Question

$Be$ and $Al$ exhibit diagonal relationship. Which of the following statements about them is/are not true?
I. Both react with $HCl$ to liberate $H_2$
II. They are made passive by $HN{O}_3$
III. Their carbides give acetylene on treatment with water
IV. Their oxides are amphoteric

• A. III and IV
• B. I and III
• C. I only
• D. II and III
• E. III only

Answer 1

Answer: (E)

(i) $Be$ and $Al$ both react with $HCl$ to liberate $H_2$ . $Be+2HCl\to BeC{l}_2+H_2\uparrow$ $2Al+6HCl\to 2AlC{l}_3+3H_2\uparrow$
(ii) Be renders passive with cone. $HN{O}_3$ and so does not react. Cone. $HN{O}_3$ is strong oxidizing agent and forms very thin layer of oxide on the surface of metal. Similarly, $Al$ become passive in cone. $HN{O}_3$ due to formation of oxide layer on the surface.
(iii) Their carbides gives methane on treatment with water.
$B{e}_{2}C+4H_{2}O\to 2Be{(OH)}_2+C{H}_4$
$A{l}_4{C}_3+12H_{2}O\to 4Al{(OH)}_3+3C{H}_4$
(iv) Their oxides, $BeO$ and $A{l}_2{O}_3$ are amphoteric.