1

### JEE Main 2019 (Online) 9th January Morning Slot

Correct statements among a to d regarding silicones are :

(a)   They are polymers with hydrophobic character.
(b)   They are biocompatible.
(c)   In general, they have high thermal stability and low dielectric strength.
(d)   Usually, they are resistant to oxidation and used as greases.
A
(a), (b), (c) and (d)
B
(a), (b) and (c) only
C
(a) and (b) only
D
(a), (b) and (d) only

## Explanation

(a) and (b) are properties of silicone.
(d) is the uses of silicone.
2

### JEE Main 2019 (Online) 9th January Morning Slot

The one that is extensively used as a piezoelectric material is :
A
tridymite
B
amorphous silica
C
quartz
D
mica

## Explanation

Those materials which produce electricity under mechanical stress are called piezoelectric material.

Quartz is an example of piezoelectric material.
3

### JEE Main 2019 (Online) 9th January Evening Slot

Good reducing nature of H3PO2 is attributed to the presence of :
A
Two P $-$ OH bonds
B
One P $-$ H bond
C
Two P $-$ H bonds
D
One P $-$ OH bond

## Explanation

H3PO2 is good reducing agent due to presence of two P $-$ H bonds.
4

### JEE Main 2019 (Online) 10th January Evening Slot

Among the following reactions of hydrogen with halogens, the one that requires a catalyst is
A
H2 + Br2 $\to$ 2HBr
B
H2 + Cl2 $\to$ 2HCl
C
H2 + F2 $\to$ 2HF
D
H2 + I2 $\to$ 2HI

## Explanation

The reaction which has slow reactivity requires catalyst.

Among halogens reactivity order is

F2 > Cl2 > Br2 > I2

So, H2 + I2 $\to$ 2HI, this reaction requires a catalyst.