Mn(OH)2 acts as an alkali solid, a salt is produced when it reacts with acid. HF is an ionic, polar weak acid with a dipole moment of 1.86 D. Let us see how Mn(OH)2 reacts with HF.
Mn(OH)2 is an antiferromagnet (at 12K) and a strong base (at pH = 9.65) but poorly soluble in water. It is a white solid and converted to a dark solid in UV light exposure due to easy oxidation. HF is a bad electric conductor due to less ionization. It can melt glass and plastics and be used in semiconductor formation.
In this article, we will discuss important facts about HF + Mn(OH)2 chemical reactions such as reaction enthalpy, the heat required, the product formed, the type of reaction, the type of intermolecular forces between their compounds, etc.
What is the product of HF + Mn(OH)2
Manganese difluoride (MnF2) and water (H2O) are formed when manganese hydroxide (Mn(OH)2) reacts with hydrogen fluoride (HF) in which MnF2 is the major product.
2HF + Mn(OH)2 → MnF2 + 2H2O
What type of reaction is HF + Mn(OH)2
HF + Mn(OH)2 is double displacement (salt metathesis), acid – base (neutralization), and an exothermic reaction.
How to balance HF + Mn(OH)2
The unbalanced molecular equation for HF + Mn(OH)2 is.
HF + Mn(OH)2 = MnF2 + H2O
To balance this equation, we should follow the steps given below:
- Here, the number of H and F atoms is not the same on both sides of the reaction. So we will multiply these atoms with some coefficients so that they become equal.
- The total number of H and F atoms on the reactant side is 3 and 1 respectively while on the product side both have 2.
- So, we multiply the HF with a coefficient of 2 on the reactant side and H2O with a coefficient of 2 on the product side. The number of H and F atoms becomes 4 and 2 respectively on both sides of the reaction.
- Similarly, 2 oxygen atoms are present on the reactant side while it is 1 on the product side of the reaction.
- So, we multiply the H2O with a coefficient of 2 on the product side and thus the number of O atoms will be 2 on both sides.
- Finally, the balanced equation is:
- 2HF (aq) + Mn(OH)2 (aq) = MnF2 (aq) + 2H2O (l)
HF + Mn(OH)2 titration
Quantitative estimation of HF is estimated by performing the titration of HF against Mn(OH)2 because HF is acid and Mn(OH)2 acts as a base, so titration of this reaction is carried out through an acid-base reaction.
Apparatus used
A burette, Pipette, measuring flask, glass funnel, clamp stand, measuring cylinder, volumetric flask, and beakers are required for this titration.
Indicator
The phenolphthalein indicator is used because it is a strong acid versus strong base reaction, and its endpoint is colorless to pink.
Procedure
- A standard amount of HF is filled into the burette and at the same time, the aqueous solution of Mn(OH)2 with the respective indicator is taken in a conical flask.
- Then HF is added dropwise into the conical flask very carefully. The constant shaking of the Mn(OH)2 solution with indicator, provides the accurate endpoint.
- The procedure is repeated at least three times until a constant endpoint comes where the indicator changes its color.
- After the successful titration, the strength of hydrogen fluoride is measured by the formula V1N1 = V2N2.
HF + Mn(OH)2 net ionic equation
The net ionic equation of HF + Mn(OH)2 is as follows:
2H+(aq) + 2OH−(aq) = H2O (l)
To get the net ionic equation for HF + Mn(OH)2, we should follow the steps given below:
- Write the general balanced molecular equation.
- 2HF + Mn(OH)2 → MnF2 + 2H2O
- Now the solubility equation for HF + Mn(OH)2 is written by labeling the state or phase (s, l, g or aq) of each substance in the balanced molecular equation of HF + Mn(OH)2.
- 2HF (aq) + Mn(OH)2 (aq) = MnF2 (aq) + 2H2O (l)
- Break all aquatic soluble ionic substances into their corresponding ions to get the balanced ionic equation.
- 2H+ (aq) +2F– (aq) + Mn2+(aq) +2OH−(aq) = Mn2+ (aq)+2F− (aq) +H2O (l)
- To get the net ionic equation, remove spectator ions (F– and Mn2+) from the reactant and product side of the balanced ionic equation.
