15 Facts on H2SO4 + NaH2PO4: What, How to Balance & FAQs

H2SO4 is a mineral acid, and NaH2PO4 is a sodium salt. Let us venture through the chemical reaction between H2SO4 and NaH2PO4 in depth.

The reaction between H2SO4 and NaH2PO4 is a multistep reaction. Concentrated H2SO4 is a highly corrosive acid. Pure Sulfuric acid is colorless and oily in nature. NaH2PO4, also known as Monosodium Phosphate is an industrial chemical. It is found in anhydrous, mono and dihydrate forms.

In this article, we will go through some important aspects, such as the reaction type, balancing equation, reaction enthalpy, ionic equation and some other crucial points.

What is the product of H2SO4 and NaH2PO4?

Sodium Bisulfate (NaHSO4), Sodium Sulfate (Na2SO4) and Phosphoric acid (H3PO4) are formed when H2SO4 reacts with NaH2PO4 .

  • H2SO4 + NaH2PO4 ==> NaHSO4 + H3PO4 (1st step)
  • NaHSO4 + NaH2PO4 <==> Na2SO4 + H3PO4  (2nd step)

What type of reaction is H2SO4 + NaH2PO4?

H2SO4 + NaH2PO4 is a reversible reaction, a type of stepwise reaction, since it consists of two steps.

How to balance H2SO4 + NaH2PO4?

The reaction for H2SO4 + NaH2PO4 is balanced using the following steps.

H2SO4 + NaH2PO4 ==> NaHSO4 + H3PO(1st step)

NaHSO4 + NaH2PO4 <==> Na2SO4 + H3PO(2nd step)

  • The number of atoms of reactants and products side must be noted down.
  • For the 1st step, the no. of atoms of Na, H, S and O on LHS and RHS is same.
ElementNo. of atoms on LHS (reactant side)Number of atoms on RHS (Product Side)
Balancing chemical equation
  • For the 2nd step also, the no. of atoms of Na, H, S and O are same.
ElementNo. of atoms on LHS (reactant side)Number of atoms on RHS (Product Side)
Balancing chemical equation
  • It is observed that the equations are already balanced since the number of atoms on LHS and RHS for both equations is the same, and there is no need to multiply by the stoichiometric coefficient.
  • Finally, the balanced equations are:
  • H2SO4 + NaH2PO4 ==> NaHSO4 + H3PO
  • NaHSO4 + NaH2PO4 <==> Na2SO4 + H3PO

H2SO4 + NaH2PO4 titration

Titration is not feasible since the reaction H2SO4 + NaH2PO4 comprises multiple steps.

H2SO4 + NaH2PO4 net ionic equation

The net ionic equations for H2SO4 + NaH2PO4 are:

For 1st step of reaction

  • 2H+(aq)+SO42-(aq) +Na+(aq)+ H2PO4(aq) ==> Na+(aq) +HSO4(aq)+3H+(aq)+ PO43-(aq)

For 2nd  step of reaction

  • Na+(aq) +HSO4(aq)+ Na+(aq)+ H2PO4(aq) <==> 2Na+(aq)+ SO42-(aq)+ 3H+(aq)+ PO43-(aq)

Following steps are used to derive the net ionic equations.

  • Firstly, write the chemical equations with the physical states of the chemical species.
  • H2SO4(aq) + NaH2PO4(aq) ==> NaHSO4(aq) + H3PO4(aq)  (1st step)
  • 2H+(aq)+SO42-(aq) +Na+(aq)+ H2PO4(aq) ==> Na+(aq) +HSO4(aq)+3H+(aq)+ PO43-(aq)
  • NaHSO4(aq) + NaH2PO4(aq) <==> Na2SO4(aq) + H3PO4(aq)  (2nd step)
  • Na+(aq) +HSO4(aq)+ Na+(aq)+ H2PO4(aq) <==> 2Na+(aq)+ SO42-(aq)+ 3H+(aq)+ PO43-(aq)
  • Thus, there will not be a net ionic reaction for such type of multistep reaction since the second step is not unidirectional.

H2SO4 + NaH2PO4 conjugate pairs

  • H2SO4 gives rise to H3O+ (Conjugate acid) and HSO4 (Conjugate base) in the presence of water.
  • NaH2PO4 produces H2PO4 as its conjugate base.

H2SO4 and NaH2PO4 intermolecular forces

H2SO4 + NaH2PO4 reaction enthalpy

There is no literature available about enthalpy for the reaction of H2SO4 and NaH2PO4.

Is H2SO4 + NaH2PO4 a buffer solution?

H2SO4 + NaH2PO4 is not a buffer solution since H2SO4 is a strong acid and NaH2PO4 is salt of H3PO4 with strong base NaOH which are unable to maintain the pH.

Is H2SO4 + NaH2PO4 a complete reaction?

H2SO4 + NaH2PO4 is not a complete reaction since the reaction is not reaching equilibrium in the 2nd step:

NaHSO4(aq) + NaH2PO4(aq) <==> Na2SO4(aq) + H3PO4(aq) .

Is H2SO4 + NaH2PO4 an exothermic or endothermic reaction?

There is no literature elaborating exothermic or endothermic nature for the reaction of H2SO4+NaH2PO4.

Is H2SO4 + NaH2PO4 a redox reaction?

H2SO4 + NaH2PO4 is not a redox reaction because there is no change in the oxidation state of the chemical species present in the reaction.

Is H2SO4 + NaH2PO4 a precipitation reaction?

H2SO4 + NaH2PO4 is not a precipitation reaction because acidic pH (due to H2SO4) will increase the solubility of NaH2PO4 , whose anion dihydrogen phosphate (H2PO4 ) is the conjugate base of a weak acid.

Is H2SO4 + NaH2PO4 reversible or irreversible reaction?

H2SO4 + NaH2PO4 is reversible in nature because it is a multistep reaction which attains dynamic equilibrium.

Is H2SO4 + NaH2PO4 displacement reaction?

H2SO4 + NaH2PO4 is not a displacement reaction because it is reversible in nature.


The reaction between H2SO4 + NaH2PO4 attains equilibrium but the forward and reverse reaction keep on going at the same rate. Sodium Sulfate is used in Kraft process of paper pulping. While Sodium Bisulfate is used in lowering the pH value and Phosphoric acid used in fertilizers.

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