The reaction between HF and Hg(OH)2 is a hydrolysis reaction as HF is a weak acid and Hg(OH)2 is a weak base. Let us discuss how HF and Hg(OH)2 react.
In the anhydrous state, HF does not show acidic properties, thus anhydrous hydrogen fluoride does not corrode metals (Potassium is an exception). Hg(OH)2 is used as fertilizer as well as a food preservative. Hg(OH)2 has the ability to absorb moisture from nature.
In this article, we will deal with the chemical characteristics of the reaction between HF and Hg(OH)2 and their properties.
What is the product of HF and Hg(OH)2?
Mercuric fluoride(HgF2) and water( H2O) are formed when HF and Hg(OH)2 react. The concentrated solution of HF is a weak acid which when reacts with weak base Hg(OH)2 undergoes hydrolysis to give mercuric fluoride (HgF2) and water( H2O) as products.
2HF + Hg(OH)2 = HgF2 + 2H2O
What type of reaction is HF + Hg(OH)2?
HF + Hg(OH)2 is an example of a displacement reaction. In this reaction, the anionic part of the reactant (F– and OH–) is interchanged with the cationic part of the reactant.
How to balance HF + Hg(OH)2?
The following steps are used to balance the unbalanced chemical reaction:
HF + Hg(OH)2→ HgF2 + H2O,
- Designate each reactant and product in the reaction with the variables (a, b, c, and d) to represent unknown coefficients.
- a HF + b Hg(OH)2 → c HgF2 + d H2O
- Now, write the relevant quantity of the coefficient of reactants and products.
- H = a + 2b = 2d, F = a = 2c, O = 2b = d, Hg = b = c
- By using the Gaussian elimination method, determine the value of all the variables and coefficients, which are as follows:
- a = 2, b = 1, c = 1, and d = 2
- Thus, the final balanced equation is,
- 2HF + Hg(OH)2 → HgF2 + 2H2O
HF + Hg(OH)2 titration
HF + Hg(OH)2 titration is not possible as Hg(OH)2 does not obtain in the pure form.
HF + Hg(OH)2 net ionic equation
The net ionic equation of HF + Hg(OH)2 is :
2H+(aq) + Hg(OH)2(s) = Hg2+(s) + 2H2O(l)
The net ionic equation is derived by using the following steps:
- First, write the balanced chemical reaction with the physical states of each reactant and product.
- HF (aq) + Hg(OH)2 (s) = HgF2 (s) + 2 H2O (l)
- Then, split the electrolytes into ions:
- 2H+(aq) + 2F–(aq) + Hg(OH)2(s) = Hg2+(s) + 2F– (s) + 2H2O(l)
- Now, cancel out the spectator ions (fluoride ions) from both sides of the ionic equation to obtain the net ionic equation as:
- 2H+(aq) + Hg(OH)2(s) = Hg2+(s) + 2H2O(l)
HF + Hg(OH)2 conjugate pairs
In the reaction between HF and Hg(OH)2, there are two pairs of conjugates that differ by a proton.
- The conjugate base of HF= F–
- The conjugate acid of water, H2O = OH –
- The conjugate pair for Hg(OH)2 is not possible as it is not present in pure isolated form.
HF and Hg(OH)2 intermolecular forces
HF + Hg(OH)2 reaction has the following intermolecular forces:
- Due to the polar nature of the HF molecule, dipole–dipole intermolecular forces are present. Interionic attractions are present in HF molecules in an aqueous solution only.
- Hg(OH)2 forms a weak hydrogen bond.
- HgF2 is ionic thus, an electrostatic force of attraction is present.
- H2O molecule has intermolecular hydrogen-bonding.
HF + Hg(OH)2 reaction enthalpy
The reaction enthalpy for HF + Hg(OH)2 is 499.6 kJ/ mol. The enthalpy of formation of each reactant and product is as follows :
- Enthalpy of formation of HF = -273 kJ/mole
- Enthalpy of formation of Hg(OH)2 = – 355.2 kJ/ mol
- Enthalpy of formation of HgF2= 170 kJ/mol
- Enthalpy of formation of H2O = – 285.8 kJ/mol
- Reaction enthalpy (ΔHf) = Standard enthalpy of formation of product – Standard enthalpy of formation of reactant
Thus, ΔHf = [(170) + 2*(-285.8)] – [(-355.2) + 2*(-273)]
ΔHf = [ -401.6] – [-901.2]
ΔHf = 499.6 kJ/mol
Is HF + Hg(OH)2 a buffer solution?
HF + Hg(OH)2 acts as a buffer solution because HgF2 and water both can control the pH of the solution as it has both acidic and basic properties at certain pH values.
Is HF + Hg(OH)2 a complete reaction?
HF + Hg(OH)2 is a complete reaction and proceeds only in one direction as the resulting HgF2 is insoluble in water.
Is HF + Hg(OH)2 an exothermic or endothermic reaction?
HF + Hg(OH)2 is an endothermic reaction as it has a positive enthalpy of reaction which is given by 499.6 kJ/mol.
Is HF + Hg(OH)2 a redox reaction?
HF + Hg(OH)2 is not a redox reaction as the oxidation states of different elements or ions do not change as the reactants convert into products.
Is HF + Hg(OH)2 a precipitation reaction?
HF + Hg(OH)2 is a precipitation reaction that forms a solid precipitate of mercury fluoride (HgF2) which is insoluble in water.
Is HF + Hg(OH)2 reversible or irreversible reaction?
HF + Hg(OH)2 is an irreversible reaction. Because the products HgF2 and H2O will not convert back into the reactants as HgF2 is insoluble in water.
Is HF + Hg(OH)2 displacement reaction?
HF + Hg(OH)2 is an example of a double displacement reaction. In a double displacement reaction, anionic counterparts of the reactant are exchanged with the respective cationic part of the reactants.
Conclusions
The reaction between HF + Hg(OH)2 gives hygroscopic white cubic crystals of mercuric fluoride (HgF2). In this reaction, a weak acid (HF) and a weak base (Hg(OH)2 ) react with each other to give a neutral solution. This neutralization reaction is not used to determine the relative strength of HF.
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