Solved: CHEMISTRY Question for NEET

NEET CHEMISTRYMedium

Which of the following statements is incorrect?

$NaHCO_3$ on heating gives $Na_2CO_3$ .

Pure sodium metal dissolves in liquid ammonia to give a blue solution.

NaOH reacts with glass to give sodium silicate.

Aluminium reacts with excess NaOH to give $Al(OH)_3$ .

Option A is correct: Sodium hydrogen carbonate ( $NaHCO_3$ ) thermally decomposes to give sodium carbonate ( $Na_2CO_3$ ), water, and carbon dioxide.
Option B is correct: Alkali metals like sodium dissolve in liquid ammonia to give deep blue solutions which are conducting in nature due to ammoniated electrons.
Option C is correct: Sodium hydroxide ( $NaOH$ ) reacts with silica ( $SiO_2$ ), a major component of glass, to form sodium silicate ( $Na_2SiO_3$ ). This causes etching of glass.
Option D is incorrect: Aluminium is an amphoteric metal. It reacts with excess aqueous sodium hydroxide to form a soluble complex, sodium tetrahydroxidoaluminate(III) (or sodium aluminate), and liberates hydrogen gas. The reaction is: $2Al(s) + 2NaOH(aq) + 6H_2O(l) \rightarrow 2Na^+[Al(OH)_4]^-(aq) + 3H_2(g)$ It does not form insoluble aluminium hydroxide ( $Al(OH)_3$ ) in excess alkali.

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