Mg(OH)2 is a metal hydroxide, also is known as “milk of magnesia” and H2SO4 (sulfuric acid) is a strong mineral acid. Let us examine how they react in detail.
Mg(OH)2 is an inorganic compound with low water solubility (Ksp = 5.61 x 10-12) and occurs in the form of the mineral brucite. H2SO4 is corrosive and a powerful dehydrating agent. Mg(OH)2 is a base that will react with an acid (H2SO4) in this case.
This article will deal with the reaction type, products, enthalpy, and molecular forces associated with the reaction of H2SO4 and Mg(OH)2.
What is the product of H2SO4 and Mg(OH)2
MgSO4 (Magnesium sulfate) and water molecules are produced in the reaction of H2SO4 + Mg(OH)2.
Mg(OH)2 + H2SO4 → MgSO4 + H2O
What type of reaction is H2SO4 + Mg(OH)2
H2SO4 + Mg(OH)2 is a neutralization reaction. H2SO4 is an acid that neutralizes the base Mg(OH)2 to form a salt.
How to balance H2SO4 + Mg(OH)2
H2SO4 + Mg(OH)2 equation is balanced by the following steps.
Mg(OH)2 + H2SO4 → MgSO4 + H2O
| Elements involved | Reactants side | Product side |
|---|---|---|
| Mg | 1 | 1 |
| H | 4 | 2 |
| S | 1 | 1 |
| O | 6 | 5 |
- The elements involved in the reaction are counted in both the reactants and the products.
- By using stoichiometric coefficients, the charges and the number of elements are equated. Coefficient 2 is added before H2O.
- Thus, the balanced equation is
- Mg(OH)2 + H2SO4 → MgSO4 + 2H2O
H2SO4 + Mg(OH)2 titration
H2SO4 + Mg(OH)2 is an example of acid-base titration. This comes under strong acid vs strong base titration.
Apparatus
Beaker, funnel, measuring cylinder, volumetric flask, burette, pipette, conical flask
Indicator
The phenolphthalein indicator is used for this titration.
Procedure
- The standard solution of Mg(OH)2 is prepared in a volumetric flask. The Mg(OH)2 solution is poured into the burette with the help of a funnel.
- 10 ml of the unknown solution of H2SO4 is taken into a conical flask and 2-3 drops of phenolphthalein is added to it.
- Mg(OH)2 is added dropwise from the burette into the conical flask with constant mixing.
- Light pink color appears at the endpoint of the reaction. The concordant readings are taken for the calculation of the concentration of the unknown H2SO4 solution.
H2SO4 + Mg(OH)2 net ionic equation
The net ionic equation for H2SO4 + Mg(OH)2 is
Mg(OH)2(s) + 2H+(aq) → Mg2+(aq) + 2H2O(l)
The net ionic equation is derived using the below steps-
- The equation is balanced in the first step.
- Mg(OH)2 + H2SO4 → MgSO4 + 2H2O
- The states of the reactants and the products are shown.
- Mg(OH)2(s) + H2SO4(aq) → MgSO4(aq) + 2H2O(l)
- The strong-electrolytes are split into their corresponding ions. H2O will not split as it is a weak electrolyte.
- Mg(OH)2(s) + 2H+(aq) +SO42-(aq) → Mg2+(aq)+ SO42-(aq) + 2H2O(l)
- The common ions are crossed out and thus net ionic equation is obtained.
- Mg(OH)2(s) + 2H+(aq) → Mg2+(aq) + 2H2O(l)
H2SO4 + Mg(OH)2 conjugate pairs
H2SO4 + Mg(OH)2 will make a conjugate pair as
H2SO4 + OH– = SO42- + H2O
- SO42- is formed as the conjugate base of H2SO4 (an acid).
- H2O is the conjugate acid of OH– (hydroxide ion) formed by accepting H+ ion.
H2SO4 and Mg(OH)2 intermolecular forces
- Ionic interactions are present in Mg(OH)2 as the compound is ionic.
- Dipole-dipole interactions, hydrogen bonding, and dispersion forces are found in H2SO4 molecules.
H2SO4 + Mg(OH)2 reaction enthalpy
H2SO4 + Mg(OH)2 reaction enthalpy is -96.8 KJ/mol.
| Products and reactants | Enthalpy in KJ/mol |
|---|---|
| H2O | -285.8 |
| MgSO4 | -1264.2 |
| Mg(OH)2 | -925 |
| H2SO4 | -814 |
- The enthalpy is calculated using the formula,
- ∆Hf°(reaction) = ∆Hf°(products) – ∆Hf°(reactants)
- = -1835.8 – (-1739.0) KJ/mol
- = -96.8 KJ/mol
Is H2SO4 + Mg(OH)2 a buffer solution
H2SO4 + Mg(OH)2 will not form a buffer as strong acid (H2SO4) and strong base [Mg(OH)2] are used in this reaction.
Is H2SO4 + Mg(OH)2 a complete reaction
H2SO4 + Mg(OH)2 is a complete reaction as the reactants get completely consumed to form the products.
Is H2SO4 + Mg(OH)2 an exothermic or endothermic reaction
H2SO4 + Mg(OH)2 is an exothermic reaction due to the liberation of heat in the process. The reaction is negative for the reaction.
Is H2SO4 + Mg(OH)2 a redox reaction
Mg(OH)2 + H2SO4 reaction is not a redox reaction as the oxidation states of elements are the same throughout.
Is H2SO4 + Mg(OH)2 a precipitation reaction
Mg(OH)2 + H2SO4 is not a precipitation reaction due to the products formed (MgSO4) is completely soluble and no precipitate formation takes place.
Is H2SO4 + Mg(OH)2 reversible or irreversible reaction
H2SO4 + Mg(OH)2 is an irreversible reaction as the backward reaction is not feasible and the products obtained will not react with each other to give the reactants.
Is H2SO4 + Mg(OH)2 displacement reaction
H2SO4 + Mg(OH)2 is a double displacement reaction where,
Mg(OH)2 + H2SO4 → MgSO4 + H2O
- Mg being more reactive displaces the hydrogen from its sulfate salt and forms MgSO4.
- H+ further combines with OH– to form H2O.
Conclusion
The reaction H2SO4 + Mg(OH)2 is exothermic and irreversible. MgSO4 (Epsom salt) is used to control the low levels of magnesium in human blood. Mg(OH)2 is used as an antacid to cure indigestion and is used in waste water management.
Hi! I am Lubna Khan. I have done my Postgraduation in Chemistry at Jamia Millia Islamia, New Delhi. I have been in academia for years and have always welcomed new opportunities, lifestyles, and cultures coming my way.
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