Question

Example 18. From 200 mg of CO2, 1021 molecules are
removed. How many moles of CO2 are left?​

Answer 1

Answer:

First of all we have to find out number of molecules present in 200mg of CO₂.

weight of CO₂ = 200mg = 200 × 10⁻³ g = 0.2g

molecular weight of CO₂ = 44g/mol

∴number of mole of CO₂ = 0.2/44

Now, number of molecules = number of moles × 6.023 × 10²³

= 0.2/44 × 6.023 × 10²³

= 0.027 × 10²³

= 2.7 × 10²¹

A/C to question,

10²¹ molecule are removed from 2.7 × 10²¹ molecules of CO₂.

so, number of molecules are left = (2.7 -1) × 10²¹ = 1.7 × 10²¹

∵ mole = number of molecules/6.023 × 10²³

= 1.7/6.023 × 10²¹⁻²³

= 0.28 × 10⁻² = 0.0028