Qualitative Analysis - Result Question 13
####13. A sodium salt of an unknown anion when treated with $MgCl _2$ gives white precipitate only on boiling. The anion is
(a) $SO _4^{2-}$
(b) $HCO _3^{-}$
(c) $CO _3^{2-}$
(d) $NO _3^{-}$
$(2004,1 M)$
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Answer:
Correct Answer: 13. (b)
Solution:
- A sodium salt of an unknown anion when treated with $MgCl$ gives white precipitate $\left(MgCO _3\right)$ only on boiling. Hence, the action must be $HCO _3^{-}$ion.
$MgCl _2+2 NaHCO _3 \xrightarrow{\Delta} MgCO _3+2 NaCl+H _2 O+CO _2$
