Question

When metal ? $M$ ? is treated with $NaOH$, a white gelatinous precipitate ?$X$? is obtained, which is soluble in excess of $NaOH$. Compound ?$X$? when heated strongly gives an oxide which is used in chromatography as an adsorbent. The metal ?$M$? is :

• A. Zn
• B. Ca
• C. Al
• D. Fe

Answer 1

Answer: (C)

Al

Answer 2

$Al ^{3+} {->[{ NaOH }]} \underset{\text{White gelatinous ppt.}}{ Al ( OH )_{3} \downarrow} {->[{{\text{ Excess}}}\,{ NaOH }]} \underset{\text{Sodium meta aluminate (soluble)}}{NaAlO _{2}}$
$2 Al ( OH )_{3} {->[{\text { Strong heating }}]} Al _{2} O _{3}+3 H _{2} O$
$Al _{2} O _{3}$ is used in column chromatography.