calculate the no of oxygen atoms present in 4.4 g of CO2

Molar mass CO_{2} = 44 g/mol

Therefore, number of moles in 4.4 g CO_{2} = 4.4/44 = 0.1 mol

Now,

1mol CO_{2} contains 6.022 x10^{23} molecules

0.1mol CO_{2} contains 6.022 x 10^{23} x 0.1 = 6.022 x 1022^{22} molecules

Also,

1molecule of CO2 contains 2 atoms of oxygen

Therefore,

6.022 x10^{23} molecules of CO_{2} will contain 6.022 x 10^{22} x 2 = 1.204 x 10^{23} atoms of oxygen

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