You visited us 1 times! Enjoying our articles? Unlock Full Access!

Laboratory Preparation of Ammonia

A is hydrated...

Question

(A) is hydrated salt. 2.48 g of (A) on heating gives 1.58 g of anhydrous salt (B).
(i) Aqueous (A) + $A g N O_{3} ⟶$ white turbidity changing to black.
(ii) Aqueous (A) decolourises $I_{2}$ in $K l$
(iii) Aqueous (A) + dil.HCl $⟶$ white turbidity
(iv) Aqueous (A) dissloves unreacted AgBr of photographic plate.
Thus, (A) is identified as hypo $N a_{2} S_{2} O_{3} x H_{2} O h y d r a t e d$ .
If true enter 1, else enter 0.
1

Open in App

Solution

The correct option is A 1
From the reactions (i) to (iv) indicate that the compound (A) is hypo solution $N a_{2} S_{2} O_{3} x H_{2} O h y d r a t e d$ . Here x represents the number of water molecules present.
Mol. wt. of compound (A) is $(N a_{2} S_{2} O_{3} . x H_{2} O) = 158 + 18 x$ g/mol
and that of anhydrous hypo (B) ( $N a_{2} S_{2} O_{3}$ ) = 158 g/mol
The ratio of the molecular weights of hydrated and anhydrous hypo is $\frac{(A)}{(B)}$ = $\frac{158 + 18 x}{158} = \frac{2.48}{1.58}$
Hence, $x = 5$ . 5 water molecules are present.
Thus the compound (A) is $N a_{2} S_{2} O_{3} 5 H_{2} O$
Explanation:
(i) Silver nitrate reacts with hypo to form white ppt of $A g_{2} S_{2} O_{3}$
$2 A g N O_{3} + N a_{2} S_{2} O_{3} ⟶ A g_{2} S_{2} O_{3} w h i t e ↓ + 2 N a N O_{3}$
$A g_{2} S_{2} O_{3}$ reacts withwater to form black ppt.
$A g_{2} S_{2} O_{3} + H_{2} O ⟶ H_{2} S O_{4} + A g_{2} S b l a c k ↓$
(ii)Hypo solution reduces iodine to NaI.
$I_{2} + 2 N a_{2} S_{2} O_{3} ⟶ 2 N a I + N a_{2} S_{4} O_{6}$
( $I_{2}$ is soluble in KI forming $K I_{3}; I_{2}$ is insoluble in $H_{2} O$ )
(iii) Hypo reacts wih S to form turbidity of S particles.
$N a_{2} S_{2} O_{3} + 2 H C l ⟶ 2 N a C l + S O_{2} + S (t u r b i d i t y) + H_{2} O$
(iv) Silver bromide reacts with hypo to form soluble $N a_{3} [A g (S_{2} O_{3})_{2}]$
$A g B r + 2 N a_{2} S_{2} O_{3} ⟶ N a_{3} [A g (S_{2} O_{3})_{2}] s o l u b l e + N a B r$

Suggest Corrections

Similar questions

M n O_{4}^{-}

C r_{2} O_{7}^{2 -}

B a C l_{2}

△ \to (B) (b l a c k i s h b r o w n) + (C) + (D)      o x i d e s o f s u l p h u r

(C) o x i d a t i o n - ------ \to (D)

K_{2} C r_{2} O_{7}

△ \to (E) d e e p y e l l o w

⟶

F e S O_{4} . 7 H_{2} O

B a C l_{2} ⟶

H N O_{3}

H_{2} S ⟶

H N O_{3}

N H_{3}

⟶

△ \to

⟶

C u S O_{4} . 5 H_{2} O

A g B r

{A g N O}_{3}

(N a_{2} S_{2} O_{3})

N a_{3} [A g (S_{2} O_{3})_{2}]

A g_{2} S_{2} O_{3}

A g_{2} S

{B a C l}_{2}

{S O}_{3}^{2 -}

{S O}_{4}^{2 -}

A g

A g N O_{3}

N O_{2}

A g C l

A g_{2} S_{2} O_{3}

A g_{2} S

Join BYJU'S Learning Program