Question

What would you obsereve if you add with shaking excess of dilute $NaOH$ solution to an aqueous solution of $AlC{l}_3$?

• A. a permanent white ppt. is formed
• B. no change at first, but a white ppt. is formed on standing
• C. a white ppt. is formed which later dissolves
• D. a green ppt. which turns red on standing in air

Answer 1

The correct option is C a white ppt. is formed which later dissolves

If you add with shaking excess of dilute $NaOH$ solution to an aqueous solution of $AlC{l}_3$, a white ppt. of $Al(OH{)}_3$ is formed which later dissolves to form sodium meta-aluminate $Na\left[Al{O}_2\right]$ $.

$AlC{l}_3+3NaOH\to Al(OH{)}_3\downarrow +3NaCl$

$Al(OH{)}_3+NaOH\to Na[Al{O}_2]+2H_{2}O$

So, the correct option is $C$