Physical Properties of Boron Family

Q. is more stable in its +1 oxidation state than +3 oxidation state.

1. In
2. Tl
3. Ga

Q. The correct order of boiling points of boron trihalides is:

1. $B{I}_3>BB{r}_3>BC{l}_3>B{F}_3$
2. $B{F}_3>BC{l}_3>BB{r}_3>B{I}_3$
3. $BC{l}_3>B{F}_3>BB{r}_3>B{I}_3$
4. $B{I}_3>BB{r}_3<B{F}_3<BC{l}_3$

Q. The structures of $BC{l}_3$ and $AlC{l}_3$ in their liquid states are, respectively:

1. Monomer and monomer
2. Dimer and dimer
3. Dimer and monomer
4. Monomer and dimer

Q. The correct order of boiling points of boron trihalides is:

1. $B{I}_3>BB{r}_3>BC{l}_3>B{F}_3$
2. $B{F}_3>BC{l}_3>BB{r}_3>B{I}_3$
3. $BC{l}_3>B{F}_3>BB{r}_3>B{I}_3$
4. $B{I}_3>BB{r}_3<B{F}_3<BC{l}_3$

Q.

Both the amorphous and crystalline forms of boron are very reactive in air.

1. False

2. True

Q.

Al and Ga have nearly the same covalent radii because of:

1. Greater shielding effect of s-electrons of Ga atoms

2. Poor shielding effect of s-electrons of Ga atoms

3. Poor shielding effect of d-electrons of Ga atoms

4. Greater shielding effect of d-electrons of Ga atoms

Q. $B^{3+}$ ion cannot exist in an aqueous medium because of its:

1. Strong reducing property
2. Strong oxidising property
3. Small size and large charge
4. Large size and small charge

Q.

The main factor responsible for weak acidic nature of B-F bonds in BF3 is -

1. Large electronegativity of F

2. Three centred two electron bonds in BF3

3. pp­- dp back bonding

4. pp- pp back bonding

Q. Which one of the following is an isotope of Boron?

1. ${}^{11}B$
2. ${}^{13}B$
3. None of the above
4. ${}^{12}B$

Q.

Which of the following statements is false?

1. Group 13 consists of p-block elements

2. The sums of the three ionization enthalpies of each group 13 element follow the order

   $B>Al>Ga>In<Tl$

3. The stability of +3 oxidation state in group 13 elements follows the order.

   $B>Al>Ga>In>Tl$

4. The correct order of atomic radii of group 13 elements is

   $B<Al<Ga<In<Tl$

Q.

In the extraction of aluminium, the function of cryolite is to:

1. Increase the melting point of alumina

2. Minimise the anodic effect

3. Lower the melting point of alumina

4. Remove impurities from alumina

Q. $Zr$ (Z=40) and $Hf$ (Z=72) have similar atomic and ionic radii because of :

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1. having similar chemical properties
2. belonging to same group
3. diagonal relationship
4. lanthanoid contraction

Q. $B^{3+}$ ion cannot exist in an aqueous medium because of its:

1. Strong reducing property
2. Strong oxidising property
3. Small size and large charge
4. Large size and small charge

Q. The structures of $BC{l}_3$ and $AlC{l}_3$ in their liquid states are, respectively:

1. Monomer and monomer
2. Dimer and dimer
3. Dimer and monomer
4. Monomer and dimer

Q. The element which exists as a liquid upto 2000∘C and can be used in high temperature thermometry is .

1. Ga
2. Al
3. B

Q. Boron has an extremely high melting point because of:

1. the strong van der waals forecs between its atoms
2. due to very strong crystalline lattice.
3. its ionic crystal structure
4. allotropy

Q. Which one of the following is an isotope of Boron?

1. ${}^{12}B$
2. ${}^{11}B$
3. ${}^{13}B$
4. None of the above

Q. Which of the following groups does not exhibit +M effect when attached with benzene?

1. $Ph-N{H}_2$
2. $Ph-\stackrel{+}{N}{H}_3$
3. $Ph-OH$
4. $Ph-Cl$

Q. The reason behind the smaller atomic radius of Ga as compared to Al is ?

1. poor screening effect of 3d electrons
2. increased force of attraction of increased nuclear charge on electrons
3. increased ionisation enthalpy of Ga as compared to Al
4. Anamolous behaviour of Ga

Q.

Which of the following forces of attraction acts among the atoms in a molecule of type $\mathrm{B}-\mathrm{A}-\mathrm{B}$, where $\mathrm{A}$ and $B$ belong to group 16 and group 17, respectively?

1. Dipole-dipole interaction

2. Hydrogen bonding

3. Van der Waals force

4. Interionic attractions

Q.

In the extraction of aluminium, the function of cryolite is to:

1. Lower the melting point of alumina

2. Increase the melting point of alumina

3. Remove impurities from alumina

4. Minimise the anodic effect

Q.

$Al\&Ga$ have nearly the same constant radii because of

1. Greater shielding effect of s electrons of Ga atoms

2. Poor shielding effect of s electrons of Ga atoms

3. Poor shielding effect of d electrons of Ga atoms

4. Greater shielding effect of d electrons of Ga atoms

Q. The element which exists as a liquid upto 2000∘C and can be used in high temperature thermometry is .

1. Ga
2. Al
3. B

Q. The element which exists as a liquid upto 2000∘C and can be used in high temperature thermometry is .

1. Ga
2. Al
3. B