15 Facts on HBr + NaH2PO4: What, How To Balance & FAQs

NaH₂PO₄ is a basic salt of sodium produced from NaOH or NaHCO₃ and it can easily react with HBr. Let us explore the mechanism of the reaction between HBr and NaH₂PO₄.

NaH₂PO₄ or monosodium phosphate is a basic salt that can be prepared from sodium phosphate where two sodium replaced by two H atoms. In NaH₂PO₄, central P is attached with one double-bonded O, two -OH, and one -O with a single bond. In HBr, there is a covalent bond present between H and Br.

Although there will be some parameters and limitations present in this reaction. Now we can discuss more the mechanism of the reaction like enthalpy, redox reaction, intermolecular force, conjugate pairs, etc with an explanation in the following part of the article.

1. What is the product of HBr and NaH₂PO₄?

Sodium bromide and phosphoric acid are formed as major products when HBr and NaH₂PO₄ were reacted together.

HBr + NaH₂PO₄ = NaBr + H₃PO₄

2. What type of reaction is HBr + NaH₂PO₄?

HBr + NaH₂PO₄ reaction is an example of a double displacement reaction, and a redox and precipitation reaction. It is also a salt metathesis reaction along with an acid production reaction.

3. How to balance HBr + NaH₂PO₄?

HBr + NaH₂PO₄ = NaBr + H₃PO₄, we have to balance the equation in the following way-

• First, we label all the reactants and products by A, B, C, and D as there are four different molecules obtained for this reaction and the reaction looks like this,
• A HBr + B NaH₂PO₄ = C NaBr + D H₃PO₄
• Equating the coefficients for the same type of elements by rearranging them.
• After the rearrangement of coefficients of the same elements by their stoichiometric proportion, we get,
• H = A = 2B = 2C = D, Br = A = C, Na = B = C, P = B = D, O = 4B = 4D
• Using the Gaussian elimination and equating all the equations we get, A = 1, B = 1, C = 1, and D = 1
• The overall balanced equation will be,
• HBr + NaH₂PO₄ = NaBr + H₃PO₄

4. HBr + NaH₂PO₄ titration

To estimate the quantity of phosphate or bromide we can perform a titration between NaH₂PO₄ and HBr_.

Apparatus used

We need a burette, conical flask, burette holder, volumetric flask, and beakers for this titration.

Titre and titrant

HBr versus NaH₂PO₄, HBr acts as a titrant taken in the burette and the molecule to be analyzed is NaH₂PO₄ taken in a conical flask.

Indicator

The whole titration is done in an acidic medium or acidic pH so the best suitable indicator will be phenolphthalein which gives perfect results for this titration at given pH.

Procedure

The burette is filled with standardized HBr. NaH₂PO₄ is taken in a conical flask along with respective indicators. HBr is added dropwise to the conical flask and the flask is shaken constantly. After a certain time, when the endpoint arrives, the indicator changes its color and the reaction is done.

We repeat the titration several times for better results and then we estimate the bromide or phosphate quantity by the formula V₁S₁ = V₂S₂.

5. HBr+ NaH₂PO₄ net ionic equation

The net ionic equation between HBr + NaH2PO4 is as follows,

H⁺(aq.) + Br^–(aq.) + Na⁺(aq.) + 2H⁺(aq.) + PO₄^3-(aq.)  = Na⁺(aq.) + Br^–(aq.) + 3H⁺(l) + PO₄^3-(l)

To derive the net ionic equation, the following steps are required,

• HBr will be ionized as proton and bromide as it is strong acid and electrolyte.
• After that NaH₂PO4 also dissociates into Na⁺ and H⁺ ions and PO₄^– as counter ion as it is also a strong electrolyte
• In the product part, NaBr is ionized into Na⁺ and Br^–as it is a strong electrolyte and salt.
• After that phosphoric acid can be ionized into three protons and phosphate ions as it is a strong acid and the dissociation constant is low.

6. HBr+ NaH₂PO₄ conjugate pairs

HBr+ NaH₂PO₄ reaction has the following pairs,

• Conjugate pair of HBr = Br^–
• Conjugate pair of PO₄^3- = HPO₄^2-
• Conjugate pair of HPO₄^2- = H₂PO₄^–
• Conjugate pair of H₂PO₄^– = H₃PO₄

7. HBr and NaH₂PO4 intermolecular forces

HBr+ NaH₂PO₄ reaction has the following intermolecular forces,

• The intermolecular force present in HBr is the strong electrostatic force between protons and bromide ions.
• In NaH₂PO₄ there are electronic interactions and coulumbic force present.
• In NaBr ionic interaction is present and for phosphoric acid H-bonding is present.

Molecule	Acting force
HBr	Electrostatic, van der waal’s Dipole interaction
NaH2PO4	Strong electrostatic force and ionic interaction, Coulumbic force
NaBr	Electrostatic force, ionic interaction,
H3PO4	Covalent force, H-bonding

8. HBr + NaH₂PO₄ reaction enthalpy

HBr + NaH₂PO₄ reaction enthalpy is -1227.66 KJ/mol which can be obtained by the formula: enthalpy of products – enthalpy of reactants.

Molecule	Enthalpy (KJ/mol)
NaH2PO4	-369
HBr	-36.45
NaBr	-361.41
H3PO4	-1271.7

9. Is HBr + NaH₂PO₄ a buffer solution?

HBr + NaH₂PO_4, reaction formed the buffer solution of the mixture of H₃PO₄ and NaBr can control the pH even after adding a base.

10. Is HBr + NaH₂PO₄ a complete reaction?

HBr + NaH₂PO₄ reaction is complete because it gives two major ones: an electrolytic salt and another phosphoric acid.

11. Is HBr + NaH₂PO₄ an exothermic or endothermic reaction?

HBr + NaH₂PO₄ reaction is exothermic in terms of thermodynamics first law. This reaction released more energy and temperature to the surroundings, where δH is always negative.

12. Is HBr + NaH₂PO₄ a redox reaction?

HBr + NaH₂PO₄ reaction is a redox reaction because in this reaction bromine gets reduced and also phosphorus gets oxidized. Where HBr acts as a reducing agent and NaH₂PO₄ acts as an oxidizing agent.

13. Is HBr + NaH₂PO₄ a precipitation reaction

HBr + NaH₂PO₄ reaction is a precipitation reaction because phosphoric acid gets precipitated in the solution at certain pH.

14. Is HBr + NaH₂PO₄ reversible or irreversible reaction?

HBr+ NaH₂PO₄ reaction is irreversible because it produced acid. Due to the production of the acid molecule the equilibrium shifts towards the right-hand side only or forward directions.

HBr + NaH₂PO₄ —-> NaBr + H₃PO₄

15. Is HBr + NaH₂PO₄ displacement reaction?

The reaction between HBr + NaH₂PO₄ is an example of a double displacement reaction. Because in the above reaction H⁺ was displaced by Na⁺ from HBr and Na is also displaced by H⁺  and attached to Br.

Conclusion

The reaction between HBr and NaH₂PO₄ is important because it can produce phosphoric acid. So, the reaction is very important in the industrial aspect. The reaction is also important for the production of sodium bromide salt.