How many moles of magnesium phosphate, Mg₃(PO₄)² will contain 0.25 mole of oxygen atoms?

• 0.02

• 3.125 × 10^–2

• 1.25 × 10^–2

• 1.25 × 10^–2

According to Bohr’s theory, the angular momentum of an electron in 5th orbit is

• 25h/ π

• 1.0h/π

• 10/π

• 10/π

Which of the following molecules/ions does not contain unpaired electrons?

Uncertainty in the position of an electron (mass = 9.1 × 10^–31 kg) moving with a velocity 300 ms–1, accurate upto 0.001%, will be

• 19.2 × 10^–2 m

• 5.76 × 10^–2 m

• 1.92 × 10^–2 m

• 1.92 × 10^–2 m

Phosphorus pentachloride dissociates as follows, in a closed reaction vessel,
PCl₅ (g) ⇌ PCl₃(g) + cl₂(g)
If total pressure at equilibrium of the reaction mixture is P and degree of dissociation of PCl₅ is x, the partial pressure of PCl₃ will be

The standard enthalpy of formation (∆_fH^o)  at 298 K for methane, CH₄(g), is –74.8 kJ mol^–1. The additional information required to determine the average energy for C – H bond formation would be

• the dissociation energy of H₂ and enthalpy of sublimation of carbon

• latent heat of vapourization of methane

• the first four ionization energies of carbon and electron gain enthalpy of hydrogen

• the first four ionization energies of carbon and electron gain enthalpy of hydrogen

Among the following mixtures, dipole-dipole as the major interaction is present in

• benzene and ethanol

• acetonitrile and acetone

• KCl and water

• KCl and water

Which one of the following sets of ions represents a collection of isoelectronic species?

• K⁺ , Cl^– , Ca²⁺, Sc³⁺

• Ba^2+, Sr²⁺, K⁺ , S^2–

• N^3–, O^2–, F^– , S^2–

• N^3–, O^2–, F^– , S^2–

In which of the following molecules/ions are all the bonds not equal?

• SF₄

• SiF₄

• XeF₄

• XeF₄

Nickel (Z = 28) combines with a uninegative monodentate ligand X–
to form a paramagnetic complex [NiX₄ ]^{2 −}. The number of unpaired electron(s) in the nickel and geometry of this complex ion are,
respectively

• one, tetrahedral

• two, tetrahedral

• one, square planar

• one, square planar