A molecule that has a complete octet is:

 1. BeCl₂(dimer)       

 2. BeH₂(dimer)

 3. BeH₂(s)               

 4. BeCl₂(s)

Mg₂C₃ reacts with water forming propyne ${\mathrm{C}}_3^{4-}$ . The number of sigma and pie bonds in \(C_{3}^{4-}\)is-  

1. Two sigma and two pi bonds.             

2. Three sigma and one pi bonds.           

3. Two sigma and one pi bonds.          

4. Two sigma and three pi bonds.

According to Born-Haber's cycle, the enthalpy of the formation of ionic compounds can be determined. The formation of NaCl involves the following steps :

(I) \(Na(s)\xrightarrow[Energy \ of \ sublimation]{S} \ Na(g)\)     

(II) \(Na(g)\xrightarrow[Ionisation \ potential]{I} \ Na^{+}(g) \ + \ e^{-}\)

(III) \(Cl_{2}(g)\xrightarrow[Bond \ dissociation \ energy]{D} \ 2Cl(g)\)

(IV) \(Cl(g) \ + e^{-}\xrightarrow[Electron \ affinity \ energy]{E} \ Cl^{-}(g)\)

 (V) \(Cl^{-}(g) \ + Na^{+}(g)\xrightarrow[Lattice \ energy \ energy]{U} \ NaCl(s)\)

The enthalpy of formation of NaCl will be :

1. $∆{\mathrm{H}}_{\mathrm{f}}=\mathrm{S}+\mathrm{I}-\frac{\mathrm{D}}{2}-\mathrm{E}-\mathrm{U}$

2. $∆{\mathrm{H}}_{\mathrm{f}}=\mathrm{S}+\mathrm{I}+\frac{\mathrm{D}}{2}-\mathrm{E}-\mathrm{U}$

3. $∆{\mathrm{H}}_{\mathrm{f}}=-\mathrm{S}-\mathrm{I}-\mathrm{D}+\frac{E}{2}+\mathrm{U}$

4. $∆{\mathrm{H}}_{\mathrm{f}}=-\mathrm{S}-\mathrm{I}-\mathrm{D}-\frac{E}{2}-\mathrm{U}$

Which of the following is the least volatile?
     

1. HCN                     
2. HF        
3. H₂O                     
4. CS₂

A : Tetracyanomethane

B : Carbondioxide

C : Benzene

D : 1,3-Buta-di-ene

Ratio of $\mathrm{\sigma }$ and $\mathrm{\pi }$ bonds is in order :       

1. A = B < C < D           

2. A = B < D < C           

3. A = B = C = D           

4.  C < D < A < B

The maximum number of 90° angles between bond pair-bond pair of electrons is observed in:

1.  sp³d²-hybridization.            

2.  sp³d-hybridization.

3.  dsp²-hybridization.             

4.  dsp³-hybridization.

The ion that has a trigonal planar shape is: 

1. ${\mathrm{SO}}_3^{2-}$

2. ${\mathrm{PO}}_4^{3-}$

3. ${\mathrm{CN}}^{-}$

4. ${\mathrm{CO}}_3^{2-}$

Which of the following molecules or ions is not linear ?               

1. BeCl₂                 

2. ${\mathrm{ICl}}_2^{-}$        

3. CS₂                     

4. ${\mathrm{ICl}}_2^{+}$

Which reaction involves a change in the electron-pair geometry for the underlined atom?

1. BF₃ $+{\mathrm{F}}^{-}\to {\mathrm{BF}}_4^{-}$ 

2. NH₃$+{\mathrm{H}}^{+}\to {\mathrm{NH}}_4^{+}$

3. 2SO₂$+{\mathrm{O}}_2\to 2{\mathrm{SO}}_3$ 

4. H₂O$+{\mathrm{H}}^{+}\to {\mathrm{H}}_3{\mathrm{O}}^{+}$   

The correct order of increasing s-character (in percentage) in the hybrid orbitals of following molecules/ion is :

(i) ${\mathrm{CO}}_3^{2-}$   (ii) XeF₄     (iii) ${\mathrm{I}}_3^{-}$       (iv) NCl₃   (v) BeCl₂

1.  ii < iii < iv < i < v

2. ii < iv < iii < v < i

3. iii < ii < i < v < iv        

4. ii < iv < iii < i < v