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Question
Which of the following has maximum number of atoms?
Options
18g of H2O
18g of O2
18g of CO2
18g of CH4
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Solution
18g of CH4
`("Mass substance" xx ("Number of atoms in the molecule") xx "N"_"A")/"Molar mass"`
18 g of O2 = 1 mole = 1 × 6.022 × 1023
= 3 × 6.022 × 1023 atoms = 1.8066 × 1024 atoms
18 g of O2 = `(18 xx 2)/32 xx 6.022 xx 10^23`
= 6.77 × 1023 atoms
18 g of CO2 = `(18 xx 3)/44 xx 6.022 xx 10^23`
= 7.39 × 1023 atoms
18 g of CH4 = `(18 xx 5)/16 xx 6.022 xx 10^23`
= 3.38 × 1024 atoms
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