NTSE Stage 2 SAT 2019 Exam Question Paper

Question : 75 of 100

Marks: +1, -0

You are provided with 18 g each of

O_2,N_2,CH_4

and

H_2O

.Which of the following is the correct decreasing order of number of atoms present in these samples?

Solution:

Given mass of

O_2,N_2,CH_4

and

H_2O=18gm

∵ Required number of atoms present in a molecule

=\text "Number of Moles"×N_A(N_A=\text "Avagadro number")

So,No. of atoms in

O_2=18/32×2N_A=1.12N_A

No. of atoms in

N_2=18/28×2N_A=1.28N_A

No. of atoms in

CH_4=18/16×5N_A=5.62N_A

No. of atoms in

H_2O=18/18×3N_A=3.0N_A

∴ The correct order will be

CH_4 > H_2O > N_2 > O_2

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