1

### JEE Main 2019 (Online) 11th January Morning Slot

The correct statements among (a) to (d) regarding H2 as a fuel are :

(a)   It produces less pollutants than petrol.

(b)   A cylinder of compressed dihydrogen weighs $\sim$ 30 times more than a petrol tank producing the same amount of energy.

(c)   Dihydrogen is stored in tanks of metal alloys like NaNi5.

(d)   On combustion, values of energy released per gram of liquid dihydrogen and LPG are 50 and 142 KJ, respectively.
A
(a) and (c) only
B
(b) and (d) only
C
(a), (b) and (c) only
D
(b), (c) and (d) only
2

### JEE Main 2019 (Online) 11th January Morning Slot

NaH is an example of :
A
metallic hydride
B
saline hydride
C
electron-rich hydrid
D
molecular hydride

## Explanation

NaH is an example of ionic hydride which is also known as saline hydride.
3

### JEE Main 2019 (Online) 12th January Morning Slot

The hardness of a water sample (in terms of equivalents of CaCO3) containing 10–3 M CaSO4 is (Molar mass of CaSO4 = 136 g mol–1)
A
90 ppm
B
100 ppm
C
50 ppm
D
10 ppm

## Explanation

nCaSO4 $\times$ Van't hoff factor = nCaCO3 $\times$ Van't hoff factor

$\Rightarrow$ 10-3 $\times$ 2 = nCaCO3 $\times$ 2

$\Rightarrow$ nCaCO3 = 10-3 mol in 1 L

$\therefore$ wCaCO3 = 100 $\times$ 10-3 g CaCO3 in 1 L solution

$\therefore$ hardness in terms of CaCO3

= ${{{w_{CaC{O_3}}}} \over {{w_{Total}}}} \times {10^6}$

= ${{100 \times {{10}^{ - 3}}} \over {1000}} \times {10^6}$

= 100 ppm
4

### JEE Main 2019 (Online) 12th January Evening Slot

The volume strength of 1M H2O2 is (Molar mass of H2O2 = 34 g mol–1)
A
5.6
B
22.4
C
11.35
D
16.8

## Explanation

At   STP,

Volume strength = 11.35 $\times$ Molarity

$\therefore$  Volume strength of H2O2 = 11.35 $\times$ 1 = 11.35