- Finally, the net ionic equation for HF + Mn(OH)2 is:
- 2H+(aq) + 2OH−(aq) = H2O (l)
HF + Mn(OH)2 conjugate pairs
The conjugate pairs (compounds differ by one proton in their respective pair) in HF + Mn(OH)2 are:
- The conjugate base of HF acid is F–.
- The conjugate base of H2O is OH–.
- Mn(OH)2 and MnF2 do not have their conjugate pairs because both compounds do not contain hydrogen atom that can remove as proton ion.
HF and Mn(OH)2 intermolecular forces
The intermolecular forces that work on HF and Mn(OH)2 are-
- Dipole-dipole force, London dispersion force, and hydrogen bonding are present in HF molecules.
- The electrostatic force of attraction and Coulomb force is present in Mn(OH)2 where Mn+2 is held with two OH-1 ions.
- The electrostatic force of attraction and Coulomb force is present in MnF2 as it is an ionic crystalline compound.
- Hydrogen bonds, dipole-induced dipole forces, and London dispersion forces exist in water due to their strong polar and ionic nature.
HF + Mn(OH)2 reaction enthalpy
The net enthalpy changes of the reaction HF + Mn(OH)2 is –121.53 kJ/mol. The value is gained from the following mathematical calculation.
| Compound | Standard Formation Enthalpy (ΔfH°(Kj/mol)) |
| HF | -272.72 |
| Mn(OH)2 | -695.4 |
| MnF2 | -790.77 |
| H2O | -285.83 |
- ΔHf = ΣΔH°f (products) – ΣΔH°f (reactants) (kJ/mol)
- ΔHf=[2 ΔH°f H2O (g) + ΔH°f MnF2 (aq) )−(2 ΔH°f HF (aq)+ ΔH°f Mn(OH)2 (g) )]
- ΔHf = [ 2*( –285.8) + (-790.77) – (2*( -272.72) -695.4) ] kJ/mol
- ΔHf = -121.53 kJ/mol
Is HF + Mn(OH)2 a buffer solution
HF+ Mn(OH)2 mixture is not a buffer solution because the aqueous solution of HF and Mn(OH)2 does not form the corresponding acid and base, a salt (MnF2) is formed instead.
Is HF + Mn(OH)2 a complete reaction
HF + Mn(OH)2 is a complete reaction because in this reaction HF and Mn(OH)2 are completely consumed and converted into the final product (MnF2) successfully.
Is HF + Mn(OH)2 an exothermic or endothermic reaction
HF+Mn(OH)2 reaction is an exothermic reaction because the net change of enthalpy is negative ((i.e., ΔHf < 0, -121.53 kJ/mol) where the -ve sign interprets the following facts about the reaction:
- 121.53 kJ/mol heat is released by the reactants HF and Mn(OH)2 due to the formation of less energetic salt MnF2.
- Heat emission by HF and Mn(OH)2 rises the energy of surroundings and makes the products stable.
Is HF + Mn(OH)2 a redox reaction
HF + Mn(OH)2 is not a redox reaction because electron acceptance and donation are not carried out during the whole reaction and thus the oxidation state of each element remains the same.
Is HF + Mn(OH)2 a precipitation reaction
HF+ Mn(OH)2 is not a precipitation reaction because the completion of the reaction provides the MnF2 as the main product that is dissolved in reaction media.
Is HF + Mn(OH)2 reversible or irreversible reaction
HF + Mn(OH)2 is an irreversible reaction because the products MnF2 and H2O are stable so they do not need to react with each other to form reactants back.
Is HF + Mn(OH)2 displacement reaction
HF+ Mn(OH)2 is a double displacement reaction because, in this reaction, fluoride ion (F–) and hydroxide ion (OH– ) exchange their places with each other to form new products, MnF2 and H2O.
Conclusion
This article concluded that HF+ Mn(OH)2 is carried out by a double displacement reaction in which heat is released by reactants and stable MnF2 is produced in reaction media. In this reaction, electron transportation does not take place so the redox characteristics are not exhibited by HF+ Mn(OH)2 reaction.
Hi, I am Kavita Singhal, Ph.D. in Chemical Sciences. My subject area of interest is Physical and Inorganic Chemistry with special emphasis on Electrochemistry, Polymer Chemistry, Nano Chemistry, Corrosion Study, Cyclic voltammetry, Supercapacitance, and Organometallic Chemistry.
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