How many number of moles of CO will be left when 2 10^21 molecules are removed from 0.28gm of CO ?

To determine the number of moles of $\mathrm{CO}$ left after removing $2\times 10^{21}$ molecules from 0.28 g of $\mathrm{CO}$, follow these steps:

1. Calculate the molar mass of $\mathrm{CO}$: $$\text{Molar mass of }\mathrm{CO}=12+16=28\text{g/mol}$$

2. Find the initial number of moles of $\mathrm{CO}$: $$\text{Moles of }\mathrm{CO}=\frac{\text{mass}}{\text{molar mass}}=\frac{0.28\text{g}}{28\text{g/mol}}=0.01\text{mol}$$

3. Convert the removed molecules to moles: $$\text{Number of moles removed}=\frac{2\times 10^{21}\text{molecules}}{6.022\times 10^{23}\text{molecules/mol}}=0.00332\text{mol}$$

4. Calculate the remaining moles of $\mathrm{CO}$: $$\text{Moles left}=0.01\text{mol}-0.00332\text{mol}=0.00668\text{mol}$$

Final answer: 0.00668 moles of $\mathrm{CO}$ will be left.