4 + Na2S2O3 a buffer solution?

H2SO4 + Na2S2O3 does not produce a buffer solution because H2SO4 is a strong acid and so does not form a buffer solution.

Is H2SO4 + Na2S2O3 a complete reaction?

H2SO4 + Na2S2O3 is a complete reaction as further reaction is not possible under normal conditions.

Is H2SO4 + Na2S2O3 an exothermic or endothermic reaction?

H2SO4 + Na2S2O3 reaction is exothermic as the enthalpy change of the reaction is negative( -619.83 KJ/mol).

Is H2SO4 + Na2S2O3 a redox reaction?

H2SO4 + Na2S2O3 is redox because the sulfur of thiosulphate is oxidized from +2 to +4 and reduced from +2 to 0 to form colloidal inorganic sulfur.

Screenshot 20230109 225500
Redox Process of the reaction

Is H2SO4 + Na2S2O3 a precipitation reaction?

H2SO4 + Na2S2O3 is a precipitation reaction because white colloidal sulfur gets precipitated in the reaction mixture.

Is H2SO4 + Na2S2O3 reversible or irreversible reaction?

The H2SO4 + Na2S2O3 reaction is irreversible in nature, and the reverse reaction is not reported.

Is H2SO4 + Na2S2O3 displacement reaction?

H2SO4 + Na2S2O3 is a double displacement reaction because the 2H+ and 2Na+ displace each other in their respective positions in H2SO4 and Na2S2O3.

Screenshot 20230109 221114
Displacement Mechanism

Conclusion

Sodium thiosulphate (Na2S2O3) is tetrahedral and is used in iodometric titration to reduce iodine(I2) to iodide(I). Sulfuric acid has got enormous chemical and industrial applications, that is why it is referred as the King of Chemicals.