Reaction of Al With NaOH (aq)

Reaction of Al With NaOH

Aim of this experiment is to study the reaction of sodium hydroxide solution with aluminium metal. Sodium hydroxide is a base. It reacts with aluminium metal to produce sodium aluminate along with hydrogen gas. Sodium aluminate, which imparts a grey colour to the solution. Hydrogen gas neither responds to red litmus nor blue litmus paper. Therefore, it can be concluded that the hydrogen gas is neutral in nature.

NaOH solution also neutralises hydrochloric acid to produce sodium chloride salt and water. The chemical reaction between aluminium and sodium hydroxide solution is given below:

• 2NaOH (aq) + 2Al (s) + 2H₂O (l) → 2NaAlO₂ (aq) + 3H₂ (g) 
• NaOH (aq) + HCl (aq) → NaCl (aq) + H₂O (l)

Apparatus and Materials Required

Apparatus:

• An aluminium piece 
• Dilute sodium hydroxide solution
• Litmus paper: Red and blue
• Test tube
• Matchbox

Procedure

The following steps to follow for the procedure:

1. Take a small piece of aluminium metal and place it in a clean and dry test tube.
2. Add about 5 mL of sodium hydroxide solution into it.
3. Observe the effervescence coming out from the reaction mixture. Look at the colour of the gas liberated. 
4. Perform the smell test on the gas liberated by fanning the gas gently towards your nose. 
5. Bring moist blue and red litmus papers to the mouth of the test tube.
6. Perform a combustion test by bringing a lighted candle near the mouth of the test tube. Does the liberated gas ignites exothermically to produce water?

Conclusion

In this experiment, we conclude that aluminium being one of the most reactive metals, readily reacts with aqueous sodium hydroxide to form sodium aluminate (grey-coloured) and hydrogen gas. 

• 2Al (s) + 2NaOH (aq) + 2H₂O (l) → 2NaAlO₂ (aq) + 3H₂ (g)

The properties of hydrogen gas were studied, and it can be concluded that:

• Hydrogen is a colourless gas.
• Hydrogen is neutral in nature.
• Hydrogen is a highly combustible substance.

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