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esidue (E). The compound (A) on heating with<br />
(NH 4 ) 2 SO 4 gives a colourless gas (F) and white<br />
residue (G). Both (E) and (G) impart bright yellow<br />
colour to Bunsen flame. The gas (C) forms white<br />
powder with strongly heated Mg metal which on<br />
hydrolysis produces Mg(OH) 2 . The gas (D) on<br />
heating with Ca gives a compound which on<br />
hydrolysis produces NH 3 . Identify compounds (A) to<br />
(G) giving chemical equations involved.<br />
Sol. The given information is as follows :<br />
(i) A ⎯ Heat ⎯⎯ → B + C<br />
Colourless Solid Colourless<br />
Solid<br />
gas<br />
(ii) B + H 2 SO 4 ⎯⎯→<br />
∆ Reddish brown gas<br />
(iii) B + NH 4 Cl ⎯⎯→<br />
∆ D + E<br />
Colourless gas<br />
(iv) A + (NH 4 ) 2 SO 4 ⎯⎯→<br />
∆ F + G<br />
olourless gas White<br />
Residue<br />
(v) E and G imparts yellow colour to the flame.<br />
(vi) C + Mg ⎯ Heat ⎯⎯ →White powder<br />
⎯ H 2<br />
⎯⎯ O →Mg(OH) 2<br />
(vii) D + Ca ⎯ Heat ⎯⎯ →Compound ⎯ H 2<br />
⎯⎯ O →NH 3<br />
Information of (v) indicates that (E) and (G) and also<br />
(A) are the salts of sodium because Na + ions give<br />
yellow coloured flame. Observations of (ii) indicate<br />
that the anion associated with Na + in (A) may be<br />
NO – 3 . Thus, the compound (A) is NaNO 3 .<br />
The reactions involved are as follows :<br />
(i) 2NaNO 3 ⎯⎯→<br />
∆ 2NaNO 2 + O 2 ↑<br />
(A) (B) (C)<br />
(ii) 2NaNO 2 + H 2 SO 4 ⎯→ Na 2 SO 4 + 2HNO 2<br />
(B) Dil.<br />
3HNO 2 ⎯→ HNO 3 + H 2 O + 2NO↑<br />
2NO + O 2 ⎯→ 2NO 2 ↑<br />
Reddish brown<br />
Fumes<br />
(iii) NaNO 2 + NH 4 Cl ⎯→ NaCl + N 2 ↑ + 2H 2 O<br />
(B) (E) (D)<br />
(iv) 2NaNO 3 + (NH 4 ) 2 SO 4 ⎯⎯→<br />
∆ Na 2 SO 4 + 2NH 3<br />
(A) (G) (F)<br />
2HNO 3<br />
(v) O 2 + 2Mg ⎯⎯→<br />
∆ 2MgO ⎯ H 2<br />
⎯⎯ O →Mg(OH) 2<br />
(C)<br />
(vi) N 2 + 3Ca ⎯⎯→<br />
∆ Ca 3 N 2<br />
(D)<br />
Ca 3 N 2 + 6H 2 O ⎯→ 3Ca(OH) 2 + 2NH 3 ↑<br />
Hence,<br />
(A) is NaNO 3 ,<br />
(B) is NaNO 2 ,<br />
(C) is O 2 ,<br />
(D) is N 2 ,<br />
(E) is NaCl,<br />
(F) is NH 3 and (G) is Na 2 SO 4 .<br />
TRUE OR FALSE<br />
1. The magnitude of charge on one gram of<br />
electrons is 1.60 × 10 –19 coulomb.<br />
2. Chromyl chloride test of Cl – radical is not given<br />
by HgCl 2 .<br />
3. The energy levels in a hydrogen atom can be<br />
compared with the steps of a ladder placed at<br />
equal distance.<br />
4. In S N 1 mechanism, the leaving group in the<br />
molecule, leaves the molecule, well before<br />
joining of an attacking group.<br />
5. Metamerism is special type of isomerism where<br />
isomers exist simultaneously in dynamic<br />
equilibrium.<br />
6. Addition of HCN with formaldehyde is an<br />
example of electrophilic addition reaction.<br />
7. Ligroin is essentially petroleum ether containing<br />
aliphatic hydrocarbons and is generally used in<br />
dry cleaning clothes.<br />
Sol.<br />
1. [False] Thomson through his experiment<br />
determined the charge to mass ratio of an<br />
electron and the value of e/m is equal to 1.76 ×<br />
10 8 coulomb/gm. Hence one gm of electrons<br />
have charge 1.76 × 10 8 C.<br />
2. [True]<br />
3. [False]<br />
4. [True] S N 1 reaction mechanism takes place in<br />
two steps as :<br />
R—X<br />
R + + OH –<br />
⎯ Slow ⎯→ ⎯ R + + X –<br />
⎯ Fast ⎯→<br />
ROH<br />
5. [False] In metamerism isomers differ in structure<br />
due to difference in distribution of carbon atoms<br />
about the functional group.<br />
For example :<br />
CH 3 CH 2 –O–CH 2 CH 3 and CH 3 –OCH 2 CH 2 CH 3<br />
Conditions mentioned in the statement are<br />
associated with phenomenon of trautomerism.<br />
6. [False]<br />
H<br />
H – C = O + H + CN –<br />
7. [True]<br />
H<br />
H – C = OH<br />
CN<br />
XtraEdge for <strong>IIT</strong>-<strong>JEE</strong> 44 DECEMBER 2009
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