1

NEET 2021

An organic compound contains 78% (by wt.) carbon and remaining percentage of hydrogen. The right option for the empirical formula of this compound is : [Atomic wt. of C is 12, H is 1]
A
CH4
B
CH
C
CH2
D
CH3

Explanation Based on above calculation, possible empirical formula is CH3.
2

NEET 2020 Phase 1

The number of protons, neutrons and electrons in 17571Lu, respectively, are :
A
104, 71 and 71
B
71, 71 and 104
C
175, 104 and 71
D
71, 104 and 71

Explanation

No. of Protons = 71 = No. of Electrons
No. of Neutrons = Mass No. $-$ No. of Protons
= 175 $-$ 71 = 104
3

NEET 2020 Phase 1

Which one of the following has maximum number of atoms?
A
1 g of Mg(s) [Atomic mass of Mg = 24]
B
1 g of O2(g) [Atomic mass of O = 24]
C
1 g of Li(s) [Atomic mass of Li = 7]
D
1 g of Ag(s) [Atomic mass of Ag = 108]

Explanation

Number of atoms
= ${w \over {molarmass}} \times {N_A} \times Atomicity$

Number of Mg atoms = ${1 \over {24}} \times {N_A}$

Number of O atoms = ${1 \over {32}} \times 2 \times {N_A}$

Number of Li atoms = ${1 \over 7} \times {N_A}$

Number of Ag atoms = ${1 \over {108}} \times {N_A}$
4

NEET 2019

The number of moles of hydrogen molecules required to produce 20 moles of ammonia through Haber’s process is :
A
10
B
20
C
30
D
40

Explanation

According to Haber's process,

N2(g) + 3H2(g) ⇌ 2NH3(g)

2 moles of NH3 uses 3 moles of H2

So, 20 moles of NH3 will use ${3 \over 2}$ $\times$ 20 moles of H2

= 30 moles of H2