1
MCQ (Single Correct Answer)

NEET 2017

It is because of inability of ns2 electrons of the valence shell to participate in bonding that
A
Sn2+ is oxidising while Pb4+ is reducing
B
Sn2+ and Pb2+ are both oxidising and reducing
C
Sn4+ is reducing while Pb4+ is oxidising
D
Sn2+ is reducing while Pb4+ is oxidising

Explanation

The inertness of s-subshell electrons towards bond formation is known as inert pair effect. This effect increases down the group thus, for Sn, +4 oxidation state is more stable, whereas, for Pb, +2 oxidation state is more stable, i.e., Sn2+ is reducing while Pb4+ is oxidising
2
MCQ (Single Correct Answer)

NEET 2016 Phase 1

Among the following the correct order of acidity is
A
HClO2 < HClO < HClO3 < HClO4
B
HClO4 < HClO2 < HClO < HClO3
C
HClO3 < HClO4 < HClO2 < HClO
D
HClO < HClO2 < HClO3 < HClO4

Explanation

The acidic character of the oxoacids increases with increase in oxidation number of the halogen atom i.e.,

HClO < HClO2 < HClO3 < HClO4

Since the stability of the anion decreases in the order.

ClO4- > ClO3- > ClO2- > ClO

Acid strength also decreases in the same order.
3
MCQ (Single Correct Answer)

NEET 2016 Phase 1

Which one of the following orders is correct for the bond dissociation enthalpy of halogen molecules?
A
Br2 > I2 > F2 > Cl2
B
F2 > Cl2 > Br2 > I2
C
I2 > Br2 > Cl2 > F2
D
Cl2 > Br2 > F2 > I2

Explanation

Bond dissociation enthalpy decreases as the bond distance increases from F2 to I2. This is due to increase in the size of the atom, on moving from F to I.

F – F bond dissociation enthalpy is smaller then Cl – Cl and even smaller than Br – Br. This is because F atom is very small and hence the three lone pairs of electrons on each F atom repel the bond pair holding the F-atoms in F2 molecules.

The order of bond dissociation enthalpy is :

Cl2 > Br2 > F2 > I2
4
MCQ (Single Correct Answer)

NEET 2016 Phase 1

When copper is heated with conc. HNO3 it produces
A
Cu(NO3)2, NO and NO2
B
Cu(NO3)2 and N2O
C
Cu(NO3)2 and NO2
D
Cu(NO3)2 and NO

Explanation

Cu +4HNO3 (conc.) $$ \to $$ Cu(NO3)2 + 2NO2 + 2H2O

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