Aluminium and Sodium Hydroxide Reaction | Al + NaOH
Aluminium reacts with aqueous sodium hydroxide (NaOH) and produce sodium aluminate (NaAlO2) and hydrogen gas as products. NaAlO2 is soluble in water. Aluminium reacts with bases because Aluminium is an amphoteric element.
written by: Heshan Nipuna, updated on: 27/05/2020
Al(s) + NaOH(aq) + H2O(l) → NaAlO2(aq) + H2(g)
For this reaction, water is contributed as a reagent. This is a redox reaction. Aluminium is oxidized to its +3 oxidation state and oxidation number of hydrogen atom is increased from +1 to 0.
Sometimes this reaction is expressed as below.
Al(s) + NaOH(aq) + H2O(l) → Na[Al(OH)4](aq) + H2(g)
Balanced equations of aluminium and sodium hydroxide reaction
Because this reaction is a redox reaction, we can follow steps of redox reactions balancing. Balanced equations for both types are mentioned below.
2Al(s) + 2NaOH(aq) + 2H2O(l) → 2NaAlO2(aq) + 3H2(g)
2Al(s) + 2NaOH(aq) + 6H2O(l) → 2Na[Al(OH)4](aq) + 3H2(g)
How to balance chemical equations of Al and NaOH reaction? step by step
Al + NaOH + H2O → NaAlO2 + H2
- Write down oxidation numbers of each element in the left side and right side.
- Identify which elements are oxidized and reduced. Aluminum is oxidized and hydrogen atoms in the water and NaOH are oxidized.
- balance number of atoms of oxidized and reduced. There are one Al in both left side and right side. Therefore Al atoms should not be equalized. Also, there are, three hydrogen atoms in the left side and two in right side. Now, we need to balance number of hydrogen atoms in right side and left side.
Balancing hydrogen atoms in right side and left side
- Make two water molecules in the left side. Then total hydrogen atoms in the left side will become five. It is not yet balanced hydrogen atoms in right side and left side.
- Make three hydrogen molecules in the right side. Now, there are six hydrogen atoms in the right side. Still, hydrogen atoms are not balanced.
- Make two NaOH in the left side. Then total hydrogen atoms in the left side will become six now. Finally, number of hydrogen atoms in both sides are equal.
oxidation number differences in oxidation and reduction
- Aluminium is oxidized from 0 to +3. Therefore, oxidation number difference of oxidation is 3.
- There are six hydrogen atoms with +1 oxidation state. In the right side, there are six hydrogen atoms with 0 oxidation state. Therefore oxidation number difference of reduction is 6.
Exchange oxidation number differences between oxidized and reduced atoms
When you exchange oxidation number differences between oxidized and reduced atoms, take the simplest ratio of oxidation number differences.
- In this reaction, oxidation number differences of oxidation and reduction is 3 to 6 (3:6). Therefore, simplest ratio is 1 to 2 (1:2)
- Exchange ratios as following.
Questions asked by students.
As aluminium, what are the other metals which can react with aqueous NaOH?
Beryllium, zinc, lead and tin react with aqueous NaOH.
Is the reaction of aluminium and sodium hydroxide corrosive?
Aluminium is protected due to its oxide layer exists on its surface. But, due to amphoteric characteristics of aluminium, it tends to react with sodium hydroxide. Aluminium oxide layer dissolves in aqueous sodium hydroxide solution.
Why is NaOH not kept in Aluminium containers?
Aluminium reacts with NaOH and emit hydrogen gas. Therefore reaction happens continuosly until one reactant is finished. Therefore, NaOH is not kept in Aluminium containers
Cannot prepare aluminium hydroxide from aluminium and sodium hydroxide?
Aluminium hydroxide is soluble in aqueous sodium hydroxide solution. When, we add excess sodium hydroxide to aluminium, sodium aluminate is given.
But, adding dilute HCl acid will neutralize OH- ions and will give Al(OH)3 white precipitate. Aluminium hydroxide is a insoluble hydroxide in water.
What are the similar reactions to aluminium and sodium hydroxide we can see in chemistry?
As aluminium, other amphoteric metals such as beryllium, zinc, lead and tin react with aqueous bases such as sodium hydroxide.
Questions
As aluminium and sodium hydroxide will give sodium aluminate, what are the other ways of preparing sodium aluminate>
Industrially, sodium aluminate is produced by dissolution of aluminium hydroxide in a caustic soda (NaOH) solution.
Will give a precipitate when aluminium reacts with sodium hydroxide solution?
Sodium aluminate is a soluble salt in water.
Uses of Al + NaOH reaction?
We know, hydrogen gas is produced in this reaction. Hydrogen gas can be used as a fuel. Usually children use this reaction to send balloons by burning produced hydrogen gas. This is a risk because balloons can be fallen down to roofs of houses and may lead to fires in those houses.