15
MCQ (Single Correct Answer)
Cement, the important building material is a mixture of oxides of several elements. Besides calcium, iron and sulphur, oxides of elements of which of the group $(s)$ are present in the mixture?
A
Group 2
B
Groups 2, 13 and 14
C
Groups 2 and 13
D
Groups 2 and 14
16
MCQ (Multiple Correct Answer)
The reason for small radius of Ga compared to Al is ............ .
A
poor screening effect of $d$ and $f$-orbitals
B
increase in nuclear charge
C
presence of higher orbitals
D
higher atomic number
17
MCQ (Multiple Correct Answer)
The linear shape of $\mathrm{CO}_2$ is due to ............ .
A
$s p^3$ hybridisation of carbon
B
$s p$ hybridisation of carbon
C
$p \pi-p \pi$ bonding between carbon and oxygen
D
$s p^2$ hybridisation of carbon
18
MCQ (Multiple Correct Answer)
$\mathrm{M}_3 \mathrm{SiO}$ is used during polymerisation of organo silicones because
A
chain length of organo silicone polymers can be controlled by adding $\mathrm{Me}_3 \mathrm{SiCl}$
B
$\mathrm{Me}_3 \mathrm{SiCl}$ blocks the end terminal of silicone polymer
C
$\mathrm{Me}_3 \mathrm{SiCl}$ improves the quality and yield of the polymer
D
$\mathrm{Me}_3 \mathrm{SiCl}$ acts as a catalyst during polymerisation
19
MCQ (Multiple Correct Answer)
Which of the following statements are correct ?
A
Fullerenes have dangling bonds
B
Fullerenes are cage-like molecules
C
Graphite is thermodynamically most stable allotrope of carbon
D
Graphite is slippery and hard and therefore used as a dry lubricant in machines.