Question

Arrange the following in the decreasing order of the total number of atoms present in one mole each of

(A) Sulphuric acid (B) Aluminium oxide

(C) Potassium dichromate (D) Ferrous sulphate

(E) Ammonium bicarbonate

• A. ECADB
• B. CAEDB
• C. CDBEA
• D. CEADB

Answer 1

The correct option is C

CDBEA

Explanation of correct answer

Number of atoms in a molecule would be higher in those compounds which are having greater molecular mass.

(A) Sulphuric acid $\left({\mathrm{H}}_2{\mathrm{SO}}_4\right)$ = $2\times \mathrm{H}+1\times \mathrm{S}+4\times \mathrm{O}=(2\times 1+1\times 32+4\times 16)=78\mathrm{g}$

(B) Aluminum oxide $\left({\mathrm{Al}}_2{\mathrm{O}}_3\right)$ = $2\times \mathrm{Al}+3\times \mathrm{O}=(2\times 26+3\times 16)=100\mathrm{g}$

(C) Potassium dichromate $\left({\mathrm{K}}_2{\mathrm{Cr}}_2{\mathrm{O}}_7\right)$ = $(2\times 39+2\times 52+7\times 16)=294\mathrm{g}$

(D) Ferrous sulphate $\left({\mathrm{FeSO}}_4\right)$ = $(56+32+64)=152\mathrm{g}$

(E) Ammonium bicarbonate $\left({\mathrm{NH}}_4{\mathrm{HCO}}_3\right)$ = $(1\times \mathrm{N}+4\times \mathrm{H}+1\times \mathrm{H}+1\times \mathrm{C}+3\times \mathrm{O})=(1\times 14+4\times 1+1\times 1+1\times 12+3\times 16)=79\mathrm{g}$

CDBEA is the correct answer according to this concept.

All order given in A, C and D are not according to the concept, hence these are wrong.