HBr is a halogen acid and Al(OH)3 is an ionic compound. Let us find out the several aspects of the reaction between HBr and Al(OH)3.
Hydrobromic acid with the chemical formula HBr is an aqueous solution of hydrogen bromide gas. Aluminium hydroxide or Al(OH)3 appears as an amorphous white powder insoluble in water. Al(OH)3 is amphoteric as it can react with both an acid as well as a base.
As we proceed, we will understand all the key features of the reaction between HBr and Al(OH)3 clearly.
What is the product of HBr and Al(OH)3
Aluminium bromide (chemical formula AlBr3) and water (chemical formula H2O) are the products of the reaction HBr + Al(OH)3.
HBr (aq) + Al(OH)3 (s) = AlBr3 (aq) + H2O (l)
What type of reaction is HBr and Al(OH)3
HBr + Al(OH)3 falls under the neutralization reaction category where HBr is acting as an acid and Al(OH)3 is acting as a base.
How to balance HBr and Al(OH)3
The unbalanced equation for the reaction HBr + Al(OH)3 is
HBr + Al(OH)3 = AlBr3 + H2O
To get the balanced equation, we should follow the below steps.
- Here, except for Al, the number of H, Br, and O atoms are not the same on left hand side and right hand side of the equation.
- The number of Br atoms, before and after the reaction is 1 and 3, respectively.
- HBr + Al(OH)3 = AlBr3 + H2O
- We will multiply HBr with 3 so that number of Br atoms becomes same.
- 3HBr + Al(OH)3 = AlBr3 + H2O
- Now, the number of H atoms, on left hand side and right hand side is 6 and 2, respectively.
- We will multiply H2O with 3 so that the number of H atoms becomes 6 on both sides.
- Under this condition, the number of O atoms is 3 on both sides.
- Finally, the balanced equation is
- 3HBr + Al(OH)3 = AlBr3 + 3H2O
HBr and Al(OH)3 titration
To determine the amount of the insoluble salt Al(OH)3 by HBr, we have to do back titration.
Apparatus
Volumetric flask, conical flask, Pipette, burette, measuring cylinder, and titration stand
Indicator
An ideal indicator is phenolphthalein for titration of HBr by NaOH.
Procedure
- Take Al(OH)3 sample in a conical flask and add HBr of known volume and concentration using a pipette.
- Stir it properly and add 2-3 drops of the indicator.
- Titrate the excess HBr with NaOH solution of known concentration taken in a burette till the color changes to light pink.
- Repeat the process 2-3 times to avoid errors and note down each burette reading.
- Finally, the amount of unreacted HBr is determined using the formula S1V1 = S2V2.
- Once we know the amount of unreacted HBr, the amount of HBr reacted with Al(OH)3 is determined.
- From the mole ratio of HBr and Al(OH)3 in the balanced equation, the amount of insoluble salt Al(OH)3 is determined.
HBr and Al(OH)3 net ionic equation
The net ionic equation for HBr + Al(OH)3 is shown below.
3H+ (aq) + Al(OH)3 (s) = Al3+ (aq) + 3H2O(l)
Follow the steps mentioned below to get the net ionic equation.
- Only HBr and AlBr3 being soluble ionic compounds can dissociate into cations and anions.
- The complete ionic equation is written as follows.
- 3H+ (aq) + 3Br– (aq) + Al(OH)3 (s) = Al3+ (aq) + 3Br– (aq) + 3H2O (l)
- Br– ion, the only spectator ion here, will be canceled from both sides.
- After canceling the spectator ions from both sides, we can get the net ionic equation shown below.
- 3H+ (aq) + Al(OH)3 (s) = Al3+ (aq) + 3H2O(l)
HBr and Al(OH)3 conjugate pairs
HBr and Al(OH)3 conjugate pairs are
- Bromide ion (Br–) is the conjugate base of the acid HBr.
- The conjugate pair for Al(OH)3 is impossible as it is a metal hydroxide.
HBr and Al(OH)3 intermolecular forces
- Dipole-dipole interaction is present in HBr molecule.
- The electrostatic force of attraction is present in Al(OH)3 molecule as it is ionic in nature.
HBr and Al(OH)3 reaction enthalpy
For HBr + Al(OH)3, the reaction enthalpy value is -100.5 kJ/mole. It is calculated using the values given in the table below.
| Compounds | Enthalpy of formation (ΔHf°) in kJ/mole |
|---|---|
| HBr (aq) | -119.6 |
| Al(OH)3 (s) | -1293.1 |
| AlBr3 (aq) | -895.0 |
| H2O(l) | -285.8 |
- Reaction Enthalpy = ΣΔHf°(products) – ΣΔHf° (reactants)
- = [(-895.0) + (-285.8)*3] – [(-119.6)*3 + (-1293.1)] KJ/mol
- = -100.5 KJ/mol
Is HBr and Al(OH)3 a buffer solution
HBr + Al(OH)3 is not a buffer solution as HBr being a strong acid dissociate completely in solution.
Is HBr and Al(OH)3 a complete reaction
HBr + Al(OH)3 is a complete reaction because after the formation of AlBr3 and H2O as products there is no further reaction.
Is HBr and Al(OH)3 an exothermic or endothermic reaction
HBr + Al(OH)3 is exothermic in nature as -100.5 kJ/mole heat is released during the reaction.
Is HBr and Al(OH)3 a redox reaction
HBr + Al(OH)3 is not a redox reaction as oxidation states are the same for all the atoms H, Br, Al, and O before and after the reaction.
Is HBr and Al(OH)3 a precipitation reaction
HBr + Al(OH)3 is not a precipitation reaction as the product AlBr3 is a water-soluble compound, and the other product is water.
Is HBr and Al(OH)3 reversible or irreversible reaction
HBr + Al(OH)3 is an irreversible reaction as it is a unidirectional reaction.
Is HBr and Al(OH)3 displacement reaction
HBr + Al(OH)3 is a double displacement reaction as Br– and HO– ions are interchanged between two reactant molecules, HBr and Al(OH)3.
Conclusion
In conclusion, one of the products AlBr3 appears as a white to pale orange solid used as a catalyst for the Friedel-Crafts alkylation reaction. It is an electron deficient compound as its octet is not complete.
Hello, I am Tuluma Das, Completed my Ph.D. in Organic Chemistry from the Indian Association for the Cultivation of Science. I have a total of 9 years of research experience including a Ph.D. and Postdoc and 3 years of teaching experience. I have published 7 papers so far in international journals. Let’s connect through Linkedin :