Which one of the following has the highest melting point?

1. Na

2. Mg

3. K

4. Al

B(OH)₃ + NaOH  $\to$ NaBO₂ + Na[B(OH)₄] +H₂O

How can this reaction is made to proceed in forward direction?

1. addition of cis 1,2 diol

2. addition of borax

3. addition of trans 1,2 diol

4. addition of Na₂HPO₄

Which of the following compounds is the weakest Lewis acid?

1. BF₃

2.  BCl₃

3. BBr₃

4.  BI₃

The element among the following that does not show inert pair effect is-

An amphoteric  oxide among the following is-

1. CO₂

2. CO

3. SnO₂

4. CaO

In B₂H₆ 

(1) there is direct boron-boron bond

(2) the structure is similar to that of C₂H₆

(3) the boron atoms are linked through hydrogen bridges

(4) all the atoms are in one plane

The number of carbon atoms per unit cell of diamond unit cell is:-

1. 4

2. 8

3. 6

4. 1

Which of the following cation can not give borax bead test?

(a) ${\mathrm{Cr}}^{3+}$                          (b) ${\mathrm{Co}}^{2+}$

(c) ${\mathrm{Ag}}^{+}$                           (d) ${\mathrm{Mn}}^{2+}$

Aluminium becomes passive in nitric acid because it-

1. Is a noble metal

2. Forms a thin film of oxide

3. Has a positive reduction potential

4.  None of the above

Hybridisation of boron in diborane is:

1.  $\mathrm{sp}$

2.  ${\mathrm{sp}}^2$

3.  ${\mathrm{sp}}^3$

4.  ${\mathrm{sp}}^3{\mathrm{d}}^2$