Given:
Amount of CO2 gas initially = 200 mg
Number of molecules removed = 10^23

To find:
Number of moles of CO2 left

Formula:
Number of moles = Mass of substance / Molar mass

Solution:
Step 1: Convert the mass of CO2 gas from milligrams to grams
Given mass = 200 mg
1 g = 1000 mg
Therefore, mass of CO2 gas = 200 mg / 1000 = 0.2 g

Step 2: Calculate the molar mass of CO2
The molar mass of CO2 is the sum of the atomic masses of carbon (C) and oxygen (O), which are 12.01 g/mol and 16.00 g/mol respectively.
Molar mass of CO2 = (12.01 g/mol) + (2 * 16.00 g/mol) = 44.01 g/mol

Step 3: Calculate the number of moles of CO2 initially
Number of moles = Mass of substance / Molar mass
Number of moles of CO2 initially = 0.2 g / 44.01 g/mol ≈ 0.00454 mol

Step 4: Calculate the number of moles of CO2 removed
Given number of molecules removed = 10^23

Since 1 mole of any substance contains Avogadro's number of particles (6.022 x 10^23), the number of moles of CO2 removed can be calculated as:
Number of moles of CO2 removed = (10^23 molecules) / (6.022 x 10^23 molecules/mol)
Number of moles of CO2 removed ≈ 0.166 mol

Step 5: Calculate the number of moles of CO2 left
Number of moles of CO2 left = Number of moles initially - Number of moles removed
Number of moles of CO2 left = 0.00454 mol - 0.166 mol ≈ -0.161 mol

Answer:
After removing 10^23 molecules from 200 mg of CO2 gas, there are approximately -0.161 moles of CO2 left. However, it is not physically possible to have a negative number of moles, so we can conclude that there is no CO2 left in this case.

200 mg of CO2 when x molecules are removed, 2.89 × 10-3 moles of CO2 are left.