Need help plz ASAP?

If an unknown solution contained carbonate ions (CO₃²⁻) or hydrogencarbonate ions (HCO₃⁻), CO₂ would be released when the solution is added to an acid. However, all soluble carbonates do not form precipitate with NaOH solution. Hence, the unknown solution contains hydrogencarbonate ions.

The unknown forms a white precipitate with NaOH, and the precipitate re-dissolves in excess NaOH solution. The solution should contains a cation which form an amphoteric hydroxide with NaOH solution. The possible cation in the unknown solution is aluminum (Al³⁺), zinc (Zn²⁺) or lead(II) (Pb²⁺) ion.

Then, the compound in the solution could be aluminum hydrogencarbonate (Al(HCO₃)₃), zinc hydrogencarbonate (Zn(HCO₃)₂) or lead(II) hydrogencarbonate (Pb(HCO₃)₂).

Aluminium carbonate.

Al2(CO3)3 + 6NaOH(aq) ----> 2Al(OH)3 (s) + 3Na2CO3 (aq)

Al2(CO3)3 + 6H+ ------> 2Al3+ + 3H2O +3CO2

I would think it is NaHCO3. It can form from NaOH absorbing CO2 from the air. But if you increase the pH by adding more NaOH it will convert to Na2CO3. The CO2 is from the neutralization reaction, either NaHCO3 or NaCO3 will neutralize an acid and form a salt plus water and CO2.