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1

### AIPMT 2000

Oxidation numbers of A, B, C are + 2, +5 and $$-$$2 respectively. Possible formula of compound is
A
A2(BC2)2
B
A3(BC4)2
C
A2(BC3)2
D
A3(B2C)2

## Explanation

In A3(BC4)2, (+2) $$\times$$ 3 + 2[+5+4(-2)]

$$\Rightarrow$$ +6 + 10 -16 = 0

$$\therefore$$ Oxidation numbers of A, B, C are + 2, +5 and $$-$$2 respectively.
2

### AIPMT 2000

Volume of CO2 obtained by the complete decomposition of 9.85 g of BaCO3 is
A
2.24 L
B
1.118 L
C
0.84 L
D
0.56 L

## Explanation

BaCO3 $$\to$$ BaO + CO2

197.34 g $$\to$$ 22.4 L at N.T.P

9.85 g $$\to$$ $${{22.4} \over {197.34}} \times 9.85 = 1.118\,L$$
3

### AIPMT 2000

In quantitative analysis of second group in laboratory, H2S gas is passed in acidic medium for precipitation. When Cu2+ react with KCN, then for product, true statement is
A
K2[Cu(CN)4] more soluble
B
K2[Cd(CN)4] less stable
C
K2[Cu(CN)2] less stable
D
K2[Cd(CN)3] more stable

## Explanation

K3[Cu(CN)2] = 3(+1)+x+2(-1) = 0

$$\Rightarrow$$ x = -1

$$\therefore$$ the oxidation no. of 'Cu' is -1 (-ve), so this complex is unstable so it is not formed.

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