Question

Which one has greater number of atoms among the following ? 72g water, 90g iron, 7mol hydrogen gas, 33g oxygen gas

Answer 1

7 mol hydrogen gas will have the most number of atoms of the other options.
every element's 1 mol contains 6.023*10^23 atoms.
hydrogen have the most number of mole in the options ,so the correct answer is 7 mol of hydrogen

Answer 2

no.of atoms=no.of moles ×avogadro's number

a)no.of atoms in water=6.022×10²³ × 4
=24.088×10²³

b)no.of atoms of iron =6/022×10²³ × 1.61
=9.69×10²³

c)no.of atoms in H2=6.022×10²³×2×7=84.308×10²³

d)no.of atoms in O2= 6.022×10²³ × 33/32
=6.21×10²³

so more no.of atoms in H2<H2O<Fe<O2