One mole of magnesium nitride on the reaction with an excess of water gives

• one mole of ammonia

• two moles of nitric acid

• Two mole of ammonia

• Two mole of ammonia

Which one of the following ores is best concentrated by froth – floatation method?

• Magnetite

• Malachite

• Galena

• Galena

Beryllium and aluminium exhibit many properties which are similar. But the two elements differ in

• exhibiting maximum covalency in compound

• exhibiting amphoteric nature in their oxides

• forming covalent halides

• forming covalent halides

Aluminium chloride exists as a dimer, Al₂Cl₆ in the solid state as well as in solution of non-polar solvents such as benzene. When dissolved in water, it gives

• Al³⁺ + 3Cl^-

• Al₂O₃ + 6HCl

• [Al(OH)₆] ^3-

• [Al(OH)₆] ^3-

The soldiers of Napolean army while at Alps during freezing winter suffered a serious problem as regards to the tin buttons of their uniforms. White metallic tin buttons got converted to grey powder. This transformation is related to

• an interaction with nitrogen of the air at very low temperatures

• an interaction with water vapour contained in the humid air

• a change in the partial pressure of oxygen in the air

• a change in the partial pressure of oxygen in the air

The  values for Cr, Mn, Fe and Co are – 0.41, +1.57, + 0.77 and +1.97 V respectively. For which one of these metals the change in oxidation state form +2 to +3 is easiest?

• Cr

• Co

• Fe

• Fe

Excess of KI reacts with CuSO₄ solution and then Na₂S₂O₃ solution is added to it. Which of the statements is incorrect for this reaction?

• Cu₂I₂ is reduced

• Evolved I₂ is reduced

• Na₂S₂O₃ is oxidized

• Na₂S₂O₃ is oxidized

48.

Among the properties (a) reducing (b) oxidising (c) complexing, the set of properties shown by CN^- ion towards metal species is

• a, b

• a, b, c

• c, a

• c, a

The coordination number of central metal atom in a complex is determined by

• The number of ligands around a metal ion bonded by sigma bonds

• The number of only anionic ligands bonded to the metal ion

• The number of ligands around a metal ion bonded by sigma and pi- bonds both

• The number of ligands around a metal ion bonded by sigma and pi- bonds both

Which one of the following complexes in an outer orbital complex?

• [Fe(CN)6]4-

• [Ni(NH₃)₆]²⁺

• [Co(NH₃)₆]³⁺

• [Co(NH₃)₆]³⁺