1
MCQ (Single Correct Answer)

### AIPMT 2004

Which one of the following statements about the zeolite is false?
A
They are used as cation exchangers.
B
They have open structure which enables them to take up small molecules.
C
Zeolites are aluminosilicates having three dimensional network.
D
Some of the SiO$_4^{4 - }$ units are replaced by AlO$_4^{5 - }$ and AlO$_6^{9 - }$ ions in zeolites.

## Explanation

Zeolites are alumino silicates having three dimensional open structure in which four or six membered ring predominates. Thus, due to open chain structure, they have cavities and can take up water and other small molecules.
2
MCQ (Single Correct Answer)

### AIPMT 2003

Which one of the following compounds is not a protonic acid?
A
B(OH)3
B
PO(OH)3
C
SO(OH)2
D
SO2(OH)2

## Explanation

B(OH)3 does not provide H+ ions in water instead it accepts OH ion and hence it is Lewis acid.

B(OH)3 + H2O ⇌ [B(OH)4]- + H+
3
MCQ (Single Correct Answer)

### AIPMT 2002

Which of the following order is wrong?
A
NH3 < PH3 < AsH3 $-$ acidic
B
Li < Be < B < C $-$ 1st IP
C
Al2O3 < MgO < Na2O < K2O $-$ basic
D
Li+ < Na+ < K+ < Cs+ $-$ ionic radius.

## Explanation

Along the period, I.P. generally increases but not regularly. Be and B are exceptions. First I.P. increases in moving from left to right in a period, but I.P. of B is lower than Be.

As in case of boron, 2p1 electron have to be removed to get B+(1s2 2s2) from B(1s2 2s2 2p1), while in case of Be (1s22s2) electron have to be removed to get Be+ (1s22s1). p electron can be removed more easily than s electron so the energy required to remove electron will be less in case of boron.
4
MCQ (Single Correct Answer)

### AIPMT 2002

Which of the following statement is true?
A
Silicon exhibits 4 coordination number in its compound.
B
Bond energy of F2 is less than Cl2.
C
Mn(III) oxidation state is more stable than Mn(II) in aqueous state.
D
Elements of 15th group shows only + 3 and +5 oxidation states.

## Explanation

Fluorine is more reactive than chlorine. So, bond energy of chlorine is greater than fluorine.

Silicon exhibits 6 coordination numbers.

In aqueous state Mn(II) is more stable.

Mn ⇌ Mn2+ + 2e-

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