Question

Which one of the following will have the largest number of atoms?
(A) 1g Fe (at mass of Fe = 56) (B) 1g Na (at mass of Na =23)
(C) 1g Li (at mass of Li = 7) (D) 1g F2 (at mass of F = 19)​

Answer 1

we have to choose one of the following options which has the largest number of atoms.

(A) 1g Fe (at mass of Fe = 56)     (B) 1g Na (at mass of Na =23)

(C) 1g Li (at mass of Li = 7)          (D) 1g F2 (at mass of F = 19)​

answer : (c) 1g of Li

explanation : we know, no of atoms = no of moles of atoms × Avogadro's number

it means, no of atoms will be the largest if the no of moles of atoms is the largest.

so we should find the no of moles of each of the following options.

(A) 1g of Fe

no of moles of Fe = mass of Fe/atomic mass of Fe = 1/56 = 0.0178 mol

(B) 1 g of Na

no of moles of Na = mass of Na/atomic mass of Na = 1/23 = 0.0434 mol

(C) 1g of Li

no of moles of Li = mass of Li/atomic mass of Li = 1/7 = 0.1428 mol

(D) 1g of F₂

no of moles of F₂ molecules = 1/19 = 0.0526 mol

∴ no of moles of F atoms in F₂ = 2 × 0.0526 = 0.1052 mol

here it is clear that no of moles of  1g of Li is the largest value. so 1g of Li has the the largest no of atoms.

therefore the correct option is (c) 1g of Li