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NEET levelSingle correct optionDifficulty 1 of 3qa003

A colourless crystalline salt is heated strongly in a dry tube. Brown fumes are evolved and a residue that is yellow on cooling remains. The salt is

A $NaNO X_{3}$
B $Pb (NO X_{3}) X_{2}$
C $PbCO X_{3}$
D $KNO X_{3}$

Answer: B

Lead nitrate decomposes as

2 Pb (NO X_{3}) X_{2} 2 PbO + 4 NO X_{2} + O X_{2}

, giving brown

NO X_{2}

and yellow PbO.

NaNO X_{3}

and

KNO X_{3}

only give the nitrite and colourless oxygen, and

PbCO X_{3}

gives no brown fumes. The salt is

Pb (NO X_{3}) X_{2}

.

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