Question

So I was studying Chemistry (Hydrogen - Uses, Properties and Preparation) from 2 different textbooks (based on Grade 9 syllabus, I.C.S.E. Board, India) and I found what seems an astounding anomaly to me.

In the two textbooks, the same reaction for liberating Hydrogen gas from a hot concentrated solution of NaOH and Al is given as follows:-

Textbook 1: 2Al+2NaOH+2H₂O⟶2NaAlO₂Sodium metaaluminate+3H₂↑

Textbook 2: 2Al+2NaOH+2H₂O⟶2NaAlO₂Sodium aluminate+3H₂↑

If the two reactions are the same, why and how is the name of the same compound (NaAlO₂, Sodium meta aluminate / Sodium aluminate) different? Secondly, what does 'meta' imply in Sodium metaaluminate?

Answer 1

The two reactions represent the same reaction. The difference in the names of the compounds is related to the presence of water molecules. Sodium metaaluminate contains two water molecules per formula unit, while sodium aluminate contains six water molecules per formula unit.

Step-by-step explanation:

The two reactions you mentioned represent the same reaction, which is the reaction between aluminum (Al) and a concentrated solution of sodium hydroxide (NaOH) and water (H₂O) to produce sodium aluminate (NaAlO₂) and hydrogen gas (H₂). The difference in the names of the compounds - sodium metaaluminate and sodium aluminate - is related to the presence of additional water molecules in the reaction.

In the second name, 'meta' implies that the compound contains less water compared to the first compound. Sodium metaaluminate (NaAlO₂) contains two water molecules per formula unit, while sodium aluminate (NaAlO₂) contains six water molecules per formula unit.