A compound forms hexagonal closed packed structure. What is the number of tetrahedral voids in \(0.8\text{ mol}\) of it?

Which transition metal ion is most stable against oxidation to its \(+3\) state?

In the depression of freezing point experiment, it is found that :
(A) The vapour pressure of the solution is less than that of the pure solvent.
(B) The vapour pressure of solution is more than that of the pure solvent.
(C) Only the solute molecules solidify at the freezing point.
(D) Only the solvent molecules solidify at the freezing point.
Choose the correct answer from the options given below :

Fuel cell involves __________.

Although chlorine is an electron-withdrawing group, it is ortho- and para-directing in electrophilic aromatic substitution because:
(A) Chlorine withdraws electrons through inductive effect.
(B) Chlorine stabilizes the intermediate carbocation formed during electrophilic substitution via resonance.
(C) Chlorine donates electrons through resonance.
(D) Chlorine is a deactivating group due to its -1 effect.
Choose the correct answer from the options below:

Alcohol is more soluble in water when comparNo Solutioned to alkanes due to formation of

p-block elements are placed in groups 13 to 18 of the periodic table. Group 15 is nitrogen family. Nitrogen makes various compounds like \(NH _3, HNO _3, N_2 O , NO _2\) etc. Phosphorus exists in the form of white and red phosphorus. White phosphorus glows in dark. \(PH _3\) gas is used as smoke screen. Group 16 is called oxygen family. Dry air contains \(21\% O _2\) gas by volume. Combined sulphur exists as sulphates such as gypsum, epsome salt, baryte etc. The allotropic forms of sulphur are Rhombic and monoclinic sulphur. \(S_2\) is paramagnetic like \(O_2\) and it stable at high temperature.
Group 17 is Halogen family. \(F_2\) is highly reactive, \(Cl _2\) is greenish yellow gas. Both \(SO _2\) and \(Cl _2\) are used for bleaching. Group 18 is Noble gas family but some noble gases also form compounds.
Complete hydrolysis of \(XeF _6\) gives HF and \(XeO _3\) as main products.
Match List - I with List - II.

List - I	List - II
(A) Ammonia	(I) Rotten fish small
(B) Nitric Acid	(II) Detection of metal ions
(C) Phosphene	(III) Chemiluminescence
(D) White Phosphorus	(IV) Ostwald Process

Choose the correct answer from the options given below :

Which is not an example of convergent evolution?

An example of inverted ecological pyramid is:

The loss of strength of a signal while propagating through a medium is known as

When light passes from air to glass, then

Which of the following statements is correct for a charged metallic shell?

In case of phosphorus, \(\text{PCl}_3\) and \(\text{PCl}_5\) are possible while nitrogen only forms \(\text{NCl}_3\), and not \(\text{NCl}_5\). This due to :