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1

AIPMT 2012 Mains

MCQ (Single Correct Answer)
In which of the following arrangements the given sequence is not strictly according to the property indicated against it?
A
HF < HCl < HBr < HI : increasing acidic strength
B
H2O < H2S < H2Se < H2Te : increasing pKa values
C
NH3 < PH3 < AsH3 < SbH3 : increasing acidic character
D
CO2 < SiO2 < SnO2 < PbO2 : increasing oxidising power

Explanation

If acidic nature is high, Ka is high and pKa is low.

since pKa = – log Ka

Hence the order of pKa will be

H2O > H2S > H2Se > H2Te
2

AIPMT 2012 Prelims

MCQ (Single Correct Answer)
Sulphur trioxide can be obtained by which of the following reaction?
A
CaSO4 + C $$\buildrel \Delta \over \longrightarrow $$
B
Fe2(SO4)3 $$\buildrel \Delta \over \longrightarrow $$
C
S + H2SO4 $$\buildrel \Delta \over \longrightarrow $$
D
H2SO4 + PCl5 $$\buildrel \Delta \over \longrightarrow $$

Explanation

Fe2(SO4)3 $$\buildrel \Delta \over \longrightarrow $$ Fe2O3 + 3SO3
3

AIPMT 2012 Prelims

MCQ (Single Correct Answer)
In which of the following compounds, nitrogen exhibits highest oxidation state?
A
N2H4
B
NH3
C
N3H
D
NH2OH

Explanation

N2H4 : Oxidation state of N = – 2

NH3 : Oxidation state of N = – 3

N3H : Oxidation state of N = – 1/3

NH2OH : Oxidation state of N = – 1

$$ \therefore $$ Highest oxidation state = –1/3
4

AIPMT 2012 Prelims

MCQ (Single Correct Answer)
Which of the following statements is not valid for oxoacids of phosphorus?
A
Orthophosphoric acid is used in the manufacture of triple superphosphate.
B
Hypophosphorous acid is a diprotic acid.
C
All oxoacids contain tetrahedral four coordinated phosphorus.
D
All oxoacids contain atleast one P$$=$$O unit and one P$$-$$OH group.

Explanation

Hypophosphorus acid is a monoprotic acid.

